装配式预应力短索自复位钢框架数值模拟

在已经完成的预应力短索自复位钢框架节点试验和数值模拟的基础上,采用ABAQUS有限元分析软件将装配式预应力短索自复位钢框架和普通自复位钢框架、刚接钢框架进行静力往复加载和动力时程的数值模拟结果进行对比分析,结果表明:两种自复位钢框架较刚接框架而言可有效减少结构损伤,且残余力较小,具有良好的自动复位和恢复结构功能的能力;装配式预应力短索自复位钢框架可以避免高空张拉钢绞线,减小了张拉难度,保证了张拉质量,具有更广阔的应用前景。     

复合承载型自复位梁柱节点有限元研究

基于损伤控制思想,提出一种复合承载型自复位梁柱节点,该节点通过高强预应力钢索为结构提供预拉力,使结构在地震作用下可以实现自复位,通过震后更换设置在节点上的狗骨削弱盖板,可实现结构震后可修复。利用有限元软件对5个节点模型进行有限元模拟,通过改变高强预应力拉索的初始索力和狗骨削弱盖板的厚度来研究两者对节点承载能力、耗能能力、自复位能力和震后修复能力的影响,获得了5组模型的荷载-位移曲线、索力变化曲线以及应力分布形态。研究表明:在保证模型实现自复位的前提下,无狗骨削弱盖板的构件塑性损伤较严重,带狗骨削弱盖板的构件可以有效降低节点主体构件的塑性损伤,增加狗骨削弱盖板的厚度和提高索力均可提高节点模型的承载能力和耗能能力,但增加狗骨削弱盖板厚度的作用更明显。     

自复位平面钢框架有限元分析对比

利用有限元软件ABAQUS对两个采用普通刚接节点、自复位节点的单榀、两跨4层钢框架进行了弹塑性拟静力循环加载分析,对比分析了各框架每层的滞回性能及塑性变形特性,得出了自复位平面钢框架复位性能良好和塑性变形较小的结论。     

装配式自复位钢框架梁柱节点低周往复试验的数值模拟

采用ABAQUS有限元分析软件,对4个装配式自复位钢框架梁柱节点在低周往复荷载作用下的试验进行数值模拟分析,并将分析结果与试验结果及理论计算结果相对比。结果表明,数值模拟结果与试验结果吻合较好,丰富了研究成果,获得对节点受力性能更准确、更全面的认识。同时梁柱节点开口处弯矩-转角的理论模型得到了验证,为进一步对节点的性能化设计及整体结构进行分析和设计奠定了基础。     

自复位预制框架边节点抗震性能试验研究

提出一种新型的自复位预应力预制节点形式PTED节点,为了研究PTED节点的抗震性能,进行5个PTED边节点的低周往复荷载试验,对试件的滞回曲线、骨架曲线、刚度退化、耗能能力、延性及残余变形等抗震性能进行分析,试验结果表明:加载到层间位移角为4%时,预应力筋保持在弹性阶段,梁柱连接处缝隙及梁自身的裂缝均能在预应力筋的回弹作用下闭合,节点残余变形较小,PTED节点具有良好的自复位的能力,提高了震后结构的可修复性。加载过程中,梁柱基本保持弹性,而通过角钢的弹塑性变形耗散能量。增大角钢厚度、长度,增大梁高及减小预应力筋的初始应力可提高节点的耗能能力。节点的承载力随梁高的增加、预应力筋初始应力的增大、角钢厚度和长度的增大而提高。在加载后期,节点承受的荷载仍持续增长,加载到4%时,PTED节点仍具有稳定的屈服后刚度。PTED节点还具有较好的延性和梁端转动能力。PTED节点具有良好的抗震性能,可在地震区推广应用。     

钢框架梁柱栓焊节点的有限元分析

在用试验验证有限元计算精度的基础上 ,对钢框架梁柱栓焊节点的滞回性能进行了有限元分析 ,得到了连接处梁端截面应力分布 ,揭示了梁翼缘发生脆断的原因 ,指出了现行规范设计方法的不足之处及对此问题的展望。     

考虑楼板效应的装配式自复位钢框架节点弯矩-转角理论研究

装配式自复位钢框架结构体系在地震中能够有效耗散地震能量、控制结构损伤,震后残余变形小易修复,但由于震时自复位钢框架节点开口的特性带来了装配式自复位钢框架自身膨胀效应,使得传统的楼板体系不适用于该类结构体系。基于课题组提出的带新型滑动次梁的楼板体系和考虑带新型滑动次梁楼板体系后自复位框架梁各轴向力的计算式和自复位钢框架节点弯矩-转角关系。通过一个算例量化分析了8度设防、8度罕遇和8度罕遇(0. 3g)三个地震动水准下楼板效应对自复位钢框架节点开口后弯矩-转角的影响程度。     

体外预应力自复位框架抗侧刚度参数分析

体外预应力自复位框架(EPSCF)是一种采用结构控制技术的抗震结构体系。结构抗侧刚度对EPSCF结构地震响应具有重要作用。首先，采用ABAQUS软件建立EPSCF结构的有限元数值模型，并采用地震振动台试验验证了模型的正确性；其次，通过改变预应力筋参数以改变结构抗侧刚度，得到结构自振特性随相对刚度比变化的规律。同时，选取合适的地震波进行弹塑性时程分析，模拟不同相对刚度比下EPSCF结构的地震响应规律，计算结果总体呈现为随相对刚度比的增大，结构位移响应减小、结构加速度和基底剪力增大；最后，求得结构层间位移放大系数及基底减震系数随相对刚度比变化的曲线，并选择基底减震系数为EPSCF结构侧向刚度的取值依据，得出相对刚度比的参考取值范围为0.02~0.10。     

预应力预制混凝土框架节点形式及设计方法

构建了一种新型的预应力预制混凝土框架节点,该节点的梁、柱构件通过预应力筋、角钢以及高强螺栓连接而成,经试验验证该类节点兼具良好的自复位能力和耗能能力。为了便于推广应用,针对这种基于角钢-高强螺栓连接的预应力预制混凝土框架节点的梁柱连接,提出设计方法,包括使用阶段的承载能力极限状态和正常使用极限状态并考虑施工阶段节点的工作状态,提出确定预应力筋的面积、初始张拉力、角钢尺寸及螺栓连接位置等设计参数的方法。     

Parametric study of hexagonal castellated beams in post-tensioned self-centering steel connections

The effects of important parameters (beam reinforcing plates, initial post-tensioning, and material properties of steel angles) on the behavior of hexagonal castellated beams in post-tensioned self-centering (PTSC) connections undergone cyclic loading up to 4% lateral drift have been investigated by finite element (FE) analysis using ABAQUS. The PTSC connection is comprised of bolted top and bottom angles as energy dissipaters and steel strands to provide self-centering capacity. The FE analysis has also been validated against the experimental test. The new formulations derived from analytical method has been proposed to predict bending moment of PTSC connections. The web-post buckling in hexagonal castellated beams has been identified as the dominant failure mode when excessive initial post-tensioning force is applied to reach greater bending moment resistance, so it is required to limit the highest initial post-tensioning force to prevent this failure. Furthermore, properties of steel material has been simulated using bilinear elastoplastic modeling with 1.5% strain-hardening which has perfectly matched with the real material of steel angles. It is recommended to avoid using steel angles with high yielding strength since they lead to the yielding of bolt shank. The necessity of reinforcing plates to prevent beam flange from local buckling has been reaffirmed.     

Experimental and numerical study on a full scale apex connection of cold-formed steel portal frames

In this paper, experimental and theoretical studies performed on apex connection of an industrial portal frame constructed with cold-formed back-to-back double sigma profile rafters are presented. By those experiments performed, local buckling behavior of the apex plate and load–displacement behavior of the system were investigated under monotonic vertical loading. This investigation was conducted for conditions that the gap between rafter ends at the apex plate are 90, 180, 360, and 450 mm and apex plate is unstiffened/stiffened. Experimental results for the model with 360 mm gap were compared to those of nonlinear quasi-static finite element analyses performed using a finite element software and a good agreement between those results was observed. The connection׳s behavior is controlled by the apex plate. No significant damage occurred on the profiles after the tests. According to the results, it is sufficient to increase the gap between rafter ends up to not higher than 360 mm in order to maximize the general load carrying capacity of the system and the stability of out of plane local buckling behavior of the apex plate. Furthermore, although stiffener plate significantly restricted local buckling of apex plate, no remarkable effect of this enhancement was observed on the flexural capacity of the system.     

梁端楔形翼缘连接钢框架低周反复荷载试验研究

提出了梁端楔形翼缘连接节点,通过2跨2层梁端楔形翼缘连接钢框架试件的低周反复加载试验,研究了结构在地震作用下的滞回性能、耗能机制、耗能能力、刚度退化和破坏形态。结果显示,试件破坏模式为延性,破坏时的顶点位移角达到了1/29,整体延性系数在4.7以上,梁上塑性铰出现在翼缘变化处,表明梁端楔形翼缘连接钢框架具有良好的抗震性能。对试件进行了静力弹塑性分析,节点域用转动弹簧来考虑其剪切变形,采用双线性特性塑性铰的计算结果与试验结果较一致。     

足尺钢梁柱刚性连接节点抗震性能试验研究

通过10个不同连接构造的足尺钢梁柱刚性连接节点的试验,研究了标准栓焊连接节点、标准全焊连接节点、梁翼缘加强型节点、梁翼缘局部削弱型节点以及梁贯通型节点在梁端往复荷载作用下的破坏过程、破坏形态、承载力和塑性变形能力等抗震性能。试验结果表明,梁翼缘局部切割削弱和梁翼缘加盖板节点的梁的极限塑性转角大于0.03,梁贯通型节点、梁下翼缘加腋节点和梁翼缘打孔节点的梁的极限塑性转角大于0.02,其余类型节点的都小于0.02。对实测的梁翼缘和腹板的应力分布的分析表明,梁根部翼缘处于三向应力状态,是其脆性断裂破坏的原因之一。建议钢框架梁柱连接优先采用梁翼缘加梯形盖板节点和梁下翼缘加腋节点。     

钢框架梁柱弱轴顶底角钢连接刚度的理论分析和试验研究

为研究梁柱弱轴连接的抗弯性能,进行了2类共6个大尺寸弱轴顶底角钢连接试件的单调加载试验,试验试件包括腹板-角钢连接试件和本文根据梁柱弱轴连接受力变形特点设计的T形钢-角钢连接试件。根据经典力学理论,推导了弱轴顶底角钢连接初始刚度的分析计算方法。梁柱弱轴角钢连接的刚度取决于各组件的刚度,角钢、螺栓和与角钢竖向肢连接的板件起决定作用,其中刚度最小的组件其几何尺寸对连接刚度的影响最明显。弱轴顶底角钢连接作为一种典型的半刚性连接,具备良好的变形能力、一定的弯矩承载能力和很好的钢材屈服后塑性强化能力。     

带耗能钢板的自复位方钢管混凝土框架抗震性能研究

为了减小"梁增长"现象对自复位框架的影响,提出一种自复位方钢管混凝土框架,该框架由钢管混凝土柱、钢梁及带耗能钢板的自复位梁柱节点组成。对3榀1/3比例的自复位方钢管混凝土框架进行低周往复荷载试验,研究其自复位性能和抗震性能。利用有限元软件ABAQUS对其进行了非线性数值分析,并验证了有限元模型的准确性,同时构建足尺模型研究了钢绞线初始预拉力和耗能钢板耗能段截面积对自复位框架性能的影响。结果表明:加载至2%层间位移角时,自复位框架表现出较好的自复位能力和耗能能力;增大钢绞线初始预拉力,结构承载能力与耗能能力增强,自复位能力先增强后减弱;增大耗能钢板耗能段截面积,结构的承载力随之增大,残余变形亦增大,自复位能力减弱。     

Development of floor slab for steel post-tensioned self-centering moment frames

A floor slab constructed in conventional moment-resisting frames (MRFs) limits opening of gaps at the beam-to-column interfaces, causing losses of self-centering capability and preventing its use in steel post-tensioned (PT) moment frames. This work presents two novel slab schemes to reduce the restraints on the seismic responses of a PT frame. The first scheme uses a slab in typical MRFs with a modification so that near the connection, the metal deck is discontinuous and the longitudinal bar in the deck is debonded from concrete to minimize slab restraints. The second scheme uses truss elements to connect the slab and beams in only one bay (rigid bay) of the PT frame for transferring inertial forces from the floor to the frame. The sliding device is provided at one end of floor beams transverse to the PT frame, where sliding of the slab is expected. The cyclic behaviors of the bare connection and the connection with the first slab scheme are also evaluated by testing four connections. Additionally, how the rigid bay affects the cyclic behavior of the frame, distribution of column shear, beam axial force variation, and gap opening response near the beam-to-column interface is evaluated by conducting frame subassembly tests. The test results demonstrate that (1) the PT frame with any of two slab schemes develops large deformation capacities with small residual deformations, and (2) the column shear and beam axial force can be estimated based on the proposed method.     

Application of fire-resistant steel to beam-to-column moment connections at elevated temperatures

This paper presents a new method of using fire-resistant steel to improve the fire-resistance of beam-to-column moment connections in steel structures. Two full-scale beam-to-column moment connection specimens were tested at elevated temperatures according to the standard ISO-834 fire to verify the feasibility of the proposed method. In addition, a detailed 3-D finite element model was developed to simulate the structural behavior of the column-tree moment connection specimens in fire. The fire test results show that the proposed method can effectively extend the fire endurance time, reduce structural deformation, and raise the critical temperature to failure for the beam-to-column moment connections. The numerical results obtained from the 3-D finite element analyses for the two specimens successfully simulated the fire test results.     

装配式自复位摇摆钢框架的恢复力模型

传统的钢框架结构在强烈地震作用下梁端和柱脚通常会出现塑性铰,导致结构产生较大的塑性变形.为此,提出了一种装配式自复位摇摆钢框架结构,阐述了该结构的构造形式与工作机理,通过理论分析建立了该结构的恢复力模型.设计了单层和双层的传统钢框架结构模型和装配式自复位摇摆钢框架结构模型,通过有限元软件ABAQUS对结构模型的滞回性能...     

钢框架梁柱节点力学性能研究

在美国的Northridge地震和日本阪神地震中,钢框架梁柱刚性连接节点发生严重的脆性破坏现象,显示出节点构造还不尽合理,需对其进行构造改进.文中提出三种改进方式,通过对改进后节点的有限元计算分析,结果表明:在反复荷载作用下,改进节点强度和刚度较好,能够满足我国抗震规范的要求;塑性铰外移,改善节点区的力学性能;加载到极限状态时,节点域变形很小,满足强节点弱杆件的抗震设计原则;且节点构造简单,易于工地现场施工.