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1
Fathi, Bitaraf F. "Membrane effects in reinforced concrete frames." Thesis, University of Leeds, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444442.
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2
Cox, Wilfred. "Nonlinear analysis of reinforced concrete portal frames." Thesis, University of East London, 2001. http://roar.uel.ac.uk/1303/.
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There are considerable difficulties in describing the properties of reinforced concrete materials and their interaction. It is therefore necessary to calibrate the mathematical model by accurate testing of laboratory specimens. It can be shown that momentcurvature relationship varies along the length of a member and at beam-column joints. This behaviour depends critically on the geometry of the joint, reinforcement details and the stress-strain characteristics of concrete and steel. Tests have been carried out on model reinforced concrete portal frames and independent specimens making up the frame to predict their non-linear behaviour. The stiffness of the joint plays an important role in the response of the complete frame structure. The behaviour of the corner joints is of particular interest because both the strength and ductility differs for opening and closing joints. The loss of stiffness at joints has a significant effect on the inelastic deformations. The non-linear finite element (FE) program developed takes into account the loss of stiffness at joints and the falling branch behaviour of the material stress-strain relationships. Constant, linear, and parabolic variation in flexural rigidity (EI) and axial rigidity (EA) are taken into consideration along the element length. The combined effect of material and geometric non-linearity is considered. The FE program may use either calculated momentcurvature relationship of different elements or the experimental data obtained from tests. The results show good agreement between the theoretical and experimental beam moment-curvature relationships. Horizontally loaded frame analysis, which involves opening and closing joints, shows that ignoring the joint effect over-estimates the strength. In the case of vertically loaded frames, which involves two closing joints, ignoring the joint effects had little or no influence. The results show good agreement between the theoretical and experimental frame force-displacement relationships throughout the loading range providing the change of stiffness at joints is taken into account for horizontally loaded frames.
3
Farjadmand, Massoumeh. "Compressive membrane effects in reinforced concrete frames." Thesis, University of Westminster, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442109.
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4
Wong, Koon-Wan. "Non-linear behaviour of reinforced concrete frames /." Title page, contents and abstract only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phw872.pdf.
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5
Kenyon, Jonn Mark. "Non-linear analysis of reinforced concrete plane frames /." Title page, table of contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phk368.pdf.
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6
Ab, Kadir Mariyana Aida. "Fire resistance of earthquake damaged reinforced concrete frames." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7969.
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The topic of structural damage caused by fires following an earthquake (FFE) has been discussed extensively by many researchers for over a decade in order to bring the two fields closer together in the context of performance based structural engineering. Edinburgh University, Heriot-Watt University, Indian Institute of Technology Roorkee (IIT Roorkee) and Indian Institute of Science initiated a collaboration to study this problem under a UK-India Engineering Research Initiative (UKIERI) funded project. The first construction of a single-storey reinforced concrete frame at IIT Roorkee was completed in summer 2011; this is known as the Roorkee Frame Test 1 throughout this thesis. This thesis presents the modelling of the Roorkee Frame Test 1 using the finite element method and assesses the capability of the numerical methodologies for analysing these two sequential events. Both two and three dimensional finite element models were developed. Beam and shell elements were chosen for the numerical modelling, which was carried out using the general purpose finite element package ABAQUS (version 6.8). The variation in material properties caused by these two types of loading, including strength and stiffness degradation, compressive hardening, tension stiffening, and thermal properties, is implemented in the numerical modelling. Constitutive material calculations are in accordance with EC4 Part 1.1, and all loading is according to IS 1893:2002 Part 1 (Indian Standard). The time-temperature curve used in the analysis is based on data from the test carried out. The behaviour of the Roorkee Frame Test 1 when subjected to monotonic, cyclic lateral loading followed by fire is presented. The capacity of the frame when subjected to lateral loading is examined using a static non-linear pushover method. Incremental lateral loading is applied in a displacement-controlled manner to induce simulated seismic damage in the frame. The capacity curve, hysteresis loops and residual displacements are presented, discussed and compared with the test results. The heat transfer analysis using three dimensional solid elements was also compared against temperature distributions recorded during the Roorkee frame fire test. Based on the smoke layer theory, two emissivity values were defined. In this study, the suitability of numerical modelling using ABAQUS to capture the behaviour of Roorkee frame test is examined. The results from this study show that the 3D ABAQUS model predicted more reliable hysteresis curves compared to the 2D ABAQUS model, but both models estimated the lateral load capacity well. However neither model was able to simulate the pinching effect clearly visible in the hysteresis curves from the test. This was due to noninclusion of the bond slip effect between reinforcing bars and concrete. The residual displacement obtained at the end of the cyclic lateral loading analysis from the 2D ABAQUS model is higher than that seen in the test. However, the result in the 3D ABAQUS model matched the trend obtained in the test. The both columns appear to stiffen under the heating and the residual displacement seems to recover slightly. Lateral displacements, obtained in the thermo-mechanical analysis of the numerical models, show that thermal expansion brings the frame back towards its initial position. Finally, correlation studies between analytical and experimental results are conducted with the objective to establish the validity of the proposed model and identify the significance of various effects on the local and global response of fire resistance earthquake damaged of reinforced concrete frames. These studies show that the effect of tension stiffening and bond-slip are very important and should always be included in finite element models of the response of reinforced concrete frame with the smeared crack model when subjected to lateral and thermal loading. The behaviour of reinforced concrete frames exposed to fire is usually described in terms of the concept of the fire resistance which defined in terms of displacement limit. This study shows the global displacement of the frame subjected to fire recover slightly due to the thermal expansion during the heating.
7
Watson, Soesianawati. "Design of reinforced concrete frames of limited ductility." Thesis, University of Canterbury. Department of Civil Engineering, 1989. http://hdl.handle.net/10092/3745.
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An experimental programme was carried out to investigate the flexural strength and ductility.
of reinforced concrete columns under simulated earthquake loading. The main variable
examined was the quantity of transverse reinforcement for concrete confinement. The experimental
results were described and compared with theoretical studies. It was found that
to achieve adequate ductility in columns, the current New Zealand concrete design code
NZS3101:1982 equations for concrete confinement need to be refined. Using design charts
for ductility, which were previously derived from a theory for cyclic moment-curvature behaviour,
a refined design equation to replace the current code equations is proposed.
The inelastic dynamic response of frames of limited ductility was examined, and compared
with the response of ductile frames. The analysis indicated that non-capacity designed
frames, designed for seismic forces corresponding to a limited ductility demand, performed
reasonably well. Although some plastic hinges did develop in the columns, the ductility
demand was acceptable and can be achieved by appropriate detailing. As a result, some
suggestions for the seismic design requirements of frames of limited ductility are presented.
8
Lam, Yuet-kee Jeffery. "Full-range analysis of reinforced concrete members and frames." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182268.
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Lam, Yuet-kee Jeffery, and 林悦基. "Full-range analysis of reinforced concrete members and frames." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182268.
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10
Susoy, Melih. "Seismic Strengthening Of Masonry Infilled Reinforced Concrete Frames With Precast Concrete Panels." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605563/index.pdf.
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Over 90% of the land area of Turkey lies over one of the most active seismic zones in the world. Hazardous earthquakes frequently occur and cause heavy damage to the economy of the country as well as human lives. Unfortunately, the majority of buildings in Turkey do not have enough seismic resistance capacity. The most commonly observed problems are faulty system configuration, insufficient lateral stiffness, improper detailing, poor material quality and mistakes during construction. Strengthening of R/C framed structures by using cast-in-place R/C infills leads to a huge construction work and is time consuming. On the other hand, using prefabricated panel infills can be preferred as a more feasible, rapid and easy technique during which the structure can remain operational.
The aim of this experimental study is to observe the seismic behavior of R/C frames strengthened by precast concrete panel infills by testing different types of panel and connection designs in eight single-story single-bay reinforced concrete
frame specimens.
11
Agar, Mehmet. "Strengthening Of Reinforced Concrete Frames By Using Steel Bracings." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609664/index.pdf.
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Structures in high seismic risk areas may be susceptible to severe damage in a major earthquake. Structures designed to meet older code requirements may be at even greater risk. When these structures are evaluated with respect to current code criteria, it is observed that they lack of lateral strength and/or ductility. Since safety and economic considerations are major problems, these structures become viable candidates for retrofit and seismic strengthening.
For the variety of structures and possible deficiencies that arise, several retrofitting techniques can be considered. Diagonal bracing system is one of the retrofitting techniques and it provides an excellent approach for strengthening and stiffening existing building for lateral forces. Also, another potential advantage of this system is the comparatively small increase in mass associated with the retrofitting scheme since this is a great problem for several retrofitting techniques.
In this study, the use of steel bracing for the strengthening of low, intermediate, and relatively high rise reinforced concrete frames are investigated analytically. The ultimate lateral load capacities of the strengthened frames are determined by a load controlled push-over analysis. The post-tensioning effect of preloading is also investigated.
12
Zhou, Wenxing. "Reliability evaluations of reinforced concrete columns and steel frames." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58250.pdf.
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13
ALMEIDA, ALEX FABIANO DE. "RELIABILITY-BASED DESIGN OPTIMIZATION OF REINFORCED CONCRETE PLANE FRAMES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11577@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Este trabalho compara o projeto ótimo determinístico (DDO)
com o projeto ótimo baseado em confiabilidade (RBDO) de
pórticos planos de concreto armado. A estrutura é modelada
por uma malha de elementos finitos usando elementos de
barras e considerando a não-linearidade geométrica e dos
materiais. Na formulação do problema de otimização proposto
as variáveis de projeto são definidas para cada elemento
finito da malha. Elas são as armaduras superior e inferior
das seções transversais de extremidade do elemento, a altura
da seção do elemento, as áreas de armadura transversal e o
parâmetro D usado para descrever os estados limites últimos
de acordo com a norma brasileira NBR 6118 (ABNT, 2004). Os
algoritmos de otimização utilizados são os de
programação quadrática seqüencial (PQS), programação linear
seqüencial (PLS) e o método das direções viáveis (MDV).
As variáveis randômicas do problema de RBDO são a
resistência à compressão do concreto, as resistências à
tração e à compressão do aço, assim como as cargas
aplicadas. As funções de comportamento são de dois tipos, a
primeira é relativa à carga crítica da estrutura e a
segunda ao controle de deslocamento para o estado limite de
utilização. Para o cálculo da probabilidade de falha de uma
função de comportamento, em cada iteração do problema de
RBDO, o método FORM (PMA) utilizará o algoritmo HMV para
obtenção do ponto de projeto. Análise de sensibilidade é
feita pelo método analítico.<br>This work compares the Deterministic Design Optimization
(DDO) with
the Reliability-Based Design Optimization (RBDO) of
reinforced concrete plane
frames. The structure is modeled by a finite element mesh
using bar elements
and considering both geometric and material nonlinearities.
In the formulation of
the proposed optimization problem the design variables are
defined for each
element of the finite element mesh. They are the areas of
tensile and
compressive reinforcement at the element ends, the depth of
the element
rectangular cross-section, the areas of shear
reinforcement, and the parameter D
used to describe the deformation limit sates for the
element cross-sections
defined according to the Brazilian code for the design of
concrete structures
NBR 6118 (ABNT, 2004). The optimization algorithms used are
the Sequential
Linear Programming (SLP), the Sequential Quadratic
Programming (SQP) and
the Method of Feasible Direction (MFD).
The random variables of the RBDO problem are the concrete
compressive
strength, the steel compressive and tensile strength, as
well as some applied
loads. The performance functions are of two types, the
first relates to the critical
load of the structure and the second to the control of
displacements in the
serviceability state. For performing the calculation of the
probability of failure
for the associated performing function in each iteration of
the RBDO problem,
the method FORM (PMA) will be used in connection with the
HMV algorithm
for obtaining the project point. The sensitivity analyses
are carried out by the
analytical method.
14
Eldawie, Alaaldeen Hassan. "COLLAPSE MODELING OF REINFORCED CONCRETE FRAMES UNDER SEISMIC LOADING." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595607477704066.
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15
Samman, Tamim Abdulhadi. "Indeterminate reinforced concrete frames subjected to inelastic cyclic deformation." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184307.
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Four full-size statically indeterminate reinforced concrete frames with two symmetrical bays were tested to obtain sufficient data to evaluate the adequacy of the current ACI-ASCE Committee 352 design recommendations, as well as to determine whether a relaxation of some of the limits in these guidelines can be justified. Each specimen contained three 8.5-foot-long columns, connected at mid-height by two 9-foot-long beams. Initially, a constant axial load was applied to each column. The specimens were then subjected to a displacement-controlled loading schedule to simulate the type of displacements a frame may experience during a severe earthquake. In designing the specimens, the latest recommendations of the ACI-ASCE Committee 352 and the ACI building code ACI 318-83 were satisfied except for the following modifications: (1) the flexural strength ratio (M(R)) in the second specimen was reduced from 1.4 to 1.2, (2) the shear-stress factors (γ) in the joints of the third specimen were increased from 12 and 15 to 15 and 20 for the exterior and interior joints respectively, and (3) the number of the transverse reinforcements inside the right exterior joint in the fourth specimen was reduced from 4 to 2 sets of hoops. The conclusion inferred from the results indicate that for drift levels within the elastic range, the elongations and the rotations of the beam regions near the faces of the columns, in addition to the joint shear strains, were not affected by the design values for the primary variables in the last three specimens. For larger excursions into the inelastic range, the relaxation of the current Committee 352 design recommendations in the last three specimens not only showed a significant effect in reducing the elongations and the rotations of the beams, or in increasing the joint shear strains but led to lower energy dissipation of the specimens. Consequently, the current design guidelines by the ACI-ASCE Committee 352 yield statically indeterminate frames which exhibit sufficient ductility.
16
Arslan, Guray. "Strengthening Of Reinforced Concrete Frames By Custom Shaped High Strength Concrete Masonry Blocks." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610335/index.pdf.
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Located on one of the highly active seismic fault systems in the world, the building stock in Turkey is mainly composed of reinforced concrete frames with 4-5 stories. Due to design and construction deficiencies resulting from the use of unqualified personnel and insufficient supervision, many of these buildings lack lateral stiffness, ductility and strength. For many structures, there is a need to alleviate these deficiencies by means of some rehabilitation techniques prior to earthquakes. One approach also used very widely in Turkey is to fill some of the frame bays by cast-in-place R/C panels. The procedure appears to be very practical at first glance. It also appears to be very economical as far as the production of the panels is concerned. However, the production phase is slow, dirty, destructive and disruptive to occupants. Moreover, it requires relatively skilled personnel and special equipment. Therefore, the real life experience shows that the actual cost in practice is much higher when all other hidden costs are taken into account.
The aim of this experimental study is to explore the potential of using infill walls made of custom shaped and high strength concrete blocks as a simpler and more practical alternative to cast-in-place R/C panels to increase the lateral load bearing capacity of frame structures. The effectiveness of FRCM (Fiber Reinforced Cementitous Matrix) system on damaged structures is also investigated in this study.
17
Ozcelik, Ramazan. "Seismic Upgrading Of Reinforced Concrete Frames With Structural Steel Elements." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613450/index.pdf.
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This thesis examines the seismic internal retrofitting of existing deficient reinforced concrete
(RC) structures by using structural steel members. Both experimental and numerical studies
were performed. The strengthening methods utilized with the scope of this work are chevron
braces, internal steel frames (ISFs), X-braces and column with shear plate. For this purpose,
thirteen strengthened and two as built reference one bay one story portal frame specimens
having 1/3 scales were tested under constant gravity load and increasing cyclic lateral
displacement excursions. In addition, two ½<br>scaled three bay-two story frame specimens
strengthened with chevron brace and ISF were tested by employing continuous pseudo
dynamic testing methods. The test results indicated that the cyclic performance of the Xbrace
and column with shear plate assemblage technique were unsatisfactory. On the other
hand, both chevron brace and ISF had acceptable cyclic performance and these two
techniques were found to be candidate solutions for seismic retrofitting of deficient RC
structures. The numerical simulations by conducting nonlinear static and dynamic analysis
were used to estimate performance limits of the RC frame and steel members. Suggested
strengthening approaches, chevron brace and ISF, were also employed to an existing five
story case study RC building to demonstrate the performance efficiency. Finally, design
approaches by using existing strengthening guidelines in Turkish Earthquake Code and
ASCE/SEI 41 (2007) documents were suggested.
18
Ozkok, Mustafa Emre. "Seismic Upgrade Of Deficient Reinforced Concrete Frames Using External Systems." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611973/index.pdf.
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There is a large building stock in seismic regions of Turkey that require seismic upgrades. In order to minimize the disturbance to occupants and not to intervene with the functioning of the building, external strengthening methods can be preferred among different alternatives. This study reports the experimental findings on the upgrading of deficient reinforced concrete frames with external installed structural components. Specimens strengthened with an externally reinforced concrete shear wall, external steel frames, steel plate shear wall and one as-built reference 1/3-scale portal frame specimens were tested under constant gravity load and increasing cyclic displacement excursions. The RC frames had deficiencies those mimic the existing deficient building stock in Turkey. The test results showed that the external upgrading can increase both the lateral stiffness and strength of deficient RC frames considerably. Finite element analyses were conducted to specimen models to investigate the behaviors numerically. Furthermore, corresponding single degree of freedom (SDOF) models of specimens were generated to perform dynamic analysis. Results show the importance of hysteretic response and enhancement of energy dissipation capability with drift control.
19
Vali, Pour Goudarzi Hamid Reza Civil & Environmental Engineering Faculty of Engineering UNSW. "Nonlinear dynamic analysis of reinforced concrete frames under extreme loadings." Publisher:University of New South Wales. Civil & Environmental Engineering, 2009. http://handle.unsw.edu.au/1959.4/43720.
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This research focuses on improvements and application of 1D finite elements for nonlinear dynamic analysis of reinforced concrete frames under extreme loadings. The concept of force interpolation is adopted for the element formulation and a solution scheme developed based on a total secant stiffness approach that provides good convergence characteristics. The geometrical nonlinearities including 2nd order P-Delta effects as well as catenary action are considered in the element formulation. It is shown that geometrical nonlinearities may have a significant effect on member (structure) response within extreme loading scenarios. In the analysis of structures subjected to extreme loadings, accurately modelling of the post peak response is vital and, in this respect, the objectivity of the solution with softening must be maintained. The softening of concrete under compression is taken into account, and the objectivity preserved, by adopting a nonlocal damage model for the compressive concrete. The capability of nonlocal flexibility-based formulation for capturing the post-peak response of reinforced concrete beam-columns is demonstrated by numerical examples. The 1D frame element model is extended for the modelling of 3D framed structures using a simplified torque-twist model that is developed to take account of interaction between normal and tangential forces at the section level. This simplified model can capture the variation of element torsional stiffness due to presence of axial force, bending moment and shear and is efficient and is shown to provide a reasonable degree of accuracy for the analysis of 3D reinforced concrete frames. The formulations and solution algorithms developed are tested for static and dynamic analysis of reinforced concrete framed structures with examples on impact analysis of beams, dynamic analysis of frames and progressive collapse assessment of frames taken from the literature. The verification shows that the formulation is very efficient and is capable of modelling of large scale framed structures, under extreme loads, quickly and with accuracy.
20
Dukuze, Augustin. "Behaviour of reinforced concrete frames infilled with brick masonry panels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0031/NQ65457.pdf.
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21
Molaei, Ali. "Seismic Retrofit of Reinforced Concrete Frames with Diagonal Prestressing Cables." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30668.
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A large number of building inventory in Canada and elsewhere in the world consists of non-ductile reinforced concrete frames, with or without masonry infill panels. These structures suffer damage when seismic force demands are higher than their force capacities. Therefore, seismic retrofitting of such frame buildings for drift control remains to be a viable option for improved building performance. A retrofit methodology has been developed in the current research project, which involves diagonal bracing of frames with prestressing strands. An experimental research project has been conducted to assess the effectiveness of diagonal prestressing in non-ductile reinforced concrete frame buildings.
The experimental program consists of two large-scale single-bay single-storey reinforced concrete frames, with a height of 3.0m and a span length of 3.5 m. The frames were designed and built to reflect the 1960’s practice in Canada, without the seismic requirements of current building codes, and hence are seismically deficient. They were retrofitted with diagonally placed prestressing strands, having two different areas of steel, prestressed to 40% of the strand capacity. One of the frames was retested after the failure of the strands, with a new set of strands without any prestressing, forming the third test.
The results indicate that lateral bracing reinforced concrete frames with high-strength prestressing strands is an effective strategy for controlling lateral drift and hence potential damage in buildings during strong earthquakes. Prestressing of the strands increases initial stiffness, as compared to non-prestressed cables, and provide superior performance. The area of diagonally placed steel (including the number of strands) and the level of initial prestressing depend on the required level of upgrade in the building in terms of seismic force requirements. The design procedure recommended in this thesis may be employed for implementing the technology. The thesis presents the details of the experimental program, and the test results. It also provides analytical verification of the approach, with a step-by-step design procedure.
22
Plumb, Alex David. "Seismic Behavior of GFRP-Reinforced Concrete Beams and Moment Frames." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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The use of fiber reinforced polymer (FRP) bars as internal reinforcement for concrete structures has grown in frequency within the past thirty years, owing mainly to the material’s resistance to corrosion. This development is prevalent in coastal regions where the chemical attack from seawater can weaken steel reinforcement, the traditional reinforcing material in concrete. However, a large obstacle remains in replacing all steel reinforcement with FRP reinforcement in these areas: coastal regions are some of the most seismically active areas in the world. Research on FRP bars shows they behave linear-elastically and exhibit brittle, as opposed to ductile, failure. This is impractical for acceptable seismic design, where the ductile performance of the structure is advantageous to absorb the earthquake loads. Due to this, the outlook for FRP reinforced concrete in seismic zones is seemingly limited. But recent research, although from a small sample size, has shown promising results. This research aims to build upon these findings and expand the knowledge of FRP reinforced concrete performance under seismic loads, especially for beams and moment frames. An analytical study was performed to examine (i) the cross-section of a hybrid glass (G)FRP-steel-reinforced beam through moment-curvature analysis and (ii) two concrete moment frames with GFRP-reinforced beams and steel-reinforced columns subjected to simulated seismic loading through pushover analysis. The performance of the primarily GFRP reinforced concrete design was evaluated by parameters such as curvature ductility (9.0), structural ductility (2.1 and 5.0), and lateral drift. The results showed significant potential for the use of GFRP in seismically active regions.
23
Pham, Ba Hung. "Stress-resultant models for optimal design of reinforced-concrete frames." Cachan, Ecole normale supérieure, 2009. http://tel.archives-ouvertes.fr/tel-00538958/fr/.
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The standard design procedure of reinforced concrete frame structures starts with linear analysis to obtain the corresponding diagrams of stress resultants (bending moment, shear and axial force), followed by the ultimate analysis of each cross section. The main disadvantage of such a design procedure concerns the (highly) statically indeterminate frames, where the failure of each beam or column would not imply the complete failure of the structure, but would lead to a significant stress resultant redistribution with respect to the result obtained by linear analysis. For that reason, we propose the performance based design procedure where the behavior until complete failure of beam-column and frames imposes to consider so-called plastic hinges corresponding to the zones where plasticity and/ or damage localizes. Engineering structures are usually statically indeterminate, so that the total failure of one member would affect the global response of the structure but it would not lead to a complete loss of the structural integrity. Moreover, being capable of describing the softening response of the members of one particular structure can provide an estimate of the residual life of a partially damaged structure. Such a procedure can also help to provide a more detailed crack description, which is needed to make decisions about the maintenance and repairs.
24
Lanzas, Lourdes Eneida 1962. "A parametric study on the behavior of slender reinforced concrete frames." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276945.
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By using a nonlinear computer analysis, a parametric study is developed in order to examine the accuracy of the Moment Magnifier Method of the American Concrete Institute Code (ACI 318-83). The variables used in the parametric study are: axial load intensity, P/Po; column reinforcement ratio, rho; slenderness ratio, klu; shape of column cross section, flexural stiffness ratio, and distribution of axial loads. In the parametric study, 216 cases of single bay fixed-base portal frames are examined. The higher moment for each one of these frames at failure are then compared with the design moment predicted by the Moment Magnifier Method of the American Concrete Institute Code (ACI 318-83). The Moment Magnifier Method proved to be very conservative when the columns are subjected to high level of axial loads and when the slenderness ratio is increased.
25
Biddah, Ashraf Mahmoud Samy. "Seismic behaviour of existing and rehabilitated reinforced concrete frame connections." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ30074.pdf.
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Baradaran, Shoraka Majid. "Collapse assessment of concrete buildings : an application to non-ductile reinforced concrete moment frames." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45000.
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Existing reinforced concrete buildings lacking details for ductile response during earthquake shaking represent prevalent construction type in high seismic zones around the world. Seismic rehabilitation of these existing buildings plays an important role in reducing urban seismic risk; however, with the massive inventory of existing concrete buildings and high costs of seismic rehabilitation, it is necessary to start by identifying and retrofitting those buildings which are most vulnerable to collapse.
The collapse of most non-ductile concrete buildings will be controlled by the loss of support for gravity loads prior to the development of a side-sway collapse mechanism. “Gravity load collapse” may be precipitated by axial-load failure of columns, punching-shear failure of slab-column connections, or axial-load failure beam-column joints. In this dissertation, system-level collapse criteria are developed and implemented in a structural analysis platform to allow for a more accurate detection of collapse in these existing moment frames.
Detailed models for primary components, which may precipitate gravity-load collapse of the concrete moment frame, are first required to achieve this objective and develop the collapse assessment framework. An analytical model based on mechanics is developed to reliably capture the lateral load–deformation response of a broad range of reinforced concrete columns with limited ductility due to degradation of shear resistance, either before or after flexural yielding.
The robust collapse performance assessment could be used for many structural applications. In this dissertation, it is used to identify collapse indicators, design and response parameters that are correlated with “elevated” collapse probability. The collapse assessment framework is also used to identify the relative collapse risk of different rehabilitation techniques. Finally, the framework is used to estimate the impact of collapse criteria on the expected financial losses for existing concrete frame buildings in high seismic zones.
This dissertation includes important contributions to (1) modeling techniques for components in existing concrete frames through the development of a mechanical model for existing concrete columns, (2) development of system-level collapse criteria, and (3) application of collapse fragilities in defining collapse indicators, improving loss estimation of existing concrete frames, and differentiating the collapse performances of existing and retrofitted concrete frames.
27
Wong, Anthony K. M. "Theoretical investigation of Australian designed reinforced concrete frames subjected to earthquake loading /." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09ENS/09ensw872.pdf.
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Hertanto, Eric. "Seismic Assessment of Pre-1970s Reinforced Concrete Structure." Thesis, University of Canterbury. Civil Engineering, 2005. http://hdl.handle.net/10092/1120.
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Reinforced concrete structures designed in pre-1970s are vulnerable under earthquakes due to lack of seismic detailing to provide adequate ductility. Typical deficiencies of pre-1970s reinforced concrete structures are (a) use of plain bars as longitudinal reinforcement, (b) inadequate anchorage of beam longitudinal reinforcement in the column (particularly exterior column), (c) lack of joint transverse reinforcement if any, (d) lapped splices located just above joint, and (e) low concrete strength. Furthermore, the use of infill walls is a controversial issue because it can help to provide additional stiffness to the structure on the positive side and on the negative side it can increase the possibility of soft-storey mechanisms if it is distributed irregularly. Experimental research to investigate the possible seismic behaviour of pre-1970s reinforced concrete structures have been carried out in the past. However, there is still an absence of experimental tests on the 3-D response of existing beam-column joints under bi-directional cyclic loading, such as corner joints. As part of the research work herein presented, a series of experimental tests on beam-column subassemblies with typical detailing of pre-1970s buildings has been carried out to investigate the behaviour of existing reinforced concrete structures. Six two-third scale plane frame exterior beam-column joint subassemblies were constructed and tested under quasi-static cyclic loading in the Structural Laboratory of the University of Canterbury. The reinforcement detailing and beam dimension were varied to investigate their effect on the seismic behaviour. Four specimens were conventional deep beam-column joint, with two of them using deformed longitudinal bars and beam bars bent in to the joint and the two others using plain round longitudinal bars and beam bars with end hooks. The other two specimens were shallow beam-column joint, one with deformed longitudinal bars and beam bars bent in to the joint, the other with plain round longitudinal bars and beam bars with end hooks. All units had one transverse reinforcement in the joint. The results of the experimental tests indicated that conventional exterior beam-column joint with typical detailing of pre-1970s building would experience serious diagonal tension cracking in the joint panel under earthquake. The use of plain round bars with end hooks for beam longitudinal reinforcement results in more severe damage in the joint core when compared to the use of deformed bars for beam longitudinal reinforcement bent in to the joint, due to the combination of bar slips and concrete crushing. One interesting outcome is that the use of shallow beam in the exterior beam-column joint could avoid the joint cracking due to the beam size although the strength provided lower when compared with the use of deep beam with equal moment capacity. Therefore, taking into account the low strength and stiffness, shallow beam can be reintroduced as an alternative solution in design process. In addition, the presence of single transverse reinforcement in the joint core can provide additional confinement after the first crack occurred, thus delaying the strength degradation of the structure. Three two-third scale space frame corner beam-column joint subassemblies were also constructed to investigate the biaxial loading effect. Two specimens were deep-deep beam-corner column joint specimens and the other one was deep-shallow beam-corner column joint specimen. One deep-deep beam-corner column joint specimen was not using any transverse reinforcement in the joint core while the two other specimens were using one transverse reinforcement in the joint core. Plain round longitudinal bars were used for all units with hook anchorage for the beam bars. Results from the tests confirmed the evidences from earthquake damage observations with the exterior 3-D (corner) beam-column joint subjected to biaxial loading would have less strength and suffer higher damage in the joint area under earthquake. Furthermore, the joint shear relation in the two directions is calibrated from the results to provide better analysis. An analytical model was used to simulate the seismic behaviour of the joints with the help of Ruaumoko software. Alternative strength degradation curves corresponding to different reinforcement detailing of beam-column joint unit were proposed based on the test results.
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Hopper, Michael W. Lepage Andres. "Analytical models for the nonlinear seismic response of reinforced concrete frames." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4752/index.html.
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Akin, Alper. "Optimum Design Of Reinforced Concrete Plane Frames Using Harmony Search Algorithm." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612293/index.pdf.
Full textAbstract:
In this thesis, the optimum design algorithm is presented for reinforced concrete special moment frames. The objective function is considered as the total cost of reinforced concrete frame which includes the cost of concrete, formwork and reinforcing steel bars. The cost of any component is inclusive of material, fabrication and labor. The design variables in beams are selected as the width and the depth of beams in each span, the diameter and the number of longitudinal reinforcement bars along the span and supports. In columns the width and the depth of the column section, the number and the diameter of bars in x and y directions are selected as design variables. The column section database is prepared which includes the width and height of column section, the diameter and the number of reinforcing bars in the column section is constructed. This database is used by the design algorithm to select appropriate sections for the columns of the frame under consideration. The design constraints are implemented from ACI 318-05 which covers the flexural and shear strength, serviceability, the minimum and maximum steel percentage for flexural and shear reinforcement, the spacing requirements for the reinforcing bars and the upper and lower bound requirements for the concrete sections. The optimum design problem formulated according to ACI 318-05 provisions with the design variables mentioned above turns out to be a combinatorial optimization problem. The solution of the design problem is obtained by using the harmony search algorithm (HS) which is one of the recent additions to meta-heuristic optimization techniques which are widely used in obtaining the solution of combinatorial optimization problems. The HS algorithm is quite simple and has few parameters to initialize and consists of simple steps which make it easy to implement. Number of design examples is presented to demonstrate the efficiency and robustness of the optimum design algorithm developed.
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Mutlu, Mehmet Basar. "Numerical Simulations Of Reinforced Concrete Frames Tested Using Pseudo-dynamic Method." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614460/index.pdf.
Full textAbstract:
Considering the deficiencies frequently observed in the existing reinforced concrete buildings, detailed assessment and rehabilitation must be conducted to avoid significant life and value loss in seismic zones. In this sense, performance based evaluation methods suggested in the regulations and codes must be examined and revised through experimental and analytical research to provide safe and economical rehabilitation solutions.
In this study, seismic behavior of three reinforced concrete frames built and tested in Middle East Technical University Structural Mechanics Laboratory is examined. The specimens are extracted from a typical interior frame of 3-story 3-bay reinforced concrete structure. One of the specimens has compliant design according to Turkish Earthquake Code (2007) and each of the other two specimens represents different types of deficiencies in terms of material strength and detailing. The test specimens were modeled using different modeling approaches and nonlinear dynamic analyses were conducted on the numerical models. Results of continuous pseudo-dynamic testing of three ground motions are presented and compared with the numerical simulations on models. Calibrated finite element models were used for evaluation of performance assessment procedure of Turkish Earthquake Code (2007) and further investigation on local deformation components in light of experimental findings and observations. Deformation sources of columns and joints were studied in terms of their interaction and contributions to the total drift. Estimated plastic hinge lengths of columns were compared with the experimental observations and the proposed expressions in the literature.
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Moni, Moniruzzaman. "Performance of shape memory alloy reinforced concrete frames under extreme loads." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36647.
Full textAbstract:
Reinforced concrete (RC) frame structures are commonly used in various parts of the world for resisting lateral loads. Over the last few decades, the influence of extreme loads on structures has received much attention by researchers and practicing engineers. In RC structures steel is mainly used as reinforcing material where its major setback is associated with a high residual deformation after yielding during an extreme load event, which may often result in structural collapse or substantial damages to the structure. Superelastic shape memory alloy (SMA) is a special material, which has the ability to undergo large deformation and recover its shape upon unloading. In the present study, a numerical investigation has been carried out to determine the potential application of SMA rebar in improving the performances of reinforced concrete (RC) frames under extreme loads.
Nine RC ductile moment-resisting frames of different stories (3, 6 and 8) designed as per CSA A23.3 located in western Canada are taken into consideration. For each storey type, three different reinforcement detailings have been considered, namely: i) steel reinforcement only (Steel RC); ii) SMA rebar used in the plastic hinge region of the beams and steel rebar in other regions (Steel-SMA RC); and iii) the beams fully reinforced with SMA rebar (SMA RC). For all 3 cases, the columns were reinforced with steel rebars. Nonlinear static pushover analyses, nonlinear incremental dynamic and linear dynamic time history analyses were performed on these buildings to determine the overstrength factor (Ro), ductility reduction factor (Rd) and the response modification factor (R) of the considered buildings. In addition, the supply and demand of the ductility reduction factor were also compared with different frame types. The results indicated that the code proposed response modification factors can be used for the SMA and Steel-SMA RC frames. Seismic vulnerability of the considered frames are also evaluated in terms of peak global roof drift, maximum inter-story drift, maximum residual roof drift and maximum residual inter-storey drift, which are considered as critical response parameters. In addition, the progressive collapse performances of the considered frames have been evaluated as per the General Service Administration (GSA, 2003) guideline by performing linear and nonlinear static and dynamic, analyses. The results showed that the performance of the Steel RC frame is better compared to that of the SMA RC frame under progressive collapse.
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Blé, Aurélie. "Analysis of crack patterns in reinforced concrete frames under seismic excitation." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34636.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.<br>Includes bibliographical references (leaves 41-42).<br>Earthquakes occur as a result of sudden displacements across a fault within the earth. The seismic waves that result from them propagate along the earth's surface and are the cause of multiple damages especially in civil engineering. The main objective of this study is to compare different types of concrete (RC, HSRC and SFRC) in order to determine the one that will contribute the most to increase the steadiness of buildings in seismic regions at the connection between beams and columns. The first part of this paper consists of introducing these different types of concrete. Then cracks patterns analyses are run at the joint between beam and column. In that part, theoretical approach precedes experimental application. Finally, explanation about benefits and advantages of using SFRC in joints of buildings subjected to seismic excitations will be provided. In fact, concrete reinforced with short steel fibers is associated with its ability to control cracking and enhances properties of concrete.<br>by Aurélie Blé.<br>M.Eng.
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Liuzza, Gabrielle. "The elongation of beams in reinforced concrete special moment resisting frames." Thesis, Kansas State University, 2018. http://hdl.handle.net/2097/38780.
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Master of Science<br>Department of Architectural Engineering and Construction Science<br>Donald J. Phillippi<br>Special moment resisting frames (SMRF) are intended to protect the structure from earthquake motions through a ductile inelastic response. This thesis evaluates the performance of reinforced concrete SMRFs with an emphasis on the second level beams. Due to previous research, it is concluded that two-dimensional finite element analyses (2D-FEA) and three-dimensional finite element analyses (3D-FEA) have different results when evaluating the same structure. Due to this, the thesis used a 3D-FEA to analyze frames based on Design Example 7 in the 2006 IBC Structural/Seismic Design Manual (Appendix A). While looking at the frame as a whole, the first of two parametric studies was performed over the columns. Using LS-DYNA the columns’ forces, displacement, moment, and curvature were evaluated. From these results, it was concluded that in SMRF, columns are not acting per current design assumptions due to the elongation of beams. Using the knowledge gained in the first parametric study, a second parametric study was performed on the second level floor beams. Focusing on the beam elongation, this thesis evaluates multiple frames with different load combinations using LS-DYNA to find the displacement of the reinforcement in the beams. With the results, an equation to calculate the elongation of beams was proposed, as well as an average percentage of the elongation in reinforced concrete SMRF. The equation and average percentage of elongation aim to provide a standard design consideration for the elongation of beams.
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Albrifkani, Sherwan. "Whole range behaviour of restrained reinforced concrete beams and frames in fire." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/whole-range-behaviour-of-restrained-reinforced-concrete-beams-and-frames-in-fire(95ff52f9-d90a-4873-8ef1-7ea301074e13).html.
Full textAbstract:
This thesis presents the results of a numerical investigation of the whole range, large deflection behaviour of axially and rotationally restrained RC beams and interactions between beams and columns in RC frame structures exposed to fire. The dynamic explicit time integration algorithm implemented in the general finite element package ABAQUS/Explicit solver was used so as to overcome various modelling challenges including temporary instability, local failure of materials, non-convergence and long simulation time. Either load factoring or mass scaling may be used to speed up the simulation process. Validity of the proposed simulation model was checked by comparison of simulation results against relevant test results of restrained RC beams at ambient temperature and in fire. The validated ABAQUS/Explicit model was then used to conduct a comprehensive study of the effects of different levels of axial and rotational restraints on the whole range behaviour of RC beams in fire, including combined bending and compression due to restrained thermal expansion, bending failure, transition from compression to tension when catenary action develops and complete fracture of reinforcement at ultimate failure. The numerical results show that different bending failure modes (middle span sagging failure, end hogging failure due to fracture of tensile reinforcement, end hogging failure due to concrete crushing) can occur under different levels of boundary restraints. Furthermore, release of a large amount of energy during the rapid transition phase from compression to tension in a beam prevents formation of a three hinge mechanism in the beam under bending. The numerical results have also revealed that reliable catenary action develops at large deflections following bending failure only if bending failure is governed by compressive failure of concrete at the end supports whereby a continuous tension path in the beam can develop in the top reinforcement. To allow fire engineering practice to take into consideration the complex restrained RC beam behaviour in fire, a simplified calculation method has been developed and validated against the numerical simulation results. The proposed method is based on sectional analysis and meets the requirements of strain compatibility and force equilibrium. The validation study results have shown that the simplified method can satisfactorily predict the various key quantities of restrained beam axial force and beam deflection-fire exposure time relationships, with the simplified method generally giving results on the safe side. The validated explicit finite element model in ABAQUS was also used to investigate structural interactions between beams and columns within an RC frame structure with different fire exposure scenarios. When fire exposure involves beams and columns located in edge bays of a frame, catenary action cannot develop. Also due to thermal expansion of the connected beam, additional bending moments can generate in the columns. Furthermore, very large hogging moments can be induced at the beam end connected to the internal bay. It is necessary to include these bending moments when designing beams and columns under such fire conditions. Catenary action can develop in interior beams of the frame when fire exposure is in interior bays where the beams have high degrees of axial restraint.
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Shalouf, Fathalla. "Seismic retrofit of reinforced concrete frames with diagonal prestressing or FRP strips." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/29260.
Full textAbstract:
Performance of reinforced concrete structures during previous earthquakes has indicated that the majority of buildings designed prior to the enactment of modern seismic codes and those designed more recently in regions where code enforcement is difficult to achieve, have suffered seismic damage associated with non-ductile frame construction. Because it is not economically feasible to replace seismically deficient building infrastructure with new and improved buildings, seismic retrofit strategy remains to be the most viable approach to seismic risk mitigation.
Currently, there are retrofit techniques available to stiffen and strengthen non-ductile concrete frames with unreinforced masonry infill panels, while other techniques are used to improve deformability of elements. The available retrofit techniques may be viewed in three categories; (i) those that involve the addition of structural elements, such as steel bracing systems or concrete shear walls to control deformations, (ii) those that involve surface treatment of masonry walls by adding concrete overlays with steel mesh, bonding steel plates on both sides and using fiber reinforced polymer (FRP) composite materials, and (iii) those that involve reinforcing masonry walls internally. The first category of retrofit methods, while stiffens and strengthens the frames, often results in a change of dynamic properties of structures by increasing mass and reducing period of the structure.
The main objective of the proposed research is to develop new and improved seismic retrofit techniques for non-ductile reinforced concrete frame structures with and without masonry infill walls. The techniques to be investigated involve the application of surface bonded and FRP anchored diagonal FRP sheets and externally applied diagonal prestressing.
The experimental and the analytical results indicate that the two techniques used in the research were able to control the structure deflection.
The initial prestressing in the cables has effect on the structure drift demand. If it is high, the strands yield and may even rupture during loading and result in high drift demand, as opposed to non-prestressed strands that may continue remaining elastic. However, the situation reverses during small drift demands, where, increased prestressing results in reduced drift demands as long as the strands remain elastic. This implies that there exists an optimum level of prestressing.
Also the results indicate that CFRP strips can be used to effectively control lateral drift during strong earthquakes, protecting non-ductile frame buildings.
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Clarke, James D. "The Optimality Criteria method used to design reinforced concrete frames to CP110." Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/28055.
Full textAbstract:
This study presents an Optimality Criteria method for the minimum cost design of in-situ, reinforced concrete frames, comprising of beam and column elements. The design process is governed by the Code of Practice for Structural Concrete CP110, from which details including manipulation of characteristic loading, methods of analysis and the provision of reinforcement have been obtained.
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Flores, Ruiz Jose Antonio. "Performance of ductile reinforced concrete moment resisting frames subject to earthquake actions." Thesis, University of Canterbury. Department of Civil and Natural Resources Engineering, 2005. http://hdl.handle.net/10092/4932.
Full textAbstract:
It has been shown that the strengths specified in the Loadings Standard NZS 4203: 1992
(Standards New Zealand 1992) to resist seismic actions are low when compared with major
international design codes (Fenwick and Davidson 1994; Fenwick et al. 2002). Few modifications to
these low strengths other than an increase in the minimum permissible base shear have been made in
the draft revision of the Standard, NZS 1170.5. Furthermore, the design procedure to allow for higher
mode effects in multi-storey structures subject to dynamic forces was developed in the 70's using a
limited number of non-linear time-history analyses with a bilinear hysteretic rule and in most cases
neglecting P-delta effects.
In this work, a four storey, a six storey, and two twelve storey buildings, in which the
resistance to lateral forces is provided by concrete moment resisting frame structures were designed
and analysed.
Through a senes of non-linear time-history analyses using a Takeda hysteretic rule and
considering P-delta effects, three main objectives were studied. The first objective was to investigate if
the strengths given to beams and columns met the objectives set by the Loadings Standard (Standards
New Zealand 1992). The second objective was to examine how well the method of determining column
actions from the NZS 3101:1995 (Standards New Zealand 1995) works when using the lateral loading
specified in NZS 4203:1992 (Standards New Zealand 1992) and the draft provisions of the proposed
Loadings Standard NZS 1170.5 and the third objective was to compare the performance of multi-storey
moment resisting frame buildings where columns are modelled as:
Elastic responding columns except at the base;
Columns designed to meet the minimum requirements as given in NZS 3101: 1995
(Standards New Zealand 1995); and
Columns designed to meet the minimum strength requirements as defined in the 2004
draft of NZS 1170.5 where limited protection to plastic hinge formation is given.
The influence of the choice of hysteretic rule was assessed and in general, the structures
studied performed in a satisfactory manner due to the use of a more realistic hysteretic model. The
individual results from the non-linear time-history analyses were very scattered making the structures
reach critical performance levels with some of the selected ground acceleration records and poor
performance was observed for structures analysed using a 2,500 year return period earthquake.
It was also shown that P-delta effects have a significant influence to the response even for the
four and six storey structures and concluded that P-delta effects should always be included in the
design and analysis of structures.
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Abou-Elfath, Hamdy Mohamed. "Rehabilitation of nonductile reinforced concrete buildings using steel systems /." *McMaster only, 1998.
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Elmorsi, Mostafa Saad Eldine. "Analytical modeling of reinforced concrete beam column connections for seismic loading." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/NQ42844.pdf.
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Poliotti, Mauro. "A framework for 3D nonlinear analysis of reinforced concrete frames under general loading." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/670036.
Full textAbstract:
Modern guidelines for design and assessment of reinforced concrete structures under seismic and other extreme loads require nonlinear analysis. The complex structural response can be obtained by means of three-dimensional finite element models, although its application is limited due to their high computational cost. Alternatively, if the structure can be assimilated by line elements, the structure can be simulated by means of frame elements. These formulations have demonstrated to be robust and efficient. The main drawback of most of the beam-column models is that they neglect or consider in an oversimplified way the interaction between axial and transverse internal forces. Consequently, most frame models are not able to trace different failure modes in reinforced concrete elements such as shear or torsional failures. Besides, the simplifications made in those models affect also their ability to reproduce even common failure modes such as flexural or axial failures.
The main goal of this thesis is to develop a robust and efficient numerical tool capable of reproducing different failure modes of reinforced concrete frame elements. It is also desired that the model is able to reproduce complex phenomena such as passive confinement in an objective way. The developed tool is aimed to be used in the design or assessment of full scale structures under general loading conditions. In order to accomplish this objective, the problem is dealt by means of a multilevel framework.
At the constitutive level, a new plastic-damage model for concrete that incorporates a variable dilatancy parameter is developed. It is demonstrated that dilatancy affects the free expansion of concrete, the softening behavior under shear stresses and the response of passively confined elements. The model is based on a well-known plastic-damage model, which is modified by means of a dilatancy parameter that depends on the plastic-damage and stress states.
At the sectional level, a new model that introduces an efficient numerical technique is developed. The new model is based on a total interaction sectional model that reproduces the kinematic behavior of the cross-section by means of a two-component displacement field. One component of the displacements satisfies the traditional hypothesis of Euler-Bernoulli while the complementary field reproduces warping and distortion. This field enables the model to obtain the triaxial stress and strain tensors on each point of the cross-section domain. The complementary displacement field is obtained by considering the inter-fiber three-dimensional equilibrium. The displacement field is expressed by means of a set of b-spline functions predefined on the cross-section domain. Thus, a significant reduction on the degrees of freedom involved on the cross section state determination is obtained compared against a finite element solution. This makes the model suitable of its implementation at the element level.
Further, at the element level a force-based formulation is used. The model strictly satisfies the equilibrium between nodal and sectional forces. On each integration point of the elements, the higher order sectional model described earlier can be used to represent the sectional behavior. The models are implemented into an open-source collaborative finite element software focused on the nonlinear seismic analysis of structures.
The presented models are validated, both separately and jointly, by comparison of numerical results with experimental tests available in the<br>Las guías modernas de diseño y evaluación de estructuras de hormigón armado sometidas a sismo u a otras cargas extremas requieren del análisis no lineal. La compleja respuesta estructural puede ser obtenida mediante modelos tridimensionales de elementos finitos, aunque su aplicación está limitada debido a su alto costo computacional. Alternativamente, si la estructura puede ser idealizada mediante elementos lineales, la estructura puede ser simulada por medio de elementos de barra. Estas formulaciones han demostrado ser robustas y eficientes. La mayor desventaja de la mayoría de los modelos de viga-columna es que los mismos desprecian o consideran de una forma simplificada la interacción entre los esfuerzos internos normales y tangenciales. Por esto, la mayoría de los modelos de barra no son capaces de reproducir diferentes modos de falla como las fallas por cortante o torsión. Además, las simplificaciones hechas en dichos modelos afectan su capacidad de reproducir modos más comunes como la falla por flexión o fuerza axial. El objetivo principal de esta tesis es desarrollar una herramienta numérica robusta y eficiente capaz de reproducir distintos tipos de falla de elementos de barra de hormigón armado. También se desea que el modelo sea capaz de reproducir fenómenos complejos como el confinamiento pasivo de manera objetiva. La herramienta desarrollada tiene por objeto ser usada en el diseño o evaluación de estructuras de escala completa bajo cargas genéricas. Para esto, el problema es abordado mediante un marco multinivel. A nivel constitutivo, se desarrolla un nuevo modelo de daño-plástico para hormigón que incorpora un parámetro de dilatancia variable. Se demuestra que la dilatancia afecta la libre expansión del hormigón, el comportamiento en ablandamiento bajo esfuerzos cortantes y la respuesta de elementos pasivamente confinados. El modelo se basa en un reconocido modelo de daño-plástico, al cual se incorpora un parámetro de dilatancia que depende de los estados de daño-plástico y de tensiones. A nivel seccional, se desarrolla un nuevo modelo que introduce una eficiente técnica numérica. El nuevo modelo se basa en un modelo seccional con interacción total que reproduce el comportamiento cinemático de la sección por medio de un campo de desplazamientos de dos componentes. Una componente satisface la tradicional hipótesis de Euler-Bernoulli mientras que el campo complementario reproduce el alabeo y la distorsión. Este último campo permite al modelo obtener los tensores tridimensionales de tensión y deformación en cada punto de la sección. Dicho campo es obtenido a través de considerar el equilibrio tridimensional entre fibras. El campo de desplazamientos es expresado mediante un conjunto de funciones b-spline predefinidas en el dominio de la sección transversal. Así, se obtiene una reducción significativa de los grados de libertad requeridos en la solución del problema seccional comparado con una solución de elementos finitos. Esto hace al modelo adecuado para su implementación a nivel elemento. A nivel del elemento se utiliza una formulación basada en fuerzas la cual satisface de forma estricta el equilibrio entre fuerzas nodales y esfuerzos internos. En cada punto de integración, el modelo seccional es utilizado para representar el comportamiento seccional. Los modelos son implementados en un programa de código abierto y colaborativo enfocado en el análisis sísmico no lineal de estructuras. Los modelos presentados son validados de forma separada y conjunta, mediante la comparación de resultados numéricos con ensayos experimentales disponibles en la literatura. Se incluye un amplio rango de resistencias de hormigón, materiales de refuerzo, geometrías de secciones y configuraciones de refuerzo. Se simulan varias condiciones de carga haciendo énfasis en la capacidad del modelo de reproducir distintos modos de falla. Finalmente, se simula un puente real de escala com
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Al-Sadoon, Zaid. "Seismic Retrofitting of Conventional Reinforced Concrete Moment-Resisting Frames Using Buckling Restrained Braces." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34755.
Full textAbstract:
Reinforced concrete frame buildings designed and built prior to the enactment of modern seismic codes of the pre-1970’s era are considered seismically vulnerable, particularly when they are subjected to strong ground motions. It is the objective of this research to develop a new and innovative seismic retrofit technology for seismic upgrading of nonductile or limited ductility reinforced concrete frame buildings involving the implementation of buckling restrained braces. To achieve this objective, combined experimental and analytical research was conducted. The experimental research involved tests of large-scales reinforced concrete frames under slowly applied lateral deformation reversals, and the analytical research involved design and nonlinear analysis of laboratory specimens, as well as design and dynamic inelastic response history analysis of selected prototype buildings in eastern and western Canada. The research project started with a comprehensive review of the building code development in Canada to assess the progression of seismic design requirements over the years, and to select a representative period within which a significant number of engineered buildings were designed and constructed with seismic deficiencies. A similar review of seismic design and detailing provisions of the Canadian Standard Association (CSA) Standard A23.3 on Design of Concrete Structures was also conducted for the same purpose. Six-storey and ten-storey prototype buildings were designed for Ottawa and Vancouver, using the seismic provisions of the 1965 National Building Code of Canada, representative of buildings in eastern and western Canadian. Preliminary static and dynamic linear elastic analyses were performed to assess the effectiveness of upgrading the ten-storey reinforced concrete building designed for Ottawa. The retrofit methods studied consisted of lateral bracing by adding reinforced concrete shear walls, diagonal steel braces, or diagonal steel cable strands. The results indicated that the retrofit techniques are effective in limiting deformations in non-ductile frame elements to
the elastic range. The numerical analyses were used to demonstrate the effectiveness of Buckling Restrained Braces (BRBs) as a retrofit method for seismically deficient reinforced concrete frame buildings. The experimental phase of research consisted of two, 2/3rd scale, single bay and single storey reinforced concrete frames, designed and constructed based on a prototype sixstorey moment resisting frame building located in Ottawa and Vancouver, following the
requirements of the 1965 edition of the NBCC. One test specimen served as a bare
control frame (BCF) that was first tested, repaired and retrofitted (RRF) to evaluate the effectiveness of the proposed retrofit methodology for buildings subjected to
earthquakes in the City of Ottawa. The control frame was assessed to be seismically
deficient. The second frame served as a companion non-damaged frame (RF) that was retrofitted with a similar retrofit concept but for buildings subjected to earthquakes in the City of Vancouver.
A new buckling restrained brace (BRB) was conceived and developed to retrofit existing sub-standard reinforced concrete frames against seismic actions. The new BRB consists of a ductile inner steel core and an outer circular sleeve that encompasses two circular steel sections of different diameters to provide lateral restraint against buckling in compression of inner steel core. Mortar is placed between the two circular sections to provide additional buckling resistance. The inner core is connected to novel end units that allow extension and contraction during tension-compression cycles under seismic loading while providing lateral restraint against buckling within the end zones. The end units constitute an original contribution to the design of Buckling Restrained Braces (BRBs), providing continuous lateral restraint along the core bar. The new technique has
been verified experimentally by testing four BRBs on the two test structures under
simulated seismic loading. The test results of the BRB retrofitted frames indicate
promising seismic performance, with substantial increases in the lateral load and
displacement ductility capacities by factors of up to 3.9 and 2.6, respectively. In addition, the test results demonstrate that the BRB technology can provide excellent drift control, increased stiffness, and significant energy dissipation, while the reinforced concrete frames continue fulfilling their function as gravity load carrying frames. The above development was further verified by an exhaustive analytical study using SAP2000. At the onset, analyses were conducted to calibrate and verify the analytical models. Two-dimensional, one-bay, one-storey models, simulating the BCF and RRF test frames, were created. The models were subjected to incrementally increasing lateral displacement reversals in nonlinear static pushover analyses, and the results were compared with those obtained in the test program. Material nonlinearity was modeled using “Links” to incorporate all lumped linear and nonlinear properties that were defined with moment-rotation properties for flexural frame members and with force-displacement properties for the diagonal buckling restrained braces. Comparison with test data demonstrated good agreement of the frame behaviour in the elastic and post-elastic ranges, and the loading and unloading stiffness. The research program was further augmented with nonlinear dynamic time history analyses to verify the feasibility of the new retrofit technique in multi-storey reinforced concrete frame buildings located in Canada and their performances relative to the performance-based design objectives stated in current codes. Prior to conducting the analyses, 450 artificial earthquake records were studied to select the best matches to the Uniform Hazard Spectra (UHS) according to the 2010 edition of the NBCC for Ottawa and Vancouver. Furthermore, additional analyses were conducted on buildings for the City of Ottawa based on amplified Uniform Hazard Spectrum compatible earthquake records. The nonlinear time-history response analyses were conducted using a model that permits inelasticity in both the frame elements and the BRBs.The results indicated that reinforced concrete buildings built before the 1970’s in the City of Ottawa do not require seismic retrofitting; they remain within the elastic range under current code-compatible earthquake records. The structural building performance is
within the Immediate Occupancy level, and all structural elements have capacities
greater than the force demands. In the City of Vancouver, buildings in their virgin state experienced maximum interstorey drifts of 2.3%, which is within the Collapse Prevention structural performance level. Improved building performance was realized by retrofitting the exterior frames with multiple uses of the BRB developed in this research project. The seismic shear demands were reduced in the columns, while limiting the deformations in the non-ductile frame elements to the elastic range. The lateral interstorey drift was limited to 0.92%, which lies within the Life Safety structural performance level.
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Salinas, Guayacundo Daniel Ricardo. "Nonlinear Truss Analysis of Non-ductile Reinforced Concrete Frames with Unreinforced Masonry Infills." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/79790.
Full textAbstract:
Non-ductile Reinforced Concrete Frames (RCF) with and without Unreinforced Masonry (URM) infills can be found in many places around the world including the Western United States, Eastern Europe, Asia and Latin America. These structures can have an unsatisfactory seismic performance which may even lead to collapse due to brittle failure modes. Furthermore, the effect of the infills on the seismic response of the structural system is not always accounted for in analysis and design. At present, there is no consensus on whether masonry infills are beneficial (by increasing the resistance of the system) or detrimental (by leading to brittle failure modes) for RCF construction.
This study focuses on the development of a simplified modeling approach for non-ductile RCF with URMI that combines the simplicity of strut-and-tie models with the accuracy of Nonlinear Finite Element Analysis (NLFEA). Despite the fact that NLFEA procedures are the most advanced way to address the structural analysis of RCF with URM infills, their conceptual complexity and computational cost may hinder their widespread adoption as an analysis and design tool. At the same time, simplified methods, such as those based on the equivalent strut concept, may be overly crude and neglect essential aspects of the nonlinear response. To address the need for an adequately accurate, but computationally and conceptually efficient analysis method, this study establishes a novel method for planar RCF with URM infills subjected to lateral loads. The method, which is based on the Nonlinear Truss Analogy (NLTA) is shown to have an accuracy comparable to that of NLFEA. Specifically, the method is shown to adequately capture the strength and stiffness degradation and the damage patterns while entailing a reduced computational cost (compared to that of NLFEA). The proposed method is expected to bridge the gap between overly crude equivalent strut models and computationally expensive NLFEA.<br>Ph. D.
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Patel, Jayendra R. "Post processor for design of reinforced concrete space frames using object oriented programming." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07292009-090457/.
Full text
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Sha'lan, Ahmad Abdulkareem Saker. "Seismic performance of self-centering frames composed of precast post-tensioned concrete encased in FRP tubes." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Fall2009/a_shalan_120709.pdf.
Full textAbstract:
Thesis (M.S. in civil engineering)--Washington State University, December 2009.<br>Title from PDF title page (viewed on Feb. 4, 2010). "Department of Civil Engineering." Includes bibliographical references (p. 134-135).
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Haselton, Curt B. Deierlein Gregory G. "Assessing seismic collapse safety of modern reinforced concrete moment-frame buildings." Berkeley, Calif. : Pacific Earthquake Engineering Research Center, 2008. http://nisee.berkeley.edu/elibrary/Text/200803261.
Full text
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Guney, Murat Efe. "A Numerical Procedure For The Nonlinear Analysis Of Reinforced Concrete Frames With Infill Walls." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606318/index.pdf.
Full textAbstract:
Materially non-linear analysis of reinforced concrete frame structures with infill walls requires appropriate mathematical models to be adopted for the beams and the columns as well as the infill walls. This study presents a mathematical model for frame elements based on a 3D Hermitian beam/column finite element and an equivalent strut model for the infill walls. The spread-of-plasticity approach is employed to model the material nonlinearity of the frame elements. The cross-section of the frame element is divided into triangular sub regions to evaluate the stiffness properties and the response of the element cross-section. By the help of the triangles spread over the actual area of the section, the bi-axial bending and the axial deformations are coupled in the inelastic range. A frame super-element is also formed by combining a number of frame finite elements.
Two identical compression-only diagonal struts are used for modeling the infill. The equivalent geometric and material properties of the struts are determined from the geometry of the infill and the strength of the masonry units
A computer code is developed using the object-oriented design paradigm and the models are implemented into this code. Efficiency and the effectiveness of the models are investigated for various cases by comparing the numerical response predictions produced by the program with those obtained from experimental studies.
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Celik, Ozan Cem. "Probabilistic Assessment of Non-Ductile Reinforced Concrete Frames Susceptible to Mid-America Ground Motions." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16208.
Full textAbstract:
The infrequent nature of earthquakes in the Central and Eastern United States (CEUS), and the fact that none with intensity comparable to the New Madrid sequence of 1811 12 or the Charleston earthquake of 1886 has occurred in the past century, have caused the earthquake hazard in the region to be ignored until quite recently. The seismic performance of reinforced concrete (RC) frames in the CEUS, which have primarily been designed for gravity load effects, is expected to be deficient when subjected to earthquakes that are judged, in recent seismological research, as being plausible in the New Madrid Seismic Zone (NMSZ). The objective of this study is to develop a set of probability-based tools for efficient uncertainty analysis and seismic vulnerability and risk assessment of such gravity load designed (GLD) RC frames and to use these tools in evaluating the seismic vulnerability of RC frames that are representative of the building inventory in Memphis, TN the largest population center close to the NMSZ.
Synthetic earthquake ground motions for the CEUS that are available from two different Mid-America Earthquake (MAE) Center projects were used in the finite element-based simulations for determining the seismic demand on the GLD RC frames by nonlinear time history analysis (NTHA). A beam-column joint model was developed to address the deficiencies in the joints of GLD frames and was incorporated in the finite element structural models. Seismic fragilities were derived for low-, mid-, and high-rise GLD RC frames. Various sources of uncertainty were propagated through the analysis, and their significance for fragility assessment was examined. These fragilities were used to evaluate the vulnerability of the RC frame inventory in Memphis, TN with regard to performance-based design objectives, defined in terms of performance levels associated with reference earthquake hazard levels. This performance appraisal indicated that GLD RC frames do not meet the life safety and collapse prevention performance objectives that are found in recent building codes and guidelines for performance-based earthquake engineering.
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Charlet, Arnaud Yves. "Hybrid simulation and its application to the gravity load collapse of reinforced concrete frames." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31585.
Full textAbstract:
The structural testing method called hybrid simulation is implemented at the University of British Columbia. A tutorial is presented to assist the user on how to perform hybrid simulation of structural systems using the finite element software OpenSees, the software framework for hybrid simulation OpenFresco and an event-driven predictor-corrector scheme ensuring continuous testing. Geographically distributed hybrid simulation is introduced and distributed tests performed between the University of British Columbia and the University of California, Berkeley, are described. A hybrid simulation test setup is developed to investigate and validate the application of hybrid simulation to the gravity load collapse of reinforced concrete frames. A shear-critical reinforced concrete column loaded through three dynamic actuators constitutes the physical substructure while a nonlinear ductile reinforced concrete frame makes up the numerical substructure within the OpenSees environment. A nonlinear transformation method is implemented to allow for an accurate application of the three-degree-of-freedom loading on the specimen through the three-actuator test setup, and a specific predictor-corrector algorithm with variable actuator speed is designed to ensure smooth continuous testing despite the use of an implicit iterative integration scheme. Furthermore, a methodology using an iterative predictor-corrector algorithm with mode-switch is developed to enable the use of force control for the actuators in combination with a displacement-based finite element analysis engine. Results from the hybrid tests are compared with a shaking table test of the same structure, and are shown to exhibit the same general behaviour: shear and axial load failure of the shear-critical column followed by gravity load redistribution. However, the inability of the analytical model to capture the residual drifts observed in the shake table tests resulted in an underprediction of the drift demand on the system.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
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Alsiwat, Jaber. "Effect of anchorage slip and inelastic shear on seismic response of reinforced concrete frames." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/7922.
Full textAbstract:
Reinforced Concrete structures located in regions of high seismic activity are expected to develop inelastic deformations in their critical regions. Therefore, inelastic dynamic analysis is required to obtain reliable predictions of structural behavior during an earthquake. Tests on reinforced concrete elements and subassemblages have shown that anchorage slip and inelastic shear deformations can be as significant as those due to inelastic flexure, in the critical regions. Hence, a proper seismic analysis should include inelastic deformations due to anchorage slip, shear and flexure. Flexural response has been researched extensively in the past. Research on the effects of anchorage slip and shear inelasticity is scarce in the literature. The effect of anchorage slip and inelastic shear on seismic response of moment-resisting reinforced concrete frames is investigated in this study. A hysteretic model for anchorage slip is developed in the first phase of the project. The model consists of a primary curve and a set of hysteretic rules. The primary curve is developed based on assuming inelastic strain distribution along the embedded length of reinforcing bars. Considerations are given for conditions existing at interior joints, exterior joints, and column-foundation interface. Hysteretic rules are derived based on observations from available experimental data. The model is verified against a large volume of experimental data conducted on single straight and hooked bars, as well as interior and exterior joints. In the second phase of the project, the hysteretic anchorage-slip model is implemented into the nonlinear dynamic analysis program Drain 2D. A recently derived hysteretic model for shear is also implemented into the program. Two major subroutines, SLIPM and SHEARM, are added in order to trace out nonlinearity in the anchorage-slip and shear models. The program is enhanced with calculations of ductility demand and energy dissipation factors. Related input and output features of the program are also enhanced. In the final phase of the project, the enhanced computer program is used to determine the seismic response of three reinforced concrete frames that were designed for this purpose. Emphasis is placed on determining effects of individual deformation components on ductility demands and overall deformation characteristics of the frames. The effect of interaction of the fundamental period of vibration of the structure and the frequency content of ground motion are also investigated. The study shows that anchorage slip reduces flexural ductility demand by up to 42%. The amount of reduction is shown to depend on the level of inelasticity experienced by the structure. Overall behavior of the structures is not affected significantly by anchorage slip. Inelastic shear is shown to have very little effect on the behavior of the frames investigated.