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厂房钢结构中常采用双坡对称梯形钢桁架组成的刚架,计算时需对桁架正中截面的惯性矩作折减。本文基于变形计算中用积分代替求和的方法,推导和讨论了较为准确和实用的折算系数公式,其中考虑桁架高度变化和腹杆变形两种影响。推导显示对不同的刚度和荷载情况应有不同的折算系数公式,其数值有较大差别,一般比习用的经验单一系数值低得多;同时对固定端弯矩和传递系数也需予以折减。文中根据公式制作了计算表供设计者使用。对常用钢屋架的弦杆腹杆截面积比值作了统计分析,以便设计者能更准确地确定计算原始参数。
In the steel structure of factory building, a rigid frame consisting of double-slope symmetric trapezoid steel truss is often used, and the moment of inertia of the middle section of the truss needs to be reduced. Based on the method of using integration instead of summation in the deformation calculation, this paper deduces and discusses the more accurate and practical formula of the conversion coefficient, taking into account the influence of the truss height and the deformation of the web. The derivation shows that for different stiffness and load conditions, there should be different formulas for the conversion coefficient, the values are quite different, generally much lower than the conventional experience of a single coefficient value; at the same time, the fixed end bending moment and the transmission coefficient must also be reduced . The calculation table is made according to the formula for use by designers. The statistical analysis of the ratio of the cross-sectional area of the chord-web rod of the common steel truss was carried out so that the designer could determine the original parameters more accurately.