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Moharrami, Gargari Mohammadreza. "Development of Novel Computational Simulation Tools to Capture the Hysteretic Response and Failure of Reinforced Concrete Structures under Seismic Loads." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71864.
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Reinforced concrete (RC) structures constitute a significant portion of the building inventory in earthquake-prone regions of the United States. Accurate analysis tools are necessary to allow the quantitative assessment of the performance and safety offered by RC structures. Currently available analytical approaches are not deemed adequate, because they either rely on overly simplified models or are restricted to monotonic loading. The present study is aimed to establish analytical tools for the accurate simulation of RC structures under earthquake loads. The tools are also applicable to the simulation of reinforced masonry (RM) structures.
A new material model is formulated for concrete under multiaxial, cyclic loading conditions. An elastoplastic formulation, with a non-associative flow rule to capture compression-dominated response, is combined with a rotating smeared-crack model to capture the damage associated with tensile cracking. The proposed model resolves issues which characterize existing concrete material laws. Specifically, the newly proposed formulation accurately describes the crack opening/closing behavior and the effect of confinement on the strength and ductility under compressive stress states. The model formulation is validated with analyses both at the material level and at the component level. Parametric analyses on RC columns subjected to quasi-static cyclic loading are presented to demonstrate the need to regularize the softening laws due to the spurious mesh size effect and the importance of accounting for the increased ductility in confined concrete. The impact of the shape of the yield surface on the results is also investigated.
Subsequently, a three-dimensional analysis framework, based on the explicit finite element method, is presented for the simulation of RC and RM components under cyclic static and dynamic loading. The triaxial constitutive model for concrete is combined with a material model for reinforcing steel which can account for the material hysteretic response and for rupture due to low-cycle fatigue. The reinforcing steel bars are represented with geometrically nonlinear beam elements to explicitly account for buckling of the reinforcement. The strain penetration effect is also accounted for in the models. The modeling scheme is validated with the results of experimental static and dynamic tests on RC columns and RC/RM walls. The analyses are supplemented with a sensitivity study and with calibration guidelines for the proposed modeling scheme.
Given the computational cost and complexity of three-dimensional finite element models in the simulation of shear-dominated structures, the development of a conceptually simpler and computationally more efficient method is also pursued. Specifically, the nonlinear truss analogy is employed to capture the response of shear-dominated RC columns and RM walls subjected to cyclic loading. A step-by-step procedure to establish the truss geometry is described. The uniaxial material laws for the concrete and masonry are calibrated to account for the contribution of aggregate interlock resistance across inclined shear cracks. Validation analyses are presented, for quasi-static and dynamic tests on RC columns and RM walls.Ph. D.
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Usami, Tsutomu, 昭. 葛西, Akira Kasai, 康文 河村, Yasufumi Kawamura, and 勉. 宇佐美. "鋼製橋脚ー基礎ー地盤連成系の大地震時挙動." 土木学会, 2000. http://hdl.handle.net/2237/8454.
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Pelecanos, Loizos. "Seismic response and analysis of earth dams." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23649.
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Many earth dams around the world are located in zones characterised by moderate to high seismicity. Their seismic stability can be particularly critical for the safety of the areas in the downstream side and therefore an in depth understanding of their response during earthquakes is required. This thesis describes a numerical study related to both the seismic response and analysis of earth dams using the finite element method. In the first part of the thesis, the effect of the upstream reservoir hydrodynamic pressures on the elastic seismic response of dams is explored. Firstly, a methodology is proposed in which the reservoir domain is modelled with finite elements focusing in particular on the accurate prediction of the hydrodynamic pressures on the upstream dam face. Secondly, a parametric study of dam-reservoir interaction is carried out to examine the effect of the reservoir on the seismic response of dams. The second part of the thesis is concerned with the nonlinear seismic behaviour of earth dams. Firstly, a well-documented case study, the La Villita dam in Mexico, is analysed in order to validate the numerical model and a good agreement is obtained between the recorded and predicted data. Subsequently, using as a reference the calibrated model, parametric studies are performed in order to obtain a better insight into the dynamic response and analysis of earth dams. The latter studies provide a means to assess the effect of different modelling considerations on the seismic analysis of dams.
4
Degirmenci, Can. "Dynamic Pull Analysis For Estimating The Seismic Response." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607833/index.pdf.
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The analysis procedures employed in earthquake engineering can be classified as linear static, linear dynamic, nonlinear static and nonlinear dynamic. Linear procedures are usually referred to as force controlled and require less analysis time and less computational effort. On the other hand, nonlinear procedures are referred to as deformation controlled and they are more reliable in characterizing the seismic performance of buildings. However, there is still a great deal of unknowns for nonlinear procedures, especially in modelling the reinforced concrete structures.
Turkey ranks high among all countries that have suffered losses of life and property due to earthquakes over many centuries. These casualties indicate that, most regions of the country are under seismic risk of strong ground motion. In addition to this phenomenon, recent studies have demonstrated that near fault ground motions are more destructive than far-fault ones on structures and these effects can not be captured effectively by recent nonlinear static procedures.
The main objective of this study is developing a simple nonlinear dynamic analysis procedure which is named as &ldquoDynamic Pull Analysis&rdquo
for estimating the seismic response of multi degree of freedom (MDOF) systems. The method is tested on a six-story reinforced concrete frame and a twelve-story reinforced concrete frame that are designed according to the regulations of TS-500 (2000) and TEC (1997).
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Burdisso, R. A. "Seismic response analysis of multiply connected secondary systems." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49996.
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An analytical formulation for seismic analysis of multiply supported secondary systems is developed. The formulation is based on the random vibration theory of structural systems subjected to correlated inputs at several points. The response of the secondary systems is expressed as a combination of the dynamic, pseudo-static and cross response components. The dynamic part is associated with the inertial effect induced by the support accelerations. The pseudo-static part is due to the relative displacement between supports, and the cross part takes into account the correlation between these two parts of the response. The seismic input in this approach is defined in terms of the auto and cross pseudo-acceleration and relative velocity floor spectra. The information about floor displacements and velocities as well as their correlations is required for calculating the pseudo-static and cross response components. These inputs can be directly obtained from the ground response spectra. The interaction effect between the primary and secondary systems is studied. This effect is specially significant when the modes of the secondary system are tuned or nearly tuned to the modes of the primary system. The floor spectral inputs are appropriately modified to take into account this interaction effect. The design response of the secondary system when computed with these modified floor inputs will incorporate the interaction effect. The applicability of the proposed methods is demonstrated by several numerical examples.Ph. D.
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Morgan, Andrew Scott. "Seismic Response of Stiffening Elastic Systems." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3491.
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Traditional seismic load resisting systems in buildings are designed to undergo inelastic deformations in order to dissipate energy, resulting in residual displacements. This work explores an approach to eliminate these residual displacements. The systems investigated have low initial stiffness which increases at a predefined displacement, and are therefore called stiffening elastic systems. This thesis begins with an examination of single-degree-of-freedom stiffening elastic systems. A case study is presented which suggests that the benefits from stiffening elastic behavior may be limited to systems which would have long periods if designed traditionally. A thorough parameter study is also presented which indicates the benefit of stiffening elastic behavior for SDOF systems with periods greater than four seconds. A final case study is presented that compares the response of a twelve-story stiffening elastic system to a ductile system and an elastic system. The stiffening elastic system was able to eliminate the residual displacements inherent in a ductile system while lowering the base shear experienced by the elastic system, but is not clearly better than the ductile system because the base shear force was much higher.
7
Javed, Khalid. "Non linear seismic response of asymmetric buildings." Thesis, University of East London, 1999. http://roar.uel.ac.uk/1260/.
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The study presented in this thesis is an attempt towards a better understanding of the coupled lateral-torsional response of buildings subject to seismic ground motion. Some of the problems identified in the past studies are thoroughly investigated and some new areas of study are explored. Some of these problems encountered in the literature include (a) the existence of several definitions of uncoupled torsional to lateral frequency ratio (b) an arbitrary selection of structural parameters in a parametric analysis resulting in a physically inadmissible structure and (c) the effect of nonlinearity. Because of the simplified models with either eccentricity in one direction or the ground motion applied in only one direction, the effects of a bi-directional loading have not been investigated in detail. These effects may include the relative differences in the amplitude or phase components of the individual accelerograms and their orientation with respect to the building. The phase properties of accelerograms are of particular interest and these have not received much attention in the past. Using analytical methods such as Chasle's[16] and Gerschgorin's[39] theorems, the equation of motion of a bi-eccentric system is derived and all of the existing problems regarding the definition of structural parameters and their bounds are studied in depth. To facilitate nonlinear parametric study, a paraboloid non-linear elastic stiffness model is proposed. Fourier spectral methods are used to study the frequency domain characteristics of the accelerogram pair. The difference in phase and amplitude of the component frequencies in each direction are studied for their effects on the response. For phase difference, cross-correlation function is used as a comparative statistical indicator. USA earthquake records obtained from US National Geophysical Data Centre are grouped into four soil types and the analysis is performed for each group in order to explore the soil-dependency of the aforementioned effects on the response. Computer programs are written in FORTRAN for both parametric and numerical model analyses. The latter can handle any number and orientation of columns with the assumed nonlinear stiffness properties. Newmark's and Runge-Kutta methods of numerical integration with adaptive step size control have been used to calculate parametric and the hysteretic responses of the system. The response to harmonic ground acceleration is used as a preliminary investigation into the response to actual accelerogram frequency components. The study has developed relationships for different definitions of the uncoupled torsional to lateral frequency ratio. Detailed derivation of the Equation of Motion has clarified the confusion that produced different definitions in the past studies. Graphical descriptions of the admissibility bounds on system parameters are produced. The variation in the response quantities is studied for a range of amplitude and phase contents of the applied ground acceleration. The difference in phase and amplitude in x and y ground accelerations have been found to affect the response quite significantly. More generally, the relationship of these differences to the torsional mode amplification has been observed. The effects of structural frequency and eccentricity parameters are also studied. Graphs showing the relationship between, the angle of incidence of the accelerogram with respect to the principal axis of the building, and the phase difference in the accelerogram pair, have been produced. The proposed analysis involving the bi-directional ground acceleration on a bi-eccentric system is an improvement on the current methods employed in design practice. Further work is, however, required before simplified design recommendations can be made and some proposals for future research are given at the end of this thesis.
8
Kasinos, Stavros. "Seismic response analysis of linear and nonlinear secondary structures." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/33728.
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Understanding the complex dynamics that underpin the response of structures in the occurrence of earthquakes is of paramount importance in ensuring community resilience. The operational continuity of structures is influenced by the performance of nonstructural components, also known as secondary structures. Inherent vulnerability characteristics, nonlinearities and uncertainties in their properties or in the excitation pose challenges that render their response determination as a non-straightforward task. This dissertation settles in the context of mathematical modelling and response quantification of seismically driven secondary systems. The case of bilinear hysteretic, rigid-plastic and free-standing rocking oscillators is first considered, as a representative class of secondary systems of distinct behaviour excited at a single point in the primary structure. The equations governing their full dynamic interaction with linear primary oscillators are derived with the purpose of assessing the appropriateness of simplified analysis methods where the secondary-primary feedback action is not accounted for. Analyses carried out in presence of pulse-type excitation have shown that the cascade approximation can be considered satisfactory for bilinear systems provided the secondary-primary mass ratio is adequately low and the system does not approach resonance. For the case of sliding and rocking systems, much lighter secondary systems need to be considered if the cascade analysis is to be adopted, with the validity of the approximation dictated by the selection of the input parameters. Based on the premise that decoupling is permitted, new analytical solutions are derived for the pulse driven nonlinear oscillators considered, conveniently expressing the seismic response as a function of the input parameters and the relative effects are quantified. An efficient numerical scheme for a general-type of excitation is also presented and is used in conjunction with an existing nonstationary stochastic far-field ground motion model to determine the seismic response spectra for the secondary oscillators at given site and earthquake characteristics. Prompted by the presence of uncertainty in the primary structure, and in line with the classical modal analysis, a novel approach for directly characterising uncertainty in the modal shapes, frequencies and damping ratios of the primary structure is proposed. A procedure is then presented for the identification of the model parameters and demonstrated with an application to linear steel frames with uncertain semi-rigid connections. It is shown that the proposed approach reduces the number of the uncertain input parameters and the size of the dynamic problem, and is thus particularly appealing for the stochastic assessment of existing structural systems, where partial modal information is available e.g. through operational modal analysis testing. Through a numerical example, the relative effect of stochasticity in a bi-directional seismic input is found to have a more prominent role on the nonlinear response of secondary oscillators when compared to the uncertainty in the primary structure. Further extending the analyses to the case of multi-attached linear secondary systems driven by deterministic seismic excitation, a convenient variant of the component-mode synthesis method is presented, whereby the primary-secondary dynamic interaction is accounted for through the modes of vibration of the two components. The problem of selecting the vibrational modes to be retained in analysis is then addressed for the case of secondary structures, which may possess numerous low frequency modes with negligible mass, and a modal correction method is adopted in view of the application for seismic analysis. The influence of various approaches to build the viscous damping matrix of the primary-secondary assembly is also investigated, and a novel technique based on modal damping superposition is proposed. Numerical applications are demonstrated through a piping secondary system multi-connected on a primary frame exhibiting various irregularities in plan and elevation, as well as a multi-connected flexible secondary system. Overall, this PhD thesis delivers new insights into the determination and understanding of the response of seismically driven secondary structures. The research is deemed to be of academic and professional engineering interest spanning several areas including seismic engineering, extreme events, structural health monitoring, risk mitigation and reliability analysis.
9
Zamiran, Siavash. "Numerical Analysis on Seismic Response of Cantilever Retaining Wall Systems and Fragility Analysis on Motion Response." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1475.
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In this investigation, seismic response of retaining walls constructed with cohesive and cohesionless backfill materials was studied. Fully dynamic analysis based on finite difference method was used to evaluate the performance of retaining walls during the earthquake. The analysis response was verified by the experimental study conducted on a retaining wall system with cohesive backfill material in the literature. The effects of cohesion and free-field peak ground acceleration (PGA) on seismic earth thrust, the point of action of earth thrust, and maximum wall moment during the earthquake were compared with analytical and experimental solutions. The numerical results were compared with various analytical solutions. The motion characteristics of the retaining wall during the earthquake were also considered. The relative displacement of the walls with various backfill cohesions, under different ground motions, and free-field PGAs were investigated. Current analytical and empirical correlations developed based on Newmark sliding block method for estimating retaining wall movement during earthquakes were compared with the numerical approach. Consequently, fragility analyses were conducted to determine the probability of damage to the retaining walls. To evaluate the fragility of the studied models, specific failure criterion was chosen for retaining walls based on the suggested methods in practice. Using numerical approaches, the effects of soil-wall interaction and wall rigidity on the seismic response of retaining walls were also evaluated in earthquake conditions for both cohesive and cohesionless backfill materials. According to the findings, practical correlations were presented for conducting the seismic design of retaining walls.
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KASAI, Akira, 昭. 葛西, Qingyun LIU, 青芸 劉, Tsutomu USAMI, and 勉. 宇佐美. "INELASTIC SEISMIC RESPONSE ANALYSIS OF ECCENTRICALLY LOADED STEEL BRIDGE PIERS." 土木学会, 2000. http://hdl.handle.net/2237/8649.
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Jeong, Seokho. "Topographic amplification of seismic motion including nonlinear response." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50325.
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Topography effects, the modification of seismic motion by topographic features, have been long recognized to play a key role in elevating seismic risk. Site response, the modification of ground motion by near surface soft soils, has been also shown to strongly affect the amplitude, frequency and duration of seismic motion. Both topography effects and 1-D site response have been extensively studied through field observations, small-scale and field experiments, analytical models and numerical simulations, but each one has been studied independently of the other: studies on topography effects are based on the assumption of a homogeneous elastic halfspace, while 1-D site response studies are almost exclusively formulated for flat earth surface conditions.
This thesis investigates the interaction between topographic and soil amplification, focusing on strong ground motions that frequently trigger nonlinear soil response. Recently, a series of centrifuge experiments tested the seismic response of single slopes of various inclination angles at the NEES@UCDavis facility, to investigate the effects of nonlinear soil response on topographic amplification. As part of this collaborative effort, we extended the search space of these experiments using finite element simulations. We first used simulations to determine whether the centrifuge experimental results were representative of free-field conditions. We specifically investigated whether wave reflections caused by the laminar box interfered with mode conversion and wave scattering that govern topographic amplification; and whether this interference was significant enough to qualitatively alter the observed amplification compared to free-field conditions. We found that the laminar box boundaries caused spurious reflections that affected the response near the boundaries; however its effect to the crest-to-free field spectral ratio was found to be insignificant. Most importantly though, we found that the baseplate was instrumental in trapping and amplifying waves scattered and diffracted by the slope, and that in absence of those reflections, topographic amplification would have been negligible. We then used box- and baseplate-free numerical models to study the coupling between topography effects and soil amplification in free-field conditions.
Our results showed that the complex wavefield that characterizes the response of topographic features with non-homogeneous soil cannot be predicted by the superposition of topography effects and site response, as is the widespread assumption of engineering and seismological models. We also found that the coupling of soil and topographic amplification occurs both for weak and strong motions, and for pressure-dependent media (Nevada sand), nonlinear soil response further aggravates topographic amplification; we attributed this phenomenon to the reduction of apparent velocity that the low velocity layers suffer during strong ground motion, which intensifies the impedance contrast and accentuates the energy trapping and reverberations in the low strength surficial layers. We finally highlighted the catalytic effects that soil stratigraphy can have in topographic amplification through a case study from the 2010 Haiti Earthquake. Results presented in this thesis imply that topography effects vary significantly with soil stratigraphy, and the two phenomena should be accounted for as a coupled process in seismic code provisions and seismological ground motion predictive models.
12
Tola, Adrian Patricio. "Development of a Comprehensive Linear Response History Analysis Procedure for Seismic Load Analysis." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/36106.
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This thesis reviews the parameters required to perform linear response history analysis according to Chapter 16 of the American Standard ASCE 7-10. A careful analysis is presented about the selection of ground motions using real records and using artificial records generated such that their response spectrum matches with a defined target spectrum; three different techniques are studied for the generation of these artificial records. Also, this document revises the scaling of ground motion techniques in the American Standard ASCE-7 as well as in other seismic codes. It presents a detailed analysis of the variables influencing the scaling of ground motions, and it suggests a new scaling technique for linear response history analysis. The assumptions made establishing the flexibility of the diaphragms are also analyzed as well as dynamic methods to include accidental torsion when doing a linear response history analysis. Other modeling issues such as the orientation of the ground motion axis, scaling of element forces and displacements, orthogonal loading, solution techniques, P-Delta effects, modeling of the basement, and calculation of drifts are also studied in the context of linear response history analysis. The thesis concludes with suggested code language for linear response history analysis intended to be considered in future editions of the American Standard ASCE 7.Master of Science
13
Kadas, Koray. "Influence Of Idealized Pushover Curves On Seismic Response." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607761/index.pdf.
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Contemporary approach performance based engineering generally relies on the approximate procedures that are based on the use of capacity curve derived from pushover analysis. The most important parameter in the displacement-based approach is the inelastic displacement demand computed under a given seismic effect and the most common procedures employed for this estimationthe Capacity Spectrum Method and the Displacement Coefficient Method are based on bi-linearization of the capacity curve. Although there are some recommendations for this approximation, there is a vital need for rational guidelines towards the selection of the most appropriate method among several alternatives. A comprehensive research has been undertaken to evaluate the influence of several existing alternatives used for approximating the capacity curve on seismic demands. A number of frames were analyzed under a set of 100 ground motions employing OpenSees. In addition, the pushover curves obtained from nonlinear static analyses were approximated using several alternatives and the resulting curves were assigned as the force-deformation relationships of corresponding equivalent single-degree-of-freedom systems. These simplified systems were later analyzed to compute the approximate seismic response parameters. Using the results of the complex and simplified analyses, the performance of each approximation method was evaluated in estimating the &
#8216
exact&
#8217
inelastic deformations of the multi-degree-of-freedom systems at various degrees of inelasticity. Dependency of the errors on ductility, strength reduction factor and period was also investigated. The interpretations made and the conclusions drawn in this study is believed to clarify the rationality and accuracy of selecting the appropriate idealization of the capacity curve.
14
Gunay, Mehmet Selim. "An Equivalent Linearization Procedure For Seismic Response Prediction Of Mdof Systems." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609447/index.pdf.
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Nonlinear response history analysis is accepted as the most accurate analytical tool for seismic response determination. However, accurate estimation of displacement responses using conceptually simple, approximate analysis procedures is preferable, since there are shortcomings in the application of nonlinear response history analysis resulting from its complexity.
An equivalent linearization procedure, which utilizes the familiar response spectrum analysis as the analysis tool and benefits from the capacity principles, is developed in this thesis study as an approximate method for predicting the inelastic seismic displacement response of MDOF systems under earthquake excitations. The procedure mainly consists of the construction of an equivalent linear system by reducing the stiffness of structural members which are expected to respond in the inelastic range. Different from similar studies in literature, equivalent damping is not explicitly employed in this study. Instead, predetermined spectral displacement demands are utilized in each mode of the equivalent linear system for the determination of global displacement demands.
Response predictions of the equivalent linearization procedure are comparatively evaluated by using the benchmark nonlinear response history analysis results and other approximate methods including conventional pushover analysis and modal pushover analysis (MPA). It is observed that the proposed procedure results in similar accuracy with approximate methods which employ nonlinear analysis. Considering the conceptual simplicity of the procedure and the conventional analysis tools used in its application, presented equivalent linearization procedure can be suggested as a practically applicable method for the prediction of inelastic seismic displacement response parameters with sufficient accuracy.
15
Wang, Jiachen. "Analysis of the seismic response of highway bridges to multiple support excitations." Thesis, University of Canterbury. Civil Engineering, 2003. http://hdl.handle.net/10092/7520.
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It is recognized that the spatial variability of the ground motion has an important effect on the seismic responses of extended structures, but it is not well known how these structural responses will be affected. The aim of this study was to gain insight of the effect of asynchronous inputs on the elastic and inelastic responses of long bridges in order to improve the earthquake resistant design of bridges.
In this research, a simple method of generating the asynchronous input motions, conditioned by the recorded time-histories, is proposed. Two assumptions were adopted in this method. The first assumption was that the spatial correlation function depended only on the predominant frequency of the earthquake motion. The second assumption was that in the time domain, there was no correlation between the acceleration elements in the same record. With the aid of these two assumptions, the modified Kriging method proposed by Hoshiya could be easily used to simulate ground motions in the time domain. Numerical examples showed that the spectra of simulated time-histories and the specified earthquake record closely correlated with each other and the variation of the simulated accelerations with the separation distance between the supports, the propagation velocity and the dispersion factor followed the trends expected.
It was observed that the velocity of propagation of seismic waves had a significant effect on the transverse response of long bridges in travelling wave cases. The transverse responses of the bridges to the travelling waves can be more critical than those to the synchronous input. The transverse response parameters investigated were the maximum pier drifts, the maximum pier shear forces and the maximum section curvature ratios of the piers. The responses of the bridges subjected to asynchronous inputs consist of two parts: the dynamic components induced by the inertial forces and the pseudo-static components due to the differential displacements between the adjacent supports. The response was dominated by the pseudostatic component when the travelling wave velocity was low. The pseudo-static component reduced and the dynamic component increased as the travelling wave velocity increased. The response was dominated by the dynamic component when the travelling wave velocity was high. The local variations of the responses with the travelling wave velocity were due to the variations in the acceleration spectra of the input motions with the travelling wave velocity.
It was found that the geometric incoherence effect also played an important role in the responses of the bridges through the pseudo-static components. In the cases that the combined geometric incoherence and wave passage effects of the spatial variability of the seismic motion were considered, the pseudo-static component of the seismic response of long bridges was not only caused by the wave passage effect, but was also due to the geometric incoherence effect. The pseudo-static component caused by the geometric incoherence effect dominated the total responses when wave dispersion was greatest. Because the variations of the accelerograms at different pier supports were random, the value of the pseudo-static component due to the geometric incoherence effect was also random. Therefore the total responses were unpredictable when the wave dispersion was great. The influence of the pseudo-static component in the total response decreased as the wave dispersion decreased. When dispersion was least the trends of the variations of the response with the travelling wave velocity were similar to those for the travelling wave cases without wave dispersion.
The longitudinal responses of the bridge models with movement joints subjected to asynchronous inputs were also investigated. It was found that the relative displacement of the bridge deck across the movement joints and the relative displacement between the girder end and the top of the abutment consist of two parts: the dynamic components due to the difference between the vibrations of the two frames separated by the movement joints and the pseudo-static components caused by the phase shifts between the vibrations. The dynamic components changed with the travelling wave velocity due to the changes of the acceleration spectra in the asynchronous motion cases. The pseudo-static components were not only dependent on the phase shifts, but were also related to the shapes of the response displacement time-histories of the bridge deck.
16
VALVERDE, MARCELO CERQUEIRA. "DEVELOPMENT OF RESPONSE SPECTRA FOR THE SEISMIC STRUCTURAL ANALYSIS OF PIPING SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1469@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICONUCLEN S.A.
Os resultados apresentados referem-se à investigação dos mecanismos de interação entre dois sistemas vitais às usinas nucleares, ou seja: os sistemas Principal (SP) e o Secundário (SS). Estes mecanismos são avaliados por meio de sua influência nos espectros de resposta, em pontos da estrutura passíveis da existência de suportes das linhas de tubulação - SS. São usados dois tipos diferentes de análises para a geração dos espectros de resposta: a primeira não considera a interação dos sistemas e a segunda avalia esta interação com a introdução, em cada ponto de suporte no SP, de um S1GL com suportes únicos ou com multi- suportes. As respostas estruturais são obtidas por integração direta da equação de movimento do sistema sujeito a dois acelerogramas simultâneos, nas direções horizontal e vertical. Os resultados são analisados e comparados para identificação das principais tendências das análises e esclarecimento dos efeitos envolvidos. Estuda-se, também, a importância de não- linearidades concentradas nos suportes da tubulação, tendo- se em vista o nível sísmico a que as centrais nucleares brasileiras estão sujeitas.
The results presented in this work refer to the investigation of the mechanics of the interaction between two important systems of nuclear power plants, i.e.: the Primary (PS) and Secondary (SS) systems. The influence of these effects on the response spectra is studied, in convenient points of the structure where could exist pipeline (SS) supports. Two different approaches are used to generate the response spectra: the first neglects the interaction between the two systems and the second considers this interaction by the addition, to every support point on the PS, of a single-supported or multi-supported SDOF system. The structural responses are obtained by the direct integration of the Primary System equations of motion subjected to two simultaneous design acceleration time-histories, in the horizontal and vertical directions. The results are analyzed and compared to identify the general trends of the solutions obtained by the two types of analysis, and to detect their effects on the SS response. The study is concerned, also, with the importance of nonlinearities concentrated in the pipeline supports; in the case of the Brazilian nuclear power plants.
Los resultados presentados se refieran a la investigación de los mecanismos de interacción entre de los los sistemas Principal (SP) y el Secundario (S) de las plantas nucleares. Estos mecanismos son evaluados por medio de su influencia en los espectros de respuesta, en puntos de la extructura donde es posible(pausibles) la existencia de soportes de las líneas de tuberías - S. Son usados dos tipos diferentes de análisis para la generación de los espectros de respuesta: la primera no considera la interacción de los sistemas y la segunda evalúa esta interacción con la introdución, en cada ponto de soporte en el SP, de un S1GL con soportes únicos o con multisoportes. Las respuestas extructurales son obtenidas por integración directa de la ecuación de movimento del sistema sujeto a dos acelerogramas simultáneos, en las direcciones horizontal y vertical. Se analizan los resultados y se comparan para identificar las principales tendencias del análisis y esclarecer los efectos involucrados. Se estudia además, la importancia de no linealidades concentradas en los soportes de la tubería, teniendo en vista el nível sísmico a que las centrales nucleares brasileras están sujetas.
17
Andrawes, Bassem Onsi. "Seismic Response and Analysis of Multiple Frame Bridges Using Superelastic Shape Memory Alloys." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6914.
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The feasibility of using superelastic shape memory alloys in the retrofit of multiple frame bridges is investigated. First, three shape memory alloy constitutive models with various levels of complexity are compared in order to determine the significance of including subloops and cyclic loading effects on the structural response. The results show that the structural response is more sensitive to the shape memory alloys strength degradation and residual deformation than the sublooping behavior. Next, two parametric studies are conducted to explore the sensitivity of hinge opening to the mechanical behavior of the superelastic shape memory alloys. The first study is focused on the hysteretic properties of the alloy that could vary depending on the chemical composition or the manufacturing process of the alloy, while the second study targets the changes in the mechanical behavior of shape memory alloys resulting from the variability in the ambient temperature. The results show that the hysteretic behavior of shape memory alloys has only a slight effect on the bridge hinge opening as long as the recentering property is maintained. A detailed study on the effect of temperature shows that a reduction in the ambient temperature tends to negatively affect the hinge opening while an increase in temperature results in a slight improvement. Next, a parametric study is conducted to examine the effectiveness of shape memory alloy retrofit devices in limiting hinge openings in bridges with various properties. In addition, a comparison is made with other devices such as conventional steel restrainers, metallic dampers, and viscoelastic solid dampers. The results illustrate that superelastic shape memory alloys are superior in their effectiveness compared to other devices in the case of bridges with moderate period ratios and high level of ductility, especially when subjected to strong earthquakes.
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Bakir, Serhan. "Evaluation Of Seismic Response Modification Factors For Steel Frames By Non-linear Analysis." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607827/index.pdf.
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In this study steel framing systems are investigated with regards to their lateral load carrying capacity and in this context seismic response modification factors of individual systems are analyzed. Numerous load resisting layouts, such as different bracing systems and un-braced moment resisting frames with various bay and story configurations are designed and evaluated in a parametric fashion. Three types of beam to column connection conditions are incorporated in evaluation
process.
Frames, designed according to Turkish seismic code, are investigated by nonlinear static analysis with the guidance of previous studies and recent provisions of FEMA. Method of analysis, design and evaluation data are presented in detail.
Previous studies in literature, history and the theory of response modification phenomenon is presented.
Results are summarized, main weaknesses and ambiguities introduced to design by the use of &ldquoR&rdquo
factors are stated depending on the observed behavior.
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Romano, Angelo. "Seismic response analysis of low-rise buildings designed according to the NBCC 1990." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59378.
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An earthquake of magnitude 5.7 occurred in the Saguenay region of the province of Quebec, Canada, on November 25, 1988. Although no loss of life or severe structural damages were caused by this earthquake the poor performance of unreinforced masonry and structures with 'tension-only' cross-bracing were reported by a site visit team.This thesis presents some of the important engineering characteristics of the 1988 Saguenay earthquake. Comparisons are made in terms of elastic and inelastic response spectra for the lateral forces to be considered for the seismic response analysis of short-period structural systems. In particular, the seismic response of a low-rise braced steel building designed according to the National Building Code of Canada is investigated in both the elastic and inelastic range.
The code-suggested equivalent lateral force method for short-period structures with a substantial strength-reduction factor does not provide a rational control of structural damage that can be expected from seismic excitation in Eastern Canada. The use of a period-dependent strength reduction factor applied to the elastic strength demand for short-period structures is proposed to take advantage of the inelastic energy dissipation capacity for this type of system on a more rational basis.
20
Xu, Yungui. "Analysis of P-wave seismic response for fracture detection : modelling and case studies." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/6185.
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This thesis addresses a few specific issues in the use of wide azimuth P-wave seismic data for fracture detection based on numerical modelling and real data. These issues include the seismic response of discrete fractures, the effects of anticline and uncertainties in real data analysis. For this, I implemented the finite difference scheme for modelling the seismic response in 3D fractured media; appropriate approaches are then selected to study discrete fracture models and the effect of the anticline with 3D seismic modelling, followed by an integrate real case study. Finite difference (FD) is widely used in seismic modelling. There are three FD schemes described in this thesis, the standard staggered grid (SSG), the rotated staggered grid (RSG), and the diamond staggered grid (DSG). Both qualitative and quantitative comparison has been made to reveal their capability in modelling 3D fractured media. The SSG has shown best performance for anisotropic media with orthorhombic symmetry or higher symmetry system. For lower anisotropy symmetry, the DSG is preferred than the RSG in terms of computation efficiency. A new solution to the diamond grid issue is developed which can simplify the DSG implementation, and an optimized workflow is proposed to simulate large 3D fractured models. The SSG scheme is implemented in three dimensions and it provides a useful tool for various practical modelling studies. With the above tool, two modelling studies have been carried out, on the effects of the discrete fractures and of the presence of anticline: the Discrete Fracture Model (DFM) study provides many insights into seismic response of discrete fracture and the link between the discrete fractures and aligned micro cracks, as well as the features in scattering waves. The modelling results demonstrate that, P-wave seismic anisotropy increases with the decrease of discrete fracture spacing, and different spacing leads to different patterns in scattering waves. The study also reveals the azimuthal AVO variation on the top of discrete fracture layer, which is similar to that we find in homogenous anisotropic media. The study of the anticline structure with vertical fractures, which is built with the parameters from a real case, is to assess the anticline structure effect on fracture parameter inversion based on the Singular Value Decomposition (SVD) method. The fracture density can be resolved accurately at the top of the anticline, whilst that on the flanks tends to be over-estimated. The results also indicate that the SVD method is a reliable approach for directly estimating the fracture density. P-wave azimuthal attributes are commonly employed to invert fracture density and orientation. Many factors may affect the accuracy of the inversion results. The integrated study in this thesis shows that azimuthal coverage, offset-depth ratio, data quality and geological structures all affect the final prediction, and different attributes shows different sensitivities to these factors. Furthermore, the combined analysis of both geological observation and pre- and post-stack seismic attributes can reduce the uncertainties for fracture detection.
21
Hensley, Gregory Martin. "Finite Element Analysis of the Seismic Behavior of Guyed Masts." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33900.
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Seismic design of guyed masts, commonly used in the broadcasting and telecommunications industries, has not been fully addressed in the United States. There is no specific design code, and only a limited amount of research has been reported on the subject. This research investigates the behavior of guyed masts incorporating synthetic ropes as guys, with a particular focus on the effect of snap loads on the mast behavior. This is the third phase of a multi-stage project aimed at analyzing the potential for Snapping-Cable Energy Dissipators (SCEDs) to minimize lateral response in structures.
A finite element model of a 120-m-tall guyed mast was developed with the commercial program ABAQUS. The three-dimensional behavior of the mast was observed when subjected to two ground motion records: Northridge and El Centro. Three orthogonal earthquake components were input, two horizontal and one vertical. A series of parametric studies was conducted to determine the sensitivity of the response to guy pretension, which is a measure of the potential slackness in the guys during response. Additionally, the studies examined the effects of guy stiffness, mast properties, and directionality of input motion.
Deflections, bending moments, guy tensions, and base shears were examined. The results were used to characterize the trends in the structural response of guyed masts. The level of slackness in the guys changed the behavior, and the lessons learned will be used to continue research on the application of SCEDs in structures.Master of Science
22
Leung, Colin. "SENSITIVITY OF SEISMIC RESPONSE OF A 12 STORY REINFORCED CONCRETE BUILDING TO VARYING MATERIAL PROPERTIES." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/681.
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The main objective of this investigation is to examine how various material properties, governed by code specification, affect the seismic response of a twelve- story reinforced concrete building. This study incorporates the pushover and response history analysis to examine how varying steel yield strength (Fy), 28 day nominal compressive concrete strength (f’c), modes, and ground motions may affect the base shear capacity and displacements of a reinforced concrete structure.
Different steel and concrete strengths were found to have minimal impact on the initial stiffness of the structure. However, during the post-yielding phase, higher steel and concrete compressive strengths resulted in larger base shear capacities of up to 22%. The base shear capacity geometric median increased as f’c or Fy increased, and the base shear capacity dispersion measure decreased as f’c or Fy increased. Higher mode results were neglected in this study due to non-convergent pushover analyses results.
According to the response history analysis, larger yield and concrete compressive strengths result in lower roof displacement. The difference in roof displacement was less than 12% throughout. This displays the robustness of both analysis methods because material properties have insignificant impact on seismic response. Therefore, acceptable yield and compressive strengths governed by seismic code will result in acceptable building performance.
23
Motamed, Maryam. "Effects of Site Response on the Correlation Structure of Ground Motion Residuals." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/25333.
Full textAbstract:
Seismic hazard analyses require an estimate of earthquake ground motions from future events. These predictions are achieved through Ground Motion Prediction Equations, which include a prediction of the median and the standard deviation of ground motion parameters. The differences between observed and predicted ground motions, when normalized by the standard deviation, are referred to as epsilon (𝜖). For spectral accelerations, the correlation structure of normalized residuals across oscillator periods is important for guiding ground motion selection. Correlation structures for large global datasets have been studied extensively. These correlation structures reflect effects that are averaged over the entire dataset underlying the analyses. This paper considers the effects of site response, at given sites, on the correlation structure of normalized residuals. This is achieved by performing site response analyses for two hypothetical soil profiles using a set of 85 rock input motions. Results show that there is no significant difference between correlation coefficients for rock ground motions and correlation coefficients after considering the effects of site response for the chosen sites.Master of Science
24
Tabatabaei, Araghi Pedram. "Seismic analysis of concrete structures within nuclear industry." Thesis, KTH, Betongbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147215.
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Earthquake has always been a hazard for civil structures and keeping the structures integrity during and after an earthquake is of vital importance. This phenomenon’s impact is sudden and there is little or no warning to make the preparations for this natural disaster. Much damage has been done on structures which have led to major collapses and loss of many lives. Civil structures such as nuclear power plants are designed to withstand earthquakes and in the event of a major seismic event, to shut down safely. The aim of this thesis is to present the seismic design procedures for concrete structures, in basic and detailed design, according to Eurocode 8. Also to describe and understand the difference between Eurocode 8 and the DNB in seismic analysis of nuclear power plants. To evaluate the use of DNB instead of Eurocode 8 with Swedish seismic conditions is also another aim in this thesis. Loads and actions which apply on a structure in a seismic design and corresponding load combinations are presented for Eurocode 8 and the DNB. An example is also given to clarify the design of primary seismic beams and columns with high ductility class (DCH). A case study of a nuclear structure from a test project named SMART2013 has been made by analyzing and comparing the results from Eurocode 8 and the DNB with a finite element model in FEM-Design software. Natural frequencies of the model are compared with the tested model in SMART2013-project to evaluate the finite element modeling. The model is seismically analyzed with load combinations from Eurocode 8 and the DNB with Swedish elastic ground response spectrum with the probability of 10-5. Results obtained from the primary seismic beams and columns are compared and analyzed. Being on the safe and conservative side of the design values is always preferred in seismic analysis of a vital and sensitive structure such as nuclear power plants. The results from this thesis shows that, purely structural, combination of Swedish elastic ground response spectrum with the Eurocode 8 load combination will give more conservative values than the DNB.I stora delar av världen har jordbävningar alltid varit ett hot för byggnaders integritet. Karaktären av en jordbävning är plötslig och föranleds av små eller inga varningar. Om jordbävningen medför att byggnader kollapsar sker ofta stora förluster av människoliv direkt eller indirekt. Kärnkraftsverk är anläggningar som dimensioneras för att klara jordbävningar och ska kunna gå till säker avställning vid en sådan händelse. Syftet med föreliggande rapport är att presentera hur betongkonstruktioner dimensioneras för jordbävning enligt Eurokod 8. Rapporten redogör även för skillnader mellan att dimensionera enligt Eurokod 8 och DNB (Dimensionering av nukleära byggnadskonstruktioner) samt hur det slår att använda Eurokod med svenska seismiska förhållanden. Laster och lastkombinationer som används vid jordbävningsdimensionering av betongbyggnader är presenterad enligt både Eurokod och DNB. Ett exempel presenteras för att visa hur primära balkar och pelare med hög duktilitetsklass (DCH) dimensioneras för seismisk påverkan. En fallstudie av en nukleär byggnad från ett internationellt projekt, SMART2013, har använts för att analysera och utvärdera resultaten från Eurokod och DNB. Byggnaden har analyserats med finita element med programvaran FEM Design. Modellens riktighet har verifierats genom att jämföra bland annat egenfrekvenser med de från officiella rapporter från SMART2013. Byggnaden är analyserad för seismisk last enligt svenska förhållanden med markresponsspektra 10-5, och primära balkar och pelare har analyserats och utvärderats enligt både Eurokod och DNB.
25
Chen, Xiaoxu. "Application of base isolation in China and seismic response analysis of a base-isolated building." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3337/.
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Jarrett, Jordan Alesa. "Performance Assessment of Seismic Resistant Steel Structures." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/24773.
Full textAbstract:
This work stems from two different studies related to this performance assessment of seismic resistant systems. The first study compares the performance of newly developed and traditional seismic resisting systems, and the second study investigates many of the assumptions made within provisions for nonlinear response history analyses.
In the first study, two innovative systems, which are hybrid buckling restrained braces and collapse prevention systems, are compared to their traditional counterparts using a combination of the FEMA P-695 and FEMA P-58 methodologies. Additionally, an innovative modeling assumption is investigated, where moment frames are evaluated with and without the lateral influence of the gravity system. Each system has a unique purpose from the perspective of performance-based earthquake engineering, and analyses focus on the all intensity levels of interest. The comparisons are presented in terms consequences, including repair costs, repair duration, number of casualties, and probability of receiving an unsafe placard, which are more meaningful to owners and other decision makers than traditional structural response parameters. The results show that these systems can significantly reduce the consequences, particularly the average repair costs, at the important intensity levels.
The second study focuses on the assumptions made during proposed updates to provisions for nonlinear response history analyses. The first assumption investigated is the modeling of the gravity system's lateral influence, which can have significant effect on the system behavior and should be modeled if a more accurate representation of the behavior is needed. The influence of residual drifts on the proximity to collapse is determined, and this work concludes that a residual drift check is unnecessary if the only limit state of interest is collapse prevention. This study also finds that spectrally matched ground motions should cautiously be used for near-field structures. The effects of nonlinear accidental torsion are also examined in detail and are determined to have a significant effect on the inelastic behavior of the analyzed structure. The final investigation in this study shows that even if a structure is designed per ASCE 7, it may not have the assumed probability of collapse under the maximum considered earthquake when analyzed using FEMA P-695.Ph. D.
27
Naga, Pradeep. "Analyzing the Effect of Moving Resonance on Seismic Response of Structures using Wavelet Transforms." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/34646.
Full textAbstract:
Nonlinear structures, when subjected to multiple ground motion records that are scaled to consistent ground motion intensity show significant variation in their response. This effect of ground motion randomness on the variation of structural response is defined as Record-to-Record (RTR) Variability. Ground motion characteristics that contribute to this variability in response includes the variation of signal composition (frequency content) with time (spectral nonstationarity).The phenomenon of moving resonance which occurs when the frequency content of the ground motion shifts in a similar manner as the natural frequencies of the structural response, is likely a contributor to variability. This brings the need to further understand the sources of variability due to moving resonance.
The present study was carried out to develop a method to analyze the time-frequency content of a ground motion to assess the occurrence of moving resonance and to quantify its potential in effecting the structural systems. Bilinear elastic and elastoplastic hysteretic behavior was considered. Detailed analysis is done to quantify the effect of moving resonance on structural systems due to 22 far field ground motion records.
The wavelet coefficient plots gave very good detail of the characteristics of the ground motions that were not clear from the acceleration time histories and response spectra plots. Instances of moving resonance were found out to be significant. Amplification due to moving resonance was found to be quite large. One instance studied in detail (accelerogram of Northridge earthquake at Beverly Hills) had peak displacement amplified by 6 times compared to the amount of peak displacement expected if the system did not exhibit moving resonance. Based on the analyses results, the characteristics of the ground motion records that donâ t cause significant moving resonance effect on structural systems were observed. Similarly, the characteristics of the ground motions that do cause moving resonance effect on structural systems were examined.Master of Science
28
Asgarian, Amin. "State-of-the-art review: Seismic response analysis of Operational and Functional Components (OFCs) in buildings." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121058.
Full textAbstract:
A building is composed of two main types of components: structural components (see Figure 1) and non-structural components (NSCs) also called operational and functional components (OFCs) (see Figure 2). OFCs are those components or systems housed or mounted in the buildings which are not part of the main or intended load-resisting system of the structure. Therefore, the building structure is commonly called “primary structure” or “supporting structure” and OFCs are also known by alternative names such as "non-structural elements", "building attachments", "architectural, mechanical, and electrical elements", "secondary systems", and "secondary structural elements".
29
Madden, Patrick. "The influence of structural details, geotechnical factors and environs on the seismic response of framed structures." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/c24ae223-999c-407c-bd3f-b461708dcbb3.
Full textAbstract:
Seismic events around the globe directly affect all ranges of structures, from complex and expensive ‘skyscrapers’ to simple frame structures, the latter making up a higher proportion of the number of structures affected as they are a much more common type of structure. The impact of a seismic event can be devastating, especially if adequate predictions of their impact and imposed structural response are not made during the design stage of the structure. Knowing what response to expect allows the engineer to design the structure to survive an event and protect the occupants. The structural response to a seismic event is very complex and can be affected by a wide range of structural, geotechnical and environ parameters. While larger, expensive structures make use of expensive, time consuming, finite element analytical procedures to determine their response the cheaper, simpler, frame structures have to make do with existing, simplified, spectral method predictions. This research firstly involves finite element analysis of simple frame structures, considering different structural and geotechnical parameters which may influence the seismic response, namely the stiffness of the structural joints, the geometry of the structure (influencing the individual structural element flexibility) and the foundation conditions (fixed base or shallow foundations with soil structure interaction). A range of frames, of varying geometry, are considered which mobilise different amounts of inter-storey drift, local rotation and global rotation response. The influence of soil structure interaction (SSI) and frame rigidity (i.e. the properties of the joints) on the response behaviour is investigated. The finite element database is then used to validate improved methods for predicting the spectral response parameters, specifically the natural period and damping of equivalent single degree of freedom (SDOF) systems, which include the effects of frame rigidity, geometry and SSI. Dynamic centrifuge testing is also carried out in order to further validate the improved spectral model for the case of real soil with shear dependant stiffness. The physical model testing is also extended to consider how environs, such as other structures in close proximity, influence the response of a structure.
30
ZIN, NAUNG HTUN. "Assessment of Dynamic Response and Seismic Zonation of Osaka Depositional Basin Based on the Geoinformatic Database." Kyoto University, 2020. http://hdl.handle.net/2433/259027.
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Harrison, Stella, and Siri Nöjd. "Influence of Foundation Modelling on the Seismic Response of a Concrete Dam." Thesis, KTH, Betongbyggnad, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300448.
Full textAbstract:
It is of great importance to ensure the structural safety of dams during earthquakes since a failure may cause catastrophic consequences. Conventional computation of the structural response of dams is based on a simplified approach where the foundation is considered as massless. However, recent developments have produced several new analysis methods that consider the foundation mass, modelled with absorbing boundaries and free-field forces. These newer methods are intended to simulate the seismic structural response more accurately, optimize the design and minimise future unnecessary reparations. The aim of the thesis was to investigate the influence of foundation modelling in seismic time history analyses. This was done by comparing the established massless foundation approach to two approaches with foundation mass and free-field forces included; the analytical approach presented by Song et al. (2018) and the direct FE approach by Løkke (2018). Both the efficiency of the seismic wave propagation simulation and the structural response of the dam were of interest, and points on the dam and foundation were studied to accurately compare these modelling approaches. The time history analyses showed that the massless approach corresponded perfectly with the ideal theoretical velocity at the foundation surface when studying only the foundation block, as expected. The analytical and direct FE however, differed slightly from the theoretical value but still gave an accurate representation. Both methods using free-field forces obtained equivalent and realistic structural responses when studying the dam-reservoir-foundation model. The massless method however,strongly overestimated the dam response and was therefore found to not capture the actual behavior of the dam accurately, despite modifications such as increased material damping in the concrete. Additionally, another aim was to analyse the influence of modelling in 2D versus 3D for determining the dynamic characteristics of the dam such as natural frequencies and eigenmodes of the dam. These frequency analyses were made using models with and without foundation mass considered and was compared to experimental data.The massless 3D model was found to be the most effective modelling approach for deriving the dynamic characteristics of the dam since the use of a 3D model was necessary in order to study the behaviour of the whole dam and post-processing was simpler when using the massless model.Det är nödvändigt att säkerställa dammars säkerhet mot jordbävningar i design-processen eftersom ett dammbrott kan få katastrofala konsekvenser. Traditionellt används förenklade beräkningar där dammens strukturella respons beräknas med en berggrund där bergets massa är försummad. Den senaste tiden har flera nya analysmetoder tagits fram, som tar hänsyn till bergets massa och är modellerade med absorberande randvillkor och free-field forces. De nyare metoderna förväntas modellera de seismiska krafterna mer exakt för att optimera designen och minimera onödiga reparationer. Syftet med projektet var att undersöka inverkan från olika metoders sätt att beakta berggrunden vid seismiska analyser. Det utfördes genom att jämföra den etablerade masslösa metoden med två metoder som beaktar bergmassan och free-fieldforces; den analytiska metoden av Song et al. (2018) och Direct FE-metoden av Løkke (2018). Både effektiviteten i den seismiska vågutbredningssimuleringen och dammens strukturella respons var av intresse. Modelleringsmetoderna jämfördes genom att studera punkter på både dammen och berget. När enbart berggrunden studerades med den masslösa metoden så erhölls, som förväntat, god överenstämmelse med den ideala teoretiska hastigheten på bergsytan. De analytiska och Direct FE metoderna skiljde sig marginellt från det teoretiska värdet men gav fortfarande en korrekt hastighet på bergsytan. Vid analys av modeller med dam och reservoar inkluderade, gav metoderna som använde free-field forces ekvivalenta och realistiska strukturella responser. Den masslösa metoden däremot, överskattade kraftigt dammens respons och ansågs därför inte modelleradet verkliga beteendet hos dammen på ett korrekt sätt, trots modifieringar med ökad materialdämpning i betongen. Ett annat syfte var att analysera påverkan av modellering i 2D kontra 3D för att bestämma dammens dynamiska egenskaper, som egenfrekvenser och egenmoder. Dessa frekvensanalyser gjordes med hjälp av modeller som både beaktade och försummade bergets massa, och jämfördes med experimentella data. Den masslösa 3D-modellen visade sig vara den mest effektiva modelleringsmetoden för att erhållade dynamiska egenskaperna hos dammen. Det eftersom en 3D-modell var nödvändig för att studera hela dammens beteende och hantering av utdata var förenklad vid användning av den masslösa modellen.
32
Sobrado, V. H., R. Yaranga, and J. D. Orihuela. "Analysis of seismic bidirectionality on response of reinforced concrete structures with irregularities of l-shaped plan and soft story." IOP Publishing Ltd, 2020. http://hdl.handle.net/10757/656573.
Full textAbstract:
The seismic design of buildings is usually performed using one-way analysis for each of main axes independently. However, seismic events have fairly random behaviour and impose bidirectional solicitations on structures. In this work, the study of the response in structures subjects to earthquake loads with irregularity of l-shaped plan and soft story is carried out. For this, the linear time-story analysis (LTHA) of these has been carried out imposing seismic solicitations in two orthogonal directions. Thus, the structural response with incidence angle variations of 10 is obtained and compared with the response derived from the unidirectional analysis. Variations of up to 50% and 72% are obtained for model structures with l-shaped plan and soft story respectively.
33
Cornelio, Tony Justin. "Effect of infill panels on the seismic response of a typical R.C. frame." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2868/.
Full textAbstract:
Three structural typologies has been evaluated based on the nonlinear dynamic analysis (i.e. Newmark's methods for MDFs: average acceleration method with Modified Newton-Raphson iteration). Those structural typologies differ each other only for the infills presence and placement.
In particular, with the term BARE FRAME: the model of the structure has two identical frames, arranged in parallel. This model constitutes the base for the generation of the other two typologies, through the addition of non-bearing walls.
Whereas with the term INFILLED FRAME: the model is achieved by adding twelve infill panels, all placed in the same frame.
Finally with the term PILOTIS: the model has been generated to represent structures where the first floor has no walls. Therefore the infills are positioned in only one frame in its three upper floors.
All three models have been subjected to ten accelerograms using the software DRAIN 2000.
34
Shrestha, Santosh. "A COMPARATIVE STUDY OF EQUIVALENT LATERAL FORCE METHOD AND RESPONSE SPECTRUM ANALYSIS IN SEISMIC DESIGN OF STRUCTURAL FRAMES." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2561.
Full textAbstract:
Equivalent Lateral Force Method (ELF) and Response Spectrum Analysis (RSA) are the two most popular methods of seismic design of structures. This study aims to present a comparative study of the two methods using hand-calculated approach as well as computer analysis according to ASCE 7-10 Standards. The two methods have been compared in terms of base shear and story forces by analyzing various models for different number of stories and different support conditions. It was found that ELF gives conservative results in comparison to RSA. This result was more obvious in case of four-story frames. Hence, for structures of increased elevation, the analysis from ELF may not be sufficient.
35
Bleichner, Noah G. "A Comparative Study on Seismic Analysis Methods and the Response of Systems with Classical and Nonclassical Damping." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2219.
Full textAbstract:
This thesis investigated the application of seismic analysis methods and the response of idealized shear frames subjected to seismic loading. To complete this research, a Design Basis Earthquake (DBE) for a project site in San Luis Obispo, CA, and five past earthquake records were considered. The DBE was produced per the American Society of Civil Engineers’ Minimum Design Loads for Buildings and Other Structures (ASCE 7-10) and used for application of the Equivalent Lateral Force Procedure (ELFP) and Response Spectrum Analysis (RSA). When applying RSA, the modal peak responses were combined using the Absolute Sum (ABS), Square-Root-of-the-Sum-of-Squares (SRSS), and Complete Quadratic Combination (CQC) method.
MATLAB scripts were developed to produce several displacement, velocity, and acceleration spectrums for each earthquake. Moreover, MATLAB scripts were written to yield both analytical and numerical solutions for each system through application of Linear Time History Analysis (THA). To obtain analytical solutions, two implicit forms of the Newmark-beta Method were employed: the Average Acceleration Method and the Linear Acceleration Method.
To generate a comparison, the ELFP, RSA, and THA methods were applied to shear frames up to ten stories in height. The system parameters that impacted the accuracy of each method and the response of the systems were analyzed, including the effects of classical damping and nonclassical damping models. In addition to varying levels of Rayleigh damping, non-linear hysteric friction spring dampers (FSDs) were implemented into the systems. The design of the FSDs was based on target stiffness values, which were defined as portions of the system’s lateral stiffness. To perform the required Nonlinear Time History Analysis (NTHA), a SAP2000 model was developed. The efficiencies of the FSDs at each target stiffness, with and without the addition of low levels of viscous modal damping are analyzed.
It was concluded that the ELFP should be supplemented by RSA when performing seismic response analysis. Regardless of system parameters, the ELFP yielded system responses 30% to 50% higher than RSA when combing responses with the SRSS or CQC method. When applying RSA, the ABS method produced inconsistent and inaccurate results, whereas the SRSS and CQC results were similar for regular, symmetric systems. Generally, the SRSS and CQC results were within 5% of the analytical solution yielded through THA. On the contrary, for irregular structures, the SRSS method significantly underestimated the response, and the CQC method was four to five times more accurate. Additionally, both the Average Acceleration Method and Linear Acceleration Method yielded numerical solutions with errors typically below 1% when compared with the analytical solution.
When implemented into the systems, the FSDs proved to be most efficient when designed to have stiffnesses that were 50% of the lateral stiffness of each story. The addition of 1% modal damping to the FSDs resulted in quicker energy dissipation without significantly reducing the peak response of the system. At a stiffness of 50%, the FSDs reduced the displacement response by 40% to 60% when compared with 5% modal damping. Additionally, the FSDs at low stiffnesses exhibited the effects of negative lateral stiffness due to P-delta effects when the earthquake ground motions were too weak to induce sliding in the ring assemblies.
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Cabas, Mijares Ashly Margot. "Improvements to the Assessment of Site-Specific Seismic Hazards." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82352.
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The understanding of the impact of site effects on ground motions is crucial for improving the assessment of seismic hazards. Site response analyses (SRA) can numerically accommodate the mechanics behind the wave propagation phenomena near the surface as well as the variability associated with the input motion and soil properties. As a result, SRA constitute a key component of the assessment of site-specific seismic hazards within the probabilistic seismic hazard analysis framework. This work focuses on limitations in SRA, namely, the definition of the elastic half-space (EHS) boundary condition, the selection of input ground motions so that they are compatible with the assumed EHS properties, and the proper consideration of near-surface attenuation effects. Input motions are commonly selected based on similarities between the shear wave velocity (Vs) at the recording station and the materials below the reference depth at the study site (among other aspects such as the intensity of the expected ground motion, distance to rupture, type of source, etc.). This traditional approach disregards the influence of the attenuation in the shallow crust and the degree to which it can alter the estimates of site response. A Vs-κ correction framework for input motions is proposed to render them compatible with the properties of the assumed EHS at the site. An ideal EHS must satisfy the conditions of linearity and homogeneity. It is usually defined at a horizon where no strong impedance contrast will be found below that depth (typically the top of bedrock). However, engineers face challenges when dealing with sites where this strong impedance contrast takes place far beyond the depth of typical Vs measurements. Case studies are presented to illustrate potential issues associated with the selection of the EHS boundary in SRA. Additionally, the relationship between damping values as considered in geotechnical laboratory-based models, and as implied by seismological attenuation parameters measured using ground motions recorded in the field is investigated to propose alternative damping models that can match more closely the attenuation of seismic waves in the field.Ph. D.
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Moghaddasi, Kuchaksarai Masoud. "Probabilistic Quantification of the Effects of Soil-Shallow Foundation-Structure Interaction on Seismic Structural Response." Thesis, University of Canterbury. Civil and Natural Resources, 2012. http://hdl.handle.net/10092/8446.
Full textAbstract:
Previous earthquakes demonstrated destructive effects of soil-structure interaction on structural response. For example, in the 1970 Gediz earthquake in Turkey, part of a factory was demolished in a town 135 km from the epicentre, while no other buildings in the town were damaged. Subsequent investigations revealed that the fundamental period of vibration of the factory was approximately equal to that of the underlying soil. This alignment provided a resonance effect and led to collapse of the structure. Another dramatic example took place in Adapazari, during the 1999 Kocaeli earthquake where several foundations failed due to either bearing capacity exceedance or foundation uplifting, consequently, damaging the structure. Finally, the Christchurch 2012 earthquakes have shown that significant nonlinear action in the soil and soil-foundation interface can be expected due to high levels of seismic excitation and spectral acceleration. This nonlinearity, in turn, significantly influenced the response of the structure interacting with the soil-foundation underneath.
Extensive research over more than 35 years has focused on the subject of seismic soil-structure interaction. However, since the response of soil-structure systems to seismic forces is extremely complex, burdened by uncertainties in system parameters and variability in ground motions, the role of soil-structure interaction on the structural response is still controversial. Conventional design procedures suggest that soil-structure interaction effects on the structural response can be conservatively ignored. However, more recent studies show that soil-structure interaction can be either beneficial or detrimental, depending on the soil-structure-earthquake scenarios considered.
In view of the above mentioned issues, this research aims to utilise a comprehensive and systematic probabilistic methodology, as the most rational way, to quantify the effects of soil-structure interaction on the structural response considering both aleatory and epistemic uncertainties. The goal is achieved by examining the response of established rheological single-degree-of-freedom systems located on shallow-foundation and excited by ground motions with different spectral characteristics. In this regard, four main phases are followed.
First, the effects of seismic soil-structure interaction on the response of structures with linear behaviour are investigated using a robust stochastic approach. Herein, the soil-foundation interface is modelled by an equivalent linear cone model. This phase is mainly considered to examine the influence of soil-structure interaction on the approach that has been adopted in the building codes for developing design spectrum and defining the seismic forces acting on the structure. Second, the effects of structural nonlinearity on the role of soil-structure interaction in modifying seismic structural response are studied. The same stochastic approach as phase 1 is followed, while three different types of structural force-deflection behaviour are examined. Third, a systematic fashion is carried out to look for any possible correlation between soil, structural, and system parameters and the degree of soil-structure interaction effects on the structural response. An attempt is made to identify the key parameters whose variation significantly affects the structural response. In addition, it is tried to define the critical range of variation of parameters of consequent. Finally, the impact of soil-foundation interface nonlinearity on the soil-structure interaction analysis is examined. In this regard, a newly developed macro-element covering both material and geometrical soil-foundation interface nonlinearity is implemented in a finite-element program Raumoko 3D. This model is then used in an extensive probabilistic simulation to compare the effects of linear and nonlinear soil-structure interaction on the structural response.
This research is concluded by reviewing the current design guidelines incorporating soil-structure interaction effects in their design procedures. A discussion is then followed on the inadequacies of current procedures based on the outcomes of this study.
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Isbiliroglu, Levent. "Strategy for Selecting Input Ground Motion for Structural Seismic Demand Analysis." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAU009/document.
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Les signaux accélérométriques enregistrés lors de l’occurrence d’un événement sismique est très large présentent une forte variabilité, par conséquent ils ne sont pas utilisé dans les analyse dynamiques de tenue sismique des structures. En effet, l’utilisation des accélérogrammes réels, pour les analyses dynamiques non linéaires, s’avère couteuse en termes de temps de calcul. La pratique courante prévoit la minimisation (voir suppression) de telle variabilité, mais les conséquences d’une telle opération sur la réponse des structures ne sont pas clairement indiquées. L’étude ci-présente a pour scope la quantification de l’impact des méthodes de sélection qui gardent la variabilité du signal sur les résultats de l’analyse de la réponse des structures (exprimée en termes d’engineering demand parameters EDPs). En particulier les questions suivantes seront investiguées :Quel est le niveau de variabilité des accélérogrammes réels et comment ce niveau est modifié par les techniques couramment utilisées ?Quelle est l’impact de la variabilité sur la réponse de plusieurs types de structures ?Pour un scénario sismique donné, un spectre cible est défini à partir de plusieurs équation de prédiction du mouvement sismique, sélection parmi celles disponibles en littérature. Les accélérogrammes sont sélectionnés à partir de quatre familles d’accélérogrammes, chacune relative à une méthode de modification : réels (enregistrés); mise à l’échelle (multiplication, par un facteur) ; calés aux spectres cibles avec large tolérance ; calés aux spectres cibles dans une plage de tolérance étroite.Chaque jeu de signaux est composé de cinq accélérogrammes et la sélection des signaux est faite en tenant compte de deux sources de variabilité : la variabilité au sein de chaque jeu de données (intraset), et la variabilité entre les différents jeux de données (interset) tous compatibles avec le même spectre cible. Les tests sur les EDPs menés sur les signaux accélérométriques réels mènent à la quantification de la variabilité naturelle (pour le scénario considéré). Les analyses basées sur les signaux réels sont utilisés comme benchmark afin d’évaluer non seulement de combien la distribution des EDPs (en termes de valeur moyenne et variabilité) est réduite par les différentes méthodes testées, mais aussi d’évaluer l’impact des choix de l’équation de prédiction du mouvement, des plages de tolérance, du nombre d’accélérogrammes constituant chaque jeu, du nombre de jeux, de le scope de l’analyse structurale et le modèle de structure.Ce travaille nous conduit à conclure que un seul jeu d’accélérogramme, tel qu’utilisé dans la pratique courante, est insuffisant pour assurer le niveau d’EDPs indépendamment de la méthode de modification utilisés, cela est lié à la variabilité des signaux et entre les jeux d’accélérogrammes. Les signaux réels, compatibles avec le spectre définis pour le scénario sismique, are l’option plus réaliste pour l’analyse dynamique non-linéaire ; si une méthode de modification du signal est nécessaire, la plus adaptées dépend du scope de l’analyse spectrale et du modèle. Le choix de l’équation de prédiction du mouvement sismique utilisée pour définir le spectre cible impacte significativement les caractéristiques des mouvements sismiques et des EDPs. Cette observation ne dépend pas de la stratégie de de modification du signalThe observed variability is very large among natural earthquake records, which are not consolidated in the engineering applications due to the cost and the duration. In the current practice with the nonlinear dynamic analysis, the input variability is minimized, yet without clear indications of its consequences on the output seismic behavior of structures. The study, herein, aims at quantifying the impact of ground motion selection with large variability on the distribution of engineering demand parameters (EDPs) by investigating the following questions:What is the level of variability in natural and modified ground motions?What is the impact of input variability on the EDPs of various structural types?For a given earthquake scenario, target spectra are defined by ground motion prediction equations (GMPEs). Four ground motion modification and selection methods such as (1) the unscaled earthquake records, (2) the linearly scaled real records, (3) the loosely matched spectrum waveforms, and (4) the tightly matched waveforms are utilized. The tests on the EDPs are performed on a record basis to quantify the natural variability in unscaled earthquake records and the relative changes triggered by the ground motion modifications.Each dataset is composed by five accelerograms; the response spectrum compatible selection is then performed by considering the impact of set variability. The intraset variability relates to the spectral amplitude dispersion in a given set, and the interset variability relates to the existence of multiple sets compatible with the target.The tests on the EDPs are performed on a record basis to quantify the natural variability in unscaled earthquake records and the relative changes triggered by the ground motion modifications. The distributions of EDPs obtained by the modified ground motions are compared to the observed distribution by the unscaled earthquake records as a function of ground motion prediction equations, objective of structural analysis, and structural models.This thesis demonstrates that a single ground motion set, commonly used in the practice, is not sufficient to obtain an assuring level of the EDPs regardless of the GMSM methods, which is due to the record and set variability. The unscaled real records compatible with the scenario are discussed to be the most realistic option to use in the nonlinear dynamic analyses, and the ‘best’ ground motion modification method is demonstrated to be based on the EDP, the objective of the seismic analysis, and the structural model. It is pointed out that the choice of a GMPE can provoke significant differences in the ground motion characteristics and the EDPs, and it can overshadow the differences in the EDPs obtained by the GMSM methods
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Jadhav, Sagar M. "Comparative Study of Seismic Performance of Reinforced Concrete Buildings designed in accordance with the Seismic Provisions of ASCE 7-10 and IS 1893-2002." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368024755.
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Aslankaya, Güzide. "Influence of joints on the seismic response of traditional timber frames in Turkey." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/668866.
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Timber frame structures which constitute an important cultural heritage of many countries, are well known as efficient seismic resistant structures worldwide and are worth to be preserved. Himis is one common traditional Turkish timber system, which consists of a simple timber frame filled with masonry (such as bricks, adobes or stones with mortar), and a masonry ground floor, built on continuous stone foundations. These buildings are usually located in seismic areas.This thesis aims to make a review of the structural performance of Himis timber system under seismic loading, with specific emphasis on joints and following strenghening of joints with CFRP (Carbon fiber reinforced polymer). Due to the seismic demands these timber structures mostly depend on connections, so that the joints have to be evaluated accurately in terms of translational and rotational stiffness and moment resistance. Subsequently, a series of experimental tests on two different types of timber joints (lap joint and mortise-tenon) which are common in Turkish timber structures have been carried out under monotonic and cyclic bending loading. The numerical analysis, FEM (the finite element method) has been performed in order to the calibrate the results from experiments. Finally, a numerical analysis considering semi-rigid joints in traditional timber connections has been performed globally.Las estructuras de madera constituyen un importante patrimonio cultural en muchos países y son conocidas como tipologías estructurales eficientes des del punto de vista sísmico por su resistencia y ductilidad. Himis es uno de los sistemas de madera tradicional más conocidos en Turquía, consistente en marcos en forma de retícula de madera simple, relleno de mampostería en su interior (ladrillos, adobe, o piedras con mortero) en plantas piso, mientras que la planta baja es totalmente de mampostería sobre de una cimentación contínua de piedra. Esta tesis tiene como principal objetivo el de realizar una evaluación de la eficiencia estructural del sistema Himis sometido a cargas sísmicas, mediante la evaluación de la respuesta de las uniones más típicas de madera y su contribución al conjunto. Esta tesis se complementa con un análisis experimental y numérico de la contribución que aporta el refuerzo de dichas uniones mediante fibras de polímeros reforzados CFRP (polímeros reforzados con fibras de carbono). La respuesta de estas estructuras frente a sismo se debe, en parte, a la rigidez y ductilidad de las uniones entre barras de madera, por lo que éstas requieren de una especial atención en términos de rigidez traslacional y rotacional. La investigación lleva a cabo una campaña experimental, cubriendo dos tipologías básicas de uniones tradicionales entre barras de madera en Turquía (junta por solape y de espiga) bajo flexión monotónica y también cíclica. Paralelamente, se evalúan dichas uniones mediante un análisis FEM debidamente calibrado con los resultados de los ensayos experimentales, que permite reproducir el comportamiento global de estas estructuras a partir del grado de rigidez de las uniones con o sin refuerzo.
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MORISHITA, Kunihiro, 邦宏 森下, 勉. 宇佐美, Tsutomu USAMI, 祟人 阪野, Takahito BANNO, 昭. 葛西, and Akira KASAI. "鋼製橋脚の動的耐震照査法に関する検討." 土木学会, 2002. http://hdl.handle.net/2237/8628.
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Eberle, Jonathan Robert. "Investigation of Applicable Seismic Response Modification Factor For Three-Hinge Glulam Tudor Arches Using FEMA P-695." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23122.
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The objective of this research project involves determining a seismic response modification factor for three-hinge glulam Tudor arches. In an attempt to meet this objective, the methods and procedures outlined in FEMA technical document P-695 were implemented on the provided arch designs. Computational models were created using finite elements within OpenSees to accurately depict the behavior of the arch. Incremental dynamic analyses were conducted on each of the provided designs and collapse margin ratios were determined allowing performance groups to be evaluated for each of seven design R-values within two gravity load cases. With the performance groups evaluated, it was determined that only groups within the low gravity load level designs were successfully able to pass, none of the groups designed for high gravity loads passed the evaluations. Within P-695, all performance groups associated with a given design R-value must pass the evaluations for that R-value to be deemed acceptable for use in designs. Because of the implications of this requirement, a seismic response modification factor could not be determined for this type of structural system within the scope of this project.Master of Science
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Taylor, Robert Paul. "Finite Element Analysis of the Application of Synthetic Fiber Ropes to Reduce Seismic Response of Simply Supported Single Span Bridges." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34051.
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Movement of a bridge superstructure during a seismic event can result in damage to the bridge or even collapse of the span. An incapacitated bridge is a life-safety issue due directly to the damaged bridge and the possible loss of a life-line. A lost bridge can be expensive to repair at a time when a region's resources are most strained and a compromised commercial route could result in losses to the regional economy. This thesis investigates the use of Snapping-Cable Energy Dissipators (SCEDs) to restrain a simply supported single span bridge subjected to three-dimensional seismic loads. SCEDs are synthetic fiber ropes that undergo a slack to taut transition when loaded.
Finite element models of six simply supported spans were developed in the commercial finite element program ABAQUS. Two seismic records of the 1940 Imperial Valley and 1994 Northridge earthquakes were scaled to 0.7g PGA and applied at the boundaries of the structure. The SCEDs were modeled as nonlinear springs with an initial slackness of 12.7mm. Comparisons of analyses without SCEDs were made to determine how one-dimensional, axial ground motion and three-dimensional ground motion affect bridge response. Analysis were then run to determine the effectiveness of the SCEDs at restraining bridge motion during strong ground motion. The SCEDs were found to be effective at restraining the spans during strong three-dimensional ground motion.Master of Science
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Nielson, Bryant G. "Analytical Fragility Curves for Highway Bridges in Moderate Seismic Zones." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7542.
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Historical seismic events such as the San Fernando earthquake of 1971 and the Loma Prieta earthquake of 1989 did much to highlight the vulnerabilities in many existing highway bridges. However, it was not until 1990 that this awareness extended to the moderate seismic regions such as the Central and Southeastern United States (CSUS). This relatively long neglect of seismic issues pertaining to bridges in these moderate seismic zones has resulted in a portfolio of existing bridges with seismic deficiencies which must be assessed and addressed.
An emerging decision tool, whose use is becoming ever increasingly popular in the assessment of this seismic risk, is that of seismic fragility curves. Fragility curves are conditional probability statements which give the probability of a bridge reaching or exceeding a particular damage level for an earthquake of a given intensity level. As much research has been devoted to the implementation of fragility curves in risk assessment packages, a great need has arisen for bridge fragility curves which are reliable, particularly for those in moderate seismic zones. The purpose of this study is to use analytical methods to generate fragility curves for nine bridge classes which are most common to the CSUS. This is accomplished by first considering the existing bridge inventory and assessing typical characteristics and details from which detailed 3-D analytical models are created. The bridges are subjected to a suite of synthetic ground motions which were developed explicitly for the region. Probabilistic seismic demand models (PSDM) are then generated using these analyses. From these PSD models, fragility curves are generated by considering specific levels of damage which may be of interest. The fragility curves show that the most vulnerable of all the bridge nine bridge classes considered are those utilizing steel girders. Concrete girder bridges appear to be the next most vulnerable followed by single span bridges of all types. Various sources of uncertainty are considered and tracked throughout this study, which allows for their direct implementation into existing seismic risk assessment packages.
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Sakai, Kotaro. "Seismic Performance Analysis of Fill Dams Using Velocity Based Space-Time Finite Element Method." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263700.
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Allahverdiyev, Rovshan. "Effects of beam configuration on dynamic properties and seismic performances of multi-storey frame building models." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Find full textAbstract:
The present study aims at comparing the dynamic properties and seismic performances offered by reinforced concrete frame structures characterised by different beams distribution.
Multi-storey regular frame buildings are considered as reference structures. Different models are then developed according to various layout of the beams (x-direction is the longitudinal direction, whilst y-direction is the transversal one): (1) beams placed along the x-direction at the odd storeys and placed along the y-direction at the even storeys; (2) beams placed along the y-direction at the odd storeys and placed along the x-direction at the even storeys; (3) and (4) alternating beams every two storeys; (5) beams placed along the x-direction at all storeys; (6) beams placed along the y-direction at all storeys; (7) complete three-dimensional frame with beams placed along both the x- and the y-direction at all storeys. In all models, smaller perimeter beams are placed along the direction orthogonal to the one of the main beams.
Modal analysis has been conducted to evaluate the influence of beams distribution on the period of vibration. Response spectrum and time-history dynamic analyses have been carried out to assess the effects of beams distribution on the base shear and base bending moments, top-storey displacements, interstorey displacements and floor accelerations.
On the contrary of what could be expected, the results indicate that structures with beams alternating every storey do not behave unfavorably with respect to the complete three-dimensional frames. In more detail, two effects may be clearly recognized: one associated to the period and one associated to the static scheme. The former acting basically on the base shear; the latter acting mainly on the base bending moment. The understanding of the influence of beams distribution on frame structures is useful when dealing with seismic vulnerability assessment of existing buildings and design of new buildings.
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Zhang, Zhi, and Zhi Zhang. "Analytical Investigation of Inertial Force-Limiting Floor Anchorage System for Seismic Resistant Building Structures." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625385.
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This dissertation describes the analytical research as part of a comprehensive research program to develop a new floor anchorage system for seismic resistant design, termed the Inertial Force-limiting Floor Anchorage System (IFAS).
The IFAS intends to reduce damage in seismic resistant building structures by limiting the inertial force that develops in the building during earthquakes. The development of the IFAS is being conducted through a large research project involving both experimental and analytical research. This dissertation work focuses on analytical component of this research, which involves stand-alone computational simulation as well as analytical simulation in support of the experimental research (structural and shake table testing).
The analytical research covered in this dissertation includes four major parts:
(1) Examination of the fundamental dynamic behavior of structures possessing the IFAS (termed herein IFAS structures) by evaluation of simple two-degree of freedom systems (2DOF). The 2DOF system is based on a prototype structure, and simplified to represent only its fundamental mode response. Equations of motions are derived for the 2DOF system and used to find the optimum design space of the 2DOF system. The optimum design space is validated by transient analysis using earthquakes.
(2) Evaluation of the effectiveness of IFAS designs for different design parameters through earthquake simulations of two-dimensional (2D) nonlinear numerical models of an evaluation structure. The models are based on a IFAS prototype developed by a fellow researcher on the project at Lehigh University.
(3) Development and calibration of three-dimensional nonlinear numerical models of the shake table test specimen used in the experimental research. This model was used for predicting and designing the shake table testing program.
(4) Analytical parameter studies of the calibrated shake table test model. These studies include: relating the shake table test performance to the previous evaluation structure analytical response, performing extended parametric analyses, and investigating and explaining certain unexpected shake table test responses.
This dissertation describes the concept and scope of the analytical research, the analytical results, the conclusions, and suggests future work. The conclusions include analytical results that verify the IFAS effectiveness, show the potential of the IFAS in reducing building seismic demands, and provide an optimum design space of the IFAS.
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Oguz, Sermin. "Evaluation Of Pushover Analysis Procedures For Frame Structures." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606047/index.pdf.
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Pushover analysis involves certain approximations and simplifications that some
amount of variation is always expected to exist in seismic demand prediction of pushover
analysis. In literature, some improved pushover procedures have been proposed to
overcome the certain limitations of traditional pushover procedures.
The effects and the accuracy of invariant lateral load patterns utilised in pushover
analysis to predict the behavior imposed on the structure due to randomly selected
individual ground motions causing elastic and various levels of nonlinear response were
evaluated in this study. For this purpose, pushover analyses using various invariant lateral
load patterns and Modal Pushover Analysis were performed on reinforced concrete and
steel moment resisting frames covering a broad range of fundamental periods. Certain
response parameters predicted by each pushover procedure were compared with the 'exact'
results obtained from nonlinear dynamic analysis. The primary observations from the study showed that the accuracy of the pushover results depends strongly on the load path, properties of the structure and the characteristics of the ground motion. Pushover analyses were performed by both DRAIN-2DX and SAP2000. Similar pushover results were obtained from the two different softwares employed in the study provided that similar approach is used in modeling the nonlinear properties of members as well as their structural features. The accuracy of approximate procedures utilised to estimate target displacement was also studied on frame structures. The accuracy of the predictions was observed to depend on the approximations involved in the theory of the procedures, structural properties and ground motion characteristics.
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Sun, Jikai. "Simulation of Strong Ground Motions in Mashiki Town, Kumamoto, Based on the Seismic Response Analysis of Soils and the Dynamic Rupture Modeling of Sources." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263649.
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Tavano, Matteo. "Seismic response of tank-fluid systems: state of the art review and dynamic buckling analysis of a steel tank with the added mass method." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3006/.
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