各国规范中长柱二阶效应的比较

Comparison of Long-column Second Order Effect in Codes of Every Country

对于长细比在8≤L0/h≤30的长柱,均需要考虑由于附加弯矩的增大产生的二阶效应。计算长度的取值关系到偏心距增大系数η的大小,影响到二阶效应的计算结果,进而对设计配筋造成影响。中美欧各国规范对二阶效应规定均不相同,其中中国桥梁、建筑规范规定较为单一,欧美各国规范规定较为全面。欧美各国规范规定了独立柱、框架柱等有无侧移时的二阶效应的计算公式,中国桥梁规范仅规定独立柱常规约束方式的计算公式,中国建筑规范规定框架柱无侧移且常规约束方式的计算公式。经比较发现,对于长柱,应该考虑不同约束方式下,长柱有无侧移时的二阶效应的变化。

For the long column of the slenderness ratio at, it is required to consider the second order effect because of increasing the additional bending moment. The calculated length is related to the value of eccentricity amplifing coefficient η and influences the calculated results of second order effect so as to cause the influence on the design reinforcement. The provisions of the second order effect are different in the codes of China, Europe and America, in which the provision of bridge and building codes in China is relatively single, but Europe and America are more complete. The calculation formula of second order effect is stipulated in the codes of Europe and America when the free-standing column and frame column are sidesway or not, but the calculation formula of the normal constraint mode of free-standing column is only stipulated in the bridge specification of China. The calculated formula of the no-sidesway frame column by the normal constraint method is stipulated in China Building Code. By comparison, it is found that that it should consider the changes of second order effect for long column whether or not having the sidesway in different constraint modes.