基于单位荷载法的钢管混凝土组合异形柱计算长度系数研究与验证

Study and Verification on Effective Length Factors of Special-Shaped Columns Comprising Concrete-Filled Steel Tubes Based on a Unit Load Method

为解决钢管混凝土组合异形柱在进行构件稳定验算时计算长度系数不明确的问题,利用有限元软件Midas/Gen,采用单位荷载法在钢管混凝土组合异形柱框架-支撑结构整体模型下进行特征值屈曲分析,并通过欧拉公式反算得到钢管混凝土组合异形柱的计算长度系数.研究了网格划分、楼板、短梁对单肢柱计算长度系数分析结果的影响,结果表明各层异形柱沿其高度方向划分为10段、连接板宜沿其宽度方向划分为2段,同时去掉模型中的楼板、短梁可提高结果的安全度和软件分析速度.在上述分析结果基础上,建立了考虑组合异形柱网格划分、去掉模型中的楼板、短梁的整体结构模型,分析了不同异形柱平面位置、所在楼层、梁截面尺寸和楼层总数等因素影响下的单肢柱计算长度系数,结果表明:单肢柱计算长度系数随着所在楼层的上升呈现增大趋势,8~20层单肢柱计算长度系数随梁截面的增大而减小,大部分楼层的单肢柱计算长度系数随楼层总数减少而增大.根据所得数据,基于安全性和计算简便的考虑,给出了各层钢管混凝土组合异形柱中单肢柱计算长度系数建议值.基于计算长度系数的建议取值,分析得到整体模型中各单肢柱的应力比,并与直接分析设计法得到的应力比进行了对比,结果表明两种方法得到的应力比相差不大,验证了本文提出的计算长度系数建议值的可行性.

To address unclear effective length factors in stability calculations for components of special-shaped columns comprising concrete-filled steel tubes(SCFTs),we used the finite element software Midas/Gen to conduct an eigenvalue buckling analysis using a unit load method under an SCFT frame-brace system overall model.Subsequently,we inversed the effective length factors of the SCFT using Euler’s formula.The influence of grid division,floor slab,and short beam on the analysis results of the effective length factors of single columns was investigated.The results indicate that the SCFTs of each floor should be divided into ten sections along their height directions,whereas the connecting slabs should be divided into two sections along their respective width directions.Furthermore,removing the floor slabs and short beams from the model can improve safety and accelerate the software analysis.Based on the analysis results,we created an overall structural model by considering the grid division of SCFTs and removed the floor slabs and short beams from the model.In addition,we analyzed the effective length factors of single columns for different plan locations,floors,beam section sizes,and total floor numbers.The effective length factors of single columns tended to increase with an increase in the number of the floors where they were located,the effective length factors of single columns of floors 8—20 decreased with an increase in the size of beam sections,and the effective length factors of single columns for most floors increased with a decrease in the total number of floors.From these data,the recommended effective length factors of single columns of the SCFT for each floor were given considering security and simplicity of calculation.The stress ratios of single columns in the overall model were calculated based on the recommended values and compared with stress ratios obtained through direct analysis and design method.The results indicate that the stress ratios obtained by the two methods are close,verifying the feasibility of the recommended values.