地基承载力不足时桥梁施工支架变形规律分析

马文龙¹，吴国华¹，董舒静¹，展玉华¹，赵瑜隆^1,2*

1.山东交通学院交通土建工程学院，山东 济南 250357;

2.山东省智能建造装备关键技术与系统重点实验室，山东 济南 250357

摘要：为预测支架稳定状况，实现有效预警，采用有限元软件MIDAS CIVIL对桥梁承插形盘扣支架进行建模，模拟单点沉降与区域性沉降工况下支架结构的响应特征。采用现场桥梁原位试验法，将模拟数据与实际测量的支架变形数据进行对比分析，论证采用角度变化阈值进行预压和浇筑过程监控的可行性，并获得支架关键位置的变形规律。结果表明：陀螺仪实际测量的支架变形接近模拟数据，施工过程监控角度变化阈值可行。地基承载力不足导致3种不同的沉降工况：一是单点地基承载力不足时，对支架结构中间部分底部平面的四顶角支撑杆实施节点强制位移，4个测点角度变化明显但未超预警阈值，沉降发生在支座底部受支座反力最大的位置；二是部分区域地基承载力不足时，对支架结构的中间部分、左侧部分和右侧部分实施节点强制位移，对关键监测断面产生显著影响，局部结构位移变化明显，角度变化均在允许阈值内，浇筑工况下部分区域地基承载力不足时的位移折减率和角度递减率变化较小；三是各测点所在杆件底部地基承载力不足时，对监测断面底部节点同步施加节点位移，主要沉降发生在测点底部和周边底部区域，角度阈值随荷载增大而增大，验证了基于角度阈值的沉降识别与预警方法的有效性。

关键词：地基承载力；支架；变形；有限元建模分析；角度阈值

Analysis of deformation patterns of bridge construction supportunder insufficient foundation bearing capacity

MA Wenlong¹, WU Guohua¹, DONG Shujing¹, ZHAN Yuhua¹, ZHAO Yulong^1,2*

1.School of Civil Engineering, Shandong Jiaotong University, Jinan 250357, China;

2.Shandong Key Laboratory of Technologies and Systems for Intelligent Construction Equipment, Jinan 250357, China

Abstract: To predict the stability conditions of the support structure and achieve effective early warning, finite element software MIDAS CIVIL is used to model the pin-supported disc-type supports of the bridge, simulating the response characteristics of the support structure under single-point settlement and regional settlement conditions. Using in-situ testing methods on the bridge, a comparative analysis is conducted between the simulated data and the actual measurement data of the support deformation, demonstrating the feasibility of using angular change thresholds to monitor the preloading and pouring processes, and acquiring the deformation patterns at critical positions of the supports. The results show that the deformation data measured by the gyroscope closely match the simulated data, and the angular change threshold for construction process monitoring is feasible. Insufficient foundation bearing capacity leads to three different settlement conditions: first, when the single-point foundation bearing capacity is insufficient, forced displacements are applied to the four corner support rods at the bottom plane of the middle part of the support structure, resulting in significant angular changes at four measurement points, but none exceeds the warning threshold; settlement occurred at the position where the largest reaction force from the support is applied at the bottom of the support; second, when the foundation bearing capacity is insufficient in certain areas, forced displacements are applied to the middle, left, and right parts of the support structure, significantly affecting the key monitoring sections, with noticeable changes in local structural displacements; the angular changes remain within the permissible thresholds, and the reduction rates of displacement and angle during the pouring condition show minimal variation; third, when the foundation bearing capacity at the bottom of the members where each measurement point is located is insufficient, simultaneous node displacements are applied to the bottom nodes of the monitoring sections, with major settlement occurring in the regions around the bottom of the measurement points; the angular threshold increases with the increase in load, validating the effectiveness of the settlement identification and early warning method based on angular thresholds.

Keywords: foundation bearing capacity; support; deformation; finite element modeling analysis; angle threshold