《钢结构设计规范》(GB50017—2002)焊接工字梁腹板的局部稳定和考虑屈曲后强度的计算

Design Method of Local Buckling and Post buckling Strengthfor Welded I Beams

与现行《钢结构设计规范》(GBJ17—88)相比,新修订的《钢结构设计规范》(GB50017—2002)对焊接工字梁腹板屈曲临界应力和局部稳定的计算作了较大的改动,增加了梁腹板考虑屈曲后强度设计的相关条文。对弯矩、剪力和局部压力单独作用下的腹板屈曲临界应力作了修正,考虑了板件的几何缺陷和材料非弹性性能,对于直接承受动力荷载的吊车梁及类似构件或不考虑腹板屈曲后强度的焊接工字梁,要求按规定配置加劲肋,并验算腹板的局部稳定性,计算局部稳定的相关公式随着临界应力的修正也作了相应的调整;建议承受静力荷载和间接承受动力荷载的焊接工字梁宜考虑腹板屈曲后强度,按考虑腹板屈曲后强度来计算梁的的抗剪和抗弯承载力,而不再验算腹板的局部稳定。本文详细介绍了规范条文修改的理论依据,比较了新旧设计方法的差异,并通过设计实例说明了新设计方法的优越性。

Significant improvement has been implemented on local buckling calculation in the new version of Code for Design of Steel Structure (GB50017-2002). In comparson to the current version(GBJ 17-88), the post buckling strength of the web of welded I beam has been considered in the amendment. A new formula for calculating local buckling strength subjected to bending moment, shear force as well as local compression respectively is provided in the revised code taking into account the geometric imperfection and material nonlinearity of plate beam. Further modification is given on the interaction formula for calculating critical buckling stress. In case of crane girders or other welded I beams subjected to dynamic loading leaving out of consideration of the post buckling strength, the new code has specified that the stiffeners should be supplied to prevent local buckling. The new version suggests that if the post buckling strength has been considered for the welded I beams subjected to static loading, the local stability will no longer be needed to be calculated again.The theoretic basis of the revised provisions in the new code is introduced in detail with the differeces between two codes compared.Design examples are given to illustrate the advantages of the new method.