拱桥汽车设计荷载标准分析

分析了超载车辆对桥梁的影响与现行规范即《公路桥涵设计通用规范》 (JTG D60—2015) 中的汽车荷载标准对公路上运营车辆荷载的适用性, 研究了广深高速公路车辆荷载的动态称重系统(WIM) 实测数据, 利用Monte Carlo方法模拟随机车辆荷载和随机车辆间距, 编制了随机车队加载效应计算程序, 计算了无铰拱跨中和拱脚截面的弯矩效应, 采用极大值分布原理求得荷载效应在设计基准期内的标准值, 给出基于WIM实测数据的汽车荷载标准模型, 并与现行规范中的设计荷载标准进行对比。计算结果表明: 推荐车道荷载作用效应对实测荷载效应包容性和适用性良好, 拱桥跨中弯矩误差小于7%, 当跨径为25~65、110、120m时, 拱脚弯矩误差为5%~11%, 其余跨径时的拱脚弯矩误差小于5%;基于广深高速公路实测荷载推定的荷载标准与现行规范中公路-Ⅰ级车道荷载在无铰拱上产生弯矩效应的比值为1.24~2.18, 平均比值为1.80, 说明广深高速交通量大, 车辆超载超限严重, 根据实测车辆荷载推断的荷载标准与现行规范荷载标准出现了较大偏差, 广深高速桥梁设计荷载标准应在现有规范基础上适当提高。

Analysis of vehicle design load standard of arch bridge

The influence of current overload vehicles on bridge and the applicability of vehicle design load standard in General Specifications for Design of Highway Bridges and Culverts (JTG D60—2015) to the operating vehicle load on highway were analyzed.The weigh-in-motion (WIM) measured data of vehicle loads on Guangshen Expressway were studied.The Monte Carlo method was used to simulate the random load and random spacing of vehicle, the loading effect of random fleet was programmed, and the bending moment effects of clamped arch bridge sections at the midspan and arch foot were calculated.Based on the maximum value distribution principle, the characteristic values of loading effect in the design reference period were obtained, the standard model of recommended vehicle load based on the WIM measured data was presented, and the recommended load standard was compared with the design load standard in the current code (JTG D60—2015).Calculation result shows that the effect of recommended vehicle loadstandard is well applicative and inclusive to the measured values, the errors of bending moment at the midspan are less than 7%, the errors at the arch foot are 5%-11% when bridge spans are 25-65, 110 and 120 m, and the others are less than 5%.The ratios of generated bending moment effects resulting from the putative load standard based on the measured values of Guangshen Expressway and the highway I-grade lane load of current code on the clamped arch bridge are1.24-2.18, and the average ratio is 1.80, which indicates that the traffic of Guangshen Expressway is heavy, vehicle overloading is serious, and the load standard in the current code has great deviation with the deductive load standard according to the measured vehicle load of Guangshen Expressway, so the bridge design load standard of Guangshen Expressway should properly increase based on the existing standard.