Modelling the spatial distribution of heavy vehicle loads on long-span bridges based on undirected graphical model

Abstract

Vehicle load modelling is highly important for bridge design and safety evaluation. Conventional modelling approaches for vehicle loads have limitations in characterizing the spatial distribution of vehicles. This article presents a probabilistic method for modelling the spatial distribution of heavy vehicle loads on long-span bridges by using the undirected graphical model (UGM). The bridge deck is divided into grid cells, a UGM with each node corresponding to each cell is employed to model the location distribution of heavy vehicles, by which probabilities of heavy-vehicle distribution patterns can be efficiently calculated through applying the junction tree algorithm. A Bayesian inference method is also developed for updating the location model in consideration of the non-stationarity of traffic process. Gross weights of heavy vehicles are modelled by incorporating additional random variables to the vehicle-location UGM, corresponding probability distributions are constructed conditioned on ignoring correlation and considering correlation, respectively. Case studies using simulated data as well as field monitoring data have been conducted to examine the method. Compared with previous studies involving vehicle load modelling, the presented method can implement probabilistic analysis for all spatial distribution patterns of heavy vehicles on the entire bridge deck.     

Dynamic stress analysis for fatigue damage prognosis of long-span bridges

For fatigue damage prognosis of a long-span steel bridge, the dynamic stress analysis of critical structural components of the bridge under the future dynamic vehicle loading is essential. This paper thus presents a framework of dynamic stress analysis for fatigue damage prognosis of long-span steel bridges under the future dynamic vehicle loading. The multi-scale finite element (FE) model of the bridge is first developed using shell/plate elements to simulate the critical structural components (local models) and using beam/truss elements to simulate the rest part of the bridge (global model). With the appropriate coupling of the global and local models, the multi-scale FE model can accurately capture simultaneously not only the global behavior in terms of displacement and acceleration but also the local behavior in terms of stress and strain. A vehicle traffic load model is then developed for forecasting the future vehicle loading based on the recorded weigh-in-motion (WIM) data and using the agent-based traffic flow microsimulation. The forecasted future vehicle loading is finally applied on the multi-scale model of a real long-span cable-stayed bridge for dynamic stress analysis and fatigue damage prognosis. The obtained results show that the proposed framework is effective and accurate for dynamic stress analysis and fatigue damage prognosis.     

Characteristic traffic load effects from a mixture of loading events on short to medium span bridges

In recent years, highway bridge load assessment has been recognised as an area through which savings can be made by avoiding unnecessary bridge refurbishment and replacement. Load effects in bridges result from single truck crossings or multiple-truck presence events which are, statistically, not identically distributed. Conventional approaches fit statistical distributions to mixtures of non-identically distributed load effects. Inaccuracies in the conventional approach are identified and an alternative approach is developed to find the characteristic load effects. Theoretical and field data are used to show the potential implications of conventional techniques and to demonstrate the application of the new approach.     

循环载荷下纤维薄板增强RC梁的疲劳性能研究

通过建立循环载荷下碳纤维薄板(CFL)增强RC梁的累积损伤模型,并与增强梁的疲劳试验结果进行对比,研究增强构件的疲劳性能和损伤、破坏过程。试验发现CFL增强RC梁的疲劳损伤演化历程包括混凝土开裂、CFL与混凝土剥离、钢筋屈服等过程,具有明显的疲劳损伤成核、稳定扩展、失稳扩展三阶段发展规律,根据增强梁的载荷、挠度历程可以得到抗弯刚度演化历程。研究结果表明用CFL增强RC梁的剩余抗弯刚度来度量其疲劳损伤变量具有明确的物理意义,在此基础上建立的疲劳损伤演化方程能够准确模拟CFL增强RC梁的疲劳损伤破坏过程,进一步结合抗弯刚度可预测其剩余疲劳寿命。     

路面无损检测技术应用与发展探讨

针对传统路面检测方法的局限性,介绍了几种路面无损检测技术的基本原理和优点,包括频谱分析技术、图像技术、超声波技术、激光技术,对无损检测方法的主要仪器设备作了简要说明,阐述了路面无损检测技术的发展前景,以期进一步推广该技术的应用。