复合主轴端板连接的结构特性

设计中,节点最关键的结构性能是其抗弯能力、刚度和转动能力。这些都取决于连接梁的截面高度。对梁截面高度达530mm的复合端板连接进行一系列试验。试验结果显示楼板的断裂通常导致结构失效,但是这一般都发生在该处的转动变形已经充分发展之后。这些试验用来评估预测关键结构的性能,并可为设计提供依据。     

新型装配式钢管柱轻钢桁架梁节点的滞回性能

采用ABAQUS软件对一种新型装配式钢管柱轻钢桁架梁节点进行了数值模拟,重点考察分析了桁架梁连接方式、桁架梁高度、桁架梁弦杆截面、桁架梁弦杆壁厚对其滞回性能、抗弯承载力、节点转动刚度、耗能等的影响.分析结果表明:装配式钢管柱轻钢桁架梁节点的滞回曲线呈现出捏缩特征,但具有较高的抗弯承载力和理想的节点转动能力;塑性铰出现在桁架梁端部空腹节间,实现了理想的延性破坏模式;弦杆采用闭口矩形钢管截面及增加桁架梁高度和弦杆壁厚,均可提高此类节点的抗弯承载力、初始转动刚度和耗能能力.     

带接缝连接梁的预制混凝土剪力墙抗震性能试验研究

采用钢筋混凝土接缝连接梁来实现预制墙体竖向钢筋的连续性连接。通过6个高宽比为1.7、不同截面高度和位置的接缝连接梁预制混凝土剪力墙的低周反复加载试验,分析了试件的破坏形态、顶点荷载-位移滞回曲线、承载力、变形能力、刚度退化等特性,并与整体现浇墙体进行对比。试验结果表明：预制墙体试件与整体现浇墙体试件的破坏模式、破坏形态基本相同,均为墙体角部混凝土压碎、钢筋拉断或屈曲;预制墙体试件的水平承载力相当,略低于现浇墙体,接缝连接梁的位置及截面高度对承载力有一定程度的影响;预制墙体试件的变形能力略小于现浇墙体试件,但极限位移角均超过1/100;接缝连接梁可以有效传递荷载。     

H形梁-工形柱弱轴箱形节点域连接节点单调加载试验研究

提出了一种新型的适合于H形梁与工形柱弱轴箱形节点域连接节点的构造形式，该连接属于后Northridge连接方式。试验中共设计梁端标准、梁端加盖板、梁端截面削弱和梁端加腋4种不同的处理方式的足尺边框架节点试件。通过单调加载试验，得到各个试件的破坏模式、塑性铰出现位置及节点域组成板件的应力分布情况。试验现象和试验数据分析结果表明，各试件破坏时，塑性铰均出现在远离连接位置的梁截面上，节点域和工字形柱基本处于弹性工作状态，节点域组成板件的应力均较小，其转角延性系数都大于4，塑性转角都大于0.030rad，说明H形梁-工形柱弱轴箱形节点域连接节点具有较高的延性和塑性转动能力，完全能够实现“强柱弱梁”、“强节点弱构件”及“强节点域”的抗震设计目标。     

房屋钢拱梁连接节点优化设计研究

通过研究房屋钢拱梁连接节点优化设计，以达到降低房屋钢拱梁结构构建难度。以广州新客站站房为研究对象，优化该站房房屋钢拱梁连接节点后，运用有限元分析法构建连接节点的有限元模型，采用此模型分析优化后房屋钢拱梁连接节点的承载能力以及节点转动能力，承载能力主要包括抗拉、抗压强度分析与抗剪强度分析，节点转动能力包括连接节点的延性分析与塑性转动性能分析。实践表明：该方法能够通过有限元模型清晰地分析出连接节点的性能，从而有效提升了连接节点的承载能力以及节点转动能力。     

螺钉连接胶合木梁柱节点柱侧-钢板连接性能

研究1种螺钉连接胶合木梁柱节点,与螺栓连接节点相比,这种节点初始刚度大且支持胶合木柱在双向与梁连接。该节点由柱–钢板螺栓连接、钢板–梁螺钉连接2部分组成,对其中的柱–钢板螺栓连接进行试验研究,结果表明:柱–钢板连接初始刚度大,延性良好;随着端板高度的增高,节点初始刚度有明显提高,但转动能力降低。     

单调荷载作用下高强混凝土梁受弯性能尺寸效应研究

进行了不同截面尺寸高强混凝土梁的弯曲试验,研究了梁高对其受弯性能的影响。试件采用C70高强混凝土,纵向受力钢筋采用HRB400级钢筋。试件截面尺寸不同,截面长宽比、剪跨比和配筋率等参数保持一致。分析了不同截面尺寸对高强混凝土梁的名义开裂弯矩、名义屈服弯矩、名义极限弯矩、延性以及塑性转动能力的影响。研究结果表明,高强混凝土梁的名义开裂弯矩、名义屈服弯矩和名义极限弯矩无明显尺寸效应,而试件的位移延性系数和塑性铰区的塑性转动能力则表现出明显的尺寸效应,随截面尺寸的增大梁的位移延性系数和塑性铰区塑性转动能力有所降低。     

新型组合梁板连接中板的抗弯性能

在高层建筑结构设计中,由于上部荷载较大或梁的跨度较大,使得梁的截面高度较高,通常会影响建筑的有效层高和建筑的总体高度。为了减小各层梁板结构高度,有效增大各层净高,提出了一种钢箱梁嵌入现浇板的新型组合梁板连接方式。针对这种新型连接方式,对6个钢箱梁混凝土板组合连接区域进行了板承受支座负弯矩的单调加载试验,对比分析了采用钢箱梁嵌入混凝土板组合楼盖与传统栓钉连接组合楼盖中板抵抗支座负弯矩的性能差异;并利用ABAQUS对试件进行了有限元分析。试验与有限元分析结果表明:采用钢箱梁嵌入板连接组合方式,其混凝土板抵抗支座负弯矩的能力与传统连接方式板抵抗支座负弯矩能力没有明显差异。     

双肢冷弯C形钢门式刚架抗震性能

冷弯C形钢在轻钢结构中应用广泛,采用垫板加高强螺栓的连接方式,拼合形成双轴对称截面,构建了一种组合截面门式刚架结构。对5榀平面刚架试件进行拟静力试验,分析其破坏特征、耗能能力、抗侧承载力等力学性能,探究柱腹板高度及刚架跨度对此类刚架结构抗震性能的影响。研究发现：该类门式刚架结构抗震性能良好,具有较好的耗能能力,抗侧力能力满足规范要求;节点传力可靠,可实现“强节点弱构件”和“强柱弱梁”的抗震设计要求;设计时可根据荷载情况增加柱腹板高度,但对刚架跨度一定要综合考虑梁柱线刚度比的大小,避免出现斜梁约束不足无法有效传力的情况。     

钢框架梁-柱节点的塑性铰外移研究

基于对梁-柱刚性连接节点的震害的大量调查研究,总结了若干用于迫使塑性铰离开柱面的节点形式。介绍了一种新型整体式加腋节点,该节点通过增加梁端截面有效高度,提高加腋区内抗弯承载能力,改变加腋长度及坡度,使得塑性铰出现在腋区以外,节点构造简洁,节点焊接质量容易得到保证,节点整体的设计抗弯能力大,具有良好的塑性转动能力,为钢结构梁-柱的节点设计提供有益参考。     

Stability of multi-storey unbraced steel frames subjected to variable loading

Proposed in this paper is an approach of evaluating the elastic buckling loads for multi-storey unbraced steel frames subjected to variable loading or non-proportional loading. In the case of variable loading, the conventional assumption of proportional loading is abandoned, and different load patterns may cause the frame to buckle at different levels of critical loads. In light of the use of the storey-based buckling concept to characterize the lateral sway buckling of unbraced framed structures, the problems of determining the lower and upper bounds among all of the frame buckling loads associated with different load patterns are presented as a pair of minimization and maximization problems subjected to elastic stability constraints. The problems take into account the semi-rigid behaviour of beam-to-column connections and the lateral stiffness reduction of columns due to the presence of an axial compressive load. The minimization and maximization problems are then solved by a linear programming method; thus, the lower and upper bounds of the frame buckling loads subjected to variable loading are obtained. Parametrical studies on the influence of the connection rigidity to the lower and upper bounds of critical loads and the comparisons to the conventional proportional loading are also presented in this paper.     

循环荷载下侧向支撑间距对钢梁整体稳定的影响

为了验证文献[1]给出的侧向支撑间距是否合理,按其布置支撑时能否保证采用我国型钢截面钢梁的整体稳定,对两端固定的H型钢梁进行理论研究.首先借助有限元软件ANSYS建立6根长度不同的H型钢梁模型,采用位移控制的循环加载制度,按文献[1]给出的侧向支撑间距方程布置支撑,进行非线性屈曲分析.分析结果表明,我国型钢钢梁按文献[...     

偏心荷载下非弹性工字型钢梁的侧向屈曲抗力

承受梯度弯矩的工字型钢梁的侧向—扭转屈曲(LTB)强度取决于弯矩梯度系数Cb。而Cb取决于弯矩图的非均匀性、无支撑长度内所施加的横向荷载的大小和钢梁支座类型。一般地,Cb由规范根据弹性LTB分析理论给出。然而,同样的Cb被用在梁的非弹性屈曲分析中。提出1个三维有限元ANSYS模型用于工字型钢梁的非线弹性弯-扭分析,并用此模型研究了无支撑长度和偏剪心荷载(分别位于中心、上翼缘和下翼缘)对非弹性性能区域弯矩梯度的影响。研究发现AISC-LRFD的钢结构规范(AISC360-05)和结构稳定研究委员会导则给出的Cb对加载点在非弹性屈曲工字型钢梁的中心和下翼缘的情况并不准确。AISC-LRFD的抗弯公式过高评估了梯度弯矩作用下非弹性工字型钢梁的实际抗弯承载力。因此,提出了一个适用于该工况下非弹性区域的简单公式,用于替代规范给出的公式。     

无支撑钢框架在高温下的楼层稳定性

受高温影响的钢框架的侧向稳定性与其在环境温度下的稳定性不同。这是由于高温下钢框架的弹性模量的降级将导致柱的横向刚度也跟着减少。在楼层屈曲理论的基础上调查无支撑钢框架在高温下的横向稳定性。首先,模拟一个钢柱暴露于高温之下,提出一个分析模型来测试无支撑框架中的轴向载荷、高温以及受热边界限制的钢管的横向刚度所带来的影响。之后,提出一个评估无支撑钢框架在高温下的稳定承载力的方法。数值实例用于展示所提出的方法的评估过程,并且研究不同场景中框架构架暴露于高温时框架结构的稳定性。使用有限元分析对所提出方法进行了数值分析,验证了该方法的有效性。     

Storey-based stability of unbraced steel frames at elevated temperature

The evaluation of the lateral stability of steel frames subject to elevated temperatures is different from that at ambient temperature. This is because the degradation of the Young's Modulus of steel associated with elevated temperature will lead to the loss of column lateral stiffness. In this study, the lateral stability of unbraced steel frames subjected to elevated temperature is investigated based on the concept of storey based buckling. First, to simulate a steel column exposed to the elevated temperature, an analytical model was proposed to examine the effects of axial loading, elevated temperature, and thermal boundary restraints on the lateral stiffness of steel columns in unbraced frames. Then, a method of evaluating the stability capacity of unbraced steel frames at elevated temperature is proposed. Numerical examples are presented to demonstrate the evaluation procedure of the proposed method and investigate the frame stability subjected to different scenarios of frame members exposed to the elevated temperature. The validity of the proposed method is verified by the numerical analysis with the use of finite element analysis.     

Elastic buckling load of multi-story frames consisting of Timoshenko members

The objective of this paper is to propose a method for the evaluation of the elastic critical buckling load of columns in frames consisting of members susceptible to non-negligible shear deformations, such as built-up members in steel frames, based on Engesser's approach. To that effect, a stability matrix is proposed and three general stability equations are derived for the cases of unbraced, partially braced and braced frames. Indicative graphic interpretation of the solutions for the stability equations of the braced and unbraced cases is shown. Slope-deflection equations for shear-weak members with semi-rigid connections are also derived and used for the presentation of a complete set of rotational stiffness coefficients, which are then used for the replacement of members converging at the bottom and top ends of the column in question by equivalent springs. All possible rotational and translational boundary conditions at the far end of these members, as well as the eventual presence of axial force, are considered. Five examples are presented, dealing with braced, unbraced and partially braced frames, with rigid and semi-rigid beam to column connections, loaded with concentrated or uniformly distributed loads, in a symmetrical or non-symmetrical pattern. In all cases the proposed approach is in excellent agreement with finite element results.     

Elastic distortional buckling of tee-section cantilevers

The paper presents the results of a finite element study of the elastic distortional buckling of tee-section cantilevers, which can be thought of as beams fully braced at one end and unbraced at the other. The finite element procedure is described briefly, and then three loading cases, viz., a tip moment, a tip load and a uniformly distributed load are considered. All of these loading cases place the unstiffened or free edge of the stem or web into compression. The effects of distortion are quantified for the three loading cases, as are the effects of fully restraining the top flange against lateral deflection and twist by a discrete brace positioned anywhere along the cantilever. It is shown that the effects of distortion during buckling cannot be ignored in a tee-section cantilever with even a moderately slender web.     

Column effective lengths considering inter-story and inter-column interactions in sway-permitted frames

The physical meaning of the traditional effective length coefficients (ELCs) in a sway permitted frame is first explained. It is found through an example that the critical loads of columns in a story have the same percentage increase or decrease after considering the inter-story interaction. It is also pointed out that the ELCs obtained by an overall buckling analysis are applicable only in the weakest story, for the other stories their ELCs simply implied the proportional loading assumption.With three assumptions of the conventional effective length approach discarded, this paper presents a mergence approach for buckling analysis of frames in which the column linear rigidities and axial loads are summed up, and the rotational restraints provided to columns by beams are summed at the merged beam-to-column joints. Effective lengths considering both inter-story and inter-column interactions are determined in unbraced two-story and three-story frames by simple algebraic operations. For frames with more than three stories, a three-story sub-assemblage, which includes beams at far ends of the columns above and below the story under consideration, is used to find the effective lengths of columns in the middle story.For frames with different bases, a equivalence procedure transforms the frames into those with the same type of bases before the mergence. For multi-span frames, the mergence approach overestimate the story lateral stiffness, a modification is proposed to eliminate this overestimation.Although overall buckling analysis of frames is easily carried out today, the findings and the proposed method of this paper will help to understand the inter-column and the inter-story interactions in frames.     

Experimental and numerical investigation on LTB strengths of monosymmetric compact I-beams with thickness-stepped-flanges

This paper investigates the inelastic lateral torsional buckling, LTB, of doubly stepped singly symmetric compact I-beams under two concentrated loads. The results are obtained by conducting actual destructive tests on the beams using a testing machine and running simulation tests using the finite element program, ABAQUS. The main factors that are considered for the analyses are the degree of symmetry, the loading and supports, the stepped beam factors and the length. For this study, the beams have simple supports. The monosymmetric ratio of all the beams analyzed is fixed at 0.7. The unbraced lengths of the beams are 3 meters and 4 meters. The results obtained from ABAQUS are compared with the results from design specifications to determine the effects of steps and from proposed design equations to determine the equations’ applicability and safety. The results revealed that the stepped beams did have an increase in capacity in comparison with the prismatic beams and that the proposed equations are suitable to be used in predicting the strength of stepped beams under the observed loading condition.     

Dynamic buckling of fiber composite shells under impulsive axial compression

The paper deals with dynamic buckling due to impulsive loading of thin-walled carbon fiber reinforced plastics (CFRP) shell structures under axial compression. The approach adopted is based on the equations of motion, which are numerically solved using a finite element code (ABAQUS/Explicit) and using numerical models validated by experimental static buckling tests. To study the influence of the load duration, the time history of impulsive loading is varied and the corresponding dynamic buckling loads are related to the quasi-static buckling loads. To analyse the sensitivity to geometric imperfections, the initial geometric imperfections, measured experimentally on the internal surface of real shells, are introduced in the numerical models. It is shown numerically that the initial geometric imperfections as well as the duration of the loading period have a great influence on the dynamic buckling of the shells. For short time duration, the dynamic buckling loads are larger than the static ones. By increasing the load duration, the dynamic buckling loads decrease quickly and get significantly smaller than the static loads. Since the common practice is to assume that dynamic bucking loads are higher than the static ones, which means that static design is safe, careful design is recommended. Indeed, taking the static buckling load as the design point for dynamic problems might be misleading.