X型足尺相贯节点极限承载力试验研究

通过对X型相贯节点支管在轴压力、平面内弯矩、平面外弯矩共同作用下的极限承载力的试验研究,对节点加载过程中应力发展过程及位移变化进行分析。结果表明:通过对支管施加偏心荷载能够有效地模拟节点承受轴力、平面内弯矩、平面外弯矩的共同作用。节点区主管的局部屈曲是X型相贯节点的破坏模式。节点区主管部分区域在材料达到屈服强度前,应变已经呈现明显非线性。采用Eurocode 3中X型节点的承载力验算公式对支管承受轴力、平面内弯矩、平面外弯矩共同作用的X型相贯节点进行验算是可行的,验算表明节点是安全且偏保守的。     

方钢管相贯节点转动刚度研究

采用非线性有限元软件ANSYS(6.1)对方钢管Y型相贯节点在平面内弯矩作用下的转动刚度进行数值分析,分析了影响方钢管相贯节点弹性转动刚度的主要影响因素,并采用回归分析得出了方钢管Y型相贯节点在平面内弯矩作用下弹性转动刚度的计算公式.     

平面X形圆钢管混凝土节点平面外受弯性能试验研究

为了解平面X形圆钢管混凝土节点的平面外受弯性能,分别对4个主管填混凝土和4个支管填混凝土的平面X形圆钢管节点进行支管平面外弯矩作用下的试验研究。考察了支管、主管分别填混凝土2种情况下节点的破坏模式和应力分布,并分析了钢管内混凝土对节点平面外抗弯刚度及承载力的影响。试验中支管填混凝土节点出现了主管塑性、支管局部屈曲和支管受拉侧焊缝或热影响区管壁开裂的破坏模式,主管填混凝土节点则发生了支管局部屈曲及支管受拉侧焊缝开裂破坏。主管填混凝土节点与支管填混凝土节点相比,由于主管内填混凝土对于主管管壁的局部变形起到明显的约束作用,明显提高了主管的径向刚度,增大了节点的平面外抗弯刚度。实测节点承载力与欧洲规范计算的空钢管节点理论承载力比较表明,主管内填混凝土能极大提高节点平面外受弯承载力,最大可提高132%;支管内填混凝土可使节点平面外受弯承载力最大提高60%。     

单项受力状态下矩形钢管相贯节点的承载力研究

国家游泳中心采取了特殊的结构型式,使其矩形钢管相贯节点,除双平面的几何特性外,同时承受轴力和不可忽视的双向弯矩。本文的目的是研究不同型式的矩形钢管相贯节点在单项受力状态下———腹杆分别承受轴力、平面内弯矩、平面外弯矩时的承载力计算公式;节点型式主要包括T、TT、K、KT等4种单平面和多平面节点类型。以直角T型节点的单项承载力研究为基础,通过大量的有限元计算,并对计算结果进行回归分析得出节点承载力计算公式。本文还对各类节点的失效形态进行了分析。     

平面外弯矩作用下加劲肋加强T形方钢管相贯节点极限承载力研究

方钢管T形相贯节点承受平面外弯矩作用是与其它工况一样重要的一种工况,但目前规范中对这种受力模式下的加劲肋加强节点承载力计算公式没有规定,这影响着工程设计的效率与质量。在经试验验证有限元分析准确性的前提下,进行参数化分析和回归分析。结果表明:加劲肋加强节点的极限承载力是无加强节点的2.6倍,承载力提高系数ψ随加劲肋与主管厚度比τ、加劲肋与主管宽度比η的增加而增加,其中参数η的影响更大,提高系数ψ随β增加而减小。在无加劲肋方钢管相贯T形节点平面外受弯承载力计算公式的基础上,通过参数化分析得出有加劲肋时方钢管T形节点平面外弯矩作用下极限承载力计算公式,为这类节点的继续研究和工程应用提供了参考。     

复合受力状态下矩形钢管相贯节点的承载力研究

国家游泳中心的矩形钢管相贯节点,除双平面的几何特性外,同时承受轴力以及不可忽视的双向弯矩。本文的目的就是解决此类节点在这种特殊受力状态下的强度校核问题。研究工作以矩形钢管相贯节点在单项受力状态下的计算公式为基础,利用大量的有限元计算结果,回归得出T、TT、K、KT等4种类型节点在复合受力状态下———节点同时承受轴力、平面内弯矩、平面外弯矩中的两项或三项时的承载力计算公式。根据计算结果,本文还讨论分析了各类型节点的失效形态。研究表明,节点校核公式和破坏形态与节点的受力状态及节点的几何因素有关,如轴力的大小、弦杆截面高度及壁厚等。     

TX型圆管相贯节点空间作用下的极限承载力分析

空间相贯管节点构造简捷 ,较多应用于大跨度空间结构 ,其受力状况较为复杂。运用有限元方法 ,分析了TX型圆管相贯节点在平面外支管受轴向荷载、平面内支管受平面外弯矩作用下的极限承载力 ,并利用圆环模型 ,结合非线性回归分析 ,推导了理论计算公式。     

主管中灌混凝土平面X形圆钢管混凝土节点平面内抗弯性能试验研究

对主管中灌混凝土平面X形圆钢管混凝土节点在支管平面内弯矩作用下的极限承载性能进行单调加载的试验研究。实施6个不同截面几何参数的主管中灌混凝土平面X形圆钢管混凝土节点平面内抗弯极限承载力试验。介绍了节点试验方案,描述了X形圆钢管混凝土节点平面内弯曲破坏现象,给出荷载-支管端位移曲线、弯矩-主管局部变形曲线、弯矩-转角曲线以及节点区域应变强度分布曲线,并将支主管外径比β、主管径厚比γ和支主管壁厚比τ对节点平面内抗弯极限承载力和平面内抗弯刚度的影响进行讨论。试验研究结果表明:主管灌混凝土后并没有在主管中形成明显的刚域;在一定参数条件下,主管中灌混凝土的X形圆钢管混凝土节点平面内受弯极限承载力、抗弯刚度均随着β、τ值的增加和γ值的减小而提高;各试件在最大弯矩作用下,所有试件的支管根部测点都进入塑性,主管上大部分测点保持弹性状态;主管中灌混凝土对圆钢管节点平面内抗弯极限承载力有一定的提高,在一定参数条件下提高甚至达到48%,但若实际工程中取欧洲规范弯矩值与支管全截面塑性弯矩值中的最小者计算节点抗弯承载力,在一定的钢管几何参数下不一定是安全的,需要进行深入的有限元参数分析。     

圆钢管混凝土节点平面内抗弯刚度研究

对圆钢管混凝土T/Y型节点在平面内弯矩作用下的抗弯刚度进行数值分析和试验验证,比较空钢管节点和内填充混凝土钢管节点抗弯性能的差异,分析节点各无量纲参数对抗弯刚度的影响,给出钢管混凝土节点的抗弯刚度计算公式。研究表明:空钢管节点的主管内填充混凝土后,节点的抗弯刚度有明显的提高,节点刚度取决于弦杆的径向刚度和弦杆、腹杆相贯面的表面积;节点刚度随主、支管管径比β和主支管厚度比τ的增大而提高,随径厚比γ和主、支管夹角θ的增大而降低;内填充混凝土强度的变化对节点的抗弯刚度影响较小。     

矩形钢管和矩形钢管混凝土T形不等宽受拉节点 轴向刚度

为获得T形节点轴向刚度简化计算公式,根据节点受力特点,提出了适用于矩形钢管节点的平面框架模型和适用于矩形钢管混凝土节点的固端梁模型,并推导得到了2类节点的节点轴向刚度理论公式; 运用有限元方法对节点轴向刚度理论公式中的节点域有效长度l_eff进行参数分析,拟合得到l_eff简化计算公式; 将节点轴向刚度理论公式与试验及有限元结果进行了对比,并分析了主管内填混凝土对节点轴向刚度的影响。结果表明:主管高宽比和主管宽厚比对l_eff的影响较小,不予考虑; l_eff与主管宽度和支管高宽比均呈线性关系,且随之增大而增大; l_eff与支主管宽度比β呈非线性关系,且随之增大而减小; 2类节点的轴向刚度理论公式计算结果与试验结果及有限元结果均吻合较好; 主管内填混凝土可以提高节点轴向刚度,提高系数k_c/h随着主管高宽比的增大而增大,随着β的增大呈现先增大后减小的规律,且当β=0.6～0.7时提高最大。     

T形钢管混凝土插板连接节点受弯性能研究

采用精细化有限元分析方法对T形钢管混凝土插拔连接节点的平面内受弯性能进行了研究.首先通过与试验结果进行对比,验证了精细化有限元模型的正确性和准确性.在此基础上研究了主管壁厚、支管壁厚、主管形式和混凝土强度对节点破坏模式和承载力的影响.结果表明,钢管混凝土插板连接节点的破坏模式和钢管插板连接节点不同,为主管冲剪破坏和支管...     

圆管截面桁梁极限承载力试验研究

进行了上弦杆为钢管混凝土、上下弦杆均为钢管混凝土的桁梁试件和空钢管桁梁试件的对比试验研究。研究结果表明,弦杆钢管内填充混凝土可提高弦杆的抗压、抗弯和径向刚度,改变节点失效模式,提高节点强度和刚度;弦杆为钢管混凝土的桁梁试件与空钢管桁梁试件一样,结构破坏均是因节点失效引起的;由于弦杆管内填充混凝土提高了节点的强度和刚度,不仅受压的上弦杆而且受拉的下弦杆管内填充混凝土,都会提高圆管截面桁梁试件的整体承载力。最后对管节点的承载力和桁梁试件整体承载力进行了讨论。     

Hysteretic behaviour of tubular joints under cyclic loading

This paper examines the cyclic performance of CHS joints used in steel tubular structures. Quasi-static experimental study into the response of eight T-joint specimens is described. Four of them are subjected to cyclic axial load, and the other four are subjected to cyclic in-plane bending. The general test arrangement, specimen details, and most relevant results (failure modes and load-relative deformation hysteretical curves) are presented. Some indexes to assess the seismic performance of tubular joints, including strength, ductility and energy dissipation, are synthetically analyzed and compared. Test results show that failure modes of axially loaded joints mainly contain weld cracking in tension and chord plastification in compression. But for joints under cyclic in-plane bending, both punching shear and chord plastification become regular failure modes accompanied by ductile fracture of the welds. Hysteretic curves take on a plump form in general. Ultimate strengths of joints are also compared with equation values for monotonic loading from various design codes. Results indicate the strength at a certain deformation limit can be regarded as the ultimate strength of a T-joint under cyclic loading and existing codes can be used to check it. It is also found that there is a significant distinction in the energy dissipation mechanism for tubular joints under different loading conditions. Finite element analyses are performed by taking into account weld geometry to facilitate the interpretation of the test results. It is identified that high tensile stress triaxiality can be one primary cause of weld cracking which happened under low cyclic load level.     

Experiment investigation of stress concentration factor of concrete-filled tubular T joints

The aim of this paper is to study the stress concentration factors of concrete-filled tubular T joints subject to axial loading and in-plane bending. Experimental investigation was performed to investigate the Hot Spot Stress distribution along the intersection of chord and brace. Five tubular T joint specimens with self compacting concrete-filled chords were tested. In addition, three hollow steel tubular T joint specimens were also tested for comparison. Generally, it is shown that the concrete filling effectively reduces the peak stress concentration factors. The stress concentration factors obtained from the test results were compared against predictions from some well-established existing stress concentration factor equations. Generally, the predictions from those equations are very conservative for concrete-filled specimens.     

In-plane strength of concrete-filled steel tubular circular arches

More than 400 concrete-filled steel tubular (CFST) arch bridges have been constructed worldwide so far. However, design codes or guidance for the in-plane strength design of CFST arches are yet to be developed. In current design practice, the philosophy for the in-plane strength design of reinforced and prestressed concrete arches is widely adopted for CFST arches. For this, the CFST arches are considered under central or eccentric axial compression and are treated similarly to CFST columns, and the classical buckling load of CFST columns is used as the reference elastic buckling load of CFST arches. However, under transverse loading, the in-plane elastic buckling behaviour of CFST arches, particularly shallow CFST arches, is very different from that of CFST columns under axial compression. In addition, different from CFST columns under central or eccentric axial compression, CFST arches are subjected to significant nonlinear bending actions and transverse deformations prior to buckling and these will influence the strength of CFST arches greatly. Therefore, it is doubtful if the current method for in-plane strength design of CFST arches can provide correct strength predictions. In this paper, a method for the in-plane strength design of CFST circular arches, which is consistent with the current major design codes for steel structures, is developed by considering both geometric and material nonlinearities. A design equation for the in-plane strength capacity of CFST arches under uniform compression, and a lower-bound design equation for the in-plane strength check of CFST arches under combined actions of bending and compression are proposed.     

钢管混凝土圆拱的面内承载力分析

迄今为止,全世界已有400多座钢管混凝土拱桥。然而,有关钢管混凝土拱面内承载力的设计规范仍没有。目前,钢管混凝土拱的设计广泛采用钢筋混凝土及预应力混凝土拱的面内承载力设计方法。这样钢管混凝土拱可认为受轴压或偏压作用,相当于钢管混凝土柱。将钢管混凝土柱的经典屈曲荷载作为钢管混凝土拱的参考弹性屈曲荷载。然而,在横向荷载作用下,钢管混凝土拱的面内弹性屈曲性能与轴压下的钢管混凝土柱完全不同,尤其是对于薄壁钢管混凝土拱。另外,与轴压或偏压下钢管混凝土柱不同,钢管混凝土拱在屈曲之前就发生非线性弯曲和横向变形,这严重影响钢管混凝土拱的承载力。因此,钢管混凝土面内承载力的设计方法是否正确值得商榷。提出与现有钢结构设计规范基本一致的钢管混凝土圆拱承载力设计方法,并同时考虑了几何非线性和材料非线性的影响。提出均匀轴压下钢管混凝土拱的面内承载力设计方程,及弯矩和轴压共同作用下钢管混凝土拱面内承载力验算的下限设计方程。     

Strain and stress concentration of completely overlapped tubular CHS joints under basic loadings

A completely overlapped tubular circular hollow section (CHS) joint specimen is tested under lap brace axial loading (AX), in-plane (IPB) and out-of-plane bending (OPB) to determine the strain concentration factor (SNCF) at the intersection of members for the verification of a finite element (FE) model. The experimental results showed that the strain distribution on the outer surface of members near the weld toe of the joint is fairly linear. The maximum SNCF of the joint occurs at the through brace saddle near the lap brace under AX and OPB and at the lap brace crown heel under IPB. The SNCF at the intersection of the chord and through brace for the joint under IPB and OPB is negligible. For the FE analysis, the comparison of SNCF between the test specimen and the 8-node thick shell FE model under AX, IPB and OPB load cases shows reasonably good agreement with average differences of 7.9%, 10.6% and 5.8% respectively. The comparison of stress concentration factor (SCF) revealed that the existing T/Y-joint equations are not suitable for predicting the SCF of completely overlapped tubular CHS joints. The SCF of completely overlapped tubular CHS joints can effectively be reduced by proper control of its geometrical properties.     

超高压变电构架钢管混凝土Y型相贯节点平面内受弯性能研究

以国内首例采用钢管混凝土的750kV超高压变电构架工程为背景,设计了3个1:2缩尺、主管灌注混凝土的Y型相贯节点试件,其中包括2个采用不同加强方式(即瓦形板、外套筒加强)和1个作为对比的无加强节点试件,并对其进行了平面内受弯性能试验。试验结果表明：相比无加强节点,采用的2种加强节点的最终破坏形态均为支管失效破坏,均符合“强柱弱梁”的设计原则;节点的转动刚度和受弯承载力均显著提高,平面内转动刚度均可达到欧洲规范规定的刚性节点要求,且平面内受弯承载力基本可以达到支管全截面塑性时的弯矩值。此外,对节点的有限元分析表明：主管轴压比、瓦形板长度和宽度对节点刚度和承载力影响较小,而瓦形板厚度对此影响较为显著。     

Experimental investigation and design of round ended elliptical steel tubular T-joints under axial compression

圆端形椭圆钢管是一种融合圆形和矩形截面特征优势的构件，其圆端部分可以提供良好约束，矩形部分可实现快捷连接，在桁架结构中有着良好的应用前景，然而目前尚缺乏有关圆端形椭圆钢管相贯节点的受力性能研究。为此，通过对13根圆端形椭圆钢管T形相贯节点开展轴压性能试验，研究相贯类型、主支管径比、主支管夹角和是否填充混凝土等对其破坏模式、承载力、初始刚度和延性等力学性能的影响，明确圆端形椭圆钢管T形相贯节点在支管受压作用下相较圆形或矩形钢管相贯节点的承载特征差异，揭示相贯节点的受力机理，提出圆端形椭圆钢管相贯节点的轴压承载力计算式。研究结果表明，圆端形椭圆钢管T形相贯节点表现出良好的轴压性能；支管与主管圆弧段连接的相贯节点轴压承载力分别为圆形或矩形钢管相贯节点的1.07~1.66倍，具有明显的承载优势；主管填充混凝土可使圆端形椭圆钢管T形相贯节点的轴压承载力和初始刚度分别提高75.5%~103.4%和11.9%~60.6%；通过试验结果验证，提出的轴压承载力计算式可较准确地评估圆端形椭圆钢管T形相贯节点的轴压承载力。     

Geometrical effect on the stress distribution along weld toe for tubular T- and K-joints under axial loading

This paper presents general remarks of the effect of the geometrical parameters on the stress distribution in the hot spot stress region for tubular T- and K-joints subjected to brace axial loading. As the stress distribution along the weld toe is very critical for the prediction of the fatigue life of steel tubular joints, the investigation of such geometrical effect can provide integrity assessment for tubular T- and K-joints. Previous research work was mostly focused on the study of the value of the peak stress, but ignored the stress distribution principle. Generally, the location of the hot spot stress along the weld toe affects the crack initiation. Accordingly, the stress distribution has critical effect on the propagating way of the fatigue crack. The stress distribution is mainly determined by the loading type and joint geometry. The geometrical effect on the stress distribution for tubular T- and K-joints subjected to axial loading has been investigated from both numerical and experimental methods in this study. Thereafter, a parametric study has also been carried out to investigate the effect of three popularly used joint geometrical parameters on the stress distribution. From parametric study, it has been found that chord thickness has remarkable effect on the stress distribution for both T- and K-joints, while brace thickness has no effect on such stress distribution. The last geometrical parameter, the diameter ratio between the brace and the chord, has different effects on the stress distribution for tubular T- and K-joints.