冷弯薄壁型钢拼合箱形截面短柱承载力叠加法

Superposition Method for Bearing Capacity of Cold-formed Thin-walled Steel Built-up Box Section Short Columns

基于中国规范GB 50018-2002中的有效宽度法和北美规范中的有效宽度法及直接强度法,利用已有的试验数据和文章中有限元参数分析结果,计算了66根通过ST4.8自攻螺钉将单肢C形及单肢U形截面构件连接而成的冷弯薄壁型钢(CFS)拼合箱形截面短柱局部屈曲的承载力.理论值与试验和有限元值比较分析表明:中国规范GB 50018-2002和北美规范有效宽度法计算结果偏于保守,而北美规范直接强度法可以准确预测构件的承载力,但会存在不安全现象.基于以上结果,给出了关于冷弯薄壁型钢拼合箱形截面短柱局部屈曲承载力的计算方法--叠加法,并提出了关于CFS拼合箱形截面轴压短柱的理论计算公式.然后依据48根有限元试件的变参数结果,回归分析得出理论计算公式的组合系数α,得到计算拼合柱极限承载力的公式.最后通过与试验数据及中美规范计算结果对比,验证了承载力叠加法的适用性与准确性,也为CFS拼合箱形截面短柱承载力的计算提供了简易的方法.

Based on the effective width method(EWM)in the Chinese code GB50018-2002 and the EWM and direct strength method(DSM)in the North American code,the local buckling bearing capacity of 66 cold-formed thin-walled steel(CFS)built-up box section short columns composed of C-section and U-section assembles connected by ST4.8 self-tapping screws was calculated by using the available results from experiment and finite element parametric analysis.The comparison between theoretical values and experimental and finite element(FE)values shows that the calculation results obtained from the EWM in GB50018-2002 and American Iron and Steel Institute(AISI)are conservative,while the results calculated by DSM are accurate but unsafe.Based on the above results,a superposition method was presented,and a theoretical calculation model for CFS built-up box-section short columns failed in local buckling under axial compression was proposed.Then,according to the variable parameter results of 48 finite element specimens,the combination coefficient(α)of the theoretical calculation formula was obtained from regression analysis,and the formula for calculating the ultimate bearing capacity of the built-up columns was obtained.Finally,the applicability and accuracy of the proposed design method were verified by comparing with the test data and the calculation results of Chinese and American codes.It also provides a simple method for calculating the bearing capacity of CFS built-up box-section short columns.