风和随机车流下悬索桥伸缩缝纵向变形

为动态仿真与评估运营阶段风和随机车流联合作用下大跨钢桁悬索桥伸缩缝纵向变形, 建立了风-随机车流-钢桁悬索桥分析系统; 基于已有单主梁风-车-桥耦合振动分析系统, 引入弹簧单元模拟伸缩缝, 并从车-桥耦合关系和钢桁梁横断面风荷载精细化加载2个方面将分析系统从单主梁提升为梁格法; 基于监测数据仿真重现了交通流荷载, 采用建立的分析系统计算了一座典型大跨钢桁悬索桥伸缩缝在随机车流作用下的动态位移时程响应, 获取并验证了累计位移与交通流质量的相关关系; 以滑动支承耐磨材料厚度为评估指标确定了伸缩缝累计位移临界值, 评估了伸缩缝的正常工作寿命; 在不同风速和随机车流作用下对伸缩缝纵向变形性能进行了参数敏感性分析。分析结果表明: 伸缩缝在随机车流作用下的时位移极值远小于设计允许伸缩范围-880~880 mm; 伸缩缝累计位移与其对应时段内的交通流荷载具有正相关性; 在风与随机车流联合作用下, 风速小于15 m·s-1时, 影响伸缩缝纵向变形的主要荷载因素为随机车流, 风速大于15 m·s-1时, 主要荷载因素为风荷载; 伸缩缝时位移极值与时累计位移随风速的增大均呈增大趋势; 当风速增大至20 m·s-1时, 风荷载产生的伸缩缝纵向变形近似为车流荷载下的2倍; 建立的风-随机车流-钢桁悬索桥分析系统可为运营荷载下伸缩缝纵向变形的动态仿真与性能评估提供数值分析平台。 

Longitudinal deformation of expansion joint of suspension bridge under wind and random traffic flow

To dynamically simulate and evaluate the longitudinal deformation performance of expansion joint of long-span steel truss suspension bridge under the combining action of wind and random traffic flow at operation stage, an analysis system of wind-random traffic flow-steel truss suspension bridge was established. Based on the existing wind-vehicle-bridge coupling vibration analysis system of single beam, the spring element was introduced to simulate the expansion joint, and the analysis system was improved from the single beam to the grillage method via two aspects of the vehicle-bridge coupling relationship and the fine loading of wind on steel truss girder section. The traffic flow load was simulated and reproduced based on the monitoring data. The dynamic displacement time history response of expansion joint of a typical long-span steel truss suspension bridge under the action of random traffic flow was calculated through the established analysis system. The correlation between the cumulative displacement and traffic flow weight was obtained and verified. Taking the thickness of wear-resisting material of sliding support as the evaluation indicator, the critical value of cumulative displacement of expansion joint was determined, and the normal service life of expansion joint was evaluated. The parameter sensitivity analysis on the longitudinal deformation performance of expansion joint under different wind speeds and random traffic flow was carried out. Analysis result shows that the hourly maximum displacement of expansion joint under the random traffic flow is far less than the designed allowance-880-880 mm. The cumulative displacement of expansion joint is positively correlated with the traffic flow load in corresponding period. Under the combining action of wind and random traffic flow, when the wind speed is less than 15 m·s-1, the main load factor affecting the longitudinal deformation of expansion joint is random traffic flow load. When the wind speed is greater than 15 m·s-1, the main load factor is wind load. Both the hourly maximum displacement and hourly cumulative displacement of expansion joint increase with the increase of wind speed. When the wind speed increases to 20 m·s-1, the longitudinal deformation of expansion joint generated by the wind load is approximately 2 times of that under the traffic flow load. The established wind-random traffic flow-steel truss suspension bridge analysis system can provide a numerical analysis platform for dynamic simulation and performance evaluation on the longitudinal deformation of expansion joint under operation loads.