基于局部测点模态测试的简支梁桥承载刚度评定试验研究

Experimental study on the load-bearing stiffness assessment of simply supported girder bridges based on modal tests of local measurement points

摘要:

快速可靠地检测服役桥梁的承载刚度对保障道路交通线路的安全运营具有重要意义。文章提出一种基于局部测点模态测试的简支梁桥承载刚度评定方法,并以某实际工程中一座简支梁桥为试验对象,对所提方法的可行性和准确性进行验证。设计传统桥梁荷载试验的中载和偏载加载方案,测得各工况下简支梁桥跨中截面的实测静挠度,基于环境激励进行联合测点模态试验和局部测点模态试验,预测简支梁桥跨中截面的模态挠度,并结合桥梁理论挠度计算结构挠度校验系数。结果表明:中载、偏载工况下联合测点模态试验预测的跨中截面模态挠度与静载试验跨中截面实测静挠度的相对误差最大不超过5.7%,基本满足工程精度的要求；联合跨中截面测点和桥面加载点测点的联合测点模态试验能够准确评估桥梁的承载刚度；仅在跨中截面布置传感器的局部测点模态试验预测的模态挠度基本等价于联合测点模态试验预测的模态挠度,两者的相对误差小于2%,局部测点模态测试预测的跨中截面挠度校验系数与静载试验的实测挠度校验系数相比具有很好的一致性。

Abstract:

Ensuring the safe operation of road traffic routes primarily depends on the fast and reliable testing of the load-bearing stiffness of service bridges. This paper presents a load stiffness assessment method for simply supported girder bridges based on a modal test of local measurement points. An actual, simply supported girder bridge is used as the test object to verify the feasibility and accuracy of the proposed method. The schemes of symmetric and eccentric loads used in conventional bridge load tests were designed, and the measured static deflection of the mid-span section of the simply supported girder bridge under each condition was obtained. Modal tests of joint and local points were conducted based on the ambient excitation to predict the modal deflection of the mid-span section of the simply supported girder bridge, and the calibration coefficient of structural deflection was calculated with the theoretical deflection. Results show that under symmetric and eccentric loads, the maximum relative error between the modal deflection of the mid-span section predicted by the modal test of joint points and that measured in the static load test is less than 5.7%. The load-bearing stiffness of the bridge can be accurately assessed using the modal test of joint points on the mid-span section and the bridge deck. The modal deflection predicted by the modal test of local measuring points with sensors only in the mid-span section is equivalent to that predicted by the modal test of joint measuring points, and the relative error between them is less than 2%. The deflection calibration coefficient of the mid-span section predicted by the modal test of local measuring points is in good agreement with the measured value from the static load test.