塑性设计中钢梁临界侧向长细比的研究

CRITICAL LATERAL SLENDERNESS RATIO OF STEEL BEAMS IN PLASTIC DESIGN

在钢梁塑性设计中,当钢梁侧向长细比达到临界值时,需要设置侧向支撑以防止其平面外整体弯扭失稳,保证产生塑性铰的截面具有足够的转动能力。在实际工程中,钢梁真正需要的转动能力一般较低,而GB 50017—2003《钢结构设计规范》要求较高的转动能力标准致使计算公式获得的临界侧向长细比过小。为此,建立非线性有限元模型,对钢梁进行数值分析,计算结果与他人试验结果吻合良好。通过对钢梁端部弯矩比、腹板高厚比、翼缘宽厚比、残余应力分布和平面外边界条件5类影响参数的分析,并采用合理的转动能力标准,提出除翼缘宽厚比外涉及4类参数的临界侧向长细比简化计算公式。与GB 50017—2003的公式相比较,所提出的公式更加合理、符合实际。

When the lateral slenderness ratio of a steel beam reaches a critical value during plastic design , it is necessary to set lateral supports so as to prevent lateral flexural-torsional buckling and then ensure sufficient rotation capacity.Thus, the rotation capacity required by a steel beam is generally lower in engineering practice .However, higher rotation capacity was specified in The Code for Design of Steel Structure （ GB 50017-2003） which caused the critical lateral slenderness ratio from formula was too small .For this reason, the nonlinear finite element modeling for numerical analysis of steel beams was developed in this paper .The calculated results agreed well with the other scholars’ experimental results.Based on the analysis of five influence parameters such as end-moment ratio, web height-thickness ratio , flange width-thickness ratio , residual stress distribution , out-of-plane boundary condition , and using reasonable criterion for rotation capacity , a simplified formula for critical lateral slenderness ratio was proposed , which could deal with four parameters except flange width-thickness ratio .The formula proposed was more reasonable and practical, compared with the formula in The Code for Design of Steel Structure（GB 50017-2003）.