桥梁顺风向等效风荷载计算方法及其分布

桥梁等效风荷载一般被分为平均风荷载、等效背景风荷载和惯性风荷载 3部分 ,分别计算后再按一定的方式将其组合为总的等效风荷载 .对于惯性风荷载 ,一般可根据结构随机振动理论采用模态分解的方法计算得到各阶振型对应的惯性力 ,然后采用完全平方组合 (CQC)法或平方和开方 (SRSS)法将它们组合起来成为总的惯性风荷载 .对于背景风荷载 ,目前主要有荷载响应相关 (LRC)法和经典的模态分解法 .前者得到的背景荷载的分布形式与风压和结构响应的影响函数有关 ,而后者得到的分布形式则与惯性荷载相似 ,两者得到的结果可能并不相同 .这里主要研究LRC法和模态分解法 2种桥梁等效风荷载的计算方法 ,对 2种方法的区别和联系进行讨论 ,并给出风荷载 3个部分的组合方式 ,最后还给出了数值算例 ,进一步对不同计算方法和组合方式进行比较

Calculation Methods and Effective Distributions of Equivalent Alongwind Loads on Bridges

The equivalent wind load(EWL) can be expressed in a separated form in terms of mean wind load,equivalent background wind load and inertial wind load.They are calculated respectively and then combined together to make a total EWL.The inertial wind load of each vibration mode is commonly calculated using modal analysis based on random vibration theory,and then combined using complete quadratic combination (CQC) or square root of sum of squares (SRSS) approach.There are two methods available for calculating equivalent background wind load: the LRC method proposed in 1992 by Kasperski etc.and the modal analysis method.The former results in a background wind load distribution depending on the external wind load and an influence function,whereas the latter gives a distribution following the inertial load distribution,that is,these two methods may give different results.Calculation methods based on LRC method and modal analysis method are studied intensively herein,and comparisons and contrasts between them are discussed.Appropriate combination approach is also suggested in this paper,and a numerical example was given to exhibit the difference between the two calculation methods and combination methods.