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1
Toro, Andrea del Pilar. "Effect of Lateral Stiffness on Bridge Deck Performance." UNF Digital Commons, 2015. http://digitalcommons.unf.edu/etd/587.
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The use of the empirical deck design method has increased its acceptance due to the economic advantages that it presents when compared to its counterpart, the traditional method. This can be attributed to the fact that the empirical method provides an appropriate design where the deck withstands stress not only due to the steel reinforcement but to an implicit arching membrane stress set-up as an effect of the lateral restraint surrounding the deck slab known as Compressive Membrane Action (CMA).
It has been proved through research that most design codes underestimate the strength of laterally restrained slabs. However, there is still a lack of acceptance in practical bridge design codes. This thesis presents an analysis addressing the influence that the lateral stiffness of the support beams has on the overall bridge deck performance. The lateral stiffness behavior was assessed through a programmed electronic spreadsheet where a comparison with different current code requirements and an additional approach was made.
Through this analysis it was determined that not only does the support beam lateral stiffness plays an important role in the overall bridge deck slab ultimate capacity, but mapping out this influence is a priority that may also be useful in setting the basis for future design criteria.
2
Atasoy, Mehmet. "Lateral Stiffness Of Unstiffened Steel Plate Shear Wall Systems." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609219/index.pdf.
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Finite element method and strip method are two widely used techniques for analyzing steel plate shear wall (SPSW) systems. Past research mostly focused on the prediction of lateral load capacity of these systems using these numerical methods. Apart from the lateral load carrying capacity, the lateral stiffness of the wall system needs to be determined for a satisfactory design. Lateral displacements and the fundamental natural frequency of the SPSW system are directly influenced by the lateral stiffness. In this study the accuracy of the finite element method and strip method of analysis are assessed by making comparisons with experimental findings. Comparisons revealed that both methods provide in general solutions with acceptable accuracy. While both methods offer acceptable solutions sophisticated computer models need to be generated. In this study two alternative methods are developed. The first one is an approximate hand method based on the deep beam theory. The classical deep beam theory is modified in the light of parametric studies performed on restrained thin plates under pure shear and pure bending. The second one is a computer method based on truss analogy. Stiffness predictions using the two alternative methods are found to compare well with the experimental findings. In addition, lateral stiffness predictions of the alternate methods are compared against the solutions provided using finite element and strip method of analysis for a class of test structures. These comparisons revealed that the developed methods provide estimates with acceptable accuracy and are simpler than the traditional analysis techniques.
3
Caupp, Sarah N. "PMHS Shoulder Stiffness Determined by Lateral and Oblique Impacts." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397649566.
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Wong, Kin Ming. "Evolutionary structural form optimisation for lateral stiffness design of tall buildings /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202007%20WONGK.
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Hu, Ye. "Lateral Torsional Buckling of Wooden Beams with Mid-Span Lateral Bracing." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35076.
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An analytical and numerical investigation is conducted for the lateral torsional buckling analysis of wooden beam with a mid-span lateral brace subjected to symmetrically distributed loading. Two models are developed; one for the case of a rigid brace and another one for the case of a flexible brace. The analytical solutions are based on the principle of stationary potential energy and a Fourier expansion of the buckling displacement fields and bending moments. The validity of both models are verified against 3D finite element analyses in ABAQUS. Where applicable, verifications were also conducted against available solutions from previous studies. Parametric studies were conducted to investigate the effect of geometric and material parameters on the critical moments. The results indicate the presence of two separate groups of potential buckling modes, symmetric and anti-symmetric, with fundamentally different behavioural characteristics. The governing buckling mode is shown to depend on the bracing height, load height and lateral brace stiffness. The study shows that beyond a certain threshold bracing height, the critical moment is governed by the antisymmetric mode of buckling. Also, above a certain optimum bracing stiffness, no increase is observed in the critical moments. The models developed are used to construct a comprehensive database of parametric investigations which are then employed for developing simplified equations for determining the threshold heights, associated critical moments, and optimum stiffness.
6
Judd, Clinton T. "LATERAL-TORSIONAL VIBRATION OF A SIDE-LOADED ROTOR WITH ASYMMETRIC SHAFT STIFFNESS." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/288.
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Using energy equations a four degrees of freedom analytical model is developed for a two-disk rotor with shaft stiffness asymmetry. A radial constant force is applied to the outboard disk to emphasize the effects of gravity or aerodynamic side loading. Special emphasis is placed on characterizing the lateral and torsional vibration trends associated with shaft asymmetry which may be used to identify failing shafts in operational rotor systems. Simulation reveals distinct patterns in lateral and torsional response, with strong dependencies on the magnitude of the side load, magnitude of the asymmetry and proximity of the lateral and torsional natural frequencies. Notable interaction is also observed between the lateral and torsional response. Lateral response peaks are found to correlate to torsional response peaks under some conditions. An experiment is performed to compare the response of a real system with the simulated model.
7
Forrester, Merville Kenneth. "Stiffness Model of a Die Spring." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/32249.
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The objective of this research is to determine the three-dimensional stiffness matrix of a rectangular cross-section helical coil compression spring. The stiffnesses of the spring are derived using strain energy methods and Castiglianoâ s second theorem.
A theoretical model is developed and presented in order to describe the various steps undertaken to calculate the springâ s stiffnesses. The resulting stiffnesses take into account the bending moments, the twisting moments, and the transverse shear forces. In addition, the springâ s geometric form which includes the effects of pitch, curvature of wire and distortion due to normal and transverse forces are taken into consideration.
Similar methods utilizing Castiglianoâ s second theorem and strain energy expressions were also used to derive equations for a circular cross-section spring. Their results are compared to the existing solutions and used to validate the equations derived for the rectangular cross-section helical coil compression spring.
A finite element model was generated using IDEAS (Integrated Design Engineering Analysis Software) and the stiffness matrix evaluated by applying a unit load along the springâ s axis, then calculating the corresponding changes in deformation. The linear stiffness matrix is then obtained by solving the linear system of equations in changes of load and deformation. This stiffness matrix is a six by six matrix relating the load (three forces and three moments) to the deformations (three translations and three rotations). The natural frequencies and mode shapes of a mechanical system consisting of an Additional mass and the spring are also determined.
Finally, a comparison of the stiffnesses derived using the analytical methods and those obtained from the finite element analysis was made and the results presented.Master of Science
8
Barber, Melinda A. "Contribution of Shear Connections to the Lateral Stiffness and Strength of Steel Frames." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307442652.
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Voinier, Steven. "Passive Stiffness Characteristics of the Scoliotic Lumbar Torso in Trunk Flexion, Extension, Lateral bending, and Axial Rotation." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/52241.
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As the average American age increases, there is a need to study the spine biomechanics of adults with scoliosis. Most studies examining the mechanics of scoliosis have focused on in vitro testing or computer simulations, but in vivo testing of the mechanical response of a scoliotic spine has not yet been reported. The purpose of this study was to quantitatively define the passive stiffness properties of the in vivo scoliotic spine in three principle anatomical motions and identify differences relative to healthy controls.
Scoliotic (n=14) and control (n=17) participants with no history of spondylolisthesis, spinal fracture, or spinal surgery participated in three different tests (torso lateral side bending, torso axial rotation, and torso flexion/extension) that isolated mobility to the in vivo lumbar spine. Scoliotic individuals with Cobb angles ranging 15-75 degrees were accepted. Applied torque was measured using a uni-directional load cell, and inertial measurement units (IMU) recorded angular displacement of the upper torso relative to the pelvis and lower extremities. Torque-rotational displacement data were fit using a double sigmoid function, resulting in excellent overall fit (R2 > 0.901). The neutral zone (NZ) width, or the range of motion where there is minimal internal resistance, was then calculated. Stiffnesses within the NZ and outside of the NZ were also calculated. Stiffness asymmetries were also computed within each trial. These parameters were statistically compared between factor of population and within factor of direction.
There was an interaction effect between populations when comparing axial twist NZ width and lateral bend NZ width. The lateral bend NZ width magnitude was significantly smaller in scoliotic patients. NZ stiffness in the all three directions was greater in the scoliotic population. There was no significant difference in asymmetrical stiffness between populations.
The present study is the first investigation to quantify the in vivo neutral zone and related mechanics of the scoliotic lumbar spine. Future research is needed to determine if the measured lumbar spine mechanical characteristics can help explain progression of scoliosis and complement scoliosis classification systems.Master of Science
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Mensah, Frederick Ayisi. "Comparison of Strength, Stiffness and Ductility of Reduced Beam Section Subjected to Lateral Loads Only and Combined Gravity And Lateral Loads." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2434.
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Lateral loads from Northridge Earthquake in 1994 caused brittle fractures at column-beam connections in rigid frame structures which hitherto were thought to have high ductility to resist such brittle fractures. These brittle fractures were caused by the moment frame connections’ inability to undergo inelastic deformation which eventually resulted in several structural damages. Reduced beam section (RBS) connection was among one of the solutions proposed by researchers following the Northridge Earthquake. In RBS connections, part of the beam flanges or web at a distance from the face of the column is selectively cut off to reduce its capacity in order to induce plastic hinge away from the beam-column interface. Reducing the beam section, weakens the beam and allows the groove welds and the panel zone to have a higher strength compared to the beam, thereby achieving stronger column-weaker beam design which have a better seismic performance. RBS must provide adequate combination of stiffness, strength and ductility in order to ensure acceptable seismic performance. The scope of this study is to compare strength, ductility and stiffness of reduced beam section under lateral loads only and combined gravity and lateral loads. Four finite element models were created with all conditions kept constant except loading conditions on the frames. Results from this study indicates that all models have almost the same stiffness with the models under combined gravity and lateral loads having higher ductility and ultimate strength.
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Villasenor, Aguilar Jose Maria. "Lateral-Torsional Buckling Instability Caused by Individuals Walking on Wood Composite I-Joists." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19212.
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Recent research has shown that a significant number of the falls from elevation occur when laborers are working on unfinished structures. Workers walking on wood I-joists on roofs and floors are prone to fall hazards. Wood I-joists have been replacing dimension lumber for many floor systems and a substantial number of roof systems in light-frame construction. Wood I-joists are designed to resist axial stresses on the flanges and shear stresses on the web while minimizing material used. However, wood I-joists have poor resistance to applied lateral and torsional loads and are susceptible to lateral-torsional buckling instability. Workers walking on unbraced or partially braced wood I-joists can induce axial and lateral forces as well as twist. Experimental testing demonstrated that workers cause lateral-torsional buckling instability in wood I-joists. However, no research was found related to the lateral-torsional buckling instability induced by individuals walking on the wood I-joists. Furthermore, no research was found considering the effects of the supported end conditions and partial bracing in the lateral-torsional buckling instability of wood I-joists.The goal of this research was to derive mathematical models to predict the dynamic lateral-torsional buckling instability of wood composite I-joists loaded by individuals walking considering different supported end conditions and bracing system configurations. The dynamic lateral-torsional buckling instability was analyzed by linearly combining the static lateral-torsional buckling instability with the lateral bending motion of the wood I-joists. Mathematical models were derived to calculate the static critical loads for the simply supported end condition and four wood I-joist hanger supported end conditions. Additionally, mathematical models were derived to calculate the dynamic maximum lateral displacements and positions of the individual walking on the wood I-joists for the same five different supported end conditions. Three different lean-on bracing systems were investigated, non-bracing, one-bracing, and two-bracing systems. Mathematical models were derived to calculate the amount of constraint due to the lean-on bracing system. The derived mathematical models were validated by comparison to data from testing for all supported end conditions and bracing systems.
The predicted critical loads using the static buckling theoretical models for the non-bracing system and the static buckling theoretical models combined with the bracing theoretical models for the simply and hanger supported end conditions agreed well with the critical loads obtained from testing for the two wood I-joist sizes investigated. The predicted maximum lateral displacements and individual positions using the bending motion theoretical models for the simply and hanger supported end conditions agreed well with the corresponding maximum lateral displacements and individual positions obtained from testing for both wood I-joist sizes. Results showed that; a) the supported end condition influenced the critical loads, maximum lateral displacements and individual positions, b) the bracing system increased the critical loads and reduced the maximum lateral displacements, c) the critical load increased as the load position displaced away from the wood I-joist mid-span, d) the critical load reduced as the initial lateral displacement of the wood I-joist increased and e) the wood I-joist mid-span was the critical point in the dynamic lateral-torsional buckling instability.
Ph. D.
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Bamberg, Christopher Ryan. "Lateral Movement of Unbraced Wood Composite I-Joists Exposed to Dynamic Walking Loads." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/31977.
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The research summarized in this thesis is comprised of an experimental analysis of the mechanical behavior of a wood composite I-joist with different bracing configurations exposed dynamic walking loads. Three 16 in. deep GPI® 65 I-joists were simply supported and laid parallel to each other, while the bracing was attached to the top flange. Five different brace stiffnesses were used: zero stiffness (control), 1.2 lb/in., 8.5 lb/in., 14.0 lb/in. and infinitely stiff. Two different brace configurations were used: one-quarter of the span length (60 in.) and one third the span length (80 in.). The dynamic walking loads consisted of human test subjects attached to a safety platform walking across the I-joist at a designated pace. Experimental results for this research consisted of the I-joistâ s lateral accelerations, lateral displacements and twist. An Analysis of Covariance (ANCOVA) was used for the statistical analysis of the results and was performed for each measurement. The statistical analysis determined the effects of different bracing configurations, stiffnesses, measurement locations as well as test subjectsâ weight and occupation.
Test results and observed trends are provided for all test configurations. Lateral displacement and twist experienced the same trend throughout the experiment: as brace stiffness increased, lateral displacement and twist decreased. This correlated with basic beam theory and bracing fundamentals. It should be noted that as the stiffness increased, the effect on lateral displacement and twist response decreased.
However, the trend for lateral displacement and twist was not observed for the lateral accelerations. The 1.2 lb/in. brace stiffness had much larger lateral accelerations for the 60 in. brace configuration throughout the span and were also larger at the bracing point for the 80 in. brace configuration. This could have been due to the energy applied from the springs or a natural frequency of the I-joist system could have been reached during testing. However, the other four brace stiffnesses followed the same trend as the lateral displacements and twist.
In addition, this research demonstrates a method for the measurement of lateral buckling due to worker loads. The mitigation of lateral buckling can use appropriate bracing systems. The measurements of the change in lateral buckling behavior can be used to develop safety devices and ultimately ensure the protection of construction workers.
Master of Science
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Cilingir, Ulas. "A Model Study On The Effects Of Wall Stiffness And Surcharge On Dynamic Lateral Earth Pressures." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606215/index.pdf.
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A model study on laterally braced sheet pile walls retaining cohesionless soil was conducted
using 1-g shaking table. Lateral dynamic earth pressures, backfill accelerations and dynamic
displacement of walls were measured. Input accelerations were kept between 0.03g to 0.27g. A
data acquisition system consisting of dynamic pressure transducers, accelerometers,
displacement transducer, signal conditioning board and a data acquisition card compatible with a
personal computer was used during the study. Three different walls with thicknesses of 6.6, 3.2
and 2.0 mm were used in order to investigate the effects of changing wall stiffness value on
lateral seismic pressures developed on the wall. In addition to that, steel blocks were placed on
top of the backfill in order to simulate a surcharge effect of 1.57 kPa to 3.14 kPa during shaking.
Amplification of input acceleration, incremental seismic lateral thrusts and corresponding
maximum dynamic pressures, application point of the resultant, effect of stiffness and surcharge
on maximum seismic lateral thrust and dynamic wall deflections were calculated by processing
raw data stored. The results were compared to previous model studies and some analytical
methods available.
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Verma, Amber. "Influence of Column-Base Fixity On Lateral Drift of Gable Frames." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/42686.
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In a typical light metal building, the structural members are designed for the forces and moments obtained from the wind drift analysis, which assumes pinned connections at the base. The pinned connections provide no moment at the base and have zero rotational stiffness. However, in reality every connection provides some restraint and has some rotational stiffness. Hence, by considering a modeling assumption of pinned condition, the actual behavior of the connection is not captured and this results in overestimation of lateral drifts and appearance of larger moments at the knee of the gable frames. Since the structural components are designed on the basis of these highly conservative results, the cost of the project increases. This thesis investigates the real behavior of the column base connection and tries to reduce the above stated conservatism by developing a computer program or â wizardâ to calculate the initial rotational stiffness of any column base connection.
To observe the actual behavior of a column base connection under different load cases, a number of finite element models were created in SAP2000. Each finite element model of the column base connection contained base plate, column stub, anchor bolts and in some cases grout as its components. The model was mainly subjected to three load cases, namely gravity, wind and gravity plus wind. After performing many analyses, the influence of flexibility of each component on the flexibility of the connection was observed and a list of parameters was created. These parameters are the properties of above mentioned components which characterizes any column base connection. These parameters were then used as inputs to model any configuration of the column base connection in the developed wizard. The wizard uses OpenSees and SAP2000 to analyze the modeled configuration of the connection and provides values of the initial rotational stiffness and maximum bearing pressure for the provided loads. These values can be further used in any structural analysis which is done to calculate the lateral drift of a frame under lateral loads. This will also help in getting results which are less conservative than the results which one gets on assuming pinned condition at the base.Master of Science
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Basoenondo, Essy Arijoeni. "Lateral load response of Cikarang brick wall structures : an experimental study." Queensland University of Technology, 2008. http://eprints.qut.edu.au/16685/.
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Despite their poor performance, non-standard clay bricks are commonly used in construction of low-rise buildings and rural houses in Indonesia. These clay bricks are produced traditionally in home industries. Indonesia is located in an active seismic region and many masonry buildings were badly damaged or collapsed during recent earthquakes. Such buildings are classified as non-engineered structures as they are built without using any proper design standard. Lateral load response of un-reinforced masonry walls is investigated in this research project, with the aim of better understanding the behaviour of these masonry walls using low quality local bricks. A comprehensive experimental program was undertaken with masonry wall elements of 600 mm x 600 mm x 110 mm constructed from local bricks from Cikarang in West Java - Indonesia. Wall specimens were constructed and tested under a combination of constant vertical compression load and increasing horizontal or lateral in-plane loads, of monotonic, repeated and cyclical nature. The vertical compressive loading was limited to 4% of maximum brick compressive strength. Masonry mortar mix used to construct the specimens was prepared according to Indonesian National Standard. Three different types of masonry wall panels were considered, (i) (normal) brick masonry walls, (ii) surface mortared brick masonry walls and (iii) comforted surface mortared brick masonry walls. The results indicated that the lateral load bearing capacity of masonry wall is usually lower than that of mortared and comforted walls. Despite this, the lateral load capacity under cyclic loads decreased 50 % of the average capacity of the walls under monotonic and repeated lateral loads. Using the results from the experimental program, a simplified model for the equivalent diagonal spring stiffness of local clay brick walls was developed. This stiffness model derived from experimental results in then used to simplify the structural analysis of clay brick wall panels in Indonesia. The design guideline for brick masonry houses and low-rise buildings in six Indonesian seismic zones was developed, as a contribution towards the development of design guidance for constructing brick masonry houses in Indonesia.
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Sorensen, Taylor J. "Quantifying the Lateral Bracing Provided by Standing Steam Roof Systems." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/4695.
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One of the major challenges of engineering is finding the proper balance between economical and safe. Currently engineers at Nucor Corporation have ignored the additional lateral bracing provided by standing seam roofing systems to joists because of the lack of methods available to quantify the amount of bracing provided. Based on the results of testing performed herein, this bracing is significant, potentially resulting in excessively conservative designs and unnecessary costs.
This project performed 26 tests with Vulcraft joists in a pressure box to investigate the effects of how many variables influence the lateral bracing provided to joists from standing seam roofing systems, including the variables joist length, panel gauge, clip height, thermal block presence, insulation thickness, and top chord size. Two methods were developed to account for this additional bracing: finite element computer modeling and an application of the Rayleigh-Ritz method called the Column-on-Elastic-Foundation Method.
Variables influencing the pressure at failure, namely chord size and deck gauge, were those with the greatest effect on additional lateral bracing provided from standing seam roof systems. It was determined that higher roof stiffness values and higher failure pressures yield shorter effective lengths.
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Seek, Michael Walter. "Prediction of Lateral Restraint Forces in Sloped Z-section Supported Roof Systems Using the Component Stiffness Method." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28357.
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Z-sections are widely used as secondary members in metal building roof systems. Lateral restraints are required to maintain the stability of a Z-section roof system and provide resistance to the lateral forces generated by the slope of the roof and the effects due to the rotation of the principal axes of the Z-section relative to the plane of the roof sheathing. The behavior of Z-sections in roof systems is complex as they act in conjunction with the roof sheathing as a system and as a light gage cold formed member, is subject to local cross section deformations.
The goal of this research program was to provide a means of predicting lateral restraint forces in Z-section supported roof systems. The research program began with laboratory tests to measure lateral restraint forces in single and multiple span sloped roof systems. A description of the test apparatus and procedure as well as the results of the 40 tests performed is provided in Appendix II.
To better understand the need for lateral restraints and to provide a means of testing different variables of the roof system, two types of finite element models were developed and are discussed in detail in appended Paper I. The first finite element model is simplified model that uses frame stiffness elements to represent the purlin and sheathing. This model has been used extensively by previous researchers and modifications were made to improve correlation with test results. The second model is more rigorous and uses shell finite elements to represent the Z-section and sheathing.
The shell finite element model was used to develop a calculation procedure referred to as the Component Stiffness Method for predicting the lateral restraint forces in Z-section roof systems. The method uses flexural and torsional mechanics to describe the behavior of the Z-section subject to uniform gravity loads. The forces generated by the system of Z-sections are resisted by the "components" of the system: the lateral restraints, the sheathing and Z-section-to-rafter connection. The mechanics of purlin behavior providing the basis for this method are discussed in appended Paper II. The development of the method and the application of the method to supports restraints and interior restraints are provided in appended papers III, IV and V.Ph. D.
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Bolte, John Henry IV. "Injury and impact response of the shoulder due to lateral and oblique loading." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1078873704.
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Sargent, Brandon Scott. "Using Collapsible Systems to Mitigate Buckling in Thin Flexible Instruments in Robotic Surgery." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7341.
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Robotic surgery procedures may include long, thin flexible instruments that are inserted by the robot into the patient. As the robot inserts these devices, due to their geometry, they are prone to buckling failure. To mitigate buckling failure, a support system is needed on the robot. This system supports the device but also adapts to the varying ex vivo length of the device as it is inserted. This work presents four collapsible support systems designed to mitigate buckling failure of long, thin instruments while accounting for changing length. The Ori-Guide is an origami-inspired system that has enabled a part reduction from traditional rigid systems with over 70 parts to 3 parts. This system was enabled through the development of a novel origami pattern that integrates both actuation and support into the same pattern. This system was made from PET and performed as well as a rigid system. The PET used in the Ori-Guide was thermo-processed to hold a folded shape. The heat treatment put the Ori-Guide into tension and enabled a stiffer support system. Work was done to investigate the effect of thermo-processing on PET films used in origami-inspired engineering applications. It was discovered that there is a strong correlation between crystallization and the stiffness of a crease in the polymer film. The Zipper-Tube Reinforcement (ZTR) was developed to provide constant support along the entire length of the device, something that no other support device provides. This enables higher loads on the device and thinner and more flexible devices. It was developed as a tube that envelopes the device and zips to provide a tube to support the device then unzips to lay flat rolled about a mandrel for storage. The Wires in Tension concept was developed by focusing on adding tension to the support system. It provided support to the device but required high levels of force on the robot arm so the Orthogonal Beams was developed. The Orthogonal Beams employs geometry as the primary support rather than tension and therefore could provide higher support with less force on the robot. These systems all proved effective ways to support flexible devices. The concepts could also find application in other fields. The merits of each system are discussed in detail, including a discussion on other possible applications.
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Jones, Trevor Alexander. "Finite Element Modeling of Shallowly Embedded Connections to Characterize Rotational Stiffness." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/5866.
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Finite element models were created in Abaqus 6.14 to characterize the rotational stiffness of shallowly embedded column-foundation connections. Scripts were programmed to automate the model generation process and allow study of multiple independent variables, including embedment length, column size, baseplate geometry, concrete modulus, column orientation, cantilever height, and applied axial load. Three different connection types were investigated: a tied or one part model; a contact-based model; and a cohesive-zone based model. Cohesive-zone modeling was found to give the most accurate results. Agreement with previous experimental data was obtained to within 27%. Baseplate geometry was found to affect connection stiffness significantly, especially at lower embedment depths. The connection rotational stiffness was found to vary only slightly with cantilever height for typical column heights. Results from varying other parameters are also discussed.
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Hanks, Kevin N. "Rotational Strength and Stiffness of Shallowly Embedded Base Connections in Steel Moment Frames." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6261.
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Shallowly embedded column base connections with unreinforced block out concrete are a common method of connecting steel columns to their foundation. There has been little research done to accurately quantify the effects of this block out concrete on the connection strength and rigidity, and therefore there is nothing to aid the practicing engineer in accounting for this in structural analysis. Due to this lack of understanding, engineers have typically ignored the effects of shallow block out concrete in their analysis, presumably leading to a conservative design. Recent research has attempted to fill this gap in understanding. Several methods have been proposed that seek to quantify the effects of shallow block out concrete on a column base connection. Barnwell proposed a model that predicts the strength of a connection. Both Jones and Tryon used numerical modeling to predict the rotational stiffness of the connection. An experimental study was carried out to investigate the validity of these proposed models. A total of 8 test specimens were created at 2/3 scale with varying column sizes, connection details, and embedment depths. The columns were loaded laterally and cyclically at increasing displacements until the connection failed. The results show that the strength model proposed by Barnwell is reasonable and appropriate, and when applied to this series of physical tests produce predictions that have an observed/predicted ratio of between 0.95 to 1.39. The results also show that methods for estimating the rotational stiffness of the connection at the top of the block out concrete, as proposed by Jones and Tryon also produce reasonable values that had observed/predicted ratios of between 0.93 to 1.47. An alternative model for determining a design value for the rotational stiffness of a shallowly embedded column base plate is also proposed. When the embedment depth to column depth ratio is greater than 1.22, the connection is sufficiently rigid and at small deflections (less than 1% story drift) may be accurately modelled with infinite rotational stiffness (a "fixed" connection) at the base of the column.
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Broderick, Rick Davon. "Statnamic Lateral Loading Testing of Full-Scale 15 and 9 Group Piles in Clay." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/861.
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Studies of seismic and impact loading on foundation piles is an important and a focused interest in the engineering world today. Because of seismic and other natural events are unpredictable, uncontrollable and potentially unsafe it is a vital study to understand the behavior and relationship structures in motion have on there foundation. Statnamic Loading has become a popular method of studying this relationship in a controlled environment. Two groups of 9 and 15 driven hollow pipe piles were tested in saturated clay at the Salt Lake City Airport in July of 2002. The 9-pile group (3x3 configuration) was separated at 5.65 pile diameters and the 15-pile group (3x5 configuration) was separated at 3.92 pile diameters. The testing consisted of five target deflections. Each target deflection consisted of 15 cyclic lateral static loadings and a 16th lateral statnamic load. This study focuses on the statnamic loading. Damping ratios ranged from 23 to 50 percent for the 15-pile group and 29 to 49 percent for the 9-pile group. Both pile groups increased in damping as the deflections increased. The optimized mass in motion for the entire system was found to be roughly 21,000kg for the 15-pile group and 14,000 kg for the 9-pile group. Stiffness for the 15-pile group started at 50kN/mm and ended at 21kN/mm. The 9-pile group ranged from 28kN/mm to 12kN/mm.
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Vargas, Vinicius Athaydes de. "Efeitos da flexibilidade estrutural em simulações de dinâmica lateral de veículo de transporte de carga." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/34760.
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Este trabalho apresenta uma análise multicorpos de combinação veicular de carga com chassi de semirreboque flexível, para avaliação de dinâmica lateral. O contexto é dado por um breve panorama do transporte rodoviário de cargas no Brasil. No intuito de melhorar seus produtos, os fabricantes de implementos rodoviários têm utilizado metodologias de desenvolvimento baseadas em simulação virtual. Nessas circunstâncias, análises dinâmicas são realizadas, geralmente levando-se em conta a hipótese de corpos rígidos (não deformáveis). Subjetivamente, é sabido que a inclusão da flexibilidade em um modelo numérico o aproxima do fenômeno real, mas são raros os trabalhos que analisam quantitativamente essa diferença. Assim, neste estudo é proposta uma abordagem para consideração da flexibilidade estrutural do chassi de um semirreboque em simulações de tráfego. Procede-se a discretização do quadro do implemento em elementos finitos, para realização de análise de vibração livre, na qual são determinados os modos (autovetores) e as frequências naturais (autovalores) da estrutura. Utilizando metodologia de superposição modal, os modos de vibração são classificados para compor, por combinação linear, a flexibilidade da estrutura nas análises dinâmicas em ferramenta comercial de MBS (sistemas multicorpos). São realizadas, então, simulações de manobras representativas da dinâmica lateral de combinações veiculares, com ênfase à estabilidade em rolagem. Os efeitos globais da inserção de flexibilidade modal no chassi do semirreboque são avaliados por meio de métricas específicas, baseadas em normas ISO de dinâmica lateral para veículos pesados. Os resultados das simulações, apresentados em forma gráfica e tabelas, mostram a grande influência da flexibilidade estrutural do chassi no desempenho dinâmico da combinação veicular analisada. Grandezas relevantes como aceleração lateral (no domínio do tempo e da frequência), ângulo de rolagem e força atuante nos pneus, além de fenômenos físicos como a transferência lateral de carga em curvas, são fortemente afetados pela flexibilidade do quadro. Agrega-se ao trabalho desenvolvido uma forma simplificada de equacionar analiticamente a rolagem de um semirreboque flexível. É realizada também uma análise de sensibilidade da rigidez torcional do chassi quanto ao número de travessas.This work presents a lateral dynamics multibody analysis of a heavy articulated vehicle with a flexible frame for the semi-trailer. The context is given by a short perspective of the load carrying transportation scenery in Brazil. In order to build better products, the trailer manufacturers have been using development methodologies based on virtual simulation. In these circumstances, dynamic analyses are carried out, considering the hypothesis of rigid (non-deformable) bodies. Subjectively, it is known that the inclusion of flexibility in a numerical model brings it closer to reality, but very few studies work on giving numbers to this difference. Thus, this study presents an approach for taking into account the frame structural flexibility of a semi-trailer in traffic simulations. The frame of the semi-trailer is represented by a finite element model, and a free vibration analysis of this structure is carried out. The mode shapes (eigenvectors) and natural frequencies (eigenvalues) are determined. With a mode superposition method, the vibration modes are classified, for the purpose of building the structural flexibility (by linear combination) of the chassis in the dynamic analyses of the MBS software. Typical maneuvers of lateral dynamics are simulated, testing the roll stability of the combined vehicle model. The global effects for considering the mode flexibility in the semitrailer frame are evaluated through specific metrics, based on ISO standards for heavy vehicles lateral dynamics. The strong influence of the frame structural flexibility, when analyzing the articulated vehicle transient behavior, is showed by simulation results, which are presented in graphics and tables. Important measurements, such as lateral acceleration (in time and frequency domains), roll angle and vertical force on tires, besides physical phenomenon like lateral load transfer, are significantly modified by the flexibility of the frame. A simplified approach for writing the analytical equations of the flexible semi-trailer roll dynamics is added to the study. A torsional stiffness sensitivity analysis is also performed, regarding the number of transversal members in the semi-trailer chassis.
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Barnwell, Nicholas Valgardson. "Experimental Testing of Shallow Embedded Connections Between Steel Columns and Concrete Footings." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/4428.
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Shallow embedded column connections are widely used for columns resisting gravity loads in current design methods. These connections are usually considered “pinned” for structural analysis. In reality these connections fall in between a fixed and a pinned condition. Although methods exist to estimate the stiffness and strength of exposed columns or embedded columns under lateral loads, little research has been done to determine the strength of shallow embedded columns. An experimental study was carried out to investigate the strength of these connections. A total of 12 specimens with varying orientation, embedment depth, and column size were loaded laterally until failure or significant loss in strength. The results showed that shallow embedded connections are 86%-144% stronger in yielding and 32%-64% stronger in ultimate strength than current design methods would predict. This strength comes from a combination of the embedment depth and the resistance from the base plate and anchor rods. A model is proposed to explain the strength of the specimens and to conservatively estimate the strength of specimens with different variables. The specimens also exhibited stiffness ranging from 50%-75% of what would be expected from fully embedded columns.
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Bower, Owen J. "Analytical Investigation into the Effect of Axial Restraint on the Stiffness and Ductility of Diagonally Reinforced Concrete Coupling Beams." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1211065883.
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Avilla, Marcella Caon. "Análise da deslocabilidade lateral de edifícios de múltiplos andares com modelos tridimensionais de barra." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8606.
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The structural modeling of mult-storey buildings using the simplified model in which the slabs is calculated in isolation and their efforts transferred to a three-dimensional frames is now overcome by the state of the art computational analysis. Currently even with structures formed by bar elements (three-dimensional frames) it is possible to make the analysis considering the effect monolithic of concrete structures or operating as a whole. For certain cases, it is essential to consider all the structural elements participating in the bracing to the structure is presented stable in the horizontal actions combined with vertical actions, such as the flat slabs systems.Through of analysis examples of structures of buildings with multiple floors in reinforced concrete are presented advantages in performing three-dimensional modeling, comparing the results obtained with the simplified models. It shows the importance of considering the slab stiffness in flat slabs systems and how the distribution of efforts to change the three-dimensional model. Analyses are done using commercial software tool allowing verify quantitative variation of structural materials. Finally an analysis is made of the examples made showing the main differences in the new models.
A modelagem estrutural de edifícios de múltiplos andares usando o modelo simplificado no qual o pavimento é calculado de forma isolada e seus esforços transferidos para um pórtico tridimensional hoje está superada pelo estado da arte da análise computacional. Atualmente mesmo com estruturas constituídas por elementos de barras (pórticos tridimensionais) já é possível fazer a análise considerando o efeito monolítico das estruturas de concreto, ou seja, funcionando com um todo. Para determinados casos, é fundamental a consideração de todos os elementos estruturais participando do contraventamento para que a estrutura se apresente estável frente às ações horizontais combinadas com as ações verticais, como, por exemplo, os sistemas de lajes lisas. Por meio das análises de alguns exemplos de estruturas de edifícios de múltiplos pavimentos de concreto armado são apresentadas as vantagens em se realizar a modelagem tridimensional, comparando-se os resultados obtidos com os dos modelos simplificados. Mostra-se a importância da consideração da rigidez da laje em sistemas de lajes lisas e como a distribuição de esforços se altera no modelo tridimensional. As análises são feitas através de ferramenta computacional comercial permitindo assim verificar a variação de quantitativo de materiais estruturais. Por fim é feita uma análise dos exemplos realizados mostrando as principais diferenças encontradas nos novos modelos.
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Ericsson, Luis Gustavo Sigward. "Estudo da influência da rigidez do quadro na dirigibilidade de um veículo de competição Fórmula SAE em ambiente multicorpos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-21082009-105817/.
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O objetivo deste trabalho é estudar a influência da rigidez do quadro na dirigibilidade de um veículo de competição fórmula SAE (protótipo E2-M, da equipe EESC-USP) em ambiente multicorpos com o software Adams/Car. Um modelo contendo os subsistemas de suspensão, direção, pneumático, powertrain, barra estabilizadora e quadro foi construído em ambiente multicorpos com componentes modelados como corpos rígidos. Posteriormente foram elaborados três modelos de quadros flexíveis com diferentes valores de rigidez torcional para substituir o quadro rígido. Estes foram obtidos através da análise modal com o auxílio do método dos elementos finitos. Para comparação da dinâmica lateral dos modelos, típicas manobras do estudo de dirigibilidade foram consideradas tais como rampsteer, step-steer e single lane change. Os resultados obtidos foram de aceleração lateral e velocidade de guinada. Pelas condições avaliadas, pode-se concluir que a rigidez torcional de um quadro para o protótipo E2-M pode estar entre 700 e 1500 N.m/o. Essa variação de rigidez representou 5 kg de massa no quadro. Porém deve-se fazer uma avaliação modal com a massa suspensa calibrada para verificar se não existe acoplamento de modos e freqüências com outros subsistemas.This dissertation is intended to study the influence of frame stiffness in handling of a Formula SAE vehicle (E2-M prototype from EESC-USP Formula SAE team) in multibody with Adams/Car software. A model containing the subsystems of suspension, steering, tires, powertrain, frame and stabilizing bar was built considering rigid bodies. Subsequently, three models of flexible frames were developed with different values of torsional stiffness to replace the rigid frame. They were obtained through modal analysis with the aid of finite element method. For the handling investigation, maneuvers such as ramp-steer, step-steer and single lane change were considered. The results evaluated were lateral acceleration and yaw velocity. According to results, the torsional stiffness for the E2-M prototype can be between 700 and 1500 Nm/o. But an eigenvalue analyses is also necessary to verify if there is no coupling of modes of the calibrated sprung mass with other subsystems.
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Uygar, Celaletdin. "Seismic Design Of Cold Formed Steel Structures In Residential Applications." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607294/index.pdf.
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iv
ABSTRACT
SEISMIC DESIGN OF COLD FORMED STEEL STRUCTURES IN
RESIDENTIAL APPLICATIONS
Uygar, Celaletdin
M.Sc., Department of Civil Engineering
Supervisor: Prof. Dr. Çetin Yilmaz May 2005, 82 pages In this study, lateral load bearing capacities of cold formed steel framed wall panels are investigated. For this purpose lateral load bearing alternatives are analyzed numerically by computer models and results are compared with already done experimental studies and approved codes. In residential cold formed steel construction, walls are generally covered with cladding material like oriented strand board (OSB) or plywood on the exterior wall surface and these sheathed light gauge steel walls behave as shear walls with significant capacity. Oriented strand board is used in analytical models since OSB claddings are most commonly used in residential applications. The strength of shear walls depends on different parameters like screw spacing, strength of sheathing, size of fasteners used and aspect ratio. SAP2000 software is used for structural analysis of walls and joint force outputs are collected by Microsoft Excel. The yield strength of shear walls at which first screw connection reaches its shear capacity is calculated and load carrying capacity per meter length is found. The nonlinear analysis is also done by modeling the screw connections between OSB and frame as non-linear link and the nominal shear capacities of walls are calculated for different screw spacing combinations. The results are consistent with the values in shear wall design Guide and International Building Code 2003. The other lateral load bearing method is flat strap X-bracing on wall surfaces. Various parameters like wall frame section thickness, flat strap area, aspect ratio and bracing number are investigated and results are evaluated. The shear walls in which X-bracing and OSB sheathing used together are also analyzed and the results are compared with separate analyses.
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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.
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Marsh, Robert Ashall. "Passive Earth Pressures on a Pile Cap with a Dense Sand Backfill." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1958.
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Pile groups are often used to provide support for structures. Capping a pile group further adds to the system's resistance due to the passive earth pressure from surrounding backfill. While ultimate passive earth pressure under static loading conditions can be readily calculated using several different theories, the effects of cyclic and dynamic loading on the passive earth pressure response are less understood. Data derived from the full-scale testing of a pile cap system with a densely compacted sand backfill under static, cyclic, and dynamic loadings was analyzed with particular focus on soil pressures measured directly using pressure plates. Based on the testing and analyses, it was observed that under slow, cyclic loading, the backfill stiffness was relatively constant. Under faster, dynamic loading, the observed backfill stiffness decreased in a relatively linear fashion. During cyclic and dynamic loading, the pile cap gradually developed a residual offset from its initial position, accompanied by a reduction in backfill force. While the pile cap and backfill appeared to move integrally during static and cyclic loadings, during dynamic loading the backfill exhibited out-of-phase movement relative to the pile cap. Observed losses in backfill contact force were associated with both cyclic softening and dynamic out-of-phase effects. Force losses due to dynamic loading increased with increasing frequency (which corresponded to larger displacements). Losses due to dynamic loading were offset somewhat by increases in peak force due to damping. The increase in contact force due to damping was observed to be relatively proportional to increasing frequency. When quantifying passive earth forces with cyclic/dynamic losses without damping, the Mononobe-Okabe (M-O) equation with a 0.75 or 0.8 multiplier applied to the peak ground acceleration can be used to obtain a reasonable estimate of the force. When including increases in resistance due to damping, a 0.6 multiplier can similarly be used.
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Balázs, Ivan. "Klopení tenkostěnných ocelových nosníků s vazbami vybočení z roviny ohybu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-371784.
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The doctoral thesis focuses on problem of stability of steel thin-walled beams with lateral and torsional restraints along the spans. Theoretical background of lateral-torsional buckling of an ideal beam with and without restraints preventing out-of-plane buckling is briefly described. In the following chapters the problem of stabilization of steel thin-walled beams by planar members is dealt with. The state of the art in this field is summarized and some open questions are identified. The research in this field could bring new findings about actual behavior of these structural systems. The rate of stabilization can be quantified using values of shear and rotational stiffness provided to a thin-walled member by a planar member. In the frame of the thesis the problem of torsional restraint given to steel cold-formed members by sandwich panels under load is discussed. In case of the uplift load applied on the sandwich panels the torsional restraint should be verified by experimental analysis. To contribute to this field, experimental verification of rotational stiffness provided to steel cold-formed beams by sandwich panels was proposed and performed. Torsional restraint under no external load as well as under uplift load applied on the panels was investigated. The purpose was to obtain the values of the rotational stiffness provided by planar members. The performed tests indicate significant and practically applicable rate of the torsional restraint even in case of the uplift load on the surfaces of the panels. Utilization of the values of the rotational stiffness might result in more economical, effective and reliable structural design. Selected problems were investigated using numerical modeling in a finite element method based software.
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Wolfe, Sage M. "Heavy Truck Modeling and Estimation for Vehicle-to-Vehicle Collision Avoidance Systems." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405704063.
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Zhou, Guang Chun. "Application of stiffness/strength corrector and cellular automata in predicting response of laterally loaded masonry panels." Thesis, University of Plymouth, 2002. http://hdl.handle.net/10026.1/2386.
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This research has introduced a new concept, 'stiffness/strength corrector', which more accurately models variation in masonry properties at various locations (zones) within a masonry wall panel. Derivation of these correctors was based on a closer mapping of the laboratory experimental results to those obtained from a non-linear finite element analysis of full-scale masonry panels subjected to a uniformly distributed lateral load. In this research only one panel, which was tested in a previous research, was used as the "base panel" and correctors for new panels with and without openings with various boundary conditions were derived by matching similar regions and zones between the new panel and the base panel. The research has also derived the concept of zone similarity between the base panel and any new panel. It was discovered that the types of panel boundaries surrounding specific regions within the two panels govern zone similarity. At first, a manual method for matching zone similarity was proposed based on careful visual inspection to identify similar regions within the two panels. It was found that this method is difficult to implement as the user needs to have a deep knowledge of the behaviour of the panel to be able to accurately locate similar regions/zones. As it was established that the zone similarity was mainly related to the panel boundaries, this knowledge was used to derive appropriate rules for matching zone similarity. These rules were implemented in a cellular automata model which was able to automatically locate similar zones between the base panel and a new panel and assign appropriate corrector values to zones within the new panel. The stiffness/strength corrector values were used to, modify global material properties of the panel. A specialised non-linear FEA program for masonry panels was used to analyse a number of panels provided by CERAM with modified rigidities or tensile strength values. Comparison of results with laboratory experimental values shows that with this new method an average 18% improvement in the prediction of failure load, in comparison with the non-linear FEA results with smeared masonry properties, was possible. The failure patterns for the majority of panels with or without openings, having various sizes and boundary conditions, were much closer to the experimental results. The results of case studies using the new method clearly show that the proposed method is a much better representation of the true behaviour of the masonry panels which models variation in masonry properties and the boundary effects more accurately. The corrector values for any type of new panel are derived from a single base panel in which there was not sufficient data available at different locations on the panel, particularly near the panel boundaries. Thus, in some cases it uses a crude approximation of the boundary types to establish corrector values for a new panel. If sufficient data points were available more accurate results would have been possible to achieve.
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Mojžíšek, Dominik. "Dynamická analýza koleje." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372123.
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The diploma thesis deals with descriptions of vehicle - track dynamic interface. There are described basic analytical models of railway track. The numerical models are created by using finite element methods with moving load simulated axle of rail vehicle. The aim of thesis is to create the model which most accurately describes the dynamic phenomena in the track. The results from models are compared with data obtained by measuring in the track. Next aim of thesis is to determine dependency of rail cross-sectional characteristics on equivalent rail head wear and then on rail deflection.
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Hollville, Enzo. "Impact du type de surface sur la réponse à l’exercice : du muscle au mouvement Interactions between fascicles and tendinous tissues in gastrocnemius medialis and vastus lateralis during drop landing How surface properties affect fascicle-tendon interactions during drop landing? Muscle-tendon interactions in jumping: influence of surface properties." Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCB018.
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Les propriétés des surfaces sportives peuvent impacter directement la performance et le risque de blessure en modulant la part d’énergie transmise à l'athlète lors de l'impact du pied sur la surface. Les pelouses naturelle et synthétique sont couramment utilisées sur les terrains de football et de rugby. Depuis quelques années, une nouvelle génération de pelouse dite naturelle renforcée a fait son apparition dans les clubs professionnels mais son influence sur la biomécanique du geste sportif est encore mal connue. Cette thèse vise à évaluer l'influence de trois types de surfaces (gazon naturel renforcée, gazon synthétique et tartan) sur les interactions muscle-tendon et les coordinations neuromusculaires des muscles gastrocnemius medialis (GM) et vastus lateralis (VL) lors de mouvements de réception uni et bilatérale ainsi que de saut. L’analyse des données échographiques dynamiques, de cinématique 2D et d’activité musculaire nous a permis de montrer que : i) les propriétés mécaniques des surfaces peuvent altérer les interactions entre les faisceaux musculaires et les tissus tendineux ainsi que l’amplitude d’activation musculaire ; ii) la pelouse naturelle renforcée semble avoir des propriétés plus optimales que la pelouse synthétique lors de sauts et réceptions ; iii) il existe des différences de comportement marquées entre le GM et VL qui dépendent du type de surface, du type de mouvement et de son intensité. Cela souligne l’importance de ne pas se limiter à l’étude des propriétés mécaniques des surface pour comprendre leur influence sur le mouvement sportif. Par ailleurs, l’étude des comportements musculo-tendineux in vivo en condition écologique permet de mieux comprendre les interactions complexes entre l’homme et la surfaceSports surface properties can substantially alter the overall performance and risk of injury. Surface mechanical properties influence the loading of the human musculoskeletal system by modulating the amount of foot-impact energy transmitted to the athlete. Natural grass and synthetic turf are commonly used pitches in football and rugby. More recently, reinforced natural grass technology has been used at the elite-level facilities, but its influence on player is not well defined. This thesis aimed at evaluating the influence of three different surfaces (reinforced natural grass, synthetic turf and athletic track) on the muscle-tendon interactions and neuromuscular coordination of gastrocnemius medialis (GM) and vastus lateralis (VL) muscles during landings and jumping tasks. Analysis of dynamic ultrasound imaging, 2D kinematics and electromyographic data showed that: i) surface mechanical properties influenced muscle-tendon interactions as well as the level of muscle activity; ii) the reinforced natural grass surface seems to optimize the muscular response during the movement and iii) GM and VL muscles displayed specific behaviors relative to the type of movement, its intensity and the type of surface. This emphasizes that the human response cannot be predicted by only analyzing the mechanical surface properties and highlights the important role of in vivo ecological testing to better understand player-surface interaction
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Klaps, J., A. J. Day, K. Hussain, and N. Mirza. "Effect of component stiffness and deformation on vehicle lateral drift during braking." 2009. http://hdl.handle.net/10454/6052.
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Mirza, N., Khalid Hussain, Andrew J. Day, and J. Klaps. "Effect of component stiffness and deformation on vehicle lateral drift during braking." 2009. http://hdl.handle.net/10454/2610.
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This article presents a simulation study into effects of compliant (flexible) components
(such as the engine subframe and the lower control arm) and their deflections on the characteristics
of a vehicle experiencing steering drift during straight-line braking. The vehicle front and
rear suspension are modelled using multi-body dynamic analysis software. The front suspension
model represents theMacPherson strut design of the vehicle and includes a rack and pinion steering
system, brake system, engine subframe, and a powertrain unit. The model has been analysed
under two steering control methods: fixed and free control. Suspension characteristics and the
effect of deflections arising from the subframe and the lower control arm on these suspension
characteristics have been analysed.
The simulations confirmed that variation of component stiffness and interactions within components
give rise to side-to-side deflections that could affect lateral drift during braking. It is
concluded that side-to-side variation of suspension characteristics can have a detrimental effect
on lateral drift during braking and that compliant components whose stiffness varies from side
to side can cause different side-to-side deflections that can induce and influence variation in
suspension characteristics such as toe steer angle that can lead the vehicle during braking.
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Nie, Yu-Pu, and 聶玉璞. "The study of lateral stiffness aualysis model of staggered bracing steel frame." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/20102592659345687257.
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劉宗帆. "optimization of the stiffness of elastic restrains of stiffened plate under uniform lateral load." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/62088096889195778010.
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碩士國立交通大學
機械工程系所
94
In order to unify deformation of the elastic restraints for stiffened plates with elastically restrained edges under uniform lateral load, the stiffness of the elastic restraints is chosen to be the design variables and an optimization method is proposed to find the optimal stiffness of elastic restraints. The stiffened plate is composed of a plate and stiffeners. The stiffeners and the elastic restraints are taken to be beams and linear spring, respectively. The finite element method is used here for the linear analysis of stiffened plate. The triangular flat shell element and the thin-walled beam element are used here. Because the nodes of the beam element must coincide with those of the shell element, the nodes of the beam element are shifted to the mid-plane of the plate. A numerical procedure based on the Newton method is proposed to find the optimal stiffness of the elastic restraints. Numerical examples are studied to demonstrate the accuracy of the proposed method and to investigate the distribution of the optimal stiffness of the elastic restraints, the deformation of the elastic restraints and deflection of the stiffened plate for stiffened plate with different number of stiffeners, different cross section of stiffeners and different thickness of plate.
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Santoso, Stevanus Wongso, and 黃建雄. "Lateral Bracing Strength and Stiffness Requirements of H-Shaped Steel Beams under Seismic Type loading." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/enaxdk.
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碩士國立臺灣科技大學
營建工程系
107
The most common way to prevent lateral torsional buckling is by employing lateral bracing. It is well known that the lateral bracing should have sufficient strength and stiffness to minimize the lateral torsional buckling. However, the lateral bracing requirements in the current code is based on elastic model and monotonic loading on simply supported beam, and for seismic design where large inelastic deformation is expected, these requirements are also used. This action becomes questionable whether it is appropriate or not. In addition, the lateral bracing requirements may be different between simply supported beam and both ends fixed beam which is commonly found in moment resisting frame with welded-flange bolted-web connections. Therefore, an analytical study was conducted on H-beams under seismic type loading to investigate the lateral bracing requirements. Two beams were experimentally tested, and finite element model was validated to experimental result. Based on the verified finite element model, parametric study was conducted. Finally, an equation to design the required bracing strength was proposed.
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Peköz, Hasan Aydın. "Lateral drift of reinforced concrete frames with stiffness and strength degradation subjected to strong ground motions." 2007. http://www.library.wisc.edu/databases/connect/dissertations.html.
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"A MODEL STUDY ON THE EFFECTS OF WALL STIFFNESS AND SURCHARGE ON DYNAMIC LATERAL EARTH PRESSURES." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606215/index.pdf.
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Lin, Wei-Ju, and 林韋如. "Increased Stiffness of Lateral Raphe during Contraction of Transverse Abdominisin Patients with Unilateral Low Back Pain." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/70410910868004625329.
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碩士國立臺灣大學
物理治療學研究所
104
Background: Myo-fascia provides a continuous network of restricting but adjustable tension around muscles and bones. Muscle-fascia tenderness is noted in patients with low back pain (LBP). The lateral raphe (LR), part of thoracolumbar fascia, is the junction connecting lateral abdominal muscles and paraspinal muscles. Participants with LBP demonstrate a morphological deficit during the contraction of the transverse abdominals, which is termed abdominal draw-in maneuver (ADIM), decreased change of muscle thickness and muscle-fascia sliding, as well as increased fascia thickness. However, the investigation is few in tension transmission during contraction, which is an important issue related to tissue loading and lesion in musculoskeletal systems. The technology of shear wave elastography (SWE) could provide the measurement of the stiffness of soft tissue through the calculation of young''s module. However, the reliability of fascia stiffness measured by SWE is unknown. Whether the fascia stiffness is symmetry in sides, increased during ADIM in asymptomatic participants and patients with unilateral LBP is unknown, neither the difference between groups. Purposes: The purposes of this study were (1) to establish the intra-rater reliability of LR stiffness under resting and ADIM conditions by using SWE, (2) to compare the differences of LR stiffness under these conditions and between sides in asymptomatic participants, (3) to compare the LR stiffness under resting and ADIM conditions, and between painful and non-painful sides in participants with unilateral LBP, and (4) to compare the LR stiffness under resting and ADIM conditions between asymptomatic participants and patients with unilateral LBP. Method: 14 asymptomatic participants (22.4±2.8 y/o) were included in the reliability study. Patients with unilateral LBP (n=22, 29.7±6.7 y/o) and asymptomatic participants (n=20, 26.5±4.1 y/o) were recruited in the main study. The SWE (SuperSonic Imagine, Aix en Provence, France) with 5-12MHz linear transducer was used to measure the stiffness of LR. Participants were positioned in prone and asked to perform ADIM. The outcome variables included the LR stiffness of bilateral sides in resting and ADIM condition. The reliability was analyzed using intra-class correlation coefficient (ICC(3,3)). Two-way repeated ANOVA was used to analysis the stiffness of LR between bilateral sides and in resting and ADIM condition. Two-way repeated measures ANCOVA was used to analysis the difference of LR stiffness between asymptomatic participants and patients with unilateral LBP in resting and ADIM condition. Result: The intra-rater reliability of measuring the LR stiffness in resting and ADIM condition was in the range of good to excellent (ICC(3,3)=0.77-0.96); the reliability of measuring the same images by different raters were 0.85-0.88(ICC(3,1)). In participants enrolled in reliability study, no interaction between sides and conditions. The main effect of sides (left: 17.18±9.47 kPa; right: 19.73±8.42 kPa, p=0.427) and conditions (resting: 18.51±7.70 kPa; ADIM: 18.40±10.18 kPa, p=0.939) was not significant. No interaction between sides and conditions in LBP group. The main effect of sides was not significant (painful: 22.30±10.05 kPa; non-painful: 22.69±8.99 kPa, p=0.879), yet, the main effect of conditions was significant (resting: 19.48±7.61 kPa; ADIM: 25.51±10.95 kPa, p<0.00008). There was significant interaction between groups and conditions (F=15.762，p=<0.0005). Post hoc for group demonstrated that LR stiffness was greater in LBP group during ADIM (LBP: 26.12±12.87 kPa; asymptomatic: 19.40±8.07 kPa, p=0.001). Conclusion: Measuring the LR stiffness in resting and ADIM condition using SWE is reliable. The LR stiffness in asymptomatic participants was symmetrical. The LR stiffness between resting and ADIM condition was unchanged in asymptomatic group. Whereas the stiffness of both painful and non-painful sides in patients with unilateral LBP is increased during ADIM. Furthermore, LR stiffness in patients with unilateral LBP in resting was not different from asymptomatic group. The result of the present study investigating the fascia property in dynamic condition supports the concept of dynamic myo-fascial tension imbalance in patients with LBP.
44
Levine, Iris Claire. "The Effects of Body Mass Index and Gender on Pelvic Stiffness and Peak Impact Force During Lateral Falls." Thesis, 2011. http://hdl.handle.net/10012/6287.
Full textAbstract:
Fall-related hip fractures are a substantial public health issue. Unfortunately, little is known about whether the effective stiffness of the pelvis, a critical component governing impact force during lateral falls, differs substantially across different segments of the population. The objective of this thesis was to enhance the knowledge base surrounding pelvis impact dynamics by assessing the influence of gender and body mass index (BMI) on the effective stiffness of the pelvis, and on resulting peak loads applied to the hip, during sideways falls. Towards this end I conducted pelvis release trials (in which the pelvis was suspended and suddenly released onto a force plate) with males and females with low (<22) and high (>28) BMIs.
One resonance-based (kvibe), and three force-deflection based (k1st, kcombo 300, and kcombo opt) methods of effective pelvic stiffness estimation were examined. The resulting stiffness estimates, and peak forces sustained during the pelvis release experiments, were compared between each BMI and sex group.
The optimized force-deflection stiffness estimation method, kcombo opt provided the strongest fit to the experimental data. Strong main effects of BMI (f (1,13) = 10.87, p = 0.003) and sex (f (1,13) = 5.97, p = 0.022) were found for this stiffness estimation method. Additionally, a significant BMI-sex interaction was observed (f (3,6) = 5.31, p = 0.030), with low BMI males having much higher stiffness estimates than any other group. Normalized peak forces were higher in low BMI participants than in high BMI participants (f(1,13)=24.9, p<0.001). Linear regression demonstrated that peak impact force was positively associated with effective pelvic stiffness (β = 0.550, t(25) = 3.110, p=0.005), height (β = 0.326, t(25) = 2.119, p=0.045) and soft tissue thickness (β = 0.785, t(25) = 4.573, p<0.001).
This thesis has demonstrated that body habitus and sex have significant effects on the stiffness of the pelvis during lateral falls. These differences are likely related to a combination of soft tissue and pelvic anatomical differences between BMI and sex groups. Pelvic stiffness, along with other easily collected variables, may be helpful in predicting peak forces resulting from lateral falls in the elderly. Differences in pelvic stiffness estimates between BMI and sex groups, and estimation method, necessitate careful consideration. These data will aid in selecting the most appropriate pelvic stiffness parameters when modeling impact dynamics for higher energy falls.
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Chung, Jen-Chieh, and 鍾人傑. "Parametric Study for Lateral Stiffnesses of Strengthened Bundle-Tubular Structures." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/91532018380913177086.
Full textAbstract:
碩士國立交通大學
土木工程系所
102
The most generally used structural type to build a tall building is Bundled-Tube Structure, and Bundled-Tube Structure which also usually being used to build a tall building is one type of modified Framed-Tube Structure. In the case of tall buildings, displacement caused under wind load is more important than displacement caused by earthquake. Therefore, how to increase the stiffness of Framed-Tube Structure under wind load is mainly discussed in this paper. Shortening distance of every column, attaching Outrigger-Braced Structure to structure and adding Big-Bracing to structure is the main way I used for increasing stiffness of Bundled-Tube Structure. Then i did a comparative analysis between displacement caused by wind load, stress of columns and shear lag through the analysis of SAP2000.
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Zong-SianCai and 蔡宗憲. "Identification on Story Lateral Stiffnesses of Shear Buildings with Partial Measurements." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/09878083520218064600.
Full text
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Yang, Meng-Han, and 楊孟翰. "Parametric study for lateral stiffnesses of strengthened Tubular Structures with Pyramid-like Shape." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/90186172747611319058.
Full textAbstract:
碩士國立交通大學
土木工程系所
102
Framed-tube structure is a generally-used structural type for tall buildings. It’s composed by closely-spaced columns connected with deep spandrel beams at periphery of structures. In the past, the framed-tube structure has developed into tube-in-tube structure, bundled-tube structure and braced-tube structure, etc. We used SAP2000 to model and analysing a tubular structure with pyramid-like shape in this study. In the same time, we changed its parameter and enduing outrigger or bracing to compare with original model in order to understand the shear Lag Effect and characteristics of the structural behavior of the tubular structure with pyramid-like shape. Therefore, the structural behaviors are explored and well understood as the results of this study.