Lateral Force Displacement Research Articles

Experimental study on hysteric behavior of composite shear walls with steel sheets

Owing to demanding structural requirements, composite shear walls have become necessary in reinforced concrete high-rise structures subjected to earthquake forces. Composite shear walls also limit the inter-story drift angles during severe earthquakes in terms of their load-carrying system performance. Within the scope of this study, two types of shear walls were constructed on a 1:3 scale. One type is a conventional reinforced concrete shear wall having boundary zones consisting of only conventional reinforcement. The other walls tested were composite shear walls having boundary zones consisting of cold-formed steel sheets (CFSSs). The dimensions of the CFSSs used in the shear wall boundary zones were 2×L19×57×7, 4×L23×69×5, and 2×L17×49×7 (mm). The composite shear walls were tested under cyclic lateral loadings, and their behaviors were investigated. Lateral force vs. top displacement curves with envelopes were evaluated from graphs based on the measurements, and crack propagations in the element were investigated step by step. Dissipated energy, ductility capacity, and rigidity properties based on the experimental results were compared.

Analytical modelling of out-of-plane flexural response of unreinforced and strengthened masonry walls

The available literature on out-of-plane bending of masonry walls identifies two distinct phases – pre-cracking and post-cracking, in the force-displacement response. Accordingly, a semi-empirical model for out-of-plane behaviour of unreinforced and strengthened masonry walls is developed, which considers the overall load-displacement response in two phases. The pre-cracking phase model predicts the peak strength of the masonry, whereas the post-cracking model provides a hysteresis envelope (back-bone curve). A tri-linear displacement-based model is developed for one-way bending walls subjected to uniformly distributed lateral load, using a database of 38 experiments available in the literature. Analytical expressions for maximum lateral force and instability displacement are derived using the kinematic approach. Using the experimental database, two factors, λ1 and λ2 are estimated to calibrate the analytical results. The calibrated analytical model shows a good agreement with the experimental results. An analytical method for predicting the two-way out-of-plane flexural capacity in the pre-cracking phase of unreinforced and strengthened masonry walls using crackline method is also developed. This model shows reasonably good results, even with the assumption of an idealized crack pattern. However, the force-displacement parameters for obtaining two-way bending back-bone curve in the post-cracking phase show large scatter indicating that the available test results are not adequate to develop an empirically calibrated model.

Plan review two types of earthquake resistant buildings based on SNI 03-1726-2012 with computer programs

Indonesia is one of the countries that have a high earthquake intensity. Therefore, in building structure planning, there needs to be a more in-depth study of the analysis and planning of earthquake-resistant structures. The study aimed to find out the results of the building analysis reviewed in 4 Indonesian cities based on SNI 03-1726-2012 with computer programs. This research is computer-based research, with Microsoft Excel application for wall density index analysis on 1-story and 2-story buildings, and SAP2000 v.20 application on 4-story buildings for static analysis of equivalent lateral forces. In reviewing the building with analysis of wall density index, it was very influential on the magnitude of the spectral acceleration value of the earthquake. The greater of the spectral acceleration value of the earthquake in the city being reviewed, the smaller the value of the seismic capacity control of the building, which affects the level of building safety. In a building review with an equivalent static lateral force analysis, base shear and displacement values were very influential on the magnitude of the earthquake intensity if used as a comparison with other cities. In reviewing buildings with dynamic analysis of spectrum response range, base shear and displacement values were not very influential on the magnitude of the earthquake intensity if used as a comparison with other cities due to the greater burden than the earthquake load.

Hybrid approach for simulating shear–flexure interaction in RC walls with nonlinear truss and fiber models

An alternative approach to the nonlinear truss model (NLT) is proposed to simulate the seismic behavior of reinforced concrete (RC) walls with various aspect ratios (ratio between the height and the length of the wall, hw/lw). The alternative consists of a hybrid model comprising an NLT panel connected in series with a forced-based fiber-beam–column model through a rigid elastic beam element (HyNLT-F model). The HyNLT-F approach saves computational time as compared to the default NLT model while keeping the capabilities of modeling inelastic shear response and shear–flexure interaction under static cyclic or dynamic loading. These capabilities are first validated for the default NLT model using the experimental test data of two RC-wall panels subjected to reversed cyclic loading, one whose response is flexure-dominated and another with a shear–predominant behavior. The numerically computed lateral force–displacement relationships, lateral displacement contributions, shear–flexure interaction, and vertical strain distribution at different levels of drift demand show a good agreement with the experimentally recorded responses. The hybrid alternative is then validated using three RC-wall panel experiments with high (hw/lw = 3.1), moderate (hw/lw = 2.3) and low aspect ratio (hw/lw = 1.5). The capabilities of the hybridization are evaluated at the global and local level of response, as well as in terms of computational time needed to run the model in comparison with the default NLT model. As an application, a HyNLT-F model is implemented in a multistory non-ductile RC frame-wall structure, to evaluate the impact of the nonlinear shear response at the critical section in the global structural behavior under static and dynamic loading. The results show that the HyNLT-F can model features of the wall response such as inelastic shear and shear–flexure interaction at the critical section, which of interest for certain structural typologies.

Behavior of a spherical deformable rolling seismic isolator for lightweight residential construction

This paper presents a study for the development and qualification of a practical low-cost seismic isolation system for lightweight residential construction. The study concludes that single concave rolling isolators cast in high strength concrete with a deformable steel-reinforced plastic rolling ball and a displacement restraint system represent a promising isolation system. A full size isolator suitable for application to typical reinforced concrete houses in Turkey was built and tested. The vertical stiffness, creep characteristics under gravity load and the lateral force–displacement characteristics have been studied. Models for behavior have been developed and validated. These models are useful for response history analysis in commonly available commercial and open source analysis software.

Bearing Characteristics of Composite Pile Group Foundations with Long and Short Piles under Lateral Loading in Loess Areas

It is very necessary to research the bearing characteristics of composite pile group foundations with long and short piles under lateral load in loess areas, because these foundations are used widely. But few people researched this problem in loess areas up to now worldwide. In this paper, firstly, an indoor test model of a composite pile foundation with long and short piles is designed and then employed to explore the vertical load bearing characteristics and load transfer mechanisms of a single pile, a four-pile group, and a nine-pile group under different lateral loads. Secondly, ANSYS software is employed to analyze the load-bearing characteristics of the test model, and for comparison with the experimental results. The results demonstrate the following. (1) The lateral force versus pile head displacement curves of the pile foundation exhibit an obvious steep drop in section, which is a typical feature of piercing damage. A horizontal displacement limit of the pile foundation is 10 mm and 6mm for the ones sensitive to horizontal displacement. (2) The axial force along a pile and frictional resistance do not coincide, due to significant variations and discontinuities in the collapsibility of loess; a pile body exhibits multiple neutral points. Therefore, composite pile groups including both long and short piles could potentially maximize the bearing capacity and reduce pile settlement. (3) The distribution of stress and strain along the pile length is mainly concentrated from the pile head to a depth of about 1/3 of the pile length. If the lateral load is too large, short piles undergo rotation about their longitudinal axis and long piles undergo flexural deformation. Therefore, the lateral bearing capacity mainly relies on the strength of the soil at the interface with the pile or the horizontal displacement of the pile head.

A cadaveric model to evaluate the effect of unloading the medial quadriceps on patellar tracking and patellofemoral joint pressure and stability

BackgroundVastus Medialis Muscles (VMM) damage has been widely identified following patellar dislocation. Rehabilitation programmes have been suggested to strengthen the VMM and reduce clinical symptoms of pain and instability. This controlled laboratory study investigated the hypothesis that reduced Vastus Medialis Obliquus (VMO) and Vastus Medialis Longus (VML) muscle tension would alter patellar tracking, stability and PFJ contact pressures.MethodsNine fresh-frozen dissected cadaveric knees were mounted in a rig with the quadriceps and iliotibial band loaded to 205 N. An optical tracking system measured joint kinematics and pressure sensitive film between the patella and trochlea measured PFJ contact pressures. Measurements were repeated for three conditions: 1. With all quadriceps heads and iliotibial band (ITB) loaded; 2. as 1, but with the VMO muscle unloaded and 3. as 1, but with the VMO and VML unloaded. Measurements were also repeated for the three conditions with a 10 N lateral displacement force applied to the patella.ResultsReduction of VMM tension resulted in significant increases in lateral patellar tilt (2.8°) and translation (4 mm), with elevated lateral and reduced medial joint contact pressures from 0.48 to 0.14 MPa, and reduced patellar stability (all p < 0.05).ConclusionsThese findings provide basic scientific rationale to support the role of quadriceps strengthening to resist patellar lateral maltracking and rebalance the articular contact pressure away from the lateral facet in patients with normal patellofemoral joint anatomy.

Hysteretic behaviour of steel fibre RC coupled shear walls under cyclic loads: Experimental study and modelling

This paper presents the hysteretic behaviour of three 1/3-scale three-storey steel fibre reinforced concrete (SFRC) coupled shear walls (CSWs) under cyclic loads. The deformation, ductility, energy dissipation, stiffness and crack propagation of the specimens are also discussed and analysed. The results show steel fibre improves the ductility and energy dissipation capacity, and restrains the crack propagation of the CSWs, and delays the degradation of their lateral stiffness and force. Based on the experiments, a simple trilinear model is developed to simulate the skeleton curve of lateral force–displacement of the SFRC CSWs. Through analysing several typical cycles of the hysteretic of these CSWs, the feature points of the proposed hysteretic model are defined which subsequently is used to evaluate the complete hysteretic behaviour of the CSWs. Using existing experimental data and this study, several representative experimental hysteretic cycles are compared with the proposed model. The result indicates a good agreement is reached between the model and experimental results.

Analytical Study of Force\u2013Displacement Behavior and Ductility of Self-centering Segmental Concrete Columns

In this study the behavior of unbonded post-tensioned segmental columns (UPTSCs) was investigated and expressions were proposed to estimate their ductility and neutral axis (NA) depth at ultimate strength. An analytical method was first employed to predict the lateral force–displacement, and its accuracy was verified against experimental results of eight columns. Two stages of parametric study were then performed to investigate the effect of different parameters on the behavior of such columns, including concrete compressive strength, axial stress ratio, diameter and height of the column, axial stress level, duct size, stress ratio of the PT bars, and thickness and ultimate tensile strain of fiber reinforced polymer wraps. It was found that the column’s aspect ratio and axial stress ratio were the most influential factors contributing to the ductility, and axial stress ratio and column diameter were the main factors contributing to the NA depth of self-centering columns. While at aspect ratios of less than ten, as the axial stress ratio increased, the ductility increased; at aspect ratios higher than ten, the ductility tended to decrease when the axial stress ratio increased. Using the results of parametric study, nonlinear multivariate regression analyses were performed and new expressions were developed to predict the ductility and NA depth of UPTSCs.

Lateral force–displacement prediction for buried pipe under different effective stress condition

The aim of the present study is to elucidate the soil–pipe interaction in saturated sand with different effective stress. A force–displacement curve that took into account the variation of the effective stress was formulated based on the results of lateral loading experiments on a model pipe. To reproduce liquefaction experimentally, the effective stress of the soil bed was controlled by the upward seepage induced by a hydraulic gradient. The model pipe was pulled laterally under either displacement or load control. The experimental results indicate that the normalised force–displacement relationships can be well approximated by hyperbolic curves under each hydraulic gradient. When the variation in effective stress is reflected in the submerged unit weight of the soil, the two coefficients of the hyperbolic curves also show a hyperbolic dependence on the unit weight, and the ultimate resistive force increases in proportion to the unit weight. The predicted force–displacement curve fits relatively well to the experimental results.

Hybrid simulation of a carbon fibre–reinforced polymer-strengthened continuous reinforced concrete girder bridge

The behaviour of bridge columns strengthened using carbon fibre–reinforced polymer composites has been studied extensively. However, few investigations have been conducted regarding the influence of carbon fibre–reinforced polymer-strengthened columns on the seismic behaviour of reinforced concrete continuous girder bridges. This article details the hybrid simulations of a continuous reinforced concrete girder bridge whose columns are strengthened by carbon fibre–reinforced polymer jackets. In the hybrid simulations, one ductile column is selected as the experimental element, which is represented by a 1/2.5-scale specimen, and the remaining bridge parts are simultaneously modelled in OpenSees (the Open System for Earthquake Engineering Simulation). After combining the experimental element and the numerical substructure, the hybrid analysis model is developed with the established hybrid simulation system. The displacements of the bridge and the lateral force–displacement response of the experimental element in hybrid simulation are obtained. Compared with the results of numerical simulation, the stability and accuracy of the established hybrid simulation system are demonstrated. Meanwhile, the comparative hybrid simulation results of the as-built bridge and the carbon fibre–reinforced polymer-strengthened bridge also prove the effectiveness of the carbon fibre–reinforced polymer jackets’ confinement in the continuous reinforced concrete girder bridge.

Seismic analysis and design of steel-plate concrete composite shear wall piers

This paper presents results of numerical studies on the in-plane monotonic response of steel-plate concrete (SC) composite shear wall piers. Results of finite element analysis of 98 SC wall piers are used to investigate the effects of wall aspect ratio, reinforcement ratio, slenderness ratio, axial load, yield strength of the steel faceplates, and uniaxial compressive strength of concrete on in-plane response, and to formulate (a) predictive equations to establish the trilinear lateral force versus lateral displacement response of SC wall piers up to peak strength, sufficient for seismic analysis of structures including SC wall piers and (b) a mechanics-based design equation for peak flexural strength, which addresses the interaction of co-existing shear and axial force. Design of Experiments is used to select the 98 piers. The baseline finite element model was formally validated using data from reversed cyclic, inelastic in-plane tests of four large-scale SC wall piers.

Finite element analysis of the PreWEC self-centering concrete wall system

A self-centering concrete wall system has been developed that consists of a Precast Wall with End Columns (PreWEC). A finite element model was developed to investigate the cyclic lateral-load response of the PreWEC system that included allowance for uplift at the wall-to-foundation interface, inclusion of the energy dissipating O-connectors, and inelastic behaviour of the confined concrete in the toe of the wall. The model showed good correlation with the results of a large-scale experimental test of the PreWEC system for both the global and local responses, closely matched the experimental lateral force–displacement response, unbonded tendon stress, neutral axis depth, concrete compressive strains, and connector deformation. Additional analyses were conducted to investigate modifications to the PreWEC design. These modified designs highlighted the influence of the inelastic behaviour of the wall toe and showed that in the PreWEC system the axial load on the wall panel is independent of the number of energy dissipating connectors. Lastly, analyses were conducted to investigate wall-to-floor interaction with the PreWEC system. It was shown that a rigid wall-to-floor connection would result in some damage to the floor diaphragms and an overstrength that should be considered when designing the wall for shear. Alternatively, connectors could be used with the PreWEC system to isolate the floor from the uplift of the wall and eliminate damage to the floor diaphragm.

Analysis of seismic behavior of composite frame structures

There are great needs of simple but reliable mechanical nonlinear behavior analysis and performance evaluation method for frames constructed by steel and concrete composite beams or columns when the structures subjected extreme loads, such as earthquake loads. This paper describes an approach of simplified macro-modelling for composite frames consisting of steel-concrete composite beams and CFST columns, and presents the performance evaluation procedure based on the pushover nonlinear analysis results. A four-story two-bay composite frame underground is selected as a study case. The establishment of the macro-model of the composite frame is guided by the characterization of nonlinear behaviors of composite structural members. Pushover analysis is conducted to obtain the lateral force versus top displacement curve of the overall structure. The identification method of damage degree of composite frames has been proposed. The damage evolution and development of this composite frame in case study has been analyzed. The failure mode of this composite frame is estimated as that the bottom CFST columns damage substantially resulting in the failure of the bottom story. Finally, the seismic performance of the composite frame with high strength steel is analyzed and compared with the frame with ordinary strength steel, and the result shows that the employment of high strength steel in the steel tube of CFST columns and steel beam of composite beams benefits the lateral resistance and elasticity resuming performance of composite frames.

ANALYSIS OF LATERAL LOAD ON DIFFERENT ORIENTATION OF SHEAR WALL

This study describes mathematical study and relation between wind and earthquake and its effects on building as a whole with respect of Lateral force and Storey shear for different orientation of shear wall. The Effect of Storey drift and storey displacement is also estimated in study. Earthquake Lateral force, Storey Shear, Storey Drift and Storey Displacement are analyzed for Seismic zone factor II.

Cadaveric-biomechanical study on medial retinaculum: its stabilising role for the patella against lateral dislocation.

The aim of this study was to analyse the biomechanical role of medial retinaculum, as a stabilising factor against lateral patellar dislocation. This cadaveric-biomechanical study included the patellae of 10 cadaveric knees, which were surgically exposed and the medial retinaculum of each one was located. A stable 24.51 N force was applied to the four parts of the quadriceps, and an increasing lateral displacing force was applied to the patella, up to 5 mm dislocation. The study was repeated for 0o, 45o, and 90o of knee flexion, with the medial retinaculum intact and dissected. The Wilcoxon signed rank test was used for data analysis. A p value < 0.05 was considered as statistical significant. After the dissection of medial retinaculum, the lateral displacement force was lower at every angle of knee flexion (p = 0.005, p = 0.007, p = 0.005, respectively). The lateral displacement force increased as the flexion angle increased (p = 0.005), regardless of medial retinaculum integrity. Medial retinaculum acts as a stabilising factor for the patella, against its lateral dislocation in lower flexion angles. Therefore, methods of surgical reinforcement or repair of medial retinaculum could provide protection against recurrent patellar dislocation.

Flexural performance of glazed hollow bead reinforced concrete beams

Flexural static tests are conducted on glazed hollow bead reinforced concrete beams (referred to as GBLs) with a range of properties. The test variables included concrete material type and cross section depth as well as longitudinal reinforcement ratio of the flexural beams. The test results were analyzed in terms of damage mechanism, ductility, stiffness, and energy dissipation in the flexural beam. The addition of the glazed hollow bead as the lightweight aggregate was to obtain higher ductility and slower degradation of strength and stiffness. It was shown in the tests that the mechanical properties of the GBLs were better than that of normal concrete beams. A finite element model was developed for the beams and the lateral force–displacement curves obtained from analyses were compared with the experimental data. The results of this study are useful in the design and application of glazed hollow bead insulation concrete bending members.

Hybrid Jacketing for Rapid Repair of Seismically Damaged Reinforced Concrete Columns

This study proposes hybrid jacketing for rapid repair of seismically damaged concrete columns for bridge safety. The hybrid jacketing for a reinforced concrete (RC) column is composed of a thin cold-formed steel sheet wrapped around the column and its outside prestressing strands. Although the prestressing strands can prevent buckling of the confining steel sheet, the steel sheet can in turn prevent the prestressing strands from cutting into the concrete. The hybrid jacketing concept was validated with testing of a large-scale RC column with lap splice deficiency typical of pre-1970 bridge constructions in the Central United States. Results from the original and repaired columns were compared for hysteresis loops, strength, stiffness, ductility, and energy dissipation. The hybrid jacketing proved to be effective in restoring structural behavior of the damaged column to prevent bridge collapse. Such a cost-effective solution can be implemented at bridge sites in hours. Design equations to establish the lateral force–displacement relationship of the tested column to design the hybrid jacket are derived in detail.

Seismic response of timber frames with cane and mortar walls

This paper describes an experimental study into the seismic behaviour of low-cost walls incorporating timber frames with composite cane and cement mortar panels. Five cyclic tests on full-scale wall specimens of different geometric and material characteristics are described. The test set-up, wall configurations and material properties are introduced, followed by a detailed account of the experimental results and observations. Based on the results from the tests, the main behavioural features are discussed and the salient response parameters such as stiffness, strength, energy dissipation and ductility are examined. Particular emphasis is given to the assessment of key construction provisions such as mortar strength, galvanised wire mesh reinforcement and the presence of windows. The cyclic tests reported offer direct information on the lateral force–displacement response of the walls and their energy dissipation characteristics. Finally, simple expressions for determining the overall stiffness and capacity of the timber frame composite cane and mortar walls are proposed. As well as providing essential information for the future validation of more detailed numerical procedures, the experimental results presented in this paper also demonstrate the suitability of this form of low-cost construction for resisting deformation demands typical of large-magnitude earthquakes.

Performance of laterally loaded H-piles in sand

Results from experimental testing of four approximately one-third scale laterally loaded H-piles, subjected to monotonic and cyclic loading are presented. The test setups were designed to prevent torsion in the pile during testing and to eliminate the self-weight of the hydraulic actuator that could otherwise induce moment on the model piles. The tests were conducted in compacted medium dense sand and all the piles were extensively instrumented. Test results indicate that the lateral force–displacement responses under cyclic loading exhibited slight pinching behavior due to the gap that opened at the top of the soil-pile interface. Numerical simulations show that p–y curves based on the American Petroleum Institute (API) recommendations and that proposed by Reese et al. can reasonably predict the lateral response of the piles though slightly underestimate the ultimate capacities. The general pile behavior such as force–displacement response and moment distributions along the pile depth show slight sensitivity to the subgrade reaction modulus at large displacements.