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为研究实际重载交通荷载作用下简支梁桥疲劳安全水平,提出了基于随机重载车流的既有桥梁疲劳可靠度分析方法。基于高速公路桥梁动态称重车流数据建立了重载随机车流模型,采用响应面方法分析随机车辆对桥梁产生的等效疲劳应力,模拟了考虑车辆超载率上限的疲劳应力谱,估算了运营期内交通变化对简支梁桥疲劳可靠指标的影响。研究结果表明:总重相等的不同车型对简支梁桥产生的等效疲劳应力幅不同,主要表现在随着车轴数量的增长,桥梁的等效疲劳应力幅有所降低;在未控制超载车辆时,桥梁的疲劳应力谱表现出明显的双峰特征,而采用超载率上限控制措施之后,高幅疲劳应力概率密度峰值有所降低;交通量增长导致桥梁疲劳可靠指标显著降低,且随着运营期的增长该下降趋势更加明显;设置100%和50%的车辆超载率上限,将导致40m简支T梁桥在运营期内疲劳可靠指标分别由2.54升高至2.74、2.91。
In order to study the fatigue safety level of simply supported girder bridge under actual heavy traffic load, the fatigue reliability analysis method of existing bridge based on random heavy traffic flow is proposed. Based on the dynamic traffic flow data of highway bridges, a heavy load random traffic flow model was established. Response surface method was used to analyze the equivalent fatigue stress of random vehicles on bridges. The fatigue stress spectrum considering the upper limit of vehicle overloading rate was simulated. Impact of Traffic Changes on Fatigue and Reliability Indexes of Simply Supported Beam Bridge. The results show that the equivalent fatigue stress amplitude of different types of vehicles with the same total weight is different from that of the simply supported girder bridge, and the equivalent fatigue stress amplitude of the bridge decreases with the increase of the number of axles. In uncontrolled overloaded vehicles , The fatigue stress spectrum of the bridge shows obvious bimodal characteristics. However, with the control measures of the upper limit of overloading rate, the peak value of probability density density of high amplitude fatigue stress decreases. The reliability index of bridge fatigue caused by the increase of traffic volume decreases significantly. The downward trend of the growth of the period is more obvious. Setting the upper limit of 100% and 50% of the vehicle overloading rate will cause the fatigue reliability index of the 40m simply supported T girder bridge during operation period to rise from 2.54 to 2.74 and 2.91 respectively.