考虑桥梁限重标志对驾驶员行为约束的车辆荷载效应研究

通过对某市货车驾驶员进行问卷调查,研究了桥梁限重标志对货车驾驶员驾驶行为的约束作用规律;基于实测随机车流的统计分布规律,利用蒙特卡洛法编写了考虑桥梁限重标志对驾驶员行为约束作用的随机车流模拟程序.以55t桥梁限重值为例,根据《公路工程结构可靠度设计统一标准》的荷载效应分析方法,计算了简支梁桥在模拟随机车流荷载作用下的跨中弯矩和支座剪力.对日均交通量、条件约束水平和桥梁跨径进行了参数分析,并将随机车流荷载作用下的荷载效应与中国现行桥梁设计规范中对应的汽车荷载效应标准值做了比较.研究结果表明:1)只有当超重货车驾驶员均严格遵守桥梁限重规定时,桥梁限重标志才能有效地控制车辆荷载效应,从而保障桥梁的安全可靠性;2)中国现行桥梁设计规范的设计荷载可能低估了某些路段实际车流的荷载,且在小跨径桥梁上尤为突出,应当引起重视.

Study of Vehicle Load Effect Considering the Effect of Weight Limit Signs on Restricting Drivers' Behavior

This paper studied the effect of weight limit signs on restricting truck drivers' behavior based on the results from a questionnaire survey conducted among truck drivers in a province in China. Based on the statistic properties of the field measured traffic flows, models for random traffic flows were developed by using the Monte-Carlo method while taking into consideration the effect of the weight limit signs on restricting the drivers' behavior. Taking a weight limit of 55 t for example, the load effect for the midspan bending moment and end shear for simply-supported beam bridges under the generated random traffic flows were studied by using the method for analyzing the load effect provided in the Unified Standard for Reliability Design of Highway Engineering Structures. A parametric study was also conducted to study the effect of the average daily vehicle traffic, conditional restriction level, and bridge span length. The calculated load effect under the generated random traffic flow was compared with that calculated by using the design load given in the current Chinese bridge design code. The results show that: 1) the weight limit sign can effectively reduce the maximum vehicle load effect and insure the bridge safety and reliability only when the truck drivers strictly obey the weight limit regulation; and 2) the design vehicle load in the current Chinese bridge code may have underestimated the real traffic loads, especially for short-span bridges, to which special attention should be given.