An effective simplified model of composite compression struts for partially-restrained steel frame with reinforced concrete infill walls

To resolve the issue regarding inaccurate prediction of the hysteretic behavior by micro-based numerical analysis for partially-restrained（PR）steel frames with solid reinforced concrete（RC）infill walls,an innovative simplified model of composite compression struts is proposed on the basis of experimental observation on the cracking distribution,load transferring mechanism,and failure modes of RC infill walls filled in PR steel frame.The proposed composite compression struts model for the solid RC infill walls is composed ofαinclined struts and main diagonal struts.Theαinclined struts are used to reflect the part of the lateral force resisted by shear connectors along the frame-wall interface,while the main diagonal struts are introduced to take into account the rest of the lateral force transferred along the diagonal direction due to the complicated interaction between the steel frame and RC infill walls.This study derives appropriate formulas for the effective widths of theαinclined strut and main diagonal strut,respectively.An example of PR steel frame with RC infill walls simulating simulated by the composite inclined compression struts model is illustrated.The maximum lateral strength and the hysteresis curve shape obtained from the proposed composite strut model are in good agreement with those from the test results,and the backbone curve of a PR steel frame with RC infill walls can be predicted precisely when the inter-story drift is within 1%.This simplified model can also predict the structural stiffness and the equivalent viscous damping ratio well when the inter-story drift ratio exceeds 0.5%.

Study on the effect of the infill walls on the seismic performance of a reinforced concrete frame

Motivated by the seismic damage observed to reinforced concrete （RC） frame structures during the Wenchuan earthquake, the effect of infill walls on the seismic performance of a RC frame is studied in this paper. Infill walls, especially those made of masonry, offer some amount of stiffness and strength. Therefore, the effect of infill walls should be considered during the design of RC frames. In this study, an analysis of the recorded ground motion in the Wenehuan earthquake is performed. Then, a numerical model is developed to simulate the infill walls. Finally, nonlinear dynamic analysis is carried out on a RC frame with and without infill walls, respectively, by using CANNY software. Through a comparative analysis, the following conclusions can be drawn. The failure mode of the frame with infill walls is in accordance with the seismic damage failure pattern, which is strong beam and weak column mode. This indicates that the infill walls change the failure pattern of the frame, and it is necessary to consider them in the seismic design of the RC frame. The numerical model presented in this paper can effectively simulate the effect of infill walls on the RC frame.

Effects of timber infill walls on the seismic behavior of traditional Chinese timber frames

This study investigates the enhanced effect of timber infill walls on the seismic behavior of traditional Chinese timber frames.Two 1/2 scaled traditional Chinese timber infill walls(TIWs),two 1/2 scaled timber frames with timber infill walls(TFTIWs)and one 1/2 scaled timber frame(TF)were fabricated and tested under low-cyclic reversed loading.The failure modes,strength,stiffness,and energy consumption capacity of the TIWs and the TFTIWs were obtained,and the effects of the TIWs on the seismic performance of the TFTIWs were investigated.The results showed that the TIWs can increase the stiffness and ultimate bearing capacity of the TF,up to 60%and 80%,respectively.The strength degradation coefficient of the TFTIWs was slightly higher than that of the TF when the inter-story drift ratio exceeded 0.02 rad,and the TIWs helped to mitigate the strength degradation of the TFTIWs.It was also found that the TFTIWs had a higher cumulative energy dissipation when compared with the TF(up to a 60%increase),indicating the TIWs had reasonably good energy dissipation capacity.When the TIWs generated a solid contribution to the carrying capacity and energy dissipation of the TF,the lateral drift thresholds were 1/100 and 1/43 of the column height,respectively.Furthermore,the TIWs and TFTIWs presented a good ductility,and the TIW could effectively reduce the pull-out amount of the tenon from the mortise of the TF;however,the TIWs had little influence on the stiffness degradation level or improvement of the ductility of the TF.

Field measurements for calibration of simplified models of the stiffening effect of infill masonry walls in high-rise RC framed and shear-wall buildings

As a type of nonstructural component, infill walls play a significant role in the seismic behavior of high-rise buildings. However, the stiffness of the infill wall is generally either ignored or considered by simplified empirical criteria that lead to a period shortening. The difference can be greatly decreased by using a structural identification methodology. In this study, an ambient vibration test was performed on four on-site reinforced concrete high-rise buildings, and the design results were compared with the PKPM models using corresponding finite element(FE) models. A diagonal strut model was used to simulate the behavior of the infill wall, and the identified modal parameters measured from the on-site test were employed to calibrate the parameters of the diagonal strut in the FE models. The SAP2000 models with calibrated elastic modulus were used to evaluate the seismic response in the elastic state. Based on the load-displacement relationship of the infill wall, nonlinear dynamic analysis models were built in PERFORM-3 D and calibrated using the measured modal periods. The analysis results revealed that the structural performance under small/large earthquake records were both strengthened by infill walls, and the contribution of infill walls should be considered for better accuracy in the design process.

Seismic performance evaluation of an infilled rocking wall frame structure through quasi-static cyclic testing

Earthquake investigations have illustrated that even code-compliant reinforced concrete frames may suffer from soft-story mechanism.This damage mode results in poor ductility and limited energy dissipation.Continuous components offer alternatives that may avoid such failures.A novel infilled rocking wall frame system is proposed that takes advantage of continuous component and rocking characteristics.Previous studies have investigated similar systems that combine a reinforced concrete frame and a wall with rocking behavior used.However,a large-scale experimental study of a reinforced concrete frame combined with a rocking wall has not been reported.In this study,a seismic performance evaluation of the newly proposed infilled rocking wall frame structure was conducted through quasi-static cyclic testing.Critical joints were designed and verified.Numerical models were established and calibrated to estimate frame shear forces.The results evaluation demonstrate that an infilled rocking wall frame can effectively avoid soft-story mechanisms.Capacity and initial stiffness are greatly improved and self-centering behavior is achieved with the help of the infilled rocking wall.Drift distribution becomes more uniform with height.Concrete cracks and damage occurs in desired areas.The infilled rocking wall frame offers a promising approach to achieving seismic resilience.

A Theoretical Study the Effect of Openings in Infill Wall Panels on the Behavior of Structures

Two dimensional,reinforced concrete building frames built on raft foundation and having infill wall panels with openings in them are analysed using the direct stiffness method.Beams and columns are modelled by beam column elements.Wall panels are modelled by plane stress finite elements.The raft foundation is modelled by uniaxial finite elements.The soil is modelled as half space model.Openings in wall panels are introduced by using fictitious beams between real floor beams. A computer program is written to carry out the static analysis and do the necessary comparison to show the effect of openings on the structural behavior.

Shaking test research on connection modes between block infill wall and frame beam

In order to achieve an optimal anti-seismic behavior,or rather stability,the out-of-plane stability of infill wall in frame has been researched with the shaking test of four sets of two-layer infill wall,in which four different connection modes of filled with inclined bricks on the top,disconnection,flexibility and semi-flexibility were adapted.The acceleration and displacement response of the specimens were analyzed under the seismic load.Also,some feasible connection modes were gained by comparing the response of infill walls.Finally,the calculation of earthquake of infill wall was held.The results showed that seismic responses of the infill walls whose connect with frame in form of flexibility and semi-flexibility modes are weaker than others obviously,and their integrality is better.Thus the conclusion could be drawn that out-of-plane stability of the specimens with connection modes of flexibility and semi-flexibility are better than those with the connection modes of filled with inclined bricks on the top and disconnection.The research results can provide evidence for establishing specifications and directing the construction and therefore help reduce the casualties and property loss caused by earthquake disasters.

Shaking Table Test on Out-of-Plane Stability of Infill Masonry Wall

The behaviors of infill wall in earthquakes show that infill masonry walls,which are used as nonstructural elements of concrete frames,are vulnerable when they are subjected to earthquake.In order to achieve an optimal antiseismic behavior,or even stability,two methods of connection are investigated.The shaking table tests,with 1:3 scale walls of two-storey model subjected to horizontal earthquake loads,were carried out to investigate the out-of-plane behaviors with different connections between walls and beams.The test results show that the connection methods employed between walls and beams have a significant effect on the out-of-plane stability of infill walls.The walls bound by bars with the beams perform better than those with inclined bricks without gaps.

Comparative Study on Diagonal Strut Model of Infill Wall

The equivalent diagonal strut models of infill wall mainly include the single strut model and multi-strut model.Firstly,several equivalent strut models and their characteristics are introduced in this paper.Then,model analysis and pushover analysis are carried out on infilled frame models with the aid of the software SAP2000.Two typical single strut models and a typical three-strut model are used to simulate the panel of the frames respectively.It is indicated that the period reduction factor of the frame with a three-strut model is close to the value recommended by the current code.The infill wall has great influence on the overall stiffness,bearing capacity and weak position of the structure.The stiffness and the bearing capacity of the infilled frame increase with the increase of the number of the infill walls.The unfilled story is the weak position of the infilled frame,and when the unfilled story at the bottom of the infilled frame,the seismic response of the upper infill layer decreases with the increasing of the number of unfilled story.

Flexural Behavior of Cross-Connected Brick Masonry Infill Wall Panels Supported on Reinforced Concrete Beam Grids

This paper presents an experimental investigation on the flexural behavior of cross-connected brick masonry infill wall panels supported on reinforced concrete beam grids above and below the walls.The experimental program was comprised of six wall systems.The effect of change in lower beam stiffness relative to the wall and the geometry of the main walls were investigated.From the results of the experimental tests,the increase in the depth of the lower beam grid reduces the deflection,resulting in an increase in the load carrying capacity of the wall.Further,the stiffness of the main walls affects the deflection and the failure load of the cross walls.

Performance of masonry enclosure walls:lessons learned from recent earthquakes

This paper discusses the issue of performance requirements and construction criteria for masonry enclosure and infill walls. Vertical building enclosures in European countries are very often constituted by non-load-bearing masonry walls, using horizontally perforated clay bricks. These walls are generally supported and confined by a reinforced concrete frame structure of columns and beams/slabs. Since these walls are commonly considered to be nonstructural elements and their influence on the structural response is ignored, their consideration in the design of structures as well as their connection to the adjacent structural elements is frequently negligent or insufficiently detailed. As a consequence, nonstructural elements, as for wall enclosures, are relatively sensitive to drift and acceleration demands when buildings are subjected to seismic actions. Many international standards and technical documents stress the need for design acceptability criteria for nonstructural elements, however they do not specifically indicate how to prevent collapse and severe cracking, and how to enhance the overall stability in the case of moderate to high seismic loading. Furthermore, a review of appropriate measures to improve enclosure wall performance and both in-plane and out-of-plane integrity under seismic actions is addressed.

Experimental Investigation to Establish the Possibility of Realistic Simulation of the Behavior of Single Storey—One Bay Infilled R.C.Frames in Scale 1:9,Subjected to Horizontal Cyclic Loading

In order to study the dynamic behaviour of construction,specifically seismic response of structures,as many researchers did,we have resorted to modelling methods,based on the scaled internal forces.Therefore,this research includes results of an experimental investigation aimed to establish the possibility of realistic simulations of the cyclic response of small-scale models of one bay,one-storey reinforced concrete frames with masonry infills as a preliminary step for simulating the dynamic response of such structural.So,the specimens constructed were 1:9 scale R/C frames.These 1:9 scale infill frames were constructed with prototype materials and were tested in an extensive experimental sequence representing specimens of a scale near the prototype(1:3).The tested laboratory models include 1:3 scale infilled R/C frames that were built from original material such as steel,concrete and masonry infills(hollow masonry units and mortar).With the same scale,geometry and construction materials used for the construction of a 1:3 scale 5-story three dimensional building.This program consisted of 16 models,5 bare and 11 masonry infilled.all models refer to single-storey one-bay 1:9 scale as for the original structure and a one third of the scale(1:3)as for the prototype(1:3).The reinforced concrete specimens were designed in such a way as to prevent shear failure of the columns.Finally,the present paper was carried out in the Laboratory of Strength of Materials and Structures in the Department of Civil Engineering at Aristotle University of Thessaloniki.

考虑填充墙力学贡献的规范RC框架办公楼抗震韧性评价

提升建筑结构的抗震韧性是当前工程界抗震减灾的核心任务,根据现代规范设计的钢筋混凝土框架尽管具有较高的抗倒塌安全储备,但其韧性能力并不明确。既有研究在量化结构抗震韧性时,均仅采用结构构件的地震响应作为输入,忽略了非结构构件对整体结构地震响应的影响。针对上述问题,该文根据规范最低要求,设计一栋六层钢筋混凝土框架办公楼,并对其抗震韧性进行评价,明确了该办公楼的抗震韧性与《建筑抗震韧性评价标准》中建议的韧性目标的差距,揭示各类构件对结构韧性的影响。对比研究了填充墙力学贡献对办公楼抗震韧性的影响。研究结果表明:该六层框架办公楼的修复费用主要来源于填充墙和暖通类设备的修复工作,而修复时间主要由结构构件和填充墙的修复时间组成。填充墙的力学贡献会提高该办公楼的抗震韧性,减少结构构件和位移型非结构构件的修复费用和时间约50%,但对加速度型非结构构件的影响较小。

考虑非结构构件的木结构古建筑抗震性能研究综述

木结构古建筑是我国文物建筑的主体,它以木材为主要承重构件,具有深厚的历史文化价值。本文根据已有研究,从结构试验、数值模拟、抗震性能评估方法 3个方面,总结了含有隔墙、隔扇、雀替等非结构构件的古木建筑抗震性能研究现状。研究表明,非结构构件可以限制榫卯节点拔榫,改善节点受力,不同程度提高结构的强度、刚度和耗能能力,降低了结构在地震作用下坍塌的概率。最后结合我国木结构古建筑的研究现状以及与其他国家的研究差异,给出了未来木结构古建筑抗震性能的可能研究方向。

近场爆炸下波纹双钢板混凝土组合墙板的损伤破坏及抗爆性能

相对于传统的钢筋混凝土墙板和平面双钢板-混凝土组合墙板(profiled double-skin composite wall,PDSCW),波纹双钢板-混凝土组合墙板(concrete-infilled double steel corrugatedplate wall,CDSCW)具有更高的轴向抗压承载力、更大的侧向抗弯刚度以及良好的抗冲击和抗震性能,在船舶和军事领域有广阔的应用前景。制作2种CDSCW试件,通过近场爆炸试验对比分析了2种试件的损伤模式及动态响应;采用ANSYS/LS-DYNA软件建立了CDSCW和PDSCW的有限元模型,研究了近场爆炸下2种混凝土组合墙板的损伤机理和爆炸响应,并与试验结果进行对比分析;分析了混凝土厚度、钢板厚度、药量对CDSCW抗爆性能的影响。结果表明:近场爆炸作用下,相较于PDSCW,相同混凝土方量和尺寸(长、宽)的CDSCW具有更大的抗弯刚度、更强的抗变形能力以及更优的抗爆性能;增加波纹深度能有效提高CDSCW的抗爆性能,可为抗爆构件设计和相关工程研究提供参考。

半刚接钢框架内填实体RC墙结构的地震易损性能评估

为评估半刚接钢框架内填实体RC墙结构(PSRCW)的地震易损性能及倒塌储备能力,考虑层数和抗震设防烈度影响合理设计了4个PSRCW结构基准算例,采用Latin超立方抽样方法考虑型钢、混凝土、钢筋等材料力学性能及内填RC墙体厚度几何尺寸的随机性,拓展为4组共计160个PSRCW算例.通过合理选取40条汶川地区实测地震记录,与每组40个PSRCW结构样本随机组合,构成了4组40个地震-结构样本对,通过弹塑性时程分析方法确定了PSRCW结构在“弹性极限”“完全运行”“运行”“生命安全”“接近倒塌”“倒塌”性态下的地震易损性曲线,并进行了抗震性能评估,量化了PSRCW结构的倒塌储备能力.分析结果表明:PSRCW结构的倒塌安全储备系数在3.0~4.3之间,具有良好的抗地震倒塌能力.

带PC填充墙的装配式RC联肢剪力墙受力性能数值分析

为研究带预制混凝土(PC)填充墙的装配式RC联肢剪力墙在水平荷载作用下的受力性能,基于试验建立了无填充墙试件(CSW-N)和带PC填充墙试件(CSW-F和CSW-R)的有限元模型,并考察了轴压比、PC填充墙混凝土强度等级和刚性连接试件锚固钢筋布置等对装配式RC联肢剪力墙受力性能的影响。结果表明:轴压比由0.1增加至0.6时,试件CSW-F峰值承载力增加了约69.92%,延性系数下降了约40.68%;试件CSW-R的峰值承载力增加了约47.00%,延性系数下降了约42.06%。对于试件CSW-F,由于PC填充墙对剪力墙的约束作用较小,随PC填充墙混凝土强度等级增大,其峰值承载力增幅较小;对于试件CSW-R,当实心墙和夹心墙混凝土强度等级由C15增加至C30时,试件的峰值承载力分别提高了7.20%和4.32%,在相同混凝土强度下,实心墙的承载力高于夹心墙的承载力。对于试件CSW-R,锚固钢筋直径变化对剪力墙受力性能影响较小,但增加锚固钢筋数量可提高剪力墙峰值承载力。

柔性连接填充墙RC框架抗连续倒塌性能研究

为了研究柔性连接填充墙钢筋混凝土(reinforced concrete,RC)框架的抗连续倒塌性能,用ABAQUS建立了纯框架、刚性和柔性连接填充墙框架的有限元模型,并验证了建模方法的可靠性。对比了刚性与柔性连接填充墙对RC框架抗连续倒塌性能的影响,研究了墙-框连接刚度、拉结筋设置情况、构造柱数量和类型、砌块和砂浆强度对柔性连接填充墙RC框架连续倒塌抗力的影响。结果表明:柔性连接填充墙RC框架的连续倒塌抗力和延性更好;墙-框间填充高弹性材料、增加构造柱数量、提高砂浆强度有利于提高柔性连接填充墙RC框架抗连续倒塌的峰值承载力和极限承载力;墙-框间填充常规填缝材料、设置Ⅱ型构造柱、提高砌块强度会提高峰值承载力、降低极限承载力,设置拉结筋的效果则相反。

不同填充墙构造方法对RC框架抗震性能影响研究

为定量评估不同填充墙构造方法对钢筋混凝土(reinforced concrete,RC)框架抗震性能的影响,搜集整理国内外砌体填充墙RC框架拟静力试验数据,筛选出19篇文献中共68个数据较为详尽的试件作为样本,分析对比柔性连接填充墙、增强填充墙整体性及设置阻尼耗能装置三类构造方法对试件的峰值点承载力、初始刚度、位移延性系数和等效黏滞阻尼系数4个参数的影响程度。结果表明:相较于传统构造方法,柔性连接填充墙框架的承载力和刚度均有所下降,变形能力提升;增强整体性的方法可提升试件承载力、刚度和变形能力,可作为一种较好的既有框架结构的加固方法;设置阻尼耗能装置虽然结构的承载力和刚度有所降低,但提升了结构的变形能力和耗能能力,在建造成本可接受的情况下可作为新建建筑的韧性提升方案。

钢筋-砂浆面层交叉条带加固带填充墙框架抗震性能试验研究

为研究钢筋-砂浆面层交叉条带加固带填充墙框架结构的抗震性能并建立受剪承载力计算公式,设计制作了8榀低矮填充墙框架结构、3榀高窄填充墙框架结构、1榀未设钢筋-砂浆面层交叉条带加固的对照试件,进行了抗震性能试验。结果表明:钢筋-砂浆面层交叉条带加固带填充墙框架的受剪承载力受混凝土强度、框架柱截面尺寸以及交叉条带配筋量影响较大,加固后受剪承载力最高可提升40%;加固后试件的耗能能力和延性均有一定程度的提升;在填充墙上增设的钢筋-砂浆面层交叉条带可视为协助框架结构受力的拉压杆体系。对试验数据进行拟合得到加固后试件受剪承载力计算公式,结果表明:框架、填充墙和交叉条带之间有承载力协同效果,填充墙框架结构的公式计算值和试验值吻合较好。