钢骨混凝土异形柱-钢梁节点抗震性能试验研究

为了研究钢骨混凝土异形柱-钢梁节点的抗震性能,进行了4个T形钢骨混凝土柱-钢梁节点和4个L形钢骨混凝土柱-钢梁节点的拟静力试验。试验考虑了混凝土强度等级、核心区配箍率和轴压比等参数的影响,对骨架曲线、承载力、核心区剪切变形、延性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,钢骨混凝土异形柱-钢梁框架节点滞回曲线饱满,表现出良好的延性性能和耗能能力,典型破坏形态为节点核心区剪切斜压破坏和节点区焊缝失效破坏;高轴压力下节点具有较高的承载能力但延性性能降低;混凝土强度越高,节点承载能力越大,但延性性能越差;增大核心区配箍率对试件的延性和承载力有明显的提高,并能改善试件屈服后的耗能能力。     

双面叠合混凝土剪力墙平面内和平面外抗震性能研究

双面叠合混凝土剪力墙由两侧预制混凝土板和中间后浇混凝土叠合层组成,具有整体性较好、大量节省模板和支撑、便于工业化生产、经济性好等优点,应用前景广阔。该文开展了剪力墙足尺模型的高轴压比下平面内和低轴压比下平面外低周反复荷载试验,对双面叠合剪力墙的抗震性能进行了研究与探讨。研究表明:双面叠合剪力墙在平面内和平面外低周反复荷载下的破坏形态与现浇剪力墙相同,均发生受弯破坏; 4片剪力墙滞回曲线特征相似,双面叠合剪力墙的耗能性能好于现浇剪力墙;双面叠合剪力墙的平面内承载力比现浇剪力墙高约5%,平面外承载力低约12%;平面内和平面外加载时双面叠合剪力墙均具有良好的延性,其延性系数分别为2.15和3.83,比现浇剪力墙分别高约25%和20%。双面叠合剪力墙基于规范计算值的抗弯及抗剪安全系数均达到1.1以上,双面叠合剪力墙破坏时其水平接缝处的剪力远小于其接缝抗剪承载力设计值。总体而言,双面叠合剪力墙具有良好的抗震性能,可在抗震设防地区推广应用。     

A notch strain calculation of a notched specimen under axial-torsion loadings

In this paper, a notch analysis model is presented for the numerical prediction of multiaxial strains of a notched 1070 steel specimen under combined axial and torsion loadings. The proposed model is based on the notion of a structural yield surface and uses a small-strain cyclic plasticity model to describe stress–strain relations. A notch load–strain curve is calculated with Neuber’s rule and incremental nonlinear finite element analysis. The presented model is applied to simulate the notch root deformations of a circumferentially notched specimen under cyclic tension–compression–torsion loading histories. The model predictions are evaluated with strain measurements at the notch root of the specimen in a comprehensive set of cyclic tests. The computed strain loops were in accord with experimental data and matched qualitatively with measured shear–axial strain histories irrespective of loading path of the test. In proportional balanced torsion-axial loading, the nonlinear shear strain–axial strain loops were calculated properly. The modeling errors were determined to be a function of the loading path shape, and compared to shear strains, axial strain predictions were more accurate.     

不同轴压比下榫卯接缝装配整体式剪力墙受弯性能试验研究

设计了4个榫卯接缝装配整体式剪力墙试件,通过拟静力试验研究了轴压比对墙体受力性能的影响,研究结果表明,墙体均发生弯曲破坏,榫卯接缝横向凸起根部预制混凝土剥落,减弱了墙体根部混凝土压溃区域,避免突然丧失承载力。榫卯接缝整体性良好,开裂时墙体位移角为1/780~1/560。随着轴压比的提高,榫卯接缝横向凸起根部预制混凝土剥落区域增加,但墙体根部混凝土压溃区域并未增加;试验轴压比达到0.30(设计轴压比0.54),破坏状态时根部混凝土未发生压溃现象,墙体在高轴压比下表现出良好的变形能力。提高轴压比,有助于提高墙体的刚度和承载力;但峰值荷载后刚度退化速率加快;位移延性系数降低。     

A comparison of engineered cementitious composites versus normal concrete in beam-column joints under reversed cyclic loading

Engineered cementitious composites (ECC) are a class of high-performance fiber reinforced cementitious composite with strain hardening and multiple cracking properties. For a reinforced concrete member, substitution of conventional concrete with ECC can significantly improve the deformation characteristics in terms of reinforced composite tensile or shear strength and energy dissipation ability. In this paper, a number of RC/ECC composite beam-column joints have been tested under reversed cyclic loading to study the effect of substitution of concrete with ECC in the joint zone on the seismic behaviors of composite members. The experimental parameters include shear reinforcement ratio in the joint zone, axial load level on the column and substitution of concrete with ECC or not. According to the test results, for the specimens without shear reinforcement in the joint zone, substitution of concrete with ECC in the joint zone cannot change the brittle shear failure in the joint zone, but can significantly increase the load capacity and ductility of the beam-column joint specimens, as well as the energy dissipation ability due to high ductility and shear strength of ECC material. For the specimens with insufficient or proper shear reinforcement ratio, substitution of concrete with ECC in the joint zone can lead to failure mode change from brittle shear failure in the joint zone to a more ductile failure mode, i.e. flexural failure at the base of the beam, with increased load capacity, ductility and energy dissipation ability. Increase of axial load on column and shear reinforcement in the joint zone have little effect on seismic behaviors of the members when they failed by flexural failure at the base of beam. In a word, the substitution of concrete with ECC in the joint zone was experimentally proved to be an effective method to increase the seismic resistance of beam-column joint specimens.     

反复荷载下型钢混凝土异形柱空间角节点的破坏机理及损伤分析

为了研究反复荷载作用下型钢混凝土(SRC)异形柱空间角节点的破坏机理及其损伤演变过程,设计9个试件进行低周反复荷载试验,考虑了柱截面配钢形式、轴压比、加载角度和梁的形式4个变化参数。观察其裂缝发展形态,揭示其破坏机理,获取了荷载-应变滞回曲线、节点核心区剪切变形和梁截面平均曲率。基于能量守恒定律,分析了反复荷载下试件的损伤规律,并分析了各变化参数对其累积损伤的影响。研究结果表明:反复荷载作用下SRC异形柱空间角节点发生的是弯曲、剪切斜压破坏为主、扭转伴随粘结破坏为辅的破坏形态。破坏时节点核心区钢材大部分已屈服,并且型钢应变、核心区剪切角、梁截面平均曲率均随柱肢角度的增加而减小。破坏时试件的累积损伤指标介于0.69~0.84,槽钢桁架试件各级位移下的累积损伤最大;45°加载实腹配钢试件较30°加载实腹配钢试件损伤更加严重;与45°加载试件相比,0°加载试件各级位移下累积损伤程度最高增加30%;轴压比对试件的损伤影响不大;与带钢梁试件相比,带型钢混凝土梁试件累积损伤有较大程度的缓解。     

基于n阶GBT初始轴向载荷影响下FGM梁的振动特性

研究了初始轴向载荷影响下弹性地基功能梯度材料(FGM)梁的振动特性。基于一种拓展的n阶广义剪切变形梁理论(n-GBT),以轴向位移、剪切变形挠度与弯曲变形挠度为基本未知函数,应用Hamilton原理,建立了该系统自由振动问题力学模型的控制方程。引入边界控制参数,采用一种改进型广义微分求积(MGDQ)法获得了FGM梁的静动态响应。通过算例验证并给出了GBT阶次n的理想取值,丰富梁理论的同时,可供验证或改进其它各种剪切变形梁理论;提供的数值分析方法切实可行,拓展了GDQ法的使用范围。最后,着重讨论并分析了初始轴向载荷、边界条件、梯度指标、地基刚度、跨厚比等参数对FGM梁振动特性的影响。     

Comparative performance of sub-standard interior reinforced concrete beam–column connection with various joint reinforcing details

This paper discusses the effect of some important parameters on cyclic behavior of sub-substandard interior beam–column connection. The objective is to investigate the effect of joint shear stress, anchorage bond of longitudinal beam bar within the joint and horizontal joint reinforcements on the joint performance. The experiment consisted of five half-scale beam–column specimens. The control specimen (J1) represented a typical non-ductile beam–column joint in mid-rise RC buildings constructed in low seismic zone. In specimen J2, the bond between concrete and longitudinal bars was completely removed initially. In specimen J3A and J3B, a substantial amount of horizontal joint reinforcement was provided in joint core. In specimen J4, the column size was enlarged to reduce shear stress in joint. The experimental result demonstrated brittle joint shear failure in control specimen (J1), specimens J3A and J3B, beam splitting failure in specimen J2 and ductile flexural failure in specimen J4. Based on experimental results, it was found that the initial lost of bond did not cause a substantial reduction in joint capacity. Moreover, provision of substantial horizontal joint reinforcements in specimen J3A and J3B did not produce a comparable improvement in the seismic performance. With increased column size in specimen J4, the energy dissipation characteristics were greatly improved as indicated by large spindle-shaped cyclic loops.     

型钢UHTCC短柱的抗震性能研究

将具有良好控裂耗能能力和抗剥落性能的水泥基材料UHTCC应用于型钢混凝土SRC短柱,制作并完成了7个型钢-UHTCC(SUHTCC)短柱和1个SRC对比短柱的拟静力试验。试验主要变量为：配箍率、轴压比和翼缘栓钉布置。结果表明：UHTCC的使用可有效避免SRC短柱粘结裂缝的滋生,减缓剪切主裂缝的扩展,能够将SRC短柱的脆性剪切粘结混合破坏模式转变为延性较好的剪切破坏模式,大幅提升短柱的震后完整性;对SUHTCC短柱,增大配箍率对承载力几乎没有影响,但需确保箍筋最大间距以延缓粘结破坏,高配箍率的试件能显示出较好的峰后滞回曲线,具有较高的极限变形和耗能;轴压比对抗震破坏形态和力学性能影响较小,高轴压比下依然拥有较高的大变形能力和良好的抗震耗能;与型钢翼缘没有布置栓钉的SUHTCC试件相比,布置栓钉的SUHTCC短柱表现出更为饱满的峰前抗震滞回曲线,对峰前行为的影响较为显著,但峰后破坏加快导致延性降低。最后采用3种不同规范对SUHTCC短柱受剪承载力进行了预测,初步验证了现行JGJ138-2016规范受剪承载力计算公式的适用性,并对SUHTCC短柱的剪切变形进行了定量分析,讨论了各参数对剪切变...     

考虑梁轴向约束效应的RC梁柱节点受力机理及抗震性能试验研究

钢筋混凝土（RC）框架梁受弯损伤会发生轴向伸长,周边构件（抗侧力构件、现浇板）对梁伸长的约束作用会在梁中产生不可低估的轴力,从而影响梁柱构件和节点的抗震性能以及结构的强震破坏模式。分析了梁中约束轴力对节点抗剪受力机理的影响,设计了6个1/2比例的RC梁柱子结构试件,采用可直接量测约束轴力的等效约束装置代替周边构件对梁伸长的约束作用,通过低周往复加载试验考察了梁轴向约束效应对节点抗剪需求、抗剪承载力以及损伤破坏模式的影响。结果表明,约束轴力对抗剪需求的影响比抗剪承载力的影响明显,梁轴向约束效应产生的轴力较大,且随梁弯曲变形的增大而增加。与无约束试件相比,考虑梁轴向约束效应的试件节点抗剪需求增大了1.14~2.22倍,节点区斜裂缝宽度较大,损伤情况更加严重。     

纤维网格高延性混凝土加固RC柱抗剪性能试验研究

箍筋配置不当、剪跨比较小和轴压比较大的钢筋混凝土(RC)框架柱在地震作用下通常发生脆性剪切破坏。为提高框架柱的抗剪性能,提出采用碳纤维(CFRP)网格和高延性混凝土(HDC)复合加固RC柱。设计了6个RC柱试件,通过低周反复荷载试验,研究加固方式、纤维网格层数和轴压比对加固柱破坏形态、受剪承载力、延性及耗能能力的影响。结果表明:采用HDC和CFRP网格复合加固,可显著提高柱的抗剪承载力,明显改善其延性、变形性能和耗能能力;提高加固层的网格层数,对抗剪承载力影响较小,但加固柱的延性和变形能力得到较大改善;轴压比增大,复合柱的抗剪承载力稍有提高,但试件的延性、变形能力和耗能能力均降低;增加网格层数对高轴压比加固柱的增强效果和对低轴压比柱基本一致。最后基于桁架-拱模型,提出加固柱的抗剪承载力计算公式,计算结果与试验值吻合较好。     

Material ratchetting of beam under steady axial load and cyclic bending

Abstract

The purpose of this paper is to extend the applicability of the complete differential elasto‐plastic constitutive equations of the endochronic theory to describe the material ratchetting of a beam under a steady axial load and cyclic bending. Based on the assumption of the linear distribution of the through‐thickness strain of a beam under cyclic bending, the stress‐strain behavior of each through‐thickness point can be found theoretically. Experimental data of a lead alloy under a steady axial load and cyclic bending from Hyde et al. are used for comparison with theoretical predictions. It is shown that the theoretical results are in agreement with the experimental data.     

框-剪结构剪力墙可中断高度的分析研究

基于钢筋砼杆件截面的轴力-弯矩-曲率关系,建立了考虑杆件P-Δ效应和剪切变形且能分析结构极限状态的非线性有限元法。将剪力墙当作特别杆单元,对不同高度、配筋、轴压比和刚度特征值的中断剪力墙的框-剪结构进行了静力弹塑性分析。设定可中断剪力墙高度的条件。计算表明:上部剪力墙中断的相对高度值的决定因素为结构顶部的位移;相对高度值与配筋和轴压比无关;与结构高度关系较小;随着刚度特征值的增加,相对高度值随之增加,并给出了两者之间的表达式。     

Shear strength of plain concrete

Concrete shear strength is one of important parameters in structural design and analysis. Brittle failure of concrete under shear has substantial impact on performance of structure. Concrete shear strength as stipulated in standard codes of different nations is based on RC beam elements. Majority of research also focused on reinforced elements or on indirect shearing. There have been few studies performed on plain concrete subjected to pure shear. Hence, pure shear strength of plain concrete is not established. In light of foregoing, the present work attempts to build loading method that is efficient and capable of creating uniform shear force in standard specimen. The study investigates fracture behaviour of plain concrete when subjected to pure shear force. The pure shear state of specimen is verified using Mohr's circle method. FEA is performed to validate experimental data. The proposed test set-up is effective in determining pure shear strength of plain concrete.     

考虑粘结层滑移效应的组合梁弯曲

针对粘结型组合梁,在粘结层仅沿轴向剪切变形的假定下,给出了组合梁大挠度弯曲的一般非线性控制方程,指出仅在一阶近似下,组合梁子梁的轴线挠度相等.其次,在Euler-Bernoulli 梁变形的条件下,通过线性化方法,由上述非线性控制方程得到以挠度和轴向位移为基本未知量的组合梁线性弯曲耦合控制方程,该耦合方程组可分别退化为经典组合梁和叠梁的控制方程.最后,分析了悬臂组合梁在端部集中力作用下的线性弯曲,得到了问题的解析解,给出了不同梁长下组合梁自由端挠度、粘结层滑移位移和剪切应力等随粘结层剪切模量和厚度的变化曲线,进行了参数分析,结果表明:粘结层厚度和剪切模量对组合梁挠度和粘结层滑移有较为显著的影响,而对粘结层剪力影响很小.     

Seismic retrofit of substandard beam-column joint by planar joint expansion

A seismic retrofit technique for existing reinforced concrete beam-column connections using planar joint expansion is proposed. The method is based on a two-dimensional expansion of beam-column joint using cast in-situ concrete and dowel bars. The method is economical and architecturally acceptable. Three half-scale sub-standard beam-column specimens were tested under quasi-static cyclic loading. One was control specimen and the other two were retrofitted specimens with triangular and square joint expansion. According to test results, the control specimen showed brittle joint shear failure while retrofitted specimens showed beam flexural failure. The strength, stiffness, energy dissipation and ductility of retrofitted specimens were greatly improved. The planar joint expansion is effective to reduce joint shear stress and improve anchorage bond of beam bar within the joint. The plastic hinge formation can be moved away from column face, thus preventing joint shear failure. The triangular and square expansions perform almost equally well. The construction joints formed at the interfaces between specimen and joint expansion do not produce an adverse effect in cyclic behavior.     

湿-热-机-弹耦合FGM梁的稳定性及振动特性

研究了初始轴向机械载荷作用下Winkler-Pasternak弹性地基上功能梯度材料（FGM）梁在湿-热环境中的稳定性及振动特性。假设温度和湿度沿梁厚度方向稳态分布,材料的物性依赖于温度且按Voigt混合幂律模型连续分布。首先,基于一种扩展的n阶广义梁理论,应用Hamilton原理,统一建立了以轴向位移、弯曲变形项挠度及剪切变形项挠度为基本未知函数FGM梁的屈曲及自由振动方程,采用Navier解法获得了FGM简支梁静动态响应的精确解。其次,通过算例验证并给出了该广义梁理论阶次n的理想取值,丰富梁理论的同时,可供验证或改进其他各种剪切变形梁理论。最后,着重探讨了3种湿-热分布下湿度与温度增加、初始轴向机械载荷、跨厚比、地基刚度、梯度指标等诸多参数对FGM梁稳定性和振动特性的影响。     

A 3D fibre beam-column element with shear modelling for the inelastic analysis of steel structures

A force-based fiber beam-column element is proposed for the capacity assessment of frame structures under high shear. The proposed element is suitable for the performance assessment of large scale steel structures, which are not flexure-dominated. The element formulation follows the assumptions of the Timoshenko beam theory, while its kinematics are obtained through the natural-mode method. The element state-determination phase, instead of uniaxial material laws, typically associated with fiber elements, is based on a three-dimensional law taking into consideration the interaction between axial, bending, shear and torsion. Numerical examples are presented confirming the accuracy and the computational efficiency of the proposed formulation under monotonic, cyclic and dynamic/seismic loading. Compared to experimental results and the results of detailed finite element models, excellent agreement is achieved.     

Seismic performance evaluation of GLD beam–column sub-assemblages of three different scenarios

Gravity load designed (GLD) structures exhibit poor seismic performance due to inadequate reinforcement to cater for the seismic forces, lack of confinement, poor joint strength, improper anchorage, presence of weak column and strong beams. These structures are also susceptible to environmental impact leading to corrosion of reinforcement which would further degrade their seismic performance. In RC structures, beam–column joints are crucial members and dissipate the seismic energy imparted to the structure. Hence in this study, two typical cases of GLD (i) uncorroded GLD and (ii) corrosion affected GLD (corroded) exterior beam–column sub-assemblages subjected to reverse cyclic loading are investigated and compared. Reinforcement corrosion of one of the GLD specimens is accelerated by the impressed current technique. Based on the investigation on uncorroded GLD and corrosion affected GLD beam–column specimens, it is noted that the corrosion has significant effect on the seismic performance in terms of loss of energy dissipation, strength- and stiffness- degradation. To improve the seismic performance of uncorroded GLD specimens, a low invasive single steel haunch upgradation scheme (SHUS) is proposed in this study. The maximum load carried by steel haunch upgraded GLD specimen is about 30% higher than that of GLD specimen. Hence, it is noted that by implementing the proposed upgradation scheme for GLD beam–column sub-assemblage, remarkable improvement in the seismic response can be achieved. The present study provides insight into the behaviour of steel haunch upgraded GLD specimen and would also pave the way for formulating seismic upgradation of even corroded GLD beam–column sub-assemblage.     

高轴压比、低剪跨比双钢板-混凝土组合剪力墙拟静力试验研究

双钢板-混凝土组合剪力墙可减小墙体厚度、提高承载力和延性,为研究双钢板-混凝土组合剪力墙高轴压比下的抗震性能,完成了5个剪跨比为1.0的双钢板-混凝土组合剪力墙试件的拟静力试验,研究了剪力墙在低周往复荷载作用下的受力性能和破坏模式等,分析了轴压比、距厚比等因素对抗震性能的影响。试验结果表明:低剪跨比试件发生弯剪破坏;墙体钢板在平均位移角1/83时发生局部屈曲,初始屈曲形态受距厚比影响显著;试件峰值荷载、位移延性系数、刚度等受轴压比、距厚比的影响较小;试件平均极限位移角达1/72、平均有效破坏位移角达1/52,具有良好的变形能力;距厚比增大,试件滞回性能稳定性降低;试件耗能随变形增大而迅速增长,抗震性能良好。建议低剪跨比双钢板-混凝土组合剪力墙轴压比限值取0.7。