反复荷载下矩形钢管混凝土柱的抗震性能Ⅰ:试验研究

本文介绍了16根1/2比例的矩形钢管混凝土柱在常轴力和侧向低周反复荷载作用下的抗震性能试验研究，描述了构件的非线性发展过程及破坏形态，研究了不同试验参数（包括柱的轴压比、截面长宽比、含钢率、加载方向等）对矩形钢管混凝土柱抗震性能的影响。本文的工作可为矩形钢管混凝土结构的工程实践及相关标准的编制修订提供参考。     

反复荷载下矩形钢管混凝土柱的抗震性能Ⅱ:分析研究

文中首先提出了钢管与内填混凝土界面的粘结-滑移滞回模型，建立了考虑包兴格效应的钢材单轴滞回模型和考虑矩形钢管约束效应后内填混凝土的单轴应力-应变滞回模型。在截面纤维模型的基础上，建立了考虑界面粘结-滑移的矩形钢管混凝土柱分析模型，用Fortran语言编制了相应的全过程分析程序。对作者等完成的试件进行了滞回全过程数值模拟计算，分析与试验结果在荷载-位移和荷载-应变两种层次上进行了对比。之后，利用该分析程序对矩形钢管混凝土柱中有代表性的混凝土和钢单元应力-应变发展全过程进行了跟踪分析。最后，以典型试件为对象，分析了钢-混凝土界面切向粘结强度对柱滞回性能的影响。本文工作可为从事组合结构研究时提供参考。     

钢管高强混凝土压弯构件滞回性能的研究

本文根据适用于三向周期受力的钢材本构关系模型,和适用于三向周期受力改进的混凝土本构关系的边界面模型,采用有限元法对钢管高强混凝土压弯构件的荷载－位移滞回曲线进行了理论分析,并进行了6个核心混凝土的强度为77N/mm2的钢管高强混凝土压弯构件滞回性能的试验研究。将理论分析和本试验研究及其他试验研究结果进行了对比,分析了荷载－位移滞回曲线的特点。     

低周反复荷载作用下矩形钢管混凝土柱与钢梁连接节点的受力性能

本文进行了2种矩形钢管混凝土柱与钢梁连接节点——翼缘全螺栓(BFP)连接节点与外加强环(WFP-BW)连接节点在柱端低周反复荷载作用下的抗震性能试验,分析比较了这2类节点与焊接翼缘板(WFP)连接节点在不同轴压比下的滞回性能、强度与刚度退化、延性比与耗能比、破坏机理与破坏特征,得出了一些有参考价值的结论。     

薄壁波纹钢管混凝土柱滞回性能试验研究

近年来,薄壁钢管混凝土柱由于其良好的力学性能和施工性能在各类建筑结构和桥梁上得到了广泛应用,但震害表明,普通薄壁钢管混凝土柱抗局部屈曲能力和屈曲后抗震性能较差。提出了一种薄壁波纹钢管混凝土柱,为了初步探索其抗震性能,以轴压比和截面形式为主要参数,进行了2根薄壁波纹钢管混凝土柱和2根普通薄壁钢管混凝土柱低周反复加载试验研究。主要结论如下:在轴压比相同的情况下,薄壁波纹钢管混凝土柱的滞回曲线明显要比其它两种截面形式的饱满;在相同位移时,薄壁波纹钢管混凝土柱的耗能能力明显好于方形和圆形的。三种截面形式的延性较接近且延性系数均超过3,且强度退化和刚度退化趋势和程度基本一致。综合分析,薄壁波纹钢管混凝土柱抗震性能较之圆、方形薄壁钢管混凝土柱的相当或稍好。研究结果可供城市高架桥的分析与设计参考。     

钢管高性能混凝土压弯构件滞回性能试验研究

考虑钢材强度、混凝土强度、轴压比等参数，进行了18个钢管高性能混凝土试件的试验，分析在往复荷载作用下钢管高性能混凝土荷载-位移关系曲线的特点、构件的轴向变形和抗弯刚度退化情况，并初步探讨往复荷载作用下的钢管高性能混凝土压弯构件承载力。     

圆钢管混凝土压弯构件荷载-位移滞回模型研究

本文采用数值计算方法，对圆钢管混凝土压弯构件荷载-位移滞回关系曲线进行了理论分析。理论计算结果与实验结果吻合良好。基于理论模型，分析了各参数，如构件轴压比、长细比、截面含钢率和材料强度等对圆钢管混凝土压弯构件荷载-位移滞回曲线的影响。最终提出-种圆钢管混凝土压弯构件荷载-位移滞回模型及位移延性系数的简化计算方法。     

外包钢-混凝土组合梁与钢管混凝土柱连接节点的滞回性能研究

为研究外包钢-混凝土组合梁与钢管混凝土柱连接节点的抗震性能,基于外包钢-混凝土组合梁与钢管混凝土柱连接节点低周反复荷载作用下的试验结果和有限元的模拟,分析了两类试验节点的滞回特性,提出外包钢-混凝土组合梁与钢管混凝土柱连接节点的三折线恢复力模型及其特征参数的取值范围,并给出恢复力模型表达式。结果表明,试件具有良好的耗能能力,建立的恢复力模型骨架曲线与试验值接近;有限元与试验所得的滞回曲线及骨架曲线在弹性阶段吻合较好,随着荷载的反复,两者之间的差异逐渐增大。     

钢骨-钢管混凝土组合柱延性的试验研究

本文通过14根钢骨－钢管混凝土组合柱在较高轴压比和低压反复水平荷载作用下的试验，研究了这种新型组合柱的破坏形态，分析了轴压比（n）、钢骨（As）和套箍指标（Φ）等因素对构件滞回特性、承载力和延性的影响。试验结果表明，钢骨－钢管混凝土组合柱具有很好的延性和很高的承载力。     

圆钢管混凝土压弯构件荷载一位移滞回性能分析

在空钢管中填充混凝土可以避免或延缓钢管过早地发生局部屈曲，并有效地提高构件的延性，从而增强构件的抗震性能，本文在对圆钢管混凝土构件弯矩－曲率关系分析的基础上，分析了圆钢管混凝土压弯构件P－△滞回关系曲线，理论计算结果得到国内外大量结果的验证，基于理论分析模型，分析了各参，如构件轴压比，长细比，截面含钢率和材料强度等因素对圆钢管混凝土压变变构件P－△滞回关系曲线的影响，最后，确定了圆钢管混凝土压弯构件P－△恢复力学模型和延性系数的简化计算方法。     

Fiber-based hysteretic model for simulating strength and stiffness deterioration of steel hollow structural section columns under cyclic loading

An efficient component model has been developed that captures strength and stiffness deterioration of steel hollow structural section (HSS) columns. The proposed model consists of two fiber-based segments at a member's ends along with an elastic segment in between. The fibers exhibit nonlinear uniaxial stress–strain behavior, which is explicitly defined by uniaxial monotonic tensile and cyclic round coupon tests. The postbuckling behavior of an HSS column is traced through a proposed uniaxial effective stress–strain constitutive formulation, which includes a softening branch in compression and an energy-based deterioration rule to trace the influence of cyclic deterioration in the inelastic cyclic straining. These may be inferred by uniaxial stub-column tests. The component model captures the coupling between the column axial force and flexural demands. Consistent model parameters for a number of steel materials used in the steel construction in North America and Japan are proposed along with the associated model calibration process. The efficiency of the proposed model in predicting the hysteretic behavior of HSS columns is demonstrated by comparisons with physical steel column tests subjected to various loading histories, including representative ones of ratcheting prior to earthquake-induced collapse. The proposed model is implemented in an open-source finite element software for nonlinear response history analysis of frame structures. The effectiveness of the proposed model in simulating dynamic instability of steel frame buildings is demonstrated through nonlinear response simulations of a four-story steel frame building, which was tested at full-scale through collapse. Limitations as well as suggestions for future work are discussed.     

Experimental research on behavior of 460 MPa high strength steel I-section columns under cyclic loading

To investigate the seismic behavior of I-section columns made of 460 MPa high strength steel(HSS), six specimens were tested under constant axial load and cyclic horizontal load. The specimens were designed with different width-to-thickness ratios and loaded under different axial load ratios. For each specimen, the failure mode was observed and hysteretic curve was measured. Comparison of different specimens on hysteretic characteristic, energy dissipation capacity and deformation capacity were further investigated. Test results showed that the degradation of bearing capacity was due to local buckling of flange and web. Under the same axial load ratio, as width-to-thickness ratio increased, the deformation area of local buckling became smaller. And also, displacement level at both peak load and failure load became smaller. In addition, the full extent of hysteretic curve, energy dissipation capacity, ultimate story drift angle decreased, and capacity degradation occurred more rapidly with the increase of width-to-thickness ratio or axial load ratio. Based on the capacity of story drift angle, limiting values which shall not be exceeded are suggested respectively for flange and web plate of 460 MPa HSS I-section columns when used in SMFs and in IMFs in the case of axial load ratio no more than 0.2. Such values should be smaller when the axial load ratio increases.     

反复荷载下型钢混凝土柱受扭损伤试验研究

为研究型钢混凝土柱在反复荷载下的受扭损伤,完成了11根型钢混凝土柱和1根钢筋混凝土柱复合受扭试验。通过试验观察了构件的受力过程和破坏特征,研究两种不同型钢混凝土柱的裂缝开展与分布规律。基于能量守恒定律,考察了柱截面配钢形式、扭弯比、轴压比、混凝土强度等级、配箍率以及配钢率对累积损伤的影响。研究结果表明:型钢混凝土柱的损伤演变分为3个阶段:弹性阶段、弹塑性阶段和破坏阶段;配钢形式、扭弯比和配箍率是影响型钢混凝土柱损伤程度的重要因素;配型钢,降低扭弯比和提高配箍率对于损伤指标分别最大降低了22.1%、14.3%和14.0%;损伤指标受轴压比、配钢率和混凝土强度等级影响程度较小。     

Nonlinear elastic behavior of fiber-reinforced soil under cyclic loading

Experimental investigations and modeling of nonlinear elasticity of fiber-reinforced soil under cyclic loading at small strain are conducted in this paper. The investigations include three aspects. First, cyclic shear tests are conducted using conventional triaxial apparatus. Twenty-seven specimens with three different fiber contents are employed to conduct triaxial cyclic shear tests under different confining pressure and loading repetition. Effects of geofiber, confining pressure and loading repetition on elastic shear modulus of reinforced soil are studied and analyzed. Second, a hyperbolic function is introduced to describe the nonlinear stress–strain skeletal curve under cyclic loading. Nonlinear elastic modulus is expressed as a function of shear strain and two variables A and B that are related to the initial tangential modulus and ultimate cyclic loading stress, respectively. In the present paper, variables A and B both are further assumed to be functions of geofiber content, confining pressure and loading repetition. Finally, eight constitutive coefficients of the nonlinear elastic model are calibrated using stress–strain curves from cyclic triaxial shear tests. The calibration of parameters is conducted using the technique of the linear regression for multiple variables. Impacts and effects of geofiber, confining pressure and loading repetitions on soil nonlinear elastic behavior are discussed.     

Undrained deformation behavior of saturated soft clay under long-term cyclic loading

Subgrade soils of traffic infrastructures are subjected to large numbers of load applications at a stress level below their shear strength. It is therefore of great practical relevance to study the deformation behavior of soft clay under long-term cyclic loading. In this study, a series of monotonic triaxial tests and long-term cyclic (50,000 cycles) triaxial tests have been carried out to investigate the undrained deformation behavior of undisturbed soft clay from Wenzhou, China. The stress–strain hysteretic loop, resilient modulus and permanent strain of the tested samples were found significantly dependent on CSR and confining pressure. With an increase of CSR and confining pressure, the resilient modulus decreases more significantly with increasing number of cycles and the accumulation rate of permanent strain increases. Furthermore, the shape of the stress–strain hysteretic loop almost remains unchanged and the resilient modulus tends to a steady value after a large number of cycles. Based on the experimental results, two equations are established for the prediction of long-term resilient modulus and permanent strain. Finally, a new critical value of 0.65 is suggested for CSR. When CSR>0.65, the resilient modulus for large number of cycles is reduced to a so called “asymptotic stiffness” and the accumulation rate of permanent strain significantly increases.