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...     

Analytical estimation of lateral resistance of low‐shear strength masonry infilled reinforced concrete frames with openings

Presence of openings in an infill wall alters its behavior and reduces load resistance and stiffness of the infilled frame. In this paper, a simple method for estimating the lateral resistance of infilled frames with openings is proposed based on experimental data. Six half‐scale, single‐story single‐bay reinforced concrete frame specimens were tested under in‐plane lateral loading. The lateral strength of reinforced concrete (RC) frame could be estimated by assuming the formation of plastic hinges in the end regions of the members. In the specimens with central openings, the major load resistance mechanism of the infill panel was the formation of a compression strut and lateral strength of infill panel could be considered as the smallest values of the diagonal tension and corner crushing modes. In the specimens with eccentric openings, the load resistance mechanism of masonry infill was the formation of a compression strut and bed‐joint sliding in 2 opposite loading directions; thus, the lateral resistance of infill panel could be estimated in diagonal tension and corner crushing modes in one direction and bed‐joint sliding mode in another direction. Furthermore, the deformation capacity and structural performance levels are suggested for solid and perforated infill panels based on test observations.     

Experimental and analytical investigation into crack strength determination of infilled steel frames

This paper presents the results of further development of a new analytical approach for the evaluation of shear strength and cracking patterns of infill panels. This method is based on the minimum evaluated strength with reference to the failure surfaces. This paper also presents the results of an experimental investigation of small and medium scale masonry and concrete infilled frames. Eleven specimens, with and without horizontal reinforcement and bond beams, were subjected to static cyclic loads. The tests are categorized in two groups, based on their surrounding frames and scale. In the first group a small scale factor is used, and the frames have pinned connections with very stiff beams and columns representing the lower stories of tall buildings. In the second group a medium scale factor is used, and the frames have rigid connections.Both experiments and analysis have confirmed that the efficiency of horizontal reinforcement and bond beams depends on the dominant pattern of cracking. The results also indicate that as opposed to masonry infills, the corner crushing is the dominant mode of failure in concrete infills.     

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。     

Nonlinear analysis of masonry-infilled steel frames with openings using discrete element method

Nonlinear numerical modeling of masonry-infilled frames is one of the most complicated problems in structural engineering field. This complexity is attributed to the existence of joints as the major source of weakness and material nonlinearities as well as the infill-frame interaction which cannot be properly modeled using the traditional finite element methods. Although there are many numerical studies available on solid masonry-infilled steel frames’ behavior, however, few researches have been conducted on infilled frames with openings. In this paper a two-dimensional numerical model using the specialized discrete element method (DEM) software UDEC (2004) is developed for the nonlinear static analysis of masonry-infilled steel frames with openings subjected to in-plane monotonic loading. In this model, large displacements and rotations between masonry blocks are taken into account. It was found that the model can be used confidently to predict collapse load, joint cracking patterns and explore the possible failure modes of masonry-infilled steel frames with a given location for openings and relative area. Results from the numerical modeling and previous experimental studies found in the literature are compared which indicate a good correlation between them. Furthermore, a nonlinear analysis was performed to investigate the effect of door frame on lateral load capacity and stiffness of infilled frames with a central opening.     

Cyclic behaviour of hinged steel frames enhanced by masonry columns and/or infill walls with/without CFRP

Abstract

This paper investigates the in-plane seismic behaviour of hinged steel frames that are enhanced with masonry columns and/or infilled walls. First, eight half-scaled hinged steel frame specimens were constructed according to the realistic structural system of Bund 18, which is a historical building in Shanghai, China. Then, cyclic loads were exerted on these frames. The test results indicated that the seismic behaviours of the hinged steel frames can be significantly improved with the use of masonry columns and/or infilled masonry walls as well as with proper strengthening due to carbon fibre-reinforced polymer (CFRP) sheets. A simplified model was developed to simulate the seismic behaviours of these frames. In this model, infilled walls and CFRP sheets were replaced by diagonal struts, and the steel members and their surrounding elements were treated as composite members. Finally, this model was verified by experimental results.     

Influence of infill configurations on seismic responses of steel self‐centering moment resisting frames

Steel self‐centering moment resisting frames (SC‐MRFs) have been validated experimentally as resilient structural systems, mainly highlighting the minimized residual drift responses but are prone to suffering high‐mode effects. In this paper, the influence of infill configurations on seismic responses of steel SC‐MRFs was first analyzed. A comparison of the previous experimental results was conducted to investigate the effect of infills on the residual drift of steel frames. In the numerical simulation, the infills were modeled as the equivalent strut diagonals, and the force–displacement of the infills was modeled using the combination of Elastic‐No Tension Material and Hysteretic Material offered by the OpenSees program. The seismic analyses of 3‐ and 9‐story SC‐MRFs with and without infills were carried out to analyze the effects of infills on the residual drift responses and high‐mode contribution under the selected ground motions. Finally, the different infill types and infill irregularities on the seismic responses were investigated to obtain general conclusions. The plastic deformations of columns and infills are also compared in the different cases of infill configurations. The results reveal that all infilled cases experience reduced peak‐story drift and force demands at the upper stories.     

Seismic behaviour of infilled and pilotis RC frame structures with beam-column joint degradation effect

The influence of the exterior joints capacity deterioration on the local and global failure mechanisms of reinforced concrete structures with infills is investigated. Exterior beam-column joints with reduced capacity is the common case for the majority of RC structures designed according to older design standards. Nevertheless in common practise the response of these regions is typically assumed as rigid. A key parameter of this investigation is the inclusion of the joints strength and stiffness degradation in the study of the seismic performance of the structures. In this direction, a special-purpose rotational spring element that incorporates a special behaviour model is employed for the simulation of the exterior joints’ local response. The spring element has been incorporated in a well-established general program for nonlinear static and dynamic analysis. The effectiveness of the used joint element model has been demonstrated in a previous paper through comparisons with experimental data reported in literature. In this paper an attempt is presented for the investigation of the influence of the exterior joint damage on the seismic behaviour of bare and infilled RC frame structures. Two types of masonry infilled structures are considered: (a) infilled frame and (b) infilled frame without infills at the base storey (pilotis frame). A parametrical study of the overall seismic response using push over analyses and step-by-step analyses is performed. Results in terms of interstorey drifts, base shear, failure mode, ductility requirements and joints rotational requirements demonstrate that neglecting the possible local damage of the exterior joints may lead to erroneous conclusions and unsafe design or seismic behaviour evaluation that subsequently may become critical in some cases. Furthermore the influence of exterior joints degradation has been proven of vital importance for the overall behaviour of pilotis frames.     

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。     

Influence of masonry infill on the seismic performance of concentrically braced frames

This paper presents an experimental and analytical study to investigate the effect of masonry infill on the seismic performance of special Concentrically Braced Frames (CBFs). Cyclic lateral load tests are conducted on three half-scale specimens including two special CBFs with and without masonry infill and a moment resisting steel frame with masonry infill for comparison purposes. Companion analyses are performed to study the influence of masonry infill on the potential rupture of gusset plates and top-seat angle connections by using detailed FE models validated with experimental results. It is shown that the presence of masonry infill could increase the lateral stiffness and load carrying capacity of the special CBF by 33% and 41%, respectively. However, the interaction between masonry infill and the frame significantly increased the strain demands and failure potential of the connections. The results of the experimental tests and analytical simulations indicate that ignoring the influence of masonry infill in the seismic design process of CBFs results in a premature fracture of the connection weld lines and a significant reduction in the deformation capacity and ductility of the frame. This can adversely influence the seismic performance of the structure under strong earthquakes. The results of this study compare well with the damage observations after the 2003 earthquake in Bam, Iran.     

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.     

预制装配式钢筋混凝土一体化剪力墙抗震性能研究及构造方案优化

针对预制装配式剪力墙结构,提出了内置空心管的混凝土填充墙与实体剪力墙墙肢一同浇筑生产、安装施工的预制一体化剪力墙结构。通过5个外形尺寸、墙肢和连梁配筋相同的混凝土双肢剪力墙的拟静力试验,探究了无填充、砌块砌体填充和一体化整体填充的剪力墙抗震性能,总结了这三类墙体的破坏形态、受力特点、承载与变形能力、刚度、延性和耗能能力的特点。试验结果表明：预制一体化剪力墙在水平往复荷载作用下发生弯剪破坏,相比于无填充墙试件和砌体填充试件,其抗侧刚度和受剪承载力有明显提高,同时具有良好的抗震性能。最后,基于OpenSEES平台对拟静力试验结果进行了有限元验证,得到了吻合程度较好的滞回曲线、骨架曲线及墙肢纵筋应变;根据试验结果与有限元分析,提出了预制一体化混凝土剪力墙结构合理的填充墙构造方案。     

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。     

不同连接方式下新型砌体填充墙框架结构的抗震性能

试验设计了4榀足尺框架结构,其中1榀为空框架,3榀为带新型横孔空心砌块砌体填充墙,带填充墙框架试件分为刚性连接试件和柔性连接试件2种。对各试件在恒定竖向力和水平低周反复荷载作用下的抗震性能进行试验,研究了框架在不同连接形式下的破坏特征、滞回特性、骨架曲线、位移延性、刚度退化、强度退化、耗能能力。结果表明:柔性连接试件抗震性能介于空框架和刚性连接试件之间,框架梁和填充墙采用拉结筋连接试件的抗震性能相对于未设置拉结筋试件有所改善,但提高幅度有限。     

不同连接方式砌体填充墙钢筋混凝土框架抗震性能试验研究

填充墙的构造形式对框架结构的抗震性能影响较大。试验设计了7榀足尺的单层单跨钢筋混凝土框架,其中6榀为带加气混凝土砌块填充墙框架,1榀为空框架,对其进行低周反复荷载作用下的抗震性能试验。填充墙与框架的连接方式采用柔性连接和刚性连接两种。柔性连接填充墙的变化参数主要包括构造柱的构造形式和数量、框架柱中拉结筋的设置与否和填充墙上设置竖向缝的数量。分析了不同填充墙构造形式框架的破坏特征、荷载 位移滞回曲线、骨架曲线、位移延性系数、刚度退化、耗能能力。结果表明：柔性连接填充墙框架的抗震性能介于刚性连接填充墙框架和空框架之间;对于柔性连接填充墙框架,填充墙的构造措施对框架结构的抗震性能有一定的影响,但影响不大。     

阻尼填充墙钢框架抗震性能试验研究

为研究带阻尼填充墙钢框架的抗震性能,设计了足尺的阻尼填充墙钢框架、普通填充墙钢框架试件和空钢框架试件各1榀,对试件进行了低周反复荷载试验。对比分析了不同试件在低周反复荷载作用下的破坏现象、滞回性能、骨架曲线、刚度退化和耗能能力等。试验结果表明：阻尼填充墙钢框架在相同的荷载作用下墙体的开裂程度比普通填充墙的轻,墙体开裂荷载有一定提高;耗能砂浆和阻尼层起到耗散地震能量的作用,阻尼填充墙钢框架具有良好的位移延性;相对于普通填充墙钢框架墙体形成的“X”剪切裂缝,阻尼填充墙钢框架的墙体裂缝被阻尼层隔断,改变了填充墙的破坏模式;耗能砂浆和阻尼层改变了填充墙的内力分布和裂缝开展方式,提高了阻尼填充墙钢框架的抗震性能。因此,耗能砂浆和阻尼层对填充墙钢框架的受力模式、滞回性能、延性等抗震性能有利,可作为结构设计时参考应用。     

再生混凝土空心砌块填充墙-型钢再生混凝土框架结构抗震性能试验研究

通过对4榀1/2.5比例单层单跨再生混凝土空心砌块填充墙-型钢再生混凝土框架结构的抗震性能试验,研究了填充墙砌块强度、轴压比以及墙体拉筋间距等对该结构抗震性能的影响。分析了试件的破坏形态、滞回曲线及骨架曲线、承载力、层间位移角、位移延性、耗能能力以及刚度退化。结果表明：再生混凝土空心砌块填充墙-型钢再生混凝土框架结构中墙体部分先于框架部分破坏,且框架的破坏机制符合“梁铰机制”,滞回曲线较为饱满,耗能能力良好,具有较强的抗倒塌能力;随着填充墙砌块强度的降低,结构承载力下降,位移延性系数增大,初始刚度减小且刚度退化速率降低,结构破坏时层间位移角和等效黏滞阻尼系数增大;增大轴压比使结构承载力提高,位移延性系数下降,初始刚度明显提高且刚度退化速率上升,结构破坏时层间位移角以及等效黏滞阻尼系数均略有降低;减小墙体拉筋间距使结构承载力及位移延性有所提高,初始刚度增加,但刚度退化速率基本不变,结构破坏时层间位移角及等效黏滞阻尼系数均增大。     

Seismic behavior analysis for composite structures of steel frame‐reinforced concrete infill wall

The composite structure of steel frame–reinforced concrete infill wall (CSRC) combines the advantages of steel frames and reinforced concrete shear walls. Reinforced concrete infill walls increase the lateral stiffness of steel frames and reduce seismic demands on steel frames thus providing opportunities to use partially restrained connections. In order to study seismic behavior and load transfer mechanism of CSRC, a two‐story one‐bay specimen was tested under cyclic loads. With that, the main characters such as, strength, stiffness, ductility, energy dissipation, load distribution, performance of steel frames, partially restrained connections and studs, are analyzed and evaluated. The experimental results show that the structure has adequate strength redundancy and sufficient lateral stiffness. The CSRC system has good ductility and energy dissipation capability. Partially restrained connections could enhance ductility and avoid abrupt decreases in strength and stiffness after the failure of infill walls. The composite interaction is ensured by headed studs, which have failed because of low‐cycle fatigue. Steel frames bear 80%–100% of overturning moments, and the remainder is undertaken by infill walls; steel frames and infill walls resisted 10%–20% and 80%–90% of lateral loads, respectively. Furthermore, relevant design recommendations are presented. Copyright © 2011 John Wiley & Sons, Ltd.     

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。     

砌块填充墙抗震性能试验研究

墙体满足框架变形的能力及其对主体框架初始刚度的影响是研究填充墙工程中值得关注的两个问题。本文通过4个砌块填充墙原型试件拟静力试验,分别对实体填充墙和开洞填充墙自身抗震性能,以及挤塑板柔性连接对减小墙体对主框架影响的性能进行了研究。研究结果表明:开洞砌体墙体初始刚度较实体墙小,但二者对框架初始刚度影响不容忽视;实体、开洞砌体填充墙变形能力均无法满足框架抗震要求;加入挤塑板后墙体对框架初始刚度影响降低50%左右,同时墙体变形能力基本满足框架抗震要求。