悬索桥抖振响应随跨度的非线性演变分析

Nonlinear evolution analysis of buffeting response of suspension bridge with span

设计了11组不同跨度悬索桥有限元模型.通过风洞实验得到主梁截面的气动三分力系数,运用Matlab工具箱生成B类风场脉动风速时程后得到桥梁抖振力.在此基础上,分析了结构动力特性的变化规律、计算了按几何线性和几何非线性考虑的11个模型的抖振响应.结果表明,随着跨度增大,悬索桥3个方向的自振频率逐渐降低,抖振位移均方根逐渐增大.对于竖向与扭转响应,线性与非线性均方根之间的差值均随跨度逐渐增大;对于侧向响应,两者之间的差值随跨度变化较小,表明几何非线性主要影响了悬索桥竖向和扭转方向上的抖振响应.为探索抖振响应随主跨跨度的演变规律,首先通过频谱分析得到各主要模态的共振响应和背景响应的贡献,然后分析了2类贡献的变化规律,最后拟合得到了主要模态的抖振位移均方根随跨度的变化公式.以一座实际桥梁为数值算例计算了其抖振响应,并将结果与本文拟合公式进行了对比,验证了拟合公式的实用性,可快速估算悬索桥在B类风场中的抖振响应.

In the report,11 suspension bridge models with different spans were designed.The wind tunnel tests were performed to obtain the aerodynamic three-component force coefficient of the main girder section.the Matlab toolbox was used to generate the time history of fluctuating wind speed the of the B-type wind field and the buffeting forces were obtained.Based on the data,the structural dynamic characteristics were analyzed,and the buffeting responses of 11 models considering geometric linearity and nonlinearity were calculated.The results showed that with the increase of the span,the structural natural frequency decreases gradually,and the root mean square value of the buffeting displacement increases gradually.For the vertical and torsional responses,with the increase of span,the differences between the linear and nonlinear results increase.For the lateral response,the differences change slightly,which suggested that the geometric nonlinearity mainly affects the responses in the vertical and torsional directions.In order to explore the evolution of the buffeting response with the main span length,the spectrum analysis was performed to obtain the contributions of the resonance and the background components of each main mode.Then,the variation of the two contributions was analyzed.Finally,a formula describing the evolution of buffeting responses with the span length was obtained via data fitting.A bridge was used as a numerical example,the buffeting responses were calculated,and the results are compared with that by the fitted formula,which verifies the practicability of the proposed formula,and can be used as a fast evaluation tool for buffeting responses of suspension bridges immersed in B-type wind fields.