Seismic performance evaluation of hybrid coupled shear wall system with shear and flexural fuse-type steel coupling beams

Replaceable flexural and shear fuse-type coupling beams are used in hybrid coupled shear wall(HCSW)systems,enabling concrete buildings to be promptly recovered after severe earthquakes.This study aimed to analytically evaluate the seismic behavior of flexural and shear fuse beams situated in short-,medium-and high-rise RC buildings that have HCSWs.Three building groups hypothetically located in a high seismic hazard zone were studied.A series of 2D nonlinear time history analyses was accomplished in OpenSees,using the ground motion records scaled at the design basis earthquake level.It was found that the effectiveness of fuses in HCSWs depends on various factors such as size and scale of the building,allowable rotation value,inter-story drift ratio,residual drift quantity,energy dissipation value of the fuses,etc.The results show that shear fuses better meet the requirements of rotations and drifts.In contrast,flexural fuses dissipate more energy,but their sectional stiffness should increase to meet other requirements.It was concluded that adoption of proper fuses depends on the overall scale of the building and on how associated factors are considered.

An elastic-plastic analysis of short-leg shear wall structures during earthquakes

Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. To analyze the elastic-plastic response of a short-leg shear wall structure during an earthquake, this study modified the multiple-vertical-rod element model of the shear wall, considered the shear lag effect and proposed a multiple-vertical-rod element coupling beam model with a new local stiffness domain. Based on the principle of minimum potential energy and the variational principle, the stiffness matrixes of a short-leg shear wall and a coupling beam are derived in this study. Furthermore, the bending shear correlation for the analysis of different parameters to describe the structure, such as the beam height to span ratio, short-leg shear wall height to thickness ratio, and steel ratio are introduced. The results show that the height to span ratio directly affects the structural integrity; and the short-leg shear wall height to thickness ratio should be limited to a range of approximately 6.0 to 7.0. The design of short-leg shear walls should be in accordance with the ＂strong wall and weak beam＂ principle.

联肢弯剪型钢板剪力墙抗震性能试验研究

联肢钢板剪力墙结构是将2片钢板剪力墙通过钢连梁连接形成的抗侧力结构。通过对1榀1/3缩尺的4层联肢弯剪型钢板剪力墙试件进行低周往复加载试验,从滞回曲线、骨架曲线、延性、承载力及刚度退化、耗能能力等方面研究了该结构体系的抗震性能,并且对试件的屈服顺序和变形模式进行了分析。结果表明:联肢钢板剪力墙试件的延性系数达到5.03,承载力退化系数均大于0.96,承载力和刚度退化稳定,等效黏滞阻尼系数达到0.25以上,表明联肢弯剪型钢板剪力墙具有优越的抗震性能。加载过程中,连梁先于墙板发生屈服,墙板先屈曲后屈服,此后柱脚和横梁相继屈服。连梁的引入改变了结构的屈服机制,提高了整体的延性和耗能能力,能够组成多道抗震防线,且试件整体最终也体现出合理的破坏机制。整体侧移曲线呈弯剪变形模式。该试验研究更加贴合实际工程中联肢钢板剪力墙结构的应用情况,为联肢钢板剪力墙结构的进一步研究和应用提供了试验基础。

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。

带有拼缝阻尼器的自复位预制双肢剪力墙的耗能能力研究

为提升自复位预制双肢剪力墙的耗能能力,针对预制双肢剪力墙提出了一种拼缝阻尼器,该阻尼器可适应接缝附近的大变形,帮助结构同时实现自复位和耗能的性能。通过拟静力试验,获得了该阻尼器的滞回曲线,验证了所提阻尼器具备良好的耗能性能;使用Opensees把阻尼器放入预制双肢剪力墙中进行数值分析,发现所提阻尼器在不降低结构原本自复位性能的同时,大大提升了结构的耗能能力。同时,耗能主要由拼缝阻尼器承担,结构自身的耗能和损伤较小,有利于实现结构在震后的快速修复。

混合联肢PEC墙结构简化力学分析模型及承载力计算

为克服钢筋混凝土墙肢底部易发生脆性破坏的缺点,提高联肢剪力墙结构的抗震性能,采用PEC剪力墙肢代替混合联肢剪力墙结构中的钢筋混凝土剪力墙肢,形成新型混合联肢PEC墙结构.通过改变钢连梁截面尺寸、PEC墙肢宽厚比以及楼层数形成3个系列共8个模型,研究了弹性耦连比和改变弹性耦连比的方式对混合联肢PEC墙结构滞回性能和应力分布的影响.结果表明:各个系列模型滞回曲线均饱满而稳定,未出现明显捏缩现象,证明混合联肢PEC墙结构抗震性能好、耗能能力强,适用于高烈度抗震设防地区;与已有联肢墙结构研究成果一致,弹性耦连比是影响混合联肢PEC墙结构整体性能的主要因素,并不会因为实现方式不同而影响结构应力分布规律;为保证结构达极限承载能力状态时各层钢连梁均发生剪切屈服并充分发展塑性,同时避免受拉侧墙肢发生延性较差的小偏心受拉破坏,应控制弹性耦连比小于等于70%;基于有限元模型分析结果,探讨了混合联肢PEC墙结构受力机理,建立了结构简化力学分析模型,给出了极限承载力计算公式;试验及有限元模型分析结果与理论计算结果误差在15%以内,且均为理论值偏低,证明本文提出的混合联肢PEC墙结构极限承载力计算公式精度较高且偏于安全,可用于计算结构极限承载力.

钢板混凝土剪力墙拉弯剪性能试验研究

超高层建筑“细柔”特征容易引起底部剪力墙在强震下处于拉-弯-剪复合受力状态,中国《超限高层建筑工程抗震设防专项审查技术要点》(建质[2015]67号)建议墙肢采用配置型钢/钢板的方式来改善该种抗震性能,但缺乏相关试验研究。为此,进行了6片钢板混凝土剪力墙的低周往复荷载试验,研究了轴拉比、含钢率及剪跨比对墙肢拉弯剪性能的影响。研究表明:拉弯剪作用引起钢板混凝土剪力墙密集的裂缝分布和显著的钢材强化,并导致其剪切-拉弯耦合破坏。轴拉比增大,墙肢承载力、初始抗侧刚度和延性分别降低22%、41%和39%;剪跨比减小,墙肢承载力和抗侧刚度至少提升23%;同时增大含钢率和降低剪跨比,墙肢延性提高10%。相比其他国家规范,中国规范对拉弯剪作用下钢板混凝土剪力墙的抗剪承载力预测效果更好,但其未能考虑高含钢率对裂面销栓力的影响,故建议采用暗柱的初始含钢率进行修正。

混合联肢部分外包组合剪力墙基于两阶段耗能的塑性设计方法研究

混合联肢部分外包组合剪力墙结构是一种典型的两阶段耗能结构体系。依据现行设计规范设计的混合联肢部分外包组合剪力墙结构对结构弹塑性阶段的整体性能缺乏考虑,在设防地震和罕遇地震作用下结构的屈服顺序难以控制。基于混合联肢部分外包组合剪力墙结构体系“小震不坏,中震可修,大震不倒”的三水准抗震设防性能目标,提出结构两阶段耗能的塑性设计方法。以目标位移和理想破坏模式作为预测结构弹塑性受力状态性能目标,针对不同地震水准下的性能目标,考虑耦连比对结构合理耗能机制的影响,将结构的能力曲线等效为三线型,改进了传统基于能量平衡的塑性设计方法,保证结构在设防地震及罕遇地震下实现理想屈服顺序,避免薄弱层产生。采用建议的设计方法设计了一个12层结构算例,并采用ABAQUS对算例进行推覆分析和弹塑性时程分析。结果表明,采用基于两阶段耗能的塑性设计方法预测的中震及大震下结构顶点位移角与数值分析结果误差分别为0.5%和12.1%,最大层间位移角满足结构弹塑性层间位移角的要求。算例结构能够实现“强节点弱构件、强墙肢弱连梁”合理的屈服顺序,保证结构预期的失效机制和不同地震水准作用下的性能目标,验证了基于两阶段耗能的塑性设计方法的有效性。

干法连接装配式混凝土联肢墙抗震性能试验研究

为提高施工效率,充分发挥装配式结构的拼装优势,提出了一种用于装配式混凝土联肢墙的干式连接方法,在联肢墙的连梁跨中断缝,采用高强度螺栓和预埋连接钢板实现快速干法连接。为研究干法连接装配式联肢墙的抗震性能,对1片整浇联肢墙和1片采用干法连接的装配式联肢墙试件进行了低周往复加载试验。研究结果表明:干法连接节点可以有效传递预制联肢墙之间的相互作用力,实现“强墙肢和弱连梁”的性能目标;干法连接装配式联肢墙的滞回特性与现浇联肢墙相似,二者初始弹性刚度接近,加载后期因节点变形造成墙体刚度和承载力下降,但其变形能力和耗能能力更强。基于试验结果,提出的干法连接装配式混凝土联肢墙的承载力计算方法,反映了干连接节点的传力特点,可用于该连接形式的分析和设计。

基于自感知连梁的剪力墙墙肢转角变形识别及其试验验证

联肢剪力墙作为高层结构重要的抗侧体系,对建筑的震后功能可持续至关重要。近年来,带可更换构件的剪力墙结构体系被学术界提出,并成功应用于国内外高层建筑项目。需要注意的是,作为结构抗震第一道防线的易损高耗能连梁,其震后的快速诊断与更换将决定建筑结构性能与功能恢复效率。该文从带可更换连梁联肢剪力墙结构变形机理出发,基于前期提出的自感知可更换连梁,提出了一种剪力墙墙肢转角变形识别方法,实现对墙肢转角及相邻墙肢转角差等状态的识别。通过大比例剪力墙模拟体的动力加载试验,并与多种试验测量技术进行对比,验证了墙肢转角识别方法的准确性与鲁棒性。

不同耦连比的联肢钢板仓组合剪力墙抗震性能有限元分析

耦连比是影响联肢剪力墙结构抗震性能的重要参数。为研究联肢体系下新型钢板仓组合剪力墙的抗震性能和破坏特征,并确定该种结构较为适宜的设计耦连比取值范围,借助ABAQUS软件建立了10个不同耦连比的联肢钢板仓组合剪力墙有限元分析模型,并进行了单调推覆和循环往复加载。结果表明,不同耦连比下,联肢钢板仓组合剪力墙的抗震性能以及破坏特征存在明显差异。耦连比过小,钢连梁将首先破坏并造成联肢体系失效;耦连比过大,组合墙肢将在钢连梁耗能不充分的情况下提前破坏。因此,建议将塑性耦连比的取值范围控制在45%~50%之间,并将其与弹性耦连比的比值限制在90%以下,以确保钢连梁先于组合墙肢屈服,从而提高结构的抗震性能。

连梁阻尼器在高地震烈度区剪力墙结构中的应用研究

结合某高地震烈度区的实际工程项目,研究连梁阻尼器在剪力墙结构中的受力特点、设计方法,采用ETABS程序进行结构减震性能分析和弹塑性性能评估。连梁阻尼器在地震作用下不但可以成为剪力墙结构可靠的耗能构件,减小地震响应,还可有效地控制结构损伤模式,防止混凝土连梁的剪切破坏,减少混凝土构件的损伤,实现耗能构件震后的可更换性。建议采用设防烈度评估消能减震结构的性能,以“损伤控制”的概念进行设计。设置连梁阻尼器的剪力墙结构更容易实现结构构件中震少修的损伤控制目标。

钢框架-灌浆轻钢剪力墙结构抗震性能试验研究

对钢框架-灌浆轻钢剪力墙结构足尺试件进行了水平低周往复加载试验,研究了灌浆轻钢剪力墙与钢框架的耦合效应,分析了结构的破坏模式、受力特征和耗能机理,得到了结构的承载能力、抗侧刚度、延性及耗能能力等。通过与纯钢框架及冷弯薄壁型钢灌浆墙体结构的试验结果对比,发现灌浆轻钢剪力墙通过自攻螺钉采用内嵌的方式与钢框架连接,二者具有良好的协同工作性能,框剪结构的抗剪承载力和抗侧刚度分别是钢框与墙体对应值之和的1.50倍和1.64倍,结构延性系数达5.42,抗震性能优良,研究结果可为该类结构的设计研究提供科学基础。

Seismic behavior of precast concrete coupled shear walls with engineered cementitious composite (ECC) in the critical cast-in-place regions

The seismic performance of precast reinforced concrete （RC） coupled shear walls is significantly influenced by coupling beams and the beam-to-wall joints during large deformations into plastic ranges. This study investigated the use of engineered cementitious composite （ECC） in the cast-in-place beam-to-wall joints and the upper regions of the composite coupling beams as an innovative method to improve the seismic performance ofprecast RQ coupled shear walls. Two 1/2-scale precast coupled shear walls were tested under reversed cyclic loading and seismic behavior in terms of failure characteristic, mechanical characteristic value, load-displacement hysteresis curves, load-displacement envelope relationship, stiffness degradation, ductility and energy dissipation capacity were evaluated. Research results show that the substitution of concrete with ECC in the critical cast-in-place regions proved to be an effective method to improve the seismic performance of the two-story spatial of precast RC coupled shear walls.

Size-dependent sinusoidal beam model for dynamic instability of single-walled carbon nanotubes

In this study, a model for dynamic instability of embedded single-walled car- bon nanotubes （SWCNTs） is presented. SWCNTs are modeled by the sinusoidal shear deformation beam theory （SSDBT）. The modified couple stress theory （MCST） is con- sidered in order to capture the size effects. The surrounding elastic medium is described by a visco-Pasternak foundation model, which accounts for normal, transverse shear, and damping loads. The motion equations are derived based on Hamilton＇s principle. The differential quadrature method （DQM） in conjunction with the Bolotin method is used in order to calculate the dynamic instability region （DIR） of SWCNTs. The effects of differ- ent parameters, such as nonlocal parameter, visco-Pasternak foundation, mode numbers, and geometrical parameters, are shown on the dynamic instability of SWCNTs. The re- sults depict that increasing the nonlocal parameter shifts the DIR to right. The results presented in this paper would be helpful in design and manufacturing of nano-electromechanical system （NEMS） and micro-electro-mechanical system （MEMS）.

Couple stress nanofluid flow through a bifurcated artery—Application of catheterization process

In this article,we are exploring the hemodynamics of nanofluid,flowing through a bifurcated artery with atherosclerosis in the presence of a catheter.For treating obstruction in the artery,one can use the catheter whose outer surface is carrying the drug coated with nano-particles.The resultant solvent is considered as blood nano-fluid.Blood being a complex fluid,is modeled by couple stress fluid.In the presence of nano-particles,the temperature and the concentration distribution are understood in a bifurcated stenotic artery.The concluded mathematical model is governed by coupled non-linear equations,and are solved by using the homotopy perturbation method.Consequently,we have explored is the effects of fluid and the embedded geometric parameters on the hemodynamics characteristics.It is also realized that high wall shear stress exists for couple stress nano-fluid when compared to Newtonian nano-fluid.which is computed at a location corresponding to maximum constriction(z=12.5)of the artery.

A new finite element of spatial thin-walled beams

Based on the theories of Timoshenko＇s beams and Vlasov＇s thin-walled members, a new spatial thin-walled beam element with an interior node is developed. By independently interpolating bending angles and warp, factors such as transverse shear deformation, torsional shear deformation and their Coupling, coupling of flexure and torsion, and second shear stress are considered. According to the generalized variational theory of Hellinger-Reissner, the element stiffness matrix is derived. Examples show that the developed model is accurate and can be applied in the finite element analysis of thinwalled structures.

不同双轴加载路径下T形截面RC剪力墙抗震性能试验研究

为了探究复杂多维地震作用下带翼缘剪力墙的损伤机理和抗震性能,进行了5个T形截面RC剪力墙的水平单、双轴拟静力试验,研究双轴加载对T形墙破坏模式、滞回性能、承载力、延性与耗能能力的影响,考察T形墙在不同双轴加载路径下的受力机理和多维抗震性能。结果表明:T形墙在单、双轴加载下的破坏均发生在墙肢自由端底部,双轴加载加剧了裂缝的开展和混凝土的剥落,且对翼缘的损伤影响更大;T形墙两正交方向的受力行为存在明显的相关性,双轴耦合受力产生的内力重分布和局部附加应力会改变T形墙的局部受力机理和整体性能,表现为一个方向受荷时,其正交方向在位移不变的情况下荷载会产生突变;相较于单轴加载,双轴加载下T形墙各方向承载力平均降低了6.90%,极限变形能力平均降低了11.28%,单个方向破坏时的累积耗能减小,且双轴耦合效应按“十”字形、“8”字形、矩形加载路径的顺序依次增强。鉴于地震动的随机性以及结构响应的多维耦合性会显著改变带翼缘RC剪力墙在实际地震作用下的抗震能力,建议在剪力墙结构抗震设计时合理考虑承载力的折减并适当减小层间位移角限值。

The Effects of Post-Stenotic Dilatations on the Flow of Couple Stress Fluid through Stenosed Arteries

The flow of incompressible couple stress fluid in a circular tube with stenosis and dilatations has been investigated. The stenosis was assumed to be axially symmetric and mild. The flow equations have been linearized and the expressions for the resistance to the flow, velocity, pressure drop, wall shear stress have been derived. The effects of various parameters on these flow variables have been investigated. It is found that the resistance to the flow and pressure drop increase with height of the stenosis and decrease with post stenotic dilatation. Pressure drop decreases with couple stress fluid parameter for both stenosis and post stenotic dilatation. Further, the wall shear stress increases with height of the stenosis and couple stress parameter but decreases with post stenotic dilatation and couple stress fluid parameter.

带PC填充墙的装配式联肢剪力墙抗侧刚度与水平承载力计算方法研究

为研究带预制混凝土(PC)填充墙的装配式联肢剪力墙抗侧刚度与水平承载力计算方法,完成了1个无填充墙和2个带PC填充墙试件的低周往复荷载试验,考察了PC填充墙对装配式联肢剪力墙抗侧刚度和水平承载力的影响,在试验基础上建立了结构简化分析模型,提出了联肢剪力墙抗侧刚度和水平承载力计算方法。结果表明:带PC填充墙的装配式联肢剪力墙试件整体性较好,PC填充墙的存在可提高试件的抗侧刚度和水平承载力;PC填充墙与联肢剪力墙的连接形式对试件的抗侧刚度和水平承载力有较大影响;基于连续化计算方法提出的带PC填充墙的装配式联肢剪力墙抗侧刚度和水平承载力计算方法,计算结果与试验值吻合良好。