斜交梁桥频率间接识别效果的影响参数

采用过桥车辆振动响应识别桥梁自振特性的间接测量法能够避免传统动载试验测量桥频方法存在的操作复杂和成本高等缺点。根据车桥耦合振动理论和桥梁间接测量法基本原理，对实际工程中的某一斜交梁桥建立车辆与桥梁耦合振动的有限元模型，采用双轴半车模型模拟测量车辆，提取车辆匀速驶过桥梁时的车辆加速度时程响应，并利用峰值拾取法进行频谱分析，剔除已知的车辆相关频率识别出桥梁的前三阶自振频率，分析了6种不同车速、6种不同车重、8种不同桥梁斜交角度对桥梁频率识别效果的影响特点。结果表明，间接测量法能够有效地识别桥梁比较密集的频率，车速低于20 km/h时，能够较好地识别出斜交梁桥的前3阶频率，车速较高时无法识别桥梁的频率信息；相对较小的车桥质量比对桥梁频率识别有利；斜交梁桥不同的斜交角度基本不影响桥梁频率识别的精度；桥面粗糙时采用差值法仍能较好地识别。数值模拟表明，间接测量法对于不规则斜交梁桥频率仍有较好的识别效果。

Influence parameters of frequency indirect identification effect for oblique beam bridge

An indirect measurement method is adopted to identify the bridge''s natural vibration characteristics by vibration response of vehicles crossing the bridge,it can avoid the disadvantages of the traditional method of measuring bridge frequency in dynamic load test, such as complicated operation and high cost. Based on the theory of vehicle-bridge coupling vibration and the basic principle of bridge indirect measurement method, the finite element model of vehicle-bridge coupling vibration is established for a skew beam bridge in practical engineering. A biaxial half-car model is used to measure the vehicle and extract the time-history response of the vehicle acceleration when the vehicle passes the bridge at a constant speed. Excluding known vehicle-related frequencies.The first three natural frequencies of the bridge are identified.The influence of six different vehicle speeds, six different vehicle weights and eight different bridge skew angles on the bridge frequency identification is analyzed. The results show that the indirect measurement method can effectively identify the frequency of bridges with high density. When the speed is less than 20 km/h, the third-order frequency of skew beam bridge can be well recognized. When the speed is high, the frequency information of the bridge cannot be recognized.The relatively small ratio of vehicle and bridge mass to bridge frequency identification is advantageous. The accuracy of frequency identification is not affected by the different angle of oblique beam bridge.When the bridge deck is rough, the method of acceleration subtraction can still be used for frequency identification. Numerical simulation shows that the indirect measurement method still has a good recognition effect for the irregular skew beam bridge frequency. To promote the application of motion sensing indirect measurement method in bridge inspection engineering.