大跨连续刚构桥荷载试验研究

Study of Load Tests for Long-span Continuous Rigid Frame Bridge

以龙陵至瑞丽高速公路上某大跨连续刚构桥为工程背景,基于现场荷载试验方法,对其在运营状态下的承载力及动力性能进行了研究。首先,详细介绍了试验过程中应变、挠度及振动模态测点的布置方式;然后,根据荷载效应等效原则确定试验设计荷载,针对连续刚构桥结构内力分布特点,选取典型截面最不利正负弯矩的活载布置方式,确定静力加载工况,同时制定了考虑不同车速及行车方式影响的动载试验方案,通过脉动试验提取模态测点数据,利用相关仪器中快速傅里叶变换(FFT)分析得出模态结果;最后,将实测结果与有限元结果进行对比分析。结果表明:静载试验的应变和挠度实测值均小于计算值,满足规范要求;动载影响下,冲击系数对行车方式更为敏感,表现为当车速为20km·h^(-1)时,主跨跨中截面跳车时冲击系数(0.25)较匀速跑车(0.05)增大5倍;桥梁结构整体承载能力及刚度满足设计荷载(公路-Ⅰ级)正常使用要求。

Based on a long-span continuous rigid frame bridge in Longling to Ruili highway, the bearing capacity and dynamic performance of the operating state were studied by field load test method. Firstly, arrangements of the strain, deflection and modal measuring point were introduced then, test design load was determined based on load equivalent principle, and according to internal force distribution characteristics, the live load layout method of the most unfavorable positive and negative moments of the typical section was selected, and the static loading cases were determined, meanwhile dynamic load test program considering the influence of different speeds and running modes was established. Through the environmental excitation method, the modal results were obtained by using fast Fourier transform （FFT） in relevant instruments. Finally, the measured results and the finite element results were compared and analyzed. The results show that the static load test measured values of strain and deflection are less than the calculated values, and they can meet requirements of specifications the dynamic load under the influence of impact coefficient is more sensitive to the traffic way, as when the speed is 20 km·h-1 , impact coefficient of the main span of cross section is jumping to 0. 25 compared with that of the uniform velocity 0. 05, increased about 5 times; the overall loadcarrying capacity and stiffness of bridge structure meet the requirements of normal use under design load （highway-grade I ）.