大悬臂连续箱梁拓宽桥连接构件的受力特性

杨安畅，孟松，巩冠宏，刘金文^*

山东交通学院交通土建工程学院，山东 济南  250357

摘要：为研究大悬臂连续箱梁拓宽桥连接构件的受力特性，以女姑口特大桥改造工程为研究背景,采用有限元软件Midas Civil和Abaqus分别对全桥和局部进行精细化数值模拟,分析横向拓宽桥整体模型在部分受力、恒载组合、运营状态3种工况下的受力情况及拓宽前后桥梁所受弯矩变化，分析局部构件模型在运营状态下所受应力。对箱梁和横肋进行实桥应变监测，对比分析实测应力与有限元模型分析应力。运营状态为最不利工况，在此工况下，左、右幅箱梁的应力极值均位于第2跨与第15跨跨中区域。取出现最大应力和最大竖向位移的第15跨建立局部精细化模型，加载后分析横肋、榫卯、套箍在运营状态工况下的应力，横肋顺桥向、横桥向压应力对称分布，顺桥向应力从两端向中部区域递减，端部最大压应力为–5.40 MPa，最大拉应力为0.42 MPa，横桥向应力从中部向两端递减，中部最大压应力为–5.50 MPa，最大拉应力为0.39 MPa。运营状态工况下，榫卯连接钢筋的应力极值出现在靠近横肋侧壁中部区域，5^#榫卯承受最大应力21.56 MPa；套箍应力对称分布，顺桥向两侧竖向钢筋中部区域出现应力极值，4^#套箍承受最大应力71.43 MPa，10#套箍承受最小应力35.65 MPa。拓宽后的桥梁结构整体刚度增大，荷载传递路径变化，原主梁在运营状态工况下的弯矩分布明显改变，正弯矩区最大弯矩普遍减小，负弯矩区最大弯矩的绝对值小幅增大。第15跨左箱梁的顶板和底板纵向实测应力与有限元模型应力相近，横肋底面实测应力与有限元模型应力在L/4、L/2、3L/4处相差较大。

关键词：大悬臂连续箱梁；拓宽桥；连接构件；有限元模拟；实桥测试

Mechanical characteristics of connecting members in a widened bridge with long cantilever continuous box girders

YANG Anchang, MENG Song, GONG Guanhong, LIU Jinwen^*

School of Civil Engineering, Shandong Jiaotong University, Jinan 250357, China

Abstract: To study the force characteristics of the connection components of the large cantilever continuous box girder widening bridge, taking the Nügukou Bridge reconstruction project as the research background, fine numerical simulations of the entire bridge and local sections are conducted with finite element software Midas Civil and Abaqus. The stress conditions of the overall model of the widening bridge under three working conditions: partial load, constant load combination, and operational state are analyzed, along with the changes in bending moments before and after widening the bridge. The stress on the local component model is analyzed under operational conditions. Strain monitoring is performed on the box girder and transverse ribs, and a comparative analysis of the measured stresses and the stresses obtained from the finite element model is conducted. The operational state is the most unfavorable condition, under which the stress extremes of the left and right box girders are located in the middle regions of the 2nd and 15th spans. A local refined model is established for the 15th span, which exhibits the maximum stress and vertical displacement. After loading, the stresses on the transverse ribs, mortises, and stirrups are analyzed under the operational state. The compressive stresses of the transverse ribs in the longitudinal and transverse directions exhibit a symmetric distribution, with longitudinal stresses decreasing from the ends toward the middle region. The maximum compressive stress at the ends is -5.40 MPa, and the maximum tensile stress is 0.42 MPa. The transverse compressive stresses decrease from the middle to the ends, with the maximum compressive stress in the middle being –5.50 MPa and the maximum tensile stress being 0.39 MPa. Under the operational state, the extreme values of stress for the reinforcement in the mortise connections appear in the middle region near the side walls of the transverse ribs, with the 5^# mortise bearing the maximum stress of 21.56 MPa. The stirrup stresses exhibit a symmetric distribution, with extreme stresses occurring in the middle regions of the vertical reinforcements on both sides. The 4^#stirrup bears the maximum stress of 71.43 MPa, while the 10^#stirrup bears the minimum stress of 35.65 MPa. The overall stiffness of the bridge structure increases after widening, with changes in the load transfer path. The bending moment distribution of the original main beam under operational conditions is significantly altered, with the maximum bending moment in the positive moment region generally decreasing, while the absolute value of the maximum bending moment in the negative moment region slightly increases. The measured longitudinal stresses of the top and bottom plates of the left box girder in the 15th span are close to those of the finite element model, while the measured stresses on the bottom surface of the transverse ribs differ significantly from the finite element model stresses at L/4, L/2, and 3L/4.

Keywords: large cantilever continuous box girder; widened bridge; connecting member; finite element simulation; real bridge detection