Frame property of unequal storey height with specially shaped columns under cyclic loading

A 1/3-scale reinfored concrete(RC) frame of unequal storey height with specially shaped columns was tested under low frequency cyclic loading.The damage characteristic,bearing capacity,deformation capacity and ductility were analyzed.The restoring force model of the frame was obtained based on the study of the hysteresis curve measured in experiment,and the stiffness degeneration characteristics of every storey of the frame were analyzed.Finally the accumulated damage was analyzed with the damage assessment model.It is shown that the seismic behavior of this frame of unequal storey height with specially shaped columns is generally good,but the bottom of first floor column is a weak part,which should be paid more attention in design,and the restoring force model derived from this experiment can be seen as a valuable guide for design and non-linear finite element analysis for this kind of structure.

Seismic Behavior of Frame with Specially Shaped Columns Subjected to Cyclic Load

In order to study the seismic behavior of frame with specially shaped columns,the hysteretic curve was analyzed based on a quasi-static test of a two-span,three-story frame with specially shaped columns.The top layer framework curve and the corresponding resilience model were obtained from the hysteretic curve.And the stiffness and strength degeneration were also investigated.The results indicated that the stiffness degeneration is not obvious,thus the frame with specially shaped columns has high earthquake-resistant behavior.The resilience model calculated from the test can provide reference for design and nonlinear finite element analysis.

Modeling and cyclic behavior of segmental bridge column connected with shape memory alloy bars

This paper examines the quasi-static cyclic behavior, lateral strength and equivalent damping capacities of a system of post-tensioned segmental bridge columns tied with large diameter martensitic Shape Memory Alloy （SMA） link-bars. Moment-curvature constitutive relationships are formulated and analysis tools are developed for the PT column, including a modified four-spring model prepared for the SMA bars. The suggested system is exemplified using a column with an aspect ratio of 7.5 and twelve 36.5 mm diameter NiTi martensitic SMA bars. A post-tensioning force of 40% to 60% of the tendon yield strength is applied in order to obtain a self re-centering system, considering the residual stress of the martensitie SMA bars. The cyclic response results show that the lateral strength remains consistently around 10% of the total vertical load and the equivalent viscous damping ratios reach 10%-12% of critical. When large diameter NiTi superelastic SMA bars are incorporated into the column system, the cyclic response varies substantially. The creep behavior of the superelastic SMA bar is accounted for since it affects the re-centering capability of the column. Two examples are presented to emphasize the modeling sensitivities for these special bars and quantify their cyclic behavior effects within the column assembly.

Seismic Behavior of Specially Shaped Column Joints with X-Shaped Reinforcement

To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading,which imitated low to moderate earthquake force.The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity,displacement,ductility,hysteretic curve,stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region.With the damage estimation model,the accumulated damage was analyzed.The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form.The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior,ductility and hysteretic characteristic.All specimens were damaged with gradual stiffness degeneration.In addition,X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage.The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications.The test value is higher than the calculated value,which indicates that the formula is safe for the design of specially shaped column joints.

Seismic Behavior of Diaphragm-Through Connections of Concrete-Filled Square Steel Tubular Columns and H-Shaped Steel Beams

Based on the introductions of a type of diaphragm-through connection between concrete-filled square steel tubular columns (CFSSTCs) and H-shaped steel beams,a finite element model of the connection is developed and used to investigate the seismic behavior of the connection.The results of the finite element model are validated by a set of cyclic loading tests.The cyclic loading tests and the finite element analyses indicate that the failure mode of the suggested connections is plastic hinge at the beam with inelastic rotation angle exceeding 0.04 rad.The suggested connections have sufficient strength,plastic deformation and energy dissipation capacity to be used in composite moment frames as beam-to-column rigid connections.

Experimental Study on Seismic Behavior of Exterior Joints of Special-shaped Columns with Different Lengths of Limbs

Four exterior joints with special-shaped columns which have different lengths of limbs are tested under low cyclic loading. Speeial-shaped columns adopted are L- and T-shaped in section. It can be concluded that crack pattern, failure mode and shear strength of joints are affected by the length of limb, and that shear strength and ductility increase with the length of limb; the joints with the flexural failure of the beam have better seismic behavior than those with the shear failure of the joint core.

Buckling Analysis of Tapered Continuous Columns by Using Modified Buckling Mode Shapes

Elastic critical buckling load of a column depends on various parameters,such as boundary conditions,material,and crosssection geometry.The main purpose of this work is to present a new method for investigating the buckling load of tapered columns subjected to axial force.The proposed method is based on modified buckling mode shape of tapered structure and perturbation theory.The mode shape of the damaged structure can be expressed as a linear combination of mode shapes of the intact structure.Variations in length in piecewise form can be positive or negative.The method can be used for single-span and continuous columns.Comparison of results with those of finite element and Timoshenko methods shows the high accuracy and efficiency of the proposed method for detecting buckling load.

铰接方钢管组合异形柱框架抗震性能研究

为解决村镇住宅体系存在的装配式程度及标准化程度较低、现场焊接工作繁多、室内建筑面积浪费等问题,提出了一种铰接方钢管组合异形柱框架体系。该体系中异形柱采用3根空钢管通过钢板与加劲肋组合而成的L形柱,梁柱节点为腹板螺栓连接的铰接节点。通过拟静力试验对该体系的抗震性能进行研究。研究结果表明:相比于铰接钢管混凝土组合异形柱,铰接空钢管组合异形柱框架体系先于梁端出现转角,最后破坏模式为柱脚破坏,具有更优良的抗震耗能和更缓慢的强度与刚度退化,并通过对比刚接节点和铰接节点的骨架曲线,发现节点刚接程度对结构整体的抗侧刚度影响较大。

冻融循环对十字形型钢混凝土柱轴压性能影响分析

为探究十字形型钢混凝土(SRC)柱经冻融作用后力学性能的演变,考虑混凝土强度、配筋率及长细比三个影响因素,采用ABAQUS软件对十字形SRC柱进行冻融和压缩模拟研究,对比分析冻融循环对十字形SRC柱荷载-应变曲线及承载力退化规律的影响,并归纳总结其承载力退化系数表达式.结果表明:SRC试件极限承载力与冻融循环次数呈负相关趋势,冻融循环导致混凝土劣化,使构件轴压承载能力降低,100次冻融循环后,SRC柱的极限承载力最大下降8.48%;而构件轴压承载能力与配筋率呈正相关趋势,因此适当提高混凝土强度及配筋率可有效抵御构件的冻融损伤;此外,极限承载力与长细比成反比,长细比过大,构件易发生弯曲失稳破坏;所提出轴压承载力退化系数计算值与模拟值吻合度较好.

窄翼缘异形柱-波纹钢板剪力墙体系的抗震性能

针对钢结构住宅凸梁、凸柱和抗侧刚度不足的问题,提出一种新型窄翼缘异形柱-波纹钢板剪力墙体系;通过与传统H形钢柱-平钢板剪力墙体系进行对比,确定内嵌波纹钢板布置方式,采用ABAQUS软件建立所提出体系的有限元模型,对所提出体系的抗震性能进行分析,探讨外部框架截面形式与布置方式、波纹钢板厚度与剪跨比等对所提出体系的抗侧承载力、耗能能力和塑性变形能力的影响。结果表明:所提出的体系具有较大的抗侧承载力和较强的耗能能力、塑性变形能力,极限抗侧承载力为设计值的1.73倍,具备一定的安全储备;横向布置的波纹钢板能有效减小其作用于框架梁柱的荷载;采用十字形异形柱使所提出的体系有更强的塑性变形能力;所提出体系中的异形柱偏肢宜沿剪力墙面内方向布置,内嵌波纹钢板厚度宜取为3~5 mm,剪跨比宜控制在1.25左右。

钢筋混凝土不等肢L形单向偏心受压柱参数分析

本文运用了ABAQUS有限元软件,设计了14个有限元试件进行参数分析,具体分析了钢筋混凝土不等肢L形单向偏心受压柱的承载力及变形能力受混凝土强度、纵筋配筋率、偏心率等因素的影响规律。

工字形钢梁-矩形钢管柱单向螺栓节点抗弯承载力理论计算方法

针对工字形纯钢梁和钢-混凝土组合梁分别与矩形钢管柱和矩形钢管混凝土柱采用单向螺栓(也称单边拧紧螺栓)连接形成的4种节点形式,对其在弯矩作用下的受力机理及破坏模式进行分析,讨论导致节点失效的因素。总结节点在弯矩作用下的9种失效模式,包括:单向螺栓拉断、端板受弯屈服、矩形钢管柱壁翼板受拉屈服、矩形钢管柱壁翼板受压屈服、矩形钢管柱壁腹板受压屈曲、混凝土楼板局部压溃、钢筋屈服、矩形钢管柱内混凝土局部压溃、矩形钢管柱壁腹板受压屈服,进而基于破坏模式给出节点各组件承载力的计算公式。对4种节点在不同破坏模式下的正弯矩承载力和负弯矩承载力进行分析,给出节点承载力计算公式。将节点抗弯承载力的理论计算结果与试验结果进行对比,验证理论计算方法的可靠性。

长细比对内置工字形CFRP型材的圆钢管混凝土构件力学性能影响

目的 研究长细比对内置工字形CFPR型材高强圆钢管高强混凝土轴压构件力学性能的影响,为该类型柱设工程计提供依据。方法 采用ABAQUS有限元软件对组合柱进行有限元模拟,分析不同长细比下钢材强度、混凝土强度等参数对组合柱力学性能的影响。结果 组合柱发生弹性和弹塑性失稳破坏的界限长细比为66.67,经验证理论公式的预测值与模拟值平均误差为3.01%。对于弹性失稳破坏的构件,与钢材强度相比,混凝土强度对构件的极限承载能力影响较大,且钢材屈服强度对钢管内力分配占比的影响较小。在组合构件中,高强混凝土所承担的荷载比例最低可达到普通强度混凝土所承担荷载的1.2倍。结论 发生弹性失稳破坏的构件可以通过提高混凝土强度达到提高构件承载力的目的;与普通强度混凝土相比,在组合柱中采用高强混凝土和高强钢管,可以使组合柱具有更好的组合效应;工字形CFRP对于组合柱极限承载力的提升主要体现在发生弹塑性失稳破坏的构件。

异形多腔钢管混凝土分叉短柱抗震性能试验及数值计算

针对某超高层巨型框架结构中异形截面多腔钢管混凝土(concrete-filled steel tube, CFT)分叉柱,为研究截面加强构造对分叉短柱抗震性能的影响,进行了4个试件在竖向轴压力及水平往复两次的低周反复荷载下的抗震性能试验研究,试件上部为五边形四腔体钢管混凝土双柱肢,下部为八边形十三腔体钢管混凝土单柱肢,以此形成分叉柱;研究的截面构造包括四种:基本构造,钢管钢板整体加厚构造,距中和轴较远的钢管角部钢板内表面贴焊等肢角钢的局部钢板加厚构造,距中和轴较远的钢管腔体内置圆钢管构造。基于试验结果及截面构造特点,进行了数值计算。试验及数值计算结果表明:异形截面多腔钢管混凝土分叉短柱的破坏主要发生在上柱根部分叉截面处,表现为距离中性轴较远处的钢板撕裂以及局部焊缝开裂引起的整块钢板撕裂;内置圆钢管的加强构造承载力提高7.6%、变形能力提高14.4%,综合耗能能力最强,局部钢板加强构造承载力提高9.2%、变形能力下降18.7%,钢管钢板整体加厚构造承载力略有提高、但变形能力下降较多;提出的异形多腔钢管混凝土柱简化建模方法计算效率较高,精度满足工程设计要求。

T型钢连接方钢管柱-H型钢梁节点抗震性能分析

目的为了研究单边螺栓和T型钢连接的方钢管柱-H型钢梁节点的抗震特性,方法采用室内试验和数值模拟分析方法,对1∶2缩尺的边节点进行拟静力试验,并通过ABAQUS有限元软件进行数值模拟,综合分析边节点的滞回特性、承载力、刚度与耗能等力学特性。有限元分析变量为T型钢加肋、梁翼缘狗骨式和梁腹板开圆孔式。结果试验中,节点试件中连接件T型钢参与耗能且其变形最明显,梁、柱构件变形较小。塑性铰主要集中在连接构件T型钢上,T型钢腹板与翼缘交接处出现应力集中状态。试验弹性阶段,节点构件共同抵抗外部作用力。进入塑性阶段,节点损伤逐渐累积至T型钢,使T型钢最终产生塑性破坏而失效。有限元模拟中,T型钢加肋的形式对节点整体承载力影响最大,其中加3号肋的形式使节点承载力的增长量达到最大;梁翼缘狗骨式的形式对节点整体耗能能力影响最大,为44.01%。结论在T型钢上加肋板对节点的承载力和刚度提升较明显,对耗能能力影响不大;梁翼缘狗骨式和梁腹板开圆孔式均能提高节点的耗能能力,节点承载力和刚度基本不变;梁翼缘做狗骨式对节点抗震性能影响最显著。

杭州电竞中心基础及地下室设计

杭州电竞中心项目采用桩基、筏板基础等多种基础形式,采用YJK软件进行多种基础形式之间的沉降差计算,并提出多种基础形式运用于同一建筑物时的加强措施。对于三面覆土、一面开敞地下室的不平衡水、土压力问题,利用桩基抵抗不平衡水、土压力,并提出相应的加强措施。将抗拔桩、无粘结预应力抗浮锚杆以及排水泄压多种抗浮技术应用于本工程,基于连通器原理的排水泄压主动抗浮技术的应用,大大减少抗浮锚杆的数量,获得了良好的经济效应;对于工程中多向框架梁与斜柱的连接节点,采用圆形柱帽有效约束各个方向相交的框架梁,并采用ABAQUS进行了有限元分析来模拟其受力性能,证明连接节点的可靠性。最后介绍了下沉庭院大跨度无柱弧形楼梯的设计,并对其进行舒适度验算,结果满足规范要求。

U形渠道机翼柱型量水槽水力性能分析

为了详细探究机翼柱型量水槽应用于U形渠道的量水性能,设置了4个不同的量水槽收缩比开展水力性能试验。通过对流量、收缩比和上游水位等数据进行分析,拟合出机翼柱型量水槽的流量公式。研究还对测流精度、上游佛汝德数、临界淹没度等参数进行了详细分析。试验结果表明,机翼柱型量水槽水位~流量相关性极高,相关系数R^(2)达0.998,利用试验数据拟合出的流量公式简单易用,平均流量误差约为2.47%,上游佛汝德数小于0.3,临界淹没度最高为0.887。与传统的U形渠道量水槽相比,机翼柱型量水槽的流动公式简单易用,U形渠道机翼柱型量水槽的结构为进一步研究提供了新的思路和参考。

标准化Z字形钢结构梁柱连接节点转动刚度研究

为研究标准化Z字形钢结构梁柱连接节点的转动刚度,对翼缘焊接和搭接两种形式的Z字形钢结构梁柱连接节点进行了单调和往复循环加载试验及有限元分析。研究了不同连接节点设计强度对Z字形钢结构梁柱连接节点转动刚度和循环刚度退化等力学性能的影响。结果表明,翼缘焊接和搭接两种形式的Z字形钢结构梁柱连接节点均具有良好的延性和滞回性能。翼缘焊接Z形节点转动刚度表现为刚性连接,翼缘搭接Z字形钢结构节点转动刚度表现为铰接。对于翼缘焊接Z字形钢结构梁柱连接节点,其转动刚度和循环刚度退化程度受焊缝连接强度影响显著。较小的强度设计倍数(0.2~0.4)时节点破坏模式为焊缝率先发生破坏,其节点转动性能表现为半刚性。较大节点强度设计倍数(0.7~1.1)时节点破坏模式转变为构件率先发生破坏,节点表现为刚性连接且其循环刚度退化程度(转角小于0.02 rad条件下)明显小于强度设计倍数较小的Z字形钢结构节点循环刚度退化程度。总体上看,可通过改变节点强度设计倍数来调节其转动刚度。

SMA绞线预制梁-柱自复位耗能节点数值研究与参数优化

为了提高预制混凝土框架的抗震能力并控制震后残余变形,提出了一种新型的混合自复位预制混凝土梁柱节点(self-centring precast concrete beam-column connection,SC-PCBCC),其中采用了旋转摩擦阻尼器(rotational friction hinge damper,RFHD)和形状记忆合金(shape memory alloy,SMA)并联的结构。重点探讨了使用SMA绞线控制的自复位装置对SC-PCBCC进行改进。首先,介绍了SC-PCBCC的结构和工作原理;其次验证对比了1.0%、1.5%、2%和2.0%预应变下的超弹性1×7 SMA绞线、RFHD和SC-PCBCC的有限元模型,并进行了初步验证。研究结果表明,该节点具有较高的刚度、承载力、耗能能力以及较好的复位性能;最后对SC-PCBCC中SMA绞线的关键参数:SMA绞线预应变、直径和长度进行了参数分析,以优化其抗震性能。建议SC-PCBCC使用的SMA绞线初始预应变、直径和长度范围分别为1.5%~2.0%、15~18 mm和175~205 mm,以实现SC-PCBCC的优异承载性能、能量耗散和自复位性能。此外,节点中的SMA绞线和RFHD可在震后快速更换,实现高效灾后修复。总体而言,所提出的SC-PCBCC表现出了卓越的减震能力、自复位能力和可修复性。

新型异形钢管混凝土结构可更换剪切板式节点抗震性能研究

提出了一种新型异形钢管混凝土结构剪切板式节点,制作了2个可更换剪切板式梁柱节点进行拟静力试验与有限元分析,获得了2个节点的滞回曲线、延性性能和耗能能力等力学性能指标。研究表明:不同开孔形式的剪切耗能板会造成不同的破坏模式;采用腰孔型剪切耗能板的新型异形钢管混凝土结构剪切板式节点的延性性能和耗能能力较好。在试验和数值模拟的基础上,研究了板件间摩擦系数对节点抗震性能的影响,当摩擦系数增加至0.30时,节点抗震性能更好。