大跨度斜拉桥抖振时域分析理论实例验证及影响因素分析

Verification of time-domain buffeting theory and analysis of influence factors for long-span cable-stayed bridges

为了进行对现有抖振时域分析理论的实例验证,在杭州湾跨海大桥全桥模型风洞试验中,不仅对抖振位移进行了测量,还通过在塔根布设动态应变片完成了桥塔内力的实测。采用考虑桥塔风效应的抖振时域分析方法计算出大跨度斜拉桥的抖振响应,气动导纳分别取1和Sears函数,采用等效风谱法计算考虑气动导纳修正的抖振力,对风洞的空间相关性进行了测量研究并分别探讨了Sears气动导纳函数及空间相关性对抖振响应的影响,与风洞试验结果进行了对比分析。分析比较表明:当衰减因子l取实测值12.9时,风洞试验结果都介于导纳为1和导纳为Sears函数所计算的抖振响应之间,导纳取Sears函数将得到偏不安全的结果;空间相关系数对抖振响应影响较大,采用风洞实测的相关系数得到的抖振响应比采用《公路桥梁抗风设计指南》建议相关系数所得抖振响应小13%￣22%。通过杭州湾跨海大桥的实例验证发现现有抖振时域分析理论并不能完全精确预测桥梁的抖振响应,抖振响应计算值与试验值存在一定的差距。

In order to verify the current time-domain buffeting theory, not only the buffeting-induced structural displacements but also the buffeting-induced internal forces at the bottom of the towers were measured by means of dynamic strain gauges in a full model test of the Hangzhou Bay Bridge. A time-domain buffeting analysis considering pylon wind field was conducted to analyze the buffeting responses, the aerodynamic admittance function was set as 1 and Sears, respectively, and the equivalent wind spectrum method was used to calculate the buffeting loads while considering aerodynamic admittance function. A study on the spatial correlation of wind tunnel tests was carried out, and the influences of Sears admittance function and spatial correlation on the buffeting responses were investigated. The numerical results were compared with wind tunnel test results. The comparison shows that when the decay factor ~. is 12.9, wind tunnel test results fall between buffeting responses with aerodynamic admittance being set to 1 and Sears, the results calculated with Sears function being on the unsafe side. Spatial correlation greatly influences buffeting responses, the buffeting responses being reduced by about 13%-22% when the spatial correlation was changed from the one specified in （（Wind resistant design guideline for highway bridges） to the one measured in wind tunnel test. Verification of the Hangzhou Bay Bridge shows that the current time-domain buffeting theory cannot predict bridge buffeting-induced responses accurately, and there exists certain discrepency between the calculation and the tunnel test results.