压弯构件弯扭屈曲稳定系数φ_b的简化计算

Simplified calculation of the stability coefficient φ_b for flexural-torsional buckling of beam-columns

鉴于受弯构件整体稳定计算比较复杂,现行《钢结构设计规范》(GB 50017—2003)除给出了正规稳定系数φb的计算公式外,还给出了此系数的近似计算公式,后者主要用于压弯构件弯扭屈曲的计算。新修订的《钢结构设计规范》(送审稿)对梁的整体稳定计算做出较大修改,但计算依然较为复杂,仍然需要新的简化公式与之配合。经过分析和比较,推荐了工形截面和T形截面构件受弯屈曲时稳定系数φb的简化公式。为了适用于压弯构件,推演公式时紧密结合这类构件的具体情况:工形截面着眼于框架柱,T形截面着眼于承受节间荷载的桁架受压弦杆。推荐的公式具有较好的精确度,但不宜广泛用于一般受弯构件。

In the current Code for design of steel structures（ GB 50017—2003）,besides regular formulae of stability coefficient φbfor flexural members,approximate formulae of this coefficient are also given,because of the complicity of the former. The latter is mainly used in the calculation of flexural torsional buckling of beam-columns. In the final draft of the revised version of Code for design of steel structures,the overall stability calculation of beams has been changed to a large extent,but is still rather complicate,so that new simplified formulae are again in need. Based on analysis and comparison,simplified stability coefficient formulae for φbwere suggested for I-section and T-section members under bending moment.In order to be suited to beam-columns,the derivation of these formulae are closely related to the specific situation of those members： the I-section members focusing on columns of frames,and T-section members on the compressive chords of trusses subject to transverse loading between panel points. The suggested formulae have good accuracy,but are not recommended for comprehensive use to flexural members in general.