【作者】 吴亮秦；

【导师】 李自林；

【作者基本信息】 天津城市建设学院 ， 结构工程， 2008， 硕士

【摘要】 对承受支管轴力和主管轴力的N型圆钢管相贯节点(JD-A),垫板加强节点(JD-B),主管填充混凝土节点(JD-C),主管填充混凝土和垫板加强节点(JD-D)试件进行了极限承载力试验。介绍了试件的设计、加载制度和试验步骤,提出了确定试件极限承载力的方法,观察到了试验现象,得到了主要试验结果。试验结果显示:JD-A和JD-B试件的破坏模式为主管表面的塑性失效破坏,JD-C试件的破坏模式为受压支管的局部屈曲破坏,JD-D试件试件的破坏模式为加强垫板的剪切破坏。计算表明:试验所得的JD-A试件的承载力与我国规范(GB50017-2003)公式及Packer教授建议公式的计算结果的比值分别为:0.97和1.05。说明对于材料的屈服强度超过355 Mpa的N型圆管相贯节点,我国规范公式得到的极限承载力结果仍比较可靠。主管填充混凝土能大大增强主管径向刚度,从而显著提高节点极限承载力,加强垫板对节点承载力提高幅度不大,只能在一定程度上减小主管壁的变形,而当主管径向刚度已经很大时,对主管加垫板可能反而降低节点的极限承载力。考虑到对于圆钢管加强节点,垫板加工和焊接难度较大,实际成本高,在对自重要求不高的结构中,对钢管填充混凝土是提高节点承载力应优先考虑采取的加强措施。试验结果也说明在空心管节点和加强节点的设计中,关键就是控制主管径向刚度和支管轴向刚度的比值,选取最佳比值,使主管和支管均发挥最大使用率。采用ANSYS程序中四节点板壳单元对试验节点进行了弹塑性、大挠度有限元分析,比较试验和数值模拟研究所得的受压支管荷载-主管管壁变形曲线,二者吻合较好,说明试验结果可靠,研究中采用有限元分析方法可运用于实际工程的理论计算中。有限元分析所得的JD-A、JD-B、JD-C和JD-D试件的承载力与试验结果的比值分别为:1.05,1.04,0.97,1.08。二者间JD-D试件的承载力相差较大的主要原因是有限元计算时JD-D试件发生的是和JD-C试件相同的受压支管局部屈曲破坏,而试验中JD-D是因加强垫板突然的剪断破坏。比较各节点试件的应力分布规律和塑性发展过程,发现垫板的加强原理是借助于垫板的厚度效应和传力作用,将支管荷载扩散到更大的主管表面,使极限承载力也分别得到相应的提高。在主管内填充混凝土的加强原理是当沿主管受压支管相贯线周围的主管壁屈服后,核心混凝土承受支管传来的绝大部分荷载,使节点的极限承载力得到显著提高。更多还原

【Abstract】 Experiments on static behavior of a tubular N-joint(JD-A),a plate reinforced tubular N-joint(JD-B), a concrete filled tubular N-joint(JD-C) and a N-joint reinforced both by concrete and plate(JD-D) under the axial compressive stress on brace and chord were carried out. The design of test specimens、the loading scheme and the testing steps are introduced, methods to estimate the ultimate bearing capacity of the four joints are proposed, the phenomena and the main results of tests are obtained.Experimental results showed that the failure mode of specimen JD-A and JD-B were plastic fracture at the connecting face of chord;the failure mode of specimen JD-C was local buckling failure of the brace,which bear the weight of compressive stress;and the failure mode of the specimen JD-D was rupture of the reinforce plate. The calculation indicates that the ratio of the test value of ultimate capacity of specimen JD-A to the result obtained from code design formula is 0.97,and to the formula suggested by professor Packer is 1.05,it illuminate that for tubular N-joints,even if whose material yield-point preponderate over 355 Mpa,credible results of the ultimate capacity of the joints can still be obtained from the code design formula. The calculation also indicates that the ultimate capacity of joints can be remarkably enhanced by filling concrete in chord, and can be only enhanced to a certain extent by welding a reinforce plate on tubular wall of chord,for filling concrete can considerably augment the ratio of radial stiffness of chord to axial stiffness of braces,whereas the reinforce plate can’t. While welding a reinforce plate on tubular wall of chord may weaken the ultimate capacity of the joint when the radial stiffness of chord is sufficient. For reinforce tubular joints,considering the operational difficulties in machining and welding reinforce plate may aggrandize practical cost , filling concrete be given preferential consideration to reinforce tubular joints when within the confines of deadweight of the structure. Therefore the key point in designing of tubular joints and reinforced tubular joints is control the ratio of radial stiffness of chord to axial stiffness of braces to make best use of chord and braces.Making use of finite element package program ANSYS,in which four nodes shell element was employed,elastic-plastic large deflection finite element analysis(FEA) of the experimental joints was conducted. Compared the curves of load in compressive brace with deformation in tubular wall of chord obtained from experiments and finite element analysis,there is a good agreement between the experimental and analytical results,it proves experimental results are reliable,and the method employed in FEA can be used in practical project. The ratio of FEA value of ultimate capacity of specimen JD-A,JD-B,JD-C and JD-D to the results obtained from code design formula is 1.05,1.04,0.97 and 1.08. The main reason for the relative discrepancy of specimen JD-D is that the failure mode of FEA result is local buckling failure of the brace, which is different from test result. Compared the stress distribution and propagation of plasticity of the four joints find that the reinforce plate can diffuse load from braces to lager face of joint’s chord and enhance ultimate capacity of the joints, filling concrete can bear most load from braces after connecting zone of chord wall yielded, thus remarkably enhance ultimate capacity of the joint.更多还原