Risk-based importance factors for bridge networks under highway traffic loads

This paper proposes a risk analysis framework for the quantification of the importance to a highway network of bridges subjected to overweight traffic loads. First, the level of risk to the network is quantified taking into consideration current bridge safety levels and the consequences of their failures. A risk mitigation strategy is proposed through the calibration of importance factors that can be used during bridge design and rating processes to induce different levels of risk reduction in the network. The applicability of the method is illustrated through the analysis and the calibration of importance factors for bridges of a network composed by interstate highways and principal state roads in New York State (NYS) which includes 1,315 typical bridges. Analysis results show that traffic delays constitute the major consequence of bridge failure representing 61% of the total risk while the second major risk component is the maintenance of bridges that accounts for about 21%. It is also observed that the relationship between bridge importance factors and risk is well represented by a power law equation.     

桥梁结构对重载交通适应性分析

通过预测重载交通的特征,针对武汉市四环线货运重载比例较高的情况,项目引桥对重载交通适应性进行了计算分析,结果显示引桥施工图设计能适应该项目重载交通特性。     

The use of micro-simulation for congested traffic load modeling of medium- and long-span bridges

This paper presents a new approach to the modeling of congested traffic loading events on long span bridges. Conventional traffic load models are based on weigh-in-motion data of non-congested traffic, or something similar to a Poisson Arrival process. In neither case do they account for the mixing between lanes that takes place as traffic becomes congested. It is shown here that cars move out from between trucks as traffic slows down which results in a higher frequency of long platoons of trucks in the slow lane of the bridge. These longer platoons increase some characteristic load effects under the slow lane by a modest but significant amount. Micro-simulation, the process of modeling individual vehicles that is widely used in traffic modeling, is presented here as a means of predicting imposed traffic loading on long-span bridges more accurately. The traffic flow on a congested bridge is modelled using a random mixing process for trucks and cars in each lane, where each vehicle is modelled individually with driver behaviour parameters assigned randomly in a Monte Carlo process. Over a number of simulated kilometres, the vehicles move between lanes in simulated lane-changing manoeuvres. The algorithm was calibrated against video recordings of traffic on a bridge in the Netherlands. Extreme value statistics of measured strains on the bridge are then compared to the corresponding simulation statistics to validate the model. The micro-simulation algorithm shows that the histograms of truck platoon length are moderately affected by lane changing. This in turn is shown to influence some characteristic load effects of the bridge deck.     

基于损伤梁桥在控制荷载作用下的有限元分析

以洮儿河旧二号桥为例,采用大型有限元软件midas.fea进行了上部结构的无损与损伤模拟,利用两种桥梁模型做有限元分析,得到了相关理论数据,以期为今后桥梁养护工作管理提供技术指导。     

Vehicle-induced loads on traffic sign panels

The determination of the loads on traffic sign panels in the current standards does not, in general, take into account the vehicle-induced loads, as explained by Quinn, Baker and Wright (QBW in what follows) (J. Wind Eng. Ind. Aerodyn. 89 (2001) 831). On the other hand, a report from Cali and Covert (CC) (J. Wind Eng. Ind. Aerodyn. 84 (2000) 87) indicates that in highway sign support structures, vehicle-induced loads have led to premature failures in some cases. The aim of this paper is to present a mathematical model for the vehicle-induced load on a flat sign panel, simple enough to give analytical results, but able to explain the main characteristics of the phenomenon. The results of the theoretical model help to explain the behaviour observed in the experiments performed in previous studies.     

Simplified site-specific traffic load models for bridge assessment

Traffic load is identified as one of the greatest sources of uncertainty in the assessment of bridges. In recent years, simulation techniques, using measured traffic data, have been used to predict the characteristic traffic load effects on bridges. However, the techniques are complex, sensitive to the assumptions adopted and require specialist statistical expertise. This work presents a simplified site-specific traffic load model that generates comparable load effects to the corresponding results from a full simulation. While the simplified model is still sensitive to the underlying assumptions, these can be carefully reviewed prior to the method being approved. Further, the simplified method can be employed by practising engineers for bridge assessment.     

浅谈交通桥预制板吊装

介绍了交通桥的施工过程,着重阐述了交通桥预制板吊装方法,并对构件安装安全技术要求、吊装时的应急预案、吊装后产生问题的处理等作了论述,以期为类似工程提供指导。     

大跨径钢筋混凝土拱桥的静载试验研究

介绍了大跨径钢筋混凝土拱桥的静载试验，比较了试验结果与理论结果，并分析评价了二者，以期为评估桥梁状况，判断桥梁承载力，维护加固桥梁提供依据。     

A comprehensive traffic load model for bridge safety checking

In this paper a new model for the global analysis of traffic actions on roadway bridges will be presented. It has been developed in the frame of Crespo-Minguillón, C., Reliability based methodology for the definition of the limit state of decompression in prestressed concrete bridges. Ph.D. thesis, Department of Civil Engineering, Technical University of Catalunya, Barcelona, 1996. In order to make it feasible for use in the verification of most important limit states, the model includes an algorithm for the simulation of a continuous flow of traffic and another for the extrapolation of maximum results in short periods to long return periods. The model for traffic flow simulation includes a statistical treatment of most significant variables involved, and some original techniques to account for the most important correlations found in actual traffic. At the end, an example of application is shown.     

Evaluation of a steel railway bridge for dynamic and seismic loads

In this study, dynamic and seismic assessment of a railway bridge system with four discrete spans giving service on a double track railway line and located in an earthquake-prone region in Turkey is presented. A three-dimensional computer model of the bridge was generated using a commercial general finite element analysis software. Field measurements such as static and dynamic tests as well as material tests were conducted on the bridge system. Validation of the finite element model was performed based on the results of these tests. The calibrated 3D model of the bridge structure was then used for necessary calculations regarding structural assessment and evaluation according to train loads as well as seismic loads. Additional members were proposed to transmit seismic loads to supports. The fourth span, which had a permanent imperfection due to truck collision was studied in detail. Results have shown that due to excessive amount of capacity loss, the only choice was to write off the fourth span.     

A fuzzy set approach for bridge traffic safety evaluation1

On the basis of an extensive literature survey a set of factors that affect traffic safety on bridges was identified. These were grouped into three categories: bridge related, approach roadway related and environmentally related. A detailed accident analysis of a selected number of bridges in the state highway system of Indiana was conducted to verify these factors and to obtain insights into bridge accidents.

A bridge traffic safety evaluation model was developed based on fuzzy set mathematics and the concept of linguistic variables. All subjective evaluations in the model are represented as fuzzy sets which are then considered as fuzzy numbers for the purpose of calculations. The weighted averages for the fuzzy weights and fuzzy ratings are calculated for each group of contributing factors. These weighted averages are then logically combined to obtain the Bridge Safety Index.

The model takes into consideration the cumulative effect of the three groups of contributing factors related to bridge, approach roadway and environmental conditions. The resulting index, which is in the form of a fuzzy set, is transformed into the closest fuzzy number to represent the degree of bridge safety.     

Suspension bridge response due to extreme vehicle loads

A 269 tonne trailer travelled across the Tamar Suspension Bridge in October 2010, and the authors monitored the response of the structure to the load. The following investigation documents the deflection of towers and the deck during the vehicle's passage, as well as the change in cable tensions. This was achieved by studying monitored data from the bridge collected by accelerometers and strain gauges attached to the stay cables, as well as two robotic total stations that measured the deflection of the mid-span and the sway of the tower saddle. These results were subsequently compared to the response predicted by a finite element (FE) model of the bridge, indicating an accurate match. The FE model was also used to simulate the variation of the dynamic response of the structure, which suggests that the natural frequencies vary depending on the vehicle's location to each mode shape's anti-nodes.     

尼尔基坝下交通桥静载试验

阐述了尼尔基坝下交通桥加固后进行静载试验的原理及依据,介绍了试验荷载及测点布置情况,通过理论计算对测量数据进行了分析,得出荷载效率、校验系数、挠度值及残余变形均满足要求的结论.     

基于概率性能预计的桥梁养护优化关键问题研究

针对桥梁劣化过程非常复杂,缺乏足够的实际数据保证随机数学模型准确性的情况,采用多段线性能曲线模型计算桥梁构件基于时变的劣化过程,从而有效实现了基于概率性能预计的高速公路桥梁全寿命期养护优化方法。     

交通荷载作用下埋地承插口排水管道动力响应分析

近年来,由于市政排水管道灾变导致的道路坍塌事故频发,水泥混凝土管是目前应用最为广泛的市政排水管道,其在交通荷载作用下的力学响应特征尚不明确。基于ABAQUS有限元软件,建立了带承插口结构排水管道三维数值模型。在考虑承插口、橡胶圈和无限元吸收边界等的基础上计算分析了不同脉冲幅值、不同荷载作用位置和不同管道埋深对管道动力响应的影响。结果表明：管节处受力高度不连续,交通荷载对其作用位置两侧一节管长范围内的管道影响显著;承口和插口环向以受拉和受压为主;交通荷载作用位置对管顶、管底和管侧纵向Mises应力最大值无明显影响,但对管顶和管底纵向Mises应力分布有影响;管道纵向Mises应力及环向竖向应力与管道埋深成正比,应力增量与埋深增量成反比。计算结果为进一步研究交通荷载作用下排水管道的力学机理提供参考。     

连续刚构桥静动载试验研究

介绍了预应力混凝土连续刚构桥静动载试验的主要内容和测点布置以及理论计算的方法等，并给出了试验中的3个主要工况的理论与试验结果对比值，最后得出了有益的结论。     

大跨度公铁立交桥悬灌施工技术

结合工程实例，介绍了施工概况，从工艺原理、工艺流程两方面介绍了施工工艺，并对大跨度公铁立交桥施工在不中断京沪铁路及101公路行车的情况下，采用菱形挂篮悬臂灌注连续刚构的施工技术做了详细阐述。     

不中断交通桥梁铰缝加固环氧树脂的研究

研发了一种具有低粘度和较高早期强度的不中断交通桥梁铰缝加固用环氧树脂,能够在提供足够可操作时间的前提下,完成对桥梁铰缝的不中断交通加固。测试结果表明该材料具有与市场已有同类型产品相当的抗剪强度、弹性模量和拉伸强度等力学性能,抗交通荷载干扰能力强,而在低温和潮湿基面条件下,则具有更加优异的加固效果。     

Transverse displacement capacity and stiffness of steel plate girder bridge superstructures for seismic loads

Ductile end cross frames have been shown to reduce the transverse seismic demand in composite steel plate girder bridge superstructures. However, the effectiveness of these cross frames is strongly influenced by the transverse flexibility of the superstructure and its capacity for potentially large relative transverse displacements between the deck slab and bearing supports. A simplified method is developed in this paper for the calculation of these displacements based on the elastic girder stresses and transverse girder stiffnesses, which are shown to compare well with results given by the finite element method. In addition the method is shown to give results that compare well with experimental data from a 0.4 scale model subject to shake table excitation. Parametric studies are then described that show typical I-girder superstructures are able to accommodate large transverse drifts (up to 17% of the girder height) while remaining in the elastic range. These large drifts are possible without distress to the slab-to-girder connection, by omitting shear studs over a short length of the girder at the support cross frame locations. Based on the above, a step-by-step procedure is proposed for evaluating the transverse displacement, stiffness and capacity of the steel girder superstructures in the region of the end and intermediate supports.