连续梁桥影响线识别与承载能力快速评估试验研究

Test study on influence line identification and load-bearing capacity rapid evaluation for continuous girder bridge

针对桥梁静载试验过程存在的重载静置、交通阻误等问题,利用桥梁影响线具有完整反映结构各截面抗弯刚度的优势,提出一种基于影响线的桥梁承载能力快速评估方法。该方法仅利用单辆重车移动加载获取包含桥梁影响线信息、结构动力成分和车辆多轴效应的桥梁时程响应,首先采用变分模态分解剥离桥梁时程响应中的动力成分;其次根据采样频率及车辆轴距构建桥梁影响线识别数学模型,从而剔除桥梁时程响应中的车辆多轴效应,利用Tikhonov正则化解得桥梁影响线的稳定解;然后通过在桥梁影响线上开展虚拟加载,重构桥梁虚拟静力响应,并采用传统校验系数法评价桥梁承载能力。通过三跨变截面连续梁桥数值算例验证影响线识别方法的有效性,建立误差指标定量评价影响线识别结果的准确性,从而对某三跨连续钢混组合梁桥开展静载试验与承载能力快速评估试验研究,在预设车道实施车辆移动加载,识别桥梁中跨跨中截面挠度、应变影响线,进而开展虚拟加载研究,进一步验证所提承载能力快速评估方法的可行性与实用性,为桥梁承载能力“轻量化”快速筛检提供方法支撑与案例借鉴。

Here,aiming at problems of heavy load standing and traffic obstruction in static load test process of bridge,using advantage of bridge influence line fully reflecting bending stiffness of each cross-section of bridge structure,a fast evaluation method of bridge load-bearing capacity based on influence line was proposed.This method could only utilize mobile loading of a single heavy vehicle to obtain bridge time history responses containing bridge influence line information,structural dynamic components and multi-axis effect of vehicle.Firstly,variational mode decomposition(VMD)was used to remove dynamic components from bridge time history responses.Secondly,a mathematical model for identifying bridge influence line was constructed according to sampling frequency and vehicle wheelbase to eliminate multi-axis effect of vehicle in bridge time history responses.The stable solution of bridge influence line was obtained by using Tikhonov regularization.Then,virtual loading was implemented on bridge influence line to reconstruct bridge virtual static response,and the traditional verification coefficient method was used to evaluate bridge load-bearing capacity.With numerical examples of a 3-span variable cross-section continuous girder bridge,the effectiveness of the influence line identification method was verified,and an error index was established to quantitatively evaluate the correctness of influence line identification results.Furthermore,static load tests and load-bearing capacity rapid evaluation tests for a certain 3-span continuous steel-concrete composite girder bridge were conducted.Vehicle mobile loading was implemented on a preset driveway to identify deflection and strain influence lines of bridge mid-span central cross-section,and then virtual loading study was performed to further verify the feasibility and practicality of the proposed load-bearing ability rapid evaluation method,and provide method support and case reference for lightweight and rapid screening of bridge load-bearing capacity.