考虑剪力滞效应的简支箱梁自振特性

Free vibration characteristics of simply supported box girder with effect of shear lag

由于箱梁中剪力滞效应的存在,通常采用的一般梁理论计算简支箱梁的振动频率会产生较大的误差,对于宽跨比较大的简支箱梁振动计算误差尤其明显。在考虑了箱梁剪力滞效应的基础上,利用能量变分原理分析了简支箱梁的自由振动,得到了考虑剪力滞效应的简支箱梁自振基频的解析解。算例表明该法比一般梁理论计算精度有显著提高,且计算简单方便。最后,考虑剪力滞效应对箱形梁结构自振特性的影响进行了讨论,发现考虑剪力滞效应后简支箱梁的振动基频降低,且箱梁的宽跨比对其降低程度影响最为显著。

Owing to the effect of shear lag, the conventional beam theory has a larger error in the calculating of vibration frequency of simply supported box gird. The error is obvious especially in the box gird with big width span ratio. A new method which is used to analyse the free vibration of simply supported box gird is proposed, in which shear lag influence is included. The method is based on energy variational principle and an analytical fundamental frequency of simply supported box gird is obtained. The application of true example shows that the accuracy and effectiveness of this new method is much improved by comparing with the conventional beam theory. Finally, the effect of shear lag on the free vibration of simply supported box gird is discussed. It is found that the fundamental frequency of simply supported box gird decreases after taking shear lag into consideration and the decrease is closely related to the width span ratio of the box gird.