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。     

圆端形钢管混凝土短柱极限承载力计算方法研究

圆端形钢管混凝土短柱受力机理相较于圆形和矩形截面更加复杂,目前还没有一个定量的表达式用于计算圆端形钢管混凝土短柱轴压和偏压的承载力.为分析研究圆端形钢管混凝土短柱轴压和偏压的承载力性能,进行了 8个圆端形钢管混凝土短柱轴压试验和6个圆端形钢管混凝土短柱偏压试验,分别基于双剪切统一强度理论和极限平衡理论推导出相对应的圆端形钢管混凝土短柱轴压承载力计算公式,用Python语言编制基于纤维模型法的承载力计算程序,最后提出了适用于圆端形钢管混凝土短柱轴压和偏压的统一承载力公式,并用试验数据对公式进行验证.结果表明:基于双剪切统一强度理论、极限平衡理论及纤维模型法推导的三种轴压承载力计算理论公式均具有较好的精度,满足工程要求,DBJ/T 13-51规范所计算的承载力偏小,计算结果精确度最差.推导的三种理论公式中基于双剪切统一强度理论推导的承载力计算公式精度最高,更适用于圆端形钢管混凝土短柱轴压承载力计算.最后验证了修正的圆端形钢管混凝土短柱轴压和偏压承载力统一公式的准确性,计算偏压的适用范围为 e/R≤1.55.     

空间隔板焊接X形圆钢管相贯节点受力性能试验研究

对3个足尺空间隔板焊接X形圆钢管相贯节点分别进行了轴力作用下的单调加载试验和往复加载试验,得到了节点的破坏模式,并对节点的受力性能包括静力弹性刚度、承载力、延性和滞回性能等进行分析。验证了该种空间隔板焊接节点的构造措施合理,节点的承载能力相对设计工况有两倍以上的安全储备,节点受力安全可靠。运用ABAQUS软件建立有限元分析模型,并与试验结果对比,验证了有限元模型的适用性,并对节点进行设计工况下的内力校核,参数分析结果表明,管径厚比、相贯角度、椭圆连接板厚度及平面外角度对空间隔板焊接节点性能影响较大,节点刚度和承载力随着支管径厚比和平面外角度的增大而降低,随着相贯角度和椭圆连接板厚度的增大而提高。综合试验和有限元分析结果,节点设计要确保支管设计内力不大于节点承载力,增大椭圆板厚度以及补焊椭圆板隐藏焊缝对节点的受力性能改善较好;当设计该类较小相贯角度（小于20°）的节点时,需按节点承载力进行设计,同时考虑轴向刚度对节点受力性能的影响。     

T型圆钢管相贯节点损伤分析及平面内弯曲刚度研究

通过对3个主管不同截面的T型相贯节点进行低周反复静力加载试验,分析了T型相贯节点在不同荷载作用下的受力变形和应力、应变情况,同时对主管和支管上的相贯线周围进行了应力、应变分析,对T型圆钢管相贯节点的平面内弯曲刚度进行了测试。采用荷载直接垂直于支管端部的加载方式,求出3个主管不同截面的T型相贯节点的最大承载力,并与规范计算结果进行对比分析,研究了相贯节点平面内的刚度问题。研究表明:在其他参数一定的情况下,支管与主管直径相差较多时,相贯节点刚度、强度均较弱。实际工程设计中宜对节点进行加强处理;支管与主管直径接近时,能够满足节点刚接要求,且节点刚度较大。     

钢管塔正负偏心K形相贯节点的极限承载力研究

现有《钢结构设计规范》公式没有明确反映偏心距对节点承载力的影响。为了考察偏心距对钢管K形相贯节点的承载力的影响规律,建立偏心钢管相贯节点有限元模型,研究偏心相贯节点的受力机理;同时分析主管轴压力、加劲肋对节点承载力的影响规律。分析结果表明:偏心节点和无偏心节点破坏模式基本相同;偏心距影响节点承载力,负偏心增大有利于提高节点的极限承载力,正偏心降低节点极限承载力;而且相对正偏心而言负偏心对极限承载力影响更大。相贯节点的承载力模拟值比规范计算值大10%～30%,即规范公式计算结果偏于保守。     

钢管混凝土KK形相贯节点空间效应研究

为研究钢管混凝土空间相贯节点的空间效应,通过精细化有限元模拟对钢管混凝土空间相贯节点的受力性能进行了研究。建模时考虑了材料非线性、几何非线性、钢管与混凝土之间的接触非线性,建立了钢管混凝土KK形相贯节点的精确有限元模型,研究了空间效应对节点承载能力和破坏模式的影响。结果表明:钢管混凝土空间相贯节点的承载力远高于钢管空间相贯节点;钢管混凝土空间相贯节点和平面相贯节点的破坏模式相同,破坏模式有两种,一种是主管管壁冲剪破坏和受压支管屈服联合破坏,发生在支管管壁较薄的情况,另一种是主管管壁冲剪破坏;空间效应对钢管和钢管混凝土相贯节点承载力的影响不同,对于钢管混凝土相贯节点,支管空间夹角60°的节点承载力较平面节点有所降低,在设计时应该考虑空间效应的影响;空间效应对钢管混凝土空间相贯节点刚度影响不大。     

Study on spatial effect of concrete-filled steel tubular KK-joints

为研究钢管混凝土空间相贯节点的空间效应,通过精细化有限元模拟对钢管混凝土空间相贯节点的受力性能进行了研究。建模时考虑了材料非线性、几何非线性、钢管与混凝土之间的接触非线性,建立了钢管混凝土KK形相贯节点的精确有限元模型,研究了空间效应对节点承载能力和破坏模式的影响。结果表明：钢管混凝土空间相贯节点的承载力远高于钢管空间相贯节点;钢管混凝土空间相贯节点和平面相贯节点的破坏模式相同,破坏模式有两种,一种是主管管壁冲剪破坏和受压支管屈服联合破坏,发生在支管管壁较薄的情况,另一种是主管管壁冲剪破坏;空间效应对钢管和钢管混凝土相贯节点承载力的影响不同,对于钢管混凝土相贯节点,支管空间夹角60°的节点承载力较平面节点有所降低,在设计时应该考虑空间效应的影响;空间效应对钢管混凝土空间相贯节点刚度影响不大。     

主方支圆空间KT形管节点空间效应和极限承载力研究

以矩形钢管为弦杆、圆管为支杆的混合空间钢管结构因形式新颖、相贯线切割简单而在大跨空间结构中逐渐得以应用,但因支杆的几何效应和荷载效应,导致混合型钢管空间相贯节点承载力计算比较复杂。采用非线性有限元方法,应用自动步长增量法研究了主方支圆空间KT节点的空间几何效应和荷载效应。理论分析表明:相比杆件的几何效应,荷载效应对节点极限承载力的影响更为明显,T形支杆上较大的轴力将使K形支管处极限承载力显著下降。通过对空间KT形节点极限承载力的分析,绘制平面K形、T形节点和空间KT形节点承载力相关曲线,并提出计算公式供设计人员参考。     

采用垫板连接的新型T形圆钢管节点轴压承载性能有限元研究

圆钢管结构由于受力性能好、施工方便、外形美观的特点,广泛应用于建筑大跨度结构和海洋平台结构中.现有研究及实际工程表明,钢管结构破坏最容易在节点焊接处发生,因此有必要加强钢管结构的节点区域,以提高整体结构的承载性能.本文提出一种圆形钢主管与支管的新型焊接连接节点,包括主管、矩形固定钢板、前部弧形固定钢板、后部弧形固定钢板、连接垫板、支管.首先利用ABAQUS软件建立了有限元模型并准确模拟了用外加劲肋加强T形圆钢管节点的试验研究.在此基础上,对3个不同主管支管外径比(β)的新型T形圆钢管节点在轴压作用下的极限承载性能进行了有限元分析.之后为了研究影响新型节点极限承载性能的因素,对连接垫板边长和矩形固定钢板高度进行了参数化分析.结果表明,对于T1节点,当矩形固定钢板高度与支管直径比不变,连接垫板边长与支管直径比从1.1提高到1.6时,极限承载力提高了33.1％;对于T2节点,当矩形固定钢板高度与支管直径比不变,连接垫板边长与支管直径比从1.1提高到1.6时,极限承载力提高了 45.0％.当连接垫板边长与支管直径比不变,矩形固定钢板高度与支管直径比从0.2提高到0.5时,T1和T2节点的极限承载力几乎没有变化.     

圆钢管相贯节点轴向刚度的数值分析

对工程实践中常用到的圆钢管相贯节点进行了数值模拟分析,探讨了主管夹角、支管与主管的外径比、主管径厚比、支主管壁厚比、支管与主管之间的夹角、支管与主管平面夹角等参数对相贯节点轴向刚度的影响,得出了不同参数对相贯节点刚度影响的关系曲线。     

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。     

冷弯不锈钢管T型及X型节点设计

采用有限元方法,对冷弯不锈钢方管、矩形管支撑和弦杆中的T型、X型及预应力X型节点进行数值分析。考虑几何非线性和材料非线性,获得节点承载力、破坏模式及荷载-位移曲线。利用试验结果,对T型、X型矩形管、方管节点的非线性有限元模型进行修正,直到有限元结果和试验结果足够吻合。采用修正后的有限元模型对172个T型、X型节点进行参数分析,研究冷弯不锈钢管节点强度和性能的影响。将数值分析和试验中获得的节点承载力与按规范计算的设计承载力进行对比。对不锈钢管结构,采用澳大利亚规范、新西兰规范计算;对碳素钢管结构,采用国际管结构发展与研究委员会设计规范和欧洲设计规范计算。通过可靠性分析,分别评价本文提出的设计方法和现有规范的可靠度。结果表明:采用本文方法计算的设计承载力更准确、更可靠。     

Tests of concrete-filled stainless steel tubular T-joints

This paper describes a test program on a wide range of concrete-filled cold-formed stainless steel tubular T-joints fabricated from square hollow section (SHS) and rectangular hollow section (RHS) brace and chord members. A total of 27 tests was performed. The chord member of the test specimen was filled with concrete along its full length. Both high strength stainless steel (duplex and high strength austenitic) and normal strength stainless steel (AISI 304) specimens filled with nominal concrete cylinder strength of 30 MPa were tested. The axial compression force was applied to the top end of the brace member, which was welded to the center of the chord member. Local buckling failure of brace member was the main failure mode observed during the tests. Hence, the axial compression force was then applied by means of a steel bearing plate to avoid failure of brace member. The failure modes of chord face failure and chord side wall failure as well as crushing of the concrete infill were observed. All the tests were performed by supporting the chord member of the specimen along its entire length to apply the pure concentrated force without any bending moment. The test results were also compared with design rules for carbon steel tubular structures, which is the only existing design guideline for concrete-filled tubular joints. It is shown that the design strengths predicted by the current design rules are quite conservative for the test specimens. It is also recommended that the contribution of stainless steel tubes should be included in the design rules since it has significant effects on the ultimate bearing capacity of concrete-filled stainless steel tubular T-joints.     

Experimental and Numerical Study on Complex Multi-planar Welded Tubular Joints in Umbrella-Type Space Trusses with Long Overhangs

A test rig with multi-functional purposes was specifically designed and manufactured to study the behavior of multi-planar welded tubular joints subjected to multi-planar concurrent axial loading. An experimental investigation was conducted on full-scale welded tubular joints with each consisting of one chord and eight braces under monotonic loading conditions. Two pairs or four representative specimens (two specimens for each joint type) were tested, in which each pair was reinforced with two kinds of different internal stiffeners at the intersections between the chords using welded rectangular hollow steel sections (RHSSs) and the braces using rolled circular hollow steel sections (CHSSs) and welded RHSSs. The effects of different internal stiffeners at the chord–brace intersection on the load capacity of joints under concurrent multi-planar axial compression/tension are discussed. The test results of joint strengths, failure modes, and load–stress curves are presented. Finite element analyses were performed to verify the experimental results. The study results show that the two different joint types with the internal stiffeners at the chord–brace intersection under axial compression/tension significantly increase the corresponding ultimate strength to far exceed the usual design strength. The load carrying capacity of welded tubular joints decreases with a higher degree of the manufacturing imperfection in individual braces at the tubular joints. Furthermore, the interaction effect of the concurrent axial loading applied at the welded tubular joint on member stress is apparent.     

Behaviour of Concrete-Filled Double-Skin Circular Hollow Section Cross Joints Under Axial Compression

This paper presents an experimental investigation on concrete-filled double-skin circular hollow section (CHS) cross joints under axial compression. A total of twenty-two right-angled CHS cross joints with different brace to chord diameter ratio (β), inner tube to outer tube thickness ratio of chord (ω) and hollow ratio of chord (χ) were tested, in which eighteen concrete-filled double-skin CHS cross joints were studied for different shapes of inner tube of chord, two traditional empty CHS cross joints and two traditional concrete-filled CHS cross joints were tested for comparison. The joint strengths, failure modes, load-deformation curves and strain distribution curves of all specimens are reported. The effects of brace to chord diameter ratio (β), inner tube to outer tube thickness ratio of chord (ω), hollow ratio of chord (χ), shape of inner tube of chord and concrete strength on the behaviour of concrete-filled double-skin CHS cross joints under axial compression were evaluated. It is shown from the comparison that the ultimate load and initial stiffness of CHS cross joints are significantly enhanced by strengthening the chord member with inner tube and concrete infill. Furthermore, the ultimate strengths are increased with the increase of the β ratio, whereas the ultimate strengths are decreased with the increase of the χ ratio for all types of concrete-filled double-skin CHS cross joints. On the other hand, the ultimate strengths are enhanced with the increase of the ω ratio and concrete strength for all types of concrete-filled double-skin CHS cross joints, but the enhancement is insignificant. The corresponding finite element analysis was also performed and calibrated against the test results. The design equations are proposed based on the test and finite element analysis results for concrete-filled double-skin CHS cross joints, which are verified to be more accurate.     

支管灌混凝土平面X形圆钢管节点轴压性能试验研究

为研究支管灌混凝土X形圆钢管节点的轴压性能,对6个不同截面几何参数的支管灌混凝土X形圆钢管节点进行了单调加载试验。介绍了节点试验方案,揭示了节点破坏模式,给出了加载点荷载 端位移曲线、支管轴力-主管壁变形曲线以及节点区域折算应变分布曲线,并将支主管外径比β、主管径厚比γ和支主管壁厚比τ对节点轴压承载力和弹性轴压刚度的影响进行了分析。试验研究结果表明：节点试件均表现出较好延性;所有试件的主管壁最大竖向变形位移都大于0.03倍主管直径,在判定该类圆钢管节点轴压承载力时应该采用极限变形准则;节点轴压承载力与弹性轴压刚度都随着β和τ的增加以及γ的减小而提高;所有试件的支管根部测点都未进入塑性且主管都是鞍点和冠点之间的中间测点首先进入塑性;在试验参数条件下,支管灌混凝土对X形圆钢管节点轴压承载力提高不明显,甚至会降低其轴压承载力。目前GB 50017-2003《钢结构设计规范》公式不能较好地计算支管灌混凝土X形圆钢管节点轴压承载力。     

主管灌混凝土平面X形圆钢管节点受压承载力试验研究

对6个不同截面几何参数主管中灌混凝土的平面X形圆钢管节点在支管轴向压力作用下的承载性能进行单调加载试验研究。描述了X形圆钢管混凝土节点破坏现象,给出了支管轴力-整体位移曲线、支管轴力-主管管壁变形曲线以及节点区域折算应变分布曲线,并将支主管外径比β、主管径厚比γ和支主管壁厚比τ对节点承载力和抗压刚度的影响进行分析。结果表明：节点初始抗压刚度随着β、γ的增大而提高,而τ对初始抗压刚度影响很小;所有节点试件主管测点都未进入塑性,均为支管根部冠点首先进入塑性,且直到破坏时折算应变一直保持最大;主管灌混凝土使钢管节点承载力明显提高。有限元计算结果与试验结果吻合较好。     

国际期刊导读

采用有限元方法,对冷弯不锈钢方管、矩形管支撑和弦杆中的T型、X型及预应力X型节点进行数值分析。考虑几何非线性和材料非线性,获得节点承载力、破坏模式及荷载-位移曲线。利用试验结果,对T型、X型矩形管、方管节点的非线性有限元模型进行修正,直到有限元结果和试验结果足够吻合。采用修正后的有限元模型对172个T型、X型节点进行参数分析,研究冷弯不锈钢管节点强度和性能的影响。将数值分析和试验中获得的节点承载力与按规范计算的设计承载力进行对比。对不锈钢管结构,采用澳大利亚规范、新西兰规范计算;对碳素钢管结构,采用国际管结构发展与研究委员会设计规范和欧洲设计规范计算。通过可靠性分析,分别评价本文提出的设计方法和现有规范的可靠度。结果表明：采用本文方法计算的设计承载力更准确、更可靠。     

主管内填混凝土矩形和圆形钢管桁架受弯性能对比试验研究

为研究主管内填混凝土对矩形和圆形钢管桁架结构受弯性能的影响及两者区别,进行了矩形和圆形钢管桁架空管、仅受压主管内填混凝土和拉压主管均内填混凝土三种类型桁架的对比试验研究。试验结果表明:矩形截面桁架均发生节点失效,空管桁架为受压主管侧壁鼓曲破坏,仅受压主管内填混凝土和拉压主管均内填混凝土桁架发生受拉主管顶板的冲剪破坏;圆形截面空管桁架和仅受压主管内填混凝土桁架发生空管节点处的主管侧壁鼓曲破坏,拉压主管均内填混凝土桁架为受拉支管受拉断裂破坏。主管内填混凝土有助于提高主管轴向刚度,提高节点强度和刚度及整体承载力,节点承载力按规范计算结果偏于安全,桁架整体变形计算需考虑节点变形的影响。两种截面空管桁架的承载力及变形差异不明显,主管内填混凝土后,圆形截面桁架的整体和节点承载力比相应矩形截面桁架承载力要高,变形能力更好,且节点变形比例更小。