重载时变效应对在役梁桥承载力影响机理研究

A large number of vehicular overloads travel on highway bridges high frequently, which significantly threatens the safety of our infrastructure system and even causes bridge structures failure. However, the mechanism of bridge structures under overloaded trucks is still ambiguous at present. This program aims at the effect of vehicular overloads on loading capability of girder bridges in service, combining real truck data with numerical modeling and theoretical analysis, to study on the mechanical properties of existing girder bridges under typical overloads..In this step-by-step study, a WIM-data-based mathematic model is firstly built with random theory to demonstrate the entire moving process of multiple vehicles presenting on different lanes and to analyze the characteristics and configurations of vehicular overloads, furthermore, typical overweight truck models are proposed based on the understanding of the severest load effects induced. Secondly, identification of modal parameters is carried out to obtain representative mechanical properties for a real girder bridge in service and then modify its theoretical finite element model. Finally, the typical overweight truck models proposed are applied to the refined finite element model to compare the strength and deformations of reinforced concrete structures under different vehicular overloads, so that the calculating index of loading capability is developed for each loading state. As a result, the time-depending effect of vehicular overloads on loading capability of girder bridges in service could be quantified.. This program is supposed to reveal the mechanism of vehicular overloads running on bridges and provide a beneficial reference to bridge design and evaluation in the frame of reliability.

大量工业重车频繁通行，严重影响了国内在役桥梁安全以至损坏倒塌事故频发，但目前对重载作用下桥梁内力发展变化过程的认识不足。本项目针对重载对在役梁桥承载力的显著影响，拟采取实测数据、数值模拟与理论分析相结合，开展典型重载模型动态通行过程对在役梁桥构件作用机理研究。.首先利用动态称重数据，建立多车道车辆并行随机过程数理模型，深入研究车辆关键参数分布对产生效应的影响规律，提出基于最不利效应的典型重载模型；其次以某在役梁桥为现场观测对象，通过模态参数识别获取真实力学性能参量，建立经修正的梁桥有限元分析模型；最后将提出的典型重载模型应用到梁桥有限元模型加载，研究不同重载动态通行过程中结构内力变形发展变化特征，建立各受力状态下梁桥承载力量化指标，提出重载时变效应对在役梁桥承载力影响表达。.研究成果将深化车辆荷载作用机理，为完善现行桥梁设计规范和桥梁承载力可靠性评估方法提供重要依据。

因社会经济发展需要，国内大量工业重车的频繁通行严重影响了在役桥梁安全性，甚至各类损坏倒塌事故频发。但目前业界对重载特性、重载构成及重载作用下桥梁内力发展变化过程的认识不足。本项目针对重载对在役梁桥承载力的显著影响，采取实测数据、数值模拟与理论分析相结合的手段，开展了三方面的工作：首先基于海量实测车辆荷载数据，结合我国现行的桥梁设计规范要求，提出了“基于最不利效应”的重载定义及其判别方法。与使用总重、轴重和尺寸限制的常规判断方式不同，本项目提出的“最不利效应”将车辆与结构相结合，通过车辆重量的空间分布研究车辆动态通行时变过程对桥梁结构产生的作用，再以桥梁设计规范荷载为重载判别基准，建立了重载车辆模型。其次，以一座服役了近20年的预应力混凝土箱梁桥为实际工程背景，开展了基于环境激励的桥梁模态参数识别及有限元模型修正研究，通过现场试验数据和随机子空间法获取了桥梁实测模态，其与初始理论值之间存在明显差异，项目进一步研究了基于1阶法和响应面法的有限元模型修正，对比了两种方法的修正效果、优缺点、适用性等，提出了该类桥梁的有限元模型修正建议。最后，将建立的重载车辆模型加载到经修正后的桥梁有限元模型上，考虑重载的不同组合、多车道并行等情况，分别计算其产生的弯矩、应力、挠度等参量，与现行桥梁规范值比较之，开展不同重载作用下的桥梁承载力评定。. 在我国车辆超载频发、桥梁“带病服役”现象突出的现实背景下，为保证桥梁运营安全，每年检测、评估、维护和加固消耗了大量人力、物力。该领域的工作既是复杂的技术问题，更是影响经济发展和民生生活的社会问题。本项目基于海量实测数据开展了重载特性研究，相关成果可为规范设计汽车荷载的完善与修订提供前期研究积累与数据参考，从方法论层面对当前在役结构的可靠性研究形成有益补充。