基于Küssner函数的不同气动导纳模型对大跨桥梁抖振响应的影响

Effects of Küssner-function-based aerodynamic admittance models on the buffeting responses of a long-span bridge

采用Küssner类型函数对抖振力以及气动导纳在时域内进行模拟。对某大跨度悬索桥初步设计方案进行了风洞试验,得到该桥梁加劲梁断面的气动导纳。以试验气动导纳以及基于二维薄机翼理论的Sears气动导纳为基础进行了参数识别,得到相应的Küssner函数参数值。根据识别得到的Küssner函数,分别在时域内计算了考虑Sears气动导纳、试验气动导纳以及不考虑导纳时的抖振位移响应。分析结果表明采用Küssner函数法可灵活地将频域内的气动导纳转换为时域函数,从而便于考虑各类非线性后进行动力有限元分析。数值算例结果表明,当不考虑气动导纳时会得到显著偏大的抖振结果。考虑气动导纳时,基于Sears函数的抖振响应又明显高于基于试验导纳的抖振响应。因此,即使是对于采用类平板扁平箱梁的大跨度桥梁,其抖振响应分析宜采用试验测得的气动导纳代替广泛应用的Sears函数。

The Küssner-type function was adopted to simulate the buffeting forces and aerodynamic admittances(AAs)in the time domain.Wind tunnel tests were conducted with the elementary scheme of a long-span bridge to obtain the AAs of its main girder.Based on the experimentally obtained AAs and the Sears function,which was derived from thin airfoil theories,the corresponding Küssner functions were obtained via parametric identification.Finally,the buffeting responses of the concerned bridge were computed in the time domain with the Küssner functions identified from the Sears AAs,experimentally obtained AAs,and without consideration of any,respectively.The analytical results show that the Küssner function method is able to transfer frequency-domain-based AAs to time-domain flexibly,and therefore benefits inclusion of various nonlinearities in dynamic FEM simulations.Results based on the numerical example indicate that exclusion of the AAs results in extraordinarily large buffeting responses.When AAs are included,the buffeting results based on the Sears function are significantly greater than those based on experiments.Therefore,it is appropriate to employ experimentally-based AAs to replace the extensively used the Sears function for buffeting analyses of long-span bridges,even for those stiffened with flat box-girders.