Experimental and analytical study on seismic behavior of steel-concrete multienergy dissipation composite shear walls

In this paper, a steel-concrete multi-energy dissipation composite shear wall, comprised of steel-reinforced concrete （SRC） columns, steel plate （SP） deep beams, a concrete wall and energy dissipation strips, is proposed. In order to study the multi-energy dissipation behavior and restorability after an earthquake, two stages of low cyclic loading tests were carded out on ten test specimens. In the first stage, test on five specimens with different number of SP deep beams was carried out, and the test lasted until the displacement drift reached 2%. In the second stage, thin SPs were welded to both sides of the five specimens tested in the first stage, and the same test was carried out on the repaired specimens （designated as new specimens）. The load-bearing capacity, stiffness, ductility, hysteretic behavior and failure characteristics were analyzed for both stages and the results are discussed herein. Extrapolating from these results, strength calculation models and formulas are proposed herein and simulations using ABAQUS carried out, they show good agreement with the test results. The study demonstrates that SRC columns, SP deep beams, concrete wall and energy dissipation strips cooperate well and play an important role in energy dissipation. In addition, this study shows that the shear wall has good recoverability after an earthquake, and that the welding of thin SP＇s to repair a deformed wall is a practicable technique.

Research on seismic performance of shear walls with concrete filled steel tube columns and concealed steel trusses

In order to further improve the seismic performance of RC shear walls, a new composite shear wall with concrete filled steel tube （CFT） columns and concealed steel trusses is proposed. This new shear wall is a double composite shear wall; the first composite being the use of three different force systems, CFT, steel truss and shear wall, and the second the use of two different materials, steel and concrete. Three 1/5 scaled experimental specimens： a traditional RC shear wall, a shear wall with CFT columns, and a shear wall with CFT columns and concealed steel trusses, were tested under cyclic loading and the seismic performance indices of the shear walls were comparatively analyzed. Based on the data from these experiments, a thorough elastic-plastic finite element analysis and parametric analysis of the new shear walls were carried out using ABAQUS software. The finite element results of deformation, stress distribution, and the evolution of cracks in each phase were compared with the experimental results and showed good agreement. A mechanical model was also established for calculating the load-carrying capacity of the new composite shear walls. The results show that this new type of shear wall has improved seismic performance over the other two types of shear wails tested.

Nonlinear Finite Element Analysis of Mechanical Performance of Reinforced Concrete Short-Limb Shear Wall

On the basis of test, nonlinear finite element analysis of reinforcedconcrete (R. C) short-limb shear walls under monotonic horizontal load are carried out by ANSYSprogram in order to understand the evolution of cracking, deformation and failure course of thespecimens. At the same time, the results of numerical calculation are compared with the results oftest. The results indicate that, under monotonic horizontal load the failures of the specimens withflange wall and without flange wall all occur at the intersections of lintel bottom and limb ofwall, the failures also occur at the bottom of limb; the load-displacement curve of wall withoutflange is steeper than that of wall with flange, and the ductility is worse than that of wall withflange; the results, such as cracking, deformation, yield load and so on of finite element analysisagree well with the results of test. These results provide theoretical basis of study andapplication of R. C short-limb shear wall.

Post-fire cyclic behavior of reinforced concrete shear walls

The effects of fire exposure,reinforcement ratio and the presence of axial load under fire on the seismic behavior of reinforced concrete(RC) shear walls were investigated.Five RC shear walls were tested under low cyclic loading.Prior to the cyclic test,three specimens were exposed to fire and two of them were also subjected to a constant axial load.Test results indicate that the ultimate load of the specimen with lower reinforcement ratio is reduced by 15.8%after exposure to elevated temperatures.While the reductions in the energy dissipation and initial stiffness are 59.2%and 51.8%,respectively,which are much higher than those in the ultimate load.However,this deterioration can be slowed down by properly increasing reinforcement due to the strength and stiffness recovery of steel bars after cooling.In addition,the combined action of elevated temperatures and axial load results in more energy dissipation than the action of fire exposure alone.

Shaking table experimental study of recycled concrete frame-shear wall structures

In this study, four 1/5 scaled shaking table tests were conducted to investigate the seismic performance of recycled concrete frame-shear wall structures with different recycled aggregates replacement rates and concealed bracing detail. The four tested structures included one normal concrete model, one recycled coarse aggregate concrete model, and two recycled coarse and fi ne aggregate concrete models with or without concealed bracings inside the shear walls. The dynamic characteristics, dynamic response and failure mode of each model were compared and analyzed. Finite element models were also developed and nonlinear time-history response analysis was conducted. The test and analysis results show that the seismic performance of the recycled coarse aggregate concrete frame-shear wall structure is slightly worse than the normal concrete structure. The seismic resistance capacity of the recycled concrete frame-shear wall structure can be greatly improved by setting up concealed bracings inside the walls. With appropriate design, the recycled coarse aggregate concrete frame-shear wall structure and recycled concrete structure with concealed bracings inside the walls can be applied in buildings.

Experimental studies on behavior of fully grouted reinforced-concrete masonry shear walls

An experimental study is conducted on fully grouted reinforced masonry shear walls (RMSWs) made from concrete blocks with a new configuration. Ten RMSWs are tested under reversed cyclic lateral load to investigate the influence of different reinforcements and applied axial stress values on their seismic behavior. The results show that flexural strength increases with the applied axial stress, and shear strength dominated by diagonal cracking increases with both the amount of horizontal reinforcement and applied axial stress. Yield displacement, ductility, and energy dissipation capability can be improved substantially by increasing the amount of horizontal reinforcement. The critical parameters for the walls are derived from the experiment: displacement ductility values corresponding to 15% strength degradation of the walls reach up to 2.6 and 4.5 in the shear and flexure failure modes, respectively; stiffness values of flexure- and shear-dominated walls rapidly degrade to 17%–19% and 48%–57% of initial stiffness at 0.50 Dmax (displacement at peak load). The experiment suggests that RMSWs could be assigned a higher damping ratio (～14%) for collapse prevention design and a lower damping value (～7%) for a fully operational limit state or serviceability limit state.

Performance index limits of high reinforced concrete shear wall components

The deformation performance index limits of high reinforced concrete(RC) shear wall components based on Chinese codes were discussed by the nonlinear finite element method.Two typical RC shear wall specimens in the previous work were first used to verify the correctness of the nonlinear finite element method.Then,the nonlinear finite element method was applied to study the deformability of a set of high RC shear wall components designed according to current Chinese codes and with shear span ratio λ≥2.0.Parametric studies were made on the influence of shear span ratio,axial compression ratio,ratio of flexural capacity to shear capacity and main flexural reinforcement ratio of confined boundary members.Finally,the deformation performance index and its limits of high RC shear wall components under severe earthquakes were proposed by the finite element model results,which offers a reference in determining the performance status of RC shear wall components designed based on Chinese codes.

EXPERIMENTAL STUDY OF TENSILE CAPACITY OF CONCRETE IN RC SHEAR WALLS AFTER CRACKING

Through the test of 8 RC shear wall specimens and computer analysis ofstrains of steel bars with keyways in the specimens,the authors have studied the remains oftensile stress of concrete between cracks after concrete cracking and put forward a formulato calculate coefficient Ψ,the ununiform distribution factor of steel strain.This coefficientcan be used to modify the calculated steel strain in cracked zone,so as to make the resultsof using finite clement method to analyze shear walls more accurate.

Investigation on Cracking of Concrete Shear Wall under Exceeded Temperature Differences Rate

In situ, the changes of temperature, deformation, and stressing of steel bar of C40 reinforced concrete shear wall were measured, respectively. The results are obvious that the temperature change of climate is one of the most effective factors which could lead the concrete shear wall to cracking at earlier age. The temperature differences between inside and outside concrete shear wall are so large that the concrete will gain larger shrinkage. This larger shrinkage which is caused by the temperature reducing ratio will gain the strained action of head, end and reinforced steel bar of concrete shear wall. This action can lead to tensile stress on the surface and inside concrete shear wall. If the tensile stress would exceed the pull strength of concrete, the concrete shear wall would crack and cause deterioration. Thus, the enhancing curing of concrete shear wall in suit at earlier age, and controlling temperature reducing ratio and deform caused by shrinkage, will be available treatments which control occurring and developing of cracking on concrete shear wall.

Formwork lateral pressure of precast normal-concrete composite shear walls infilled with self-compacting concrete

Wall cracking and mold expanding due to concrete vibrations can be effectively solved through the application of precast normal-concrete composite shear walls infilled with self-compacting concrete(SCC). However, the high liquidity of SCC will induce a higher lateral pressure. Therefore, it is important to obtain a better understanding of the template lateral pressure. In this work, nine composite shear walls were experimentally investigated, focusing on the effects of two parameters, i.e., the casting rate and the section width of the formwork. The time-varying pressure was monitored during the SCC pouring. It is found that the increase of casting rate from 3.2 m/h to 10.3 m/h resulted in a higher maximum lateral pressure. The higher casting rate led to a longer time required for the lateral pressure to drop to a steady value. There was no correlation between the section width and the rate of decrease in the initial formwork pressure and stable value. Based on the test results, a formula considering the effect of casting speed for the calculation of SCC formwork pressure was established to fill the gap in the current standards and for engineering applications.

Analysis on Construction Quality Control Technology of Reinforced Concrete Shear Wall Structure

In the process of continuous development of construction enterprises, new requirements have been put forward for construction projects. By strengthening the construction quality control of reinforced concrete shear wall structure, the construction level of reinforced concrete can be continuously improved, the construction quality can be guaranteed, and the construction project can be successfully completed, which is worthy of extensive application and promotion in construction enterprises, thus providing a broader development space for construction enterprises.

Elasto-plastic Analysis of High-strength Concrete Shear Wall with Boundary Columns Using Fiber Model

In this study,an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load.The boundary column and shear wall were divided into fiber elements,and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens.The results show that the finite element analysis results were in good agreement with the experimental results.The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall.The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters:axis compression ratio,height to width ratio,ratio of vertical reinforcement,and ratio of longitudinal reinforcement in the boundary column.The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease.The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase.The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility.The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.

Analysis and seismic tests of composite shear walls with CFST columns and steel plate deep beams

A composite shear wall concept based on concrete filled steel tube （CFST） columns and steel plate （SP） deep beams is proposed and examined in this study. The new wall is composed of three different energy dissipation elements： CFST columns; SP deep beams; and reinforced concrete （RC） strips. The RC strips are intended to allow the core structural elements - the CFST columns and SP deep beams - to work as a single structure to consume energy. Six specimens of different configurations were tested under cyclic loading. The resulting data are analyzed herein. In addition, numerical simulations of the stress and damage processes for each specimen were carried out, and simulations were completed for a range of location and span-height ratio variations for the SP beams. The simulations show good agreement with the test results. The core structure exhibits a ductile yielding mechanism characteristic of strong column-weak beam structures, hysteretic curves are plump and the composite shear wall exhibits several seismic defense lines. The deformation of the shear wall specimens with encased CFST column and SP deep beam design appears to be closer to that of entire shear walls. Establishing optimal design parameters for the configuration of SP deep beams is pivotal to the best seismic behavior of the wall. The new composite shear wall is therefore suitable for use in the seismic design of building structures.

Effect of Eccentric Shear Stiffness of Walls on Structural Response of RC Frame Buildings

Current research study consists of determining the optimum location of the shear wall to get the maximum structural efficiency of a reinforced concrete frame building. It consists of a detailed analysis and design review of a seven-story reinforced concrete building to understand the effect of shear wall location on the response of reinforced concrete structures when subjected to different earthquake forces. Three trail locations of shear walls are selected and their performance is monitored in terms of structural response under different lateral loads. Required objectives are achieved by obtaining design and construction drawings of an existing reinforced concrete structure and modeling it on Finite Element Method (FEM) based computer software. The structure is redesigned and discussed with four different configurations (one without shear wall and three with shear walls). Main framing components (Beams, Columns and Shear walls) of the superstructure are designed using SAP 2000 V. 19.0 whereas substructure (foundation) of RC building was?designed using SAFE. American Concrete Institute (ACI) design specifications were used to calculate the cracked section stiffness or non-linear geometrical properties of the cracked section. Uniform Building Code (UBC-97) procedures were adopted to calculate the lateral earthquake loading on the structures. Structural response of the building was monitored at each story level for each earthquake force zone described by the UBC-97. The earthquake lateral forces were considered in both X and Y direction of the building. Each configuration of shear wall is carefully analyzed and effect of its location is calibrated by the displacement response of the structure. Eccentricity to the lateral stiffness of the building is imparted by changing the location of shear walls. Results of the study have shown that the location of shear wall significantly affects the lateral response of the structure under earthquake forces. It also motivates to carefully decide the center of lateral stiffness of building prior to deciding the location of shear walls.

Structural Analysis of a RC Shear Wall by Use of a Truss Model

Purpose of present work is to develop a reliable and simple method for structural analysis of RC Shear Walls. The shear wall is simulated by a truss model as the bar of a truss is the simplest finite element. An iterative method is used. Initially, there are only concrete bars. Repeated structural analyses are performed. After each structural analysis, every concrete bar exceeding tensile strength is replaced by a steel bar. For every concrete bar exceeding compressive strength, first its section area is increased. If this is not enough, a steel bar is placed at the side of it. For every steel bar exceeding tensile or compressive strength, its section area is increased. After the end of every structural analysis, if all concrete and steel bars fall within tensile and compressive strengths, the output data are written and the analysis is terminated. Otherwise, the structural analysis is repeated. As all the necessary conditions (static, elastic, linearized geometric) are satisfied and the stresses of ALL concrete and steel bars fall within the tensile and compressive strengths, the results are acceptable. Usually, the proposed method exhibits a fast convergence in 4 - 5 repeats of structural analysis of the RC Shear Wall.

High-Rise Residential Reinforced Concrete Building Optimisation

In the last few decades structure optimisation has become a main task in a civil engineering project. As a matter of fact, due to the complexity and particularity of every structure, the great amount of variables and design criteria to considerate and many other factors, a general optimisation’s method is not simple to formulate. As a result, this paper focuses on how to provide a successful optimisation method for a particular building type, high-rise reinforced concrete buildings. The optimization method is based on decomposition of the main structure into substructures: floor system, vertical load resisting system, lateral load resisting system and foundation system;then each of the subsystems using the design criteria established at the building codes is improved. Due to the effect of the superstructure optimisation on the foundation system, vertical and lateral load resisting system is the last to be considered after the improvement of floor. Finally, as a case example, using the method explained in the paper, a 30-story-high high-rise residential building complex is analysed and optimised, achieving good results in terms of structural behaviour and diminishing the overall cost of the structure.

装配式轻钢框架-轻钢骨架轻混凝土墙板结构抗震性能

为研究装配式轻钢框架-轻钢骨架轻混凝土墙板结构抗震性能,对1个足尺轻钢框架结构试件和3个足尺轻钢框架-轻钢骨架轻混凝土墙板结构试件进行了低周反复荷载下的抗震性能试验及理论分析,试件变量包括:2种装配构造,即内嵌式装配墙板、外贴式装配墙板;2种轻钢骨架轻混凝土墙板,即框架式轻钢骨架轻混凝土墙板、桁架式轻钢骨架轻混凝土墙板。研究了各试件的破坏特征和损伤演化过程,分析了结构滞回特性、承载力、变形能力、刚度退化、耗能性能和应变。结果表明:装配式轻钢框架-轻钢骨架轻混凝土墙板结构共同工作性能良好,其水平承载力相比轻钢框架提高了204.7%~210.4%,抗侧刚度提高了257.3%~512.5%,结构变形及耗能能力有显著提高;内嵌墙板的自攻钉连接构造以及外贴墙板的螺栓连接构造传力性能可靠,结构具备2道抗震防线的受力特征;基于简化塑性分析模型以及拉压杆软化桁架模型,对试件承载力进行了计算,计算结果与试验符合较好。

钢管混凝土键连接框架梁和剪力墙的受剪性能

目的 研究钢管混凝土键连接框架梁和剪力墙的受剪性能,为工程应用提供设计依据。方法 应用有限元分析软件ABAQUS对比钢管混凝土键连接与现浇连接梁墙的结构受剪性能,分析前者受剪机理及不同因素对受剪性能的影响。结果 钢管混凝土键连接梁墙的结构承载力和延性系数较现浇结构分别提高约10%和34%;钢材强度从Q235到Q390,初始刚度增加8.44%;截面高度从100 mm到120 mm,延性系数提高17.73%;截面厚度每增加2 mm,承载力提高约15%;截面长度和混凝土强度等级对承载力、初始刚度和延性系数的影响均小于15%,纵向距离对其受剪性能几乎无影响。结论 采用钢管混凝土键连接梁墙的结构总体受剪性能优于现浇结构;钢材强度和截面厚度分别是影响初始刚度和承载力的主要因素。

HPC端部加强双钢板组合剪力墙的抗震性能

为研究高性能混凝土端部加强双钢板组合剪力墙受力机理及破坏形态,以轴压比、腹部普通混凝土强度等级为关键参数,设计了4片普通试件,7片HPC端部加强试件,运用ABAQUS构建其有限元模型,研究其抗震性能。结果表明:同轴压比下,HPC端部加强试件相比普通试件屈服荷载提高16.30%,峰值荷载提升13.40%;随着轴压比提高,HPC端部加强试件峰值荷载和屈服荷载分别提高7.22%和2.72%,随着轴压比减小,HPC端部加强试件延性提升22.26%;提高腹部腔体混凝土强度等级,HPC端部加强试件的屈服荷载和峰值荷载分别提高13.01%和11.14%,延性提升16.91%。

自攻钉集块连接混凝土复合剪力墙抗震性能试验

提出了适用于装配式混凝土复合剪力墙结构的自攻钉集块连接构造,为研究自攻钉集块连接混凝土复合剪力墙的抗震性能,设计制作了3个剪跨比为1.39的足尺剪力墙试件,进行了低周反复荷载试验,主要变量包括自攻钉集块连接构造、自攻钉集块与后浇条带组合连接构造以及L形边框构造柱。分析了试件破坏模式、承载力、滞回特性、刚度及退化、变形能力、耗能性能和应变特征等。结果表明:自攻钉集块连接构造装配便捷,受力性能可靠;采用自攻钉集块与后浇条带组合连接构造试件的承载力及刚度相比自攻钉集块连接构造分别提高了8.54%和6.03%;设置L形边框构造柱的试件承载力、刚度及耗能分别提高了67.48%、129.33%和277.93%。自攻钉集块连接复合剪力墙具有良好的抗震性能,满足装配式低层住宅混凝土复合剪力墙结构的抗震设计要求,可用于实际工程。