Study on Bracing Member for Steel Member and Frame considering Coupled Buckling

本研究的目的在于说明钢结构支撑构件的结构特性及极限状态设计的概念与准则。在支撑构件的设计中，考虑了构件和连接处的耦合屈曲，分析对象为仅受拉侧有支撑的钢构件，首先，以设计准则为依据，对影响支撑屈曲强度和极限状态下变形能力的因素进行了分析，数值分析采用考虑侧向屈曲和局部屈曲的有限元方法。单元的概念采用壳单元和梁单元。分析参数为支撑刚度、支撑细部、梁截面和荷载条件，当实腹杆的受拉翼缘单独支撑时，不仅要充分考虑上述轴力，还要充分考虑弯矩。若将弯矩视为受压翼缘侧向扭转变形引起的弯矩，则当屈服轴力的2.5%作为水平力F施加时，可将弯矩视为支撑弯矩M=Fh。在将约束受拉内弦杆的构件连接和固定到桁架构件上时，必须小心。重复荷载对强度和变形能力的影响如下降低这些能力。连接处脆性断裂与构件屈曲的关系与构件端部应变水平有关，为了避免连接处的脆性断裂，连接宽厚比在屈曲强度范围内较大，建议中没有提到抗震设计中弯矩重分布或延性的支撑要求。局部屈曲后，横截面是不对称的，垂直载荷产生非常显著的平面外载荷分量。

The purposes of this study are to explain structural properties of bracing members and design concept and rule for limit state on structural design for steel structures. On the design of bracing members, the couple buckling on members and connection.The object for analysis is steel members having the bracing members on tension side only.Firstly, the factors that affect bracing requirements for buckling strength and deformation capacity on the limit state for design criteria.Numerical analysis is finite element method considering lateral buckling and local buckling. Concept of element are used shell element and beam element. Analytical parameters are bracing rigidities, bracing detail, beam section, and loading condition.When the tension flange alone of a solid web member is braced, it is necessary to pay full attention not only to the above mentioned axial force, but also to the bending moment. If the bending moment is taken as bending moment due to the lateral torsion deflection of the compression flange, it can be considered as bracing moment M=Fh when 2.5% of the yield axial force is imposed as horizontal force F.Therefor, due care must be exercised when joining and attaching members restraining inner chord members in tension to the truss members.The effects of repeated loading for strength and deformation capacities are decrease these capacities. Especially, on tension sides only bracing the effects are large.The relationships of brittle fractures on connection and buckling of member are related strain level of member end, To escape the brittle fracture at connection wide-thickness ratio are large within to buckling strength,The recommendations do not address the bracing requirements for moment redistribution or ductility in seismic design.After local buckling the cross section is unsymmetrical and vertical loads develop very significant out of plane loading components.