考虑节点半刚性的输电塔钢管构件稳定承载力分析

Analysis on Stability Bearing Capacity of Steel Tubular Members Considering Semi-Rigid Joints in Transmission Towers

输电塔钢管构件的连接形式应是介于铰接与刚接之间的半刚性连接,故研究半刚性连接钢管构件的承载能力更贴合实际的受力情况。为此,研究了输电钢管塔K型节点的半刚性特性,并对考虑节点半刚性的轴心受压钢管构件承载能力进行了有限元分析。首先,以实际工程中的输电塔为原型建立K型节点的有限元模型,分析了主材规格、主材轴压比、主斜材夹角、节点板厚度、螺栓数量、插板厚度、插板宽度、斜材长度、斜材规格和钢材强度对节点半刚性特性的影响,总结了K型节点的大致初始转动刚度范围;然后,在节点半刚性特性的研究基础上,对考虑节点半刚性约束的轴心受压钢管构件承载能力进行了有限元分析,探究了转动刚度、端部连接形式和钢材强度在长细比变化时对轴心受压钢管构件承载能力的影响,并将分析结果与规范中的稳定系数-长细比关系曲线进行了对比。结果表明:K型节点的节点板受压区和受压斜材的插板首先达到屈服强度,随即发生破坏;K型节点中受压构件的弯矩-转角关系呈现非线性,节点板厚度、连接螺栓数量、插板厚度和宽度、斜材长度和规格以及钢材强度都对节点的半刚性特性有较大影响,主材规格、主材轴压比、主斜材夹角对节点的半刚性特性影响较小;K型节点的初始转动刚度范围为247.89~983.67 kN·m/rad;考虑节点半刚性的钢管构件的稳定承载力比铰接构件的稳定承载力要高,且两者间的差距随着长细比的增大而增大,当长细比大于80时,半刚接构件与铰接构件的差距均大于10%,当长细比大于140时,半刚接构件与铰接构件的差距均大于20%,这表明长细比越大,端部的约束作用越大;考虑节点半刚性的钢管构件的跨中位移均小于铰接构件的跨中位移,这表明半刚性约束可以降低钢管构件的变形;转动刚度、端部连接形式和钢材强度均会不同程度地影响半刚性节点钢管构件的稳定承载力。

The connection form of the steel tubular members in transmission towers should be the semi-rigid connection which falls in between rigid and pinned connections.Therefore,studying the bearing capacity of steel tubular members of semi-rigid connection is more suitable for the actual loading case.Accordingly,semi-rigid characteristics of K-joints in transmission tubular towers were studied and the finite element(FE)analysis on the stability bearing capacity of steel tubular members under axial compression load considering semi-rigid joints in transmission towers was carried out.First,based on the original model of the transmission tower in actual engineering,the FE model of the K-joint was established.Additionally,the influence,including the dimension of main chord,the axial compression ratio of main chord,the angle between the main chord and the bracing member,the thickness of the gusset plate,the number of the bolts,the thickness and width of the inserted plate,the length and dimension of the bracing member,and the strength of steel,on semi-rigid characteristics of K-joint was analyzed.Moreover,the approximate range of the initial rotational stiffness of K-joints was summarized.Then,based on the study of semi-rigid characteristics of K-joints,the FE analysis on the stability bearing capacity of steel tubular members under axial compression load considering semi-rigid joints was conducted.In addition,the effect of the rotational stiffness,the form of end connection,and the steel grade on steel tubular members with the varied slenderness ratio under axial compression load was investigated.Besides,the stability-coefficient-slenderness-ratio curve between design codes and analysis results was compared.Results show that the failure of K-joints is exhibited at the compressional area of gusset plate and the inserted plate of compression bracing member.The moment-rotation relationship of the compression steel tubular member of K-joints is nonlinear.The thickness of gusset plate,the number of bolts,the thickness and width of inserted plate,the length and dimension of the bracing member,and strength of steel have a much influence on its semi-rigid characteristics,while the dimension of main chord,the axial compression ratio of main chord,the angle between the main chord and the bracing member have a little influence on that.The range of the initial rotational stiffness of K-joints was about 247.89-983.67 kN·m/rad.In addition,the stability bearing capacity of steel tubular members considering semi-rigid joints is higher than that with hinged connection,and the difference between them is increased with the increasing of the slenderness ratio.When the slenderness ratio is larger than 80,the difference is higher than 10%.When he slenderness ratio is larger than 140,the difference is higher than 20%.It indicates that the larger slenderness ratio is and the stronger end restraint effects are.The mid-span displacement of steel tubular members considering semi-rigid joints is less than that with pinned connections,which means that semi-rigid restraints can decrease the deformation of steel tubular members.The rotational stiffness,the form of connection,and the strength of steel can have an influence in different degree on the stability bearing capacity of steel tubular members considering semi-rigid joints.