Investigation on the behavior of brick-infilled steel frames with openings, experimental and analytical approaches

This article deals with an experimental program to investigate the in-plane seismic behavior of steel frames with clay brick masonry infills having openings. Six large-scale, single-story, single-bay frame specimens were tested under in-plane cyclic loading applied at roof level. The infill panel specimens included masonry infills having central openings of various dimensions. The experimental results indicate that infill panels with and without openings can improve the seismic performance of steel frames and the amount of cumulative dissipated energy of the infill panels with openings, at ultimate state are almost identical. Furthermore, contrary to the literature, the results indicate that infilled frames with openings are not always more ductile than the ones with solid infill. It seems that the ductility of such frames depends on the failure mode of infill piers. This experimental investigation shows that infilled frames with openings experienced pier diagonal tension or toe crushing failure and have smaller ductility factors than those frames with solid infill. Furthermore, a simple analytical method is proposed to estimate the maximum shear capacity of masonry infilled steel frames with window and door openings.     

密肋复合墙板框格单元破坏模式研究

框格单元是密肋复合墙板的基本受力单元,为了详细研究框格单元的破坏过程、破坏模式及填充砌块与框格的相互作用机理,进行了3个框格单元的单调对角加载试验。试验表明:加载过程中首先在填充块对角线附近出现一至二条贯通的主拉裂缝;接着框格上、下节点及框格梁柱上出现垂直裂缝;填充块上下角区出现圆弧状受压裂缝后框格单元达到承载力极限状态,其最终破坏形式与填充块和框格相对刚度有关。基于弹性地基梁理论分析了加载过程中框格和填充材料的受力特点,指出框格单元存在三种破坏形式:砌块对角压碎破坏、砌块角部压碎破坏、肋柱肋梁节点局部受压破坏。其中第二种形式与复合墙板的各阶段破坏形式相对应,且塑性铰转动充分,是一种合理的破坏模式。最后结合试验及理论分析将填充块等效为铰接于框格的对角斜压杆,提出等效斜压杆宽度、强度和刚度的计算方法,建立单元格简化分析模型,为墙板的受力分析提供了理论基础。     

钢框架内嵌角部圆弧缺口AAC砌体填充墙滞回性能研究

基于在填充墙的角部设置缺口可弱化拉(压)力带的原理,设计了一系列钢框架内嵌角部圆弧缺口填充墙试件,包括1个纯钢框架、1个无缺口蒸压轻质加气混凝土(AAC)砌体填充墙钢框架和9个带不同尺寸圆弧缺口的AAC砌体填充墙钢框架,采用ABAQUS软件对各试件进行了有限元模拟分析.研究了填充墙角部设置的圆弧缺口构造对钢框架滞回性能...     

A macro-modelling approach for the analysis of infilled frame structures considering the effects of openings and vertical loads

During the last decades, several macro-models have been proposed for the modelling of the infill panels' contribution to the lateral strength of frames. Despite all this effort, a robust model, which takes into account the influence of the vertical load, is not yet available. Furthermore, the influence of the very common case of infill walls with openings, such as windows and doors, has been neglected in all the code provisions that have been published so far. In this paper, an updated macro-model, based on the equivalent pin-jointed diagonal compressive strut, is presented. The proposed macro-model is able to represent the stiffening effect of the infill panel with openings by taking into account both the size of the opening and the vertical load acting on the frame. Detailed and in-depth parametrical investigation, based on finite element analysis, shows that the proposed mathematical macro-model can be used as a reliable and useful tool for the determination of the equivalent compressive strut width since it accounts for a large number of parameters, which are not generally accounted for by the already available models in the literature.     

Experimental evaluation of seismic performance of low‐shear strength masonry infills with openings in reinforced concrete frames with deficient seismic details

The influence of openings on lateral behaviour of low‐shear strength masonry infilled reinforced concrete frames is investigated. The design of the reinforced concrete frames in this study are aimed to reflect common seismic design deficiencies, such as location of lap splices at bottom of columns, insufficient transverse reinforcements at column and beam ends and lack of stirrups at beam‐column joints. Six half‐scale single‐storey, single‐bay frame specimens were tested under in‐plane lateral loading. The investigated parameters include shape (window and door), size (regular and large windows) and location of the openings (eccentric and central). The results indicate that presence of openings alters the failure mode, increases the damage level and reduces ductility, strength and stiffness of the infilled frame. The door opening led to reductions of 29% in strength, 34% in the effective stiffness and 23% in the energy dissipation capacity. The window openings led to average reductions of 23% in strength, 8% in effective stiffness and 11% in the energy dissipation capacity. Empirical equations are proposed for estimating overall reductions in stiffness and strength of infilled frames because of the presence of openings, which take into account the effects of size, shape and location of openings. Copyright © 2013 John Wiley & Sons, Ltd.     

An innovative scheme for retrofitting masonry-infilled non-ductile reinforced concrete frames

An innovative retrofit scheme is proposed for masonry-infilled non-ductile reinforced concrete frames to remedy the brittle shear failure caused by the huge strut force exerted by the un-reinforced masonry (URM) panel on the columns following corner crushing of the panel. The URM panel is separated from the columns, and steel brackets are provided to transfer the strut forces from the panel to the beam, thereby totally eliminating transfer of large strut force to the columns. This scheme has a beneficial effect of increasing the shear capacity of the beam due to the large compression induced in it to resist theshear component caused by the strut force. Cyclic load test on a 3/4 scale specimen of a single-bay, single-story frame assembly retrofitted with the proposed scheme has revealed much enhanced performance over the un-retrofitted one, with the drift capacity increased five folds while retaining most of the strength and stiffness.     

多层砌体填充墙框架结构抗震性能试验研究

为了研究砌体填充墙沿框架层不连续布置对框架结构抗震性能的影响,进行了3榀两层单跨砌体填充墙框架结构模型、1榀单层单跨砌体填充墙框架结构模型、1榀两层单跨框架结构模型和1榀单层单跨框架结构模型的对比试验,分析了各试件的破坏特征、滞回曲线、骨架曲线、位移延性、刚度退化、承载力退化和耗能性能等抗震性能指标。结果表明：无论是单层单跨还是两层单跨的砌体填充墙框架结构,其水平峰值荷载和初始刚度比相应的纯框架结构均有较大幅度的提高,且其刚度退化程度比相应纯框架结构要缓慢;砌体填充墙的存在提高了框架结构的抗侧刚度和水平峰值荷载,使框架结构的变形由剪切型逐渐转变为弯剪型;砌体填充墙参与了结构的滞回耗能,填充墙框架的位移延性和累积耗能能力明显优于框架;砌体填充墙沿框架层不连续布置会引起框架结构层间侧移刚度和层间受剪承载力发生突变,影响框架结构的破坏形态,但由于砌体填充墙参与了框架结构的滞回耗能,故其仍具有较好的抗震性能。     

钢框架内填混凝土墙结构体系有限元分析

对钢框架—内填混凝土墙结构体系进行了非线性有限元分析,得到了该体系在单向荷载作用下的变形及应力分布状况。为了简化计算,采用对角单压杆模型模拟内填墙的受力特性,并将计算结果同有限元实体模型以及纯钢框架模型结果进行比较,得出了一些结论。     

带砌体填充墙框架弹性抗侧刚度计算方法对比分析

对于带砌体填充墙框架,当填充墙与框架紧密接触时,填充墙将会提高纯框架的侧向刚度,可能改变结构的平面及竖向侧向刚度分布,影响其在地震作用下的承载力及耗能能力等抗震性能。 为研究带填充墙框架在弹性阶段抗侧刚度的合理计算方法, 整理了以等效斜压杆模型为主的国内外相关计算公式, 并结合近年来带填充墙的框架在低周往复荷载作用下的试验, 将理论计算结果与试验实测值进行对比分析。结果表明： 在带填充墙的RC框架中,直接考虑填充墙弯曲变形和剪切变形得到的弹性阶段抗侧刚度计算值为实测值的1.94~8.05倍;在等效斜压杆模型中,斜压杆的宽度对抗侧刚度的计算结果影响很大;斜压杆宽度的取值应考虑填充墙与框架之间相对刚度的影响,其中MSJC提出的斜压杆宽度计算公式较为合理。     

钢筋混凝土框架填充墙结构抗震性能分析

针对砌体填充墙框架结构在地震作用下的受力特点,结合汶川地震,分析了填充墙框架结构产生震害的主要原因。建立了填充墙简化分析的等效双压杆模型。着重研究了地震荷载作用下,填充墙对框架性能的影响。结果表明,砌体填充墙对提高结构的抗侧刚度和强度有一定的作用,改变了框架结构塑性铰的分布和发展水平。同时也表明,砌体填充墙在地震作用时有一定的耗能能力。     

Experimental study of lateral load behavior of H‐shaped precast reinforced concrete shear walls with bolted steel connections

This paper presents an experimental study of H‐shaped precast reinforced concrete shear walls involving vertical connections under combined vertical and lateral loading. The H‐wall is composed of two prefabricated flange wall panels: one prefabricated web wall panel and vertical bolted steel connections between the flange and web panels. The assembling of the H‐wall is completely dry without any in situ casting. Three H‐wall specimens were constructed and tested to investigate the mechanical behavior and seismic performance of them. The lateral load‐bearing capacity, ductility, energy dissipation, lateral stiffness, strain in the connecting steel frame, and sliding within the bolted steel connections are presented and discussed to evaluate the effectiveness of the vertical connections. The ultimate shear‐resistance mechanism of the precast H‐wall assembly is also analyzed. The H‐wall assemblies generally possess high load‐bearing capacity, favorable ductility, and good energy‐dissipating capacity. The thickness of the steel plates in the connecting steel frame affects the lateral stiffness and the ultimate load‐bearing capacity of the H‐walls. Furthermore, the encasing steel plates for the web wall panel not only helps transfer the stress in the wall steel bars but also confines the concrete resulting in improved ductility.     

考虑全填充墙作用的钢筋混凝土框架抗连续倒塌性能分析

为探究钢筋混凝土(RC)全填充墙框架在边中柱失效情况下的抗连续倒塌性能及其承载力计算方法,基于已有试验和有限元程序OpenSees建立宏观有限元数值模型展开研究。数值模型中的梁柱采用基于力的纤维梁单元模拟,填充墙则转化为等效斜撑并用桁架单元进行表征。填充墙宏观模型涉及等效斜撑的宽度、数量和相应材料属性的确定,为此对比了不同等效斜撑模型的适用性,确定了一种连续倒塌工况下全填充墙的宏观模拟方案。进而利用验证的数值模型,揭示全填充墙框架防倒塌的荷载传递机制,并研究了层数和填充墙砌体抗压强度对抗倒塌性能的影响。结果表明：全填充墙框架荷载主要通过墙体对角传递且全填充墙会与周围框架形成一种桁架机制;随填充墙砌体抗压强度降低,结构抗力峰值呈下降趋势。最后,以填充墙和周边框架竖向承载刚度比为基本参数,建立了通过求得填充墙和框架刚度以及纯框架理论弯曲承载力,便可快速评估规则RC填充墙框架防倒塌能力的回归模型。     

An engineered infilled frame: Behavior and calibration

The results of an experimental investigation on some engineered infilled frames with high ductility and adjustable strength are presented in this paper. To achieve an engineered infilled frame, an element is added to the infill, called Frictional Sliding Fuses (FSFs). The fuse acts before infill corner crushing and controls the infill so that it is not overloaded. Consequently, it increases the deformation capacity and decreases the strength deterioration. An FSF has a frictional nature, based on which the infill has more appropriate hysteresis cycles, leading to more structural energy damping during earthquakes. The results show that the engineered infilled frames have adjustable strength, as well as high ductility and damping.     

基于遗传算法的偏心支撑结构优化

提出一种遗传算法,确定偏心支撑结构中的最佳连接点及最大侧向屈曲荷载。这种支撑结构常用于地震区,可给予建筑师更多的设计空间。通过非对角线杆件对结构施加偏心,并通过第3根杆件与框架角点相连。设计这种结构时,常反复试验以确定支撑杆件连接点位置,考虑各种参数,如:开口和框架尺寸、支撑杆件的横截面面积及支撑杆件连接点位置。采用传统方法,通过最大侧向屈曲荷载来确定最佳连接点是很难的。以不同框架为例,证明遗传算法的有效性。     

面内往复荷载作用下足尺砌体填充墙的易损性研究

为了研究钢筋混凝土(RC)框架结构中砌体填充墙的地震易损性，进行了6个足尺含填充墙RC框架试件的面内往复加载试验。各试件中RC框架的设计参数均相同，其中3个试件含普通黏土砖填充墙，另外3个试件含水泥空心砌块填充墙。试验过程中，记录了砌体填充墙的损伤发展过程，并以墙体裂缝宽度和破碎坠落现象作为损伤指标，定义了“明显破坏”、“严重破坏”和“危及安全”等3个损伤状态。在此基础上，以层间位移角作为工程需求参数，建立了普通黏土砖和水泥空心砌块填充墙的易损性曲线。易损性分析结果表明，当试件的面内侧向变形达到GB 50011—2010《建筑抗震设计规范》规定的框架结构弹性层间位移角限值时，黏土砖和空心砌块填充墙均极有可能达到或超越“明显破坏”状态，且空心砌块填充墙尚有22%的概率达到或超越“严重破坏”状态。与黏土砖填充墙相比，水泥空心砌块填充墙的易损性参数具有更大的离散性，且其整体性更差，当侧向变形较大时会出现破碎砌块坠落的现象。根据试验结果，给出了砌体墙最大残余裂缝宽度、最大裂缝宽度和层间位移角之间的近似相关关系。     

内嵌CCA板填充墙对钢框架结构受力性能的影响

为了研究蒸压无石棉纤维素纤维水泥板(CCA板)填充墙对钢框架结构受力性能的影响,对纯框架和带CCA板填充墙钢框架进行了低周往复加载试验,并利用有限元软件ABAQUS进行了模拟分析。根据试验及有限元模拟结果对带CCA板填充墙钢框架的承载能力、抗侧刚度和耗能能力等抗震性能指标进行了分析。结果表明:在低周往复荷载作用下,CCA板填充墙提高了钢框架结构的承载能力、抗侧刚度;CCA板填充墙参与了钢框架结构的滞回耗能,带CCA板填充墙钢框架的累积耗能能力明显优于纯框架;与纯框架相比,带CCA板填充墙钢框架的初始刚度有所提高;当位移角达到某一限值时,CCA板填充墙的损坏会引起钢框架结构的刚度发生突变,钢框架结构非弹性设计不应考虑CCA板填充墙对钢框架结构刚度的提高作用;所得结论可为带CCA板填充墙钢框架的工程应用提供参考。     

砌体填充墙RC框架结构平面内抗震性能有限元模拟

砌体填充墙RC框架结构是我国建筑结构中普遍采用的结构形式,历次地震震害表明填充墙的刚度效应和约束效应改变了主体结构的传力机理,导致整体结构的严重破坏。为了分析其砌体填充墙RC框架侧向承载力和刚度,研究砌体填充墙与RC框架之间的相互协同工作机理和砌体填充墙的开裂模式以及砂浆层的滑移,该文利用三维实体单元和基于表面的粘性接触面模型和摩擦原理,建立一种能够较好地模拟其平面内抗震性能的分离式有限元模型。对一个已有试验分别建立普通有限元模型和分离式有限元模型,二者的分析结果与试验结果的对比表明,分离式有限元模拟方法可以更加准确地预测砌体填充墙RC框架结构的侧向承载力和刚度,并且可以有效地模拟出砌体填充墙的开裂模式,通过塑性应变可以判断出RC构件的失效。     

对部分填充钢筋混凝土框架的试验研究

通过在合适的地方填充钢筋混凝土是一种很常用的加固方法。有时考虑到建筑上的需要,在加固中会将窗户或者门的开口留出来。但是目前我们对在水平循环荷载作用下的部分填充钢筋混凝土结构的行为还不十分了解。本研究旨在探究水平循环荷载下,通过部分填充而加固的柔性钢筋混凝土结构的性能。试验对象为9个三分之一比例的单层单开间模型,对其施加反复荷载。填充墙的纵横比(lw/hw,长度/高度)和安放的位置是试验中需要考虑的两个参数。试验结果指出,与无填充墙的结构相比,部分填充的RC结构显示出了明显更高的最终强度和更高的初始刚度。当填充墙的纵横比增大,结构的抗侧强度和刚度也有显著增加。此外,从试验中还可以看到,结构和填充墙之间的连接同样会影响填充结构的性能,那些同时连接到柱子和梁的部分填充墙模型显示出了最优的性能。     

Seismic behavior of T‐shaped steel reinforced concrete shear walls in tall buildings under cyclic loading

Shear walls are often used as the primary lateral load resisting elements in high‐rise buildings because of their large in‐plane stiffness and strength. It is a common practice to combine rectangular walls to form T‐shaped, I‐shaped and L‐shaped walls for functionality and esthetic reasons. Three relatively slender steel reinforced concrete (SRC) shear walls with T‐shaped cross‐sections were constructed and tested to failure under cyclic lateral loading. This research was conducted to assess the failure mechanism, hysteretic behavior, ductility and energy dissipating capacity of SRC T‐shaped walls under various axial load ratios. All the specimens exhibited a flexural mode characterized by crushing of the concrete and buckling of the steel at the free web boundary. The experimental results showed good hysteretic characteristics without pinching phenomena. The ductility coefficient varied from 2.3 to 4.1, and the deformation capability decreased with the increasing of axial load ratios. The stiffness, strength and ductility of T‐shaped walls are dependent upon the direction of the applied lateral loads. Higher stiffness and strength and lower ductility are achieved when the flange is in tension. The failure mechanism suggested that special attention should be paid to the design of the free web boundary to prevent premature failure under compression. Copyright © 2014 John Wiley & Sons, Ltd.     

水平荷载作用下洞口对填充墙RC框架结构受力性能影响的非线性分析

在3个单层单跨、开洞率不同的填充墙钢筋混凝土框架水平荷载试验模型分析的基础上,用同样的模拟方法,对设计的19个单层单跨、不同洞口情况的填充墙钢筋混凝土框架模型进行了水平荷载作用下全过程模拟分析。分析结果表明通窗、窗洞左置和门洞右置为不利洞口情况,通窗可导致"短柱效应",使框架柱剪力明显增大,洞口率越高(或窗洞左移、门洞右移)则水平承载力和侧移刚度越低,通窗填充墙框架结构按现行方法设计存在安全隐患而非通窗类洞口填充墙框架结构是安全的。