大跨度桥梁多目标等效静力风荷载基向量法

Multi-target equivalent static wind loads of long-span bridges based on proper orthogonal modes

由于结构抖振响应计算复杂,目前主流风荷载设计规范均采用等效静力风荷载做等代替换。文中以桥梁结构为研究对象,对抖振响应的多目标等效静力风荷载计算方法进行研究。首先,采用经典的荷载-响应相关(LRC)法获得大跨度桥梁主梁各节点处的等效静力风荷载向量,并组成荷载矩阵FLRC;其次,采用本征正交分解(POD)技术获得FLRC的本征模态矩阵ΦLRC;然后,以主梁的抖振响应极值为等效目标,选取ΦLRC的前i阶本征模态作为构建等效静力风荷载的基向量,获得最小二乘意义的多目标等效静力风荷载;最后,以东海大桥为例对该方法的有效性进行验证。结果表明,由于ΦLRC同时包含了脉动风荷载和抖振响应的主要信息,同时是依据重要程度排序,按照文中方法获得的多目标等效静力风荷载在抖振响应计算精度和荷载分布的合理性方面均表现良好。

The buffeting response of a structure is very complex,and in main wind resistant design codes/specifications of structures,the equivalent static wind loads(ESWL)is adopted to instead the real dynamic buffeting analysis.The multi-target ESWL calculation method of long-span bridges is studied from a new perspective.Firstly,load response correlation(LRC)method was used to estimate ESWL vectors at the nodes of girders of the long-span bridge and then to form the ESWL matrix FLRC.Secondly,the proper orthogonal decomposition(POD)technique was applied to attaining the proper orthogonal matrixΦLRC of FLRC.Thirdly,with the buffeting response extreme values of the girder regarded as the equivalent targets,the first i-order proper modes ofΦLRC were used as the base vectors to reconstruct ESWL,so that the multi-target ESWL can be obtained in least square meaning.Finally,East Sea cable-stayed bridge was used as an example to validate the effectiveness of the method.The results indicate that the accuracy of buffeting responses calculated by multi-target ESWL and the rationality of ESWL distribution are acceptable by using the proposed method,because after POD,the matrixΦLRC contains both the fluctuating wind pressure information and the buffeting response information,which are ordered according to the significance.