Force Analysis Of The Replacement Structure And Jacking Load Analysis During Jacking And Tilt Correctio

During the jacking-up rectification process,structural underpinning is one of the key technology.Unlike underpinning techniques employed in building relocation or synchronous jacking,jacking rectification involves significant relative displacement between underpinning joints.Thus,it becomes imperative to investigate the mechanical behavior of underpinning structures,taking into account the relative displacement of joints.This paper primarily focuses on the following research endeavors:(1)Firstly,the experimental specimen of underpinning structure included two UJs connected by girders(CG).A spring support was adopted for one joint,and a roller support for another joint,to simulate the relative displacement between the two joints.Three specimens were designed with different heights of the connection girders between the two UJs.It was found that diagonal cracks appeared on both joints and shear failure of the underpinning joint on the spring support occurred.The bearing capacity of the underpinning structure was higher with connection girder higher.However,the bearing capacity was 14.1-21.5% lower than the single joint under the condition of relative displacement.(2)Finite element analysis was utilized to analyze the underpinning joint test,and the results were compared with the experimental findings.Steel strain,joint settlement,and joint failure mode were evaluated and compared.The finite element analysis results demonstrated good agreement with the experimental results.Stress analysis of the underpinning beam revealed that the inclination angle of the compression zone in the underpinning structure was smaller and more dispersed compared to that of the single joint,resulting in a lower bearing capacity for the underpinning structure.Analysis of the connection girder indicated that one end was subjected to tensile stress while the other end experienced compressive stress.Parameter analysis for different relative displacements showed that the bearing capacity of the underpinning joint increased with decreasing relative displacement.Therefore,the consideration of relative displacement in the design is crucial to avoid potential safety issues associated with an inadequate design.(3)Based on a practical engineering rectification project,numerical simulations were employed to assess the influence of both local and overall settlement on the structural response.Load application and structural design were conducted based on real-world conditions.The local settlement analyses were performed to investigate the variations in internal forces of critical components under different settlement scenarios.Furthermore,actual overall settlement was applied to analyze the settlement effects and determine the real structural response.Based on these research,a method was proposed to calculate the jacking load considering the axial force changes before and after structural settlement.Through comparison with actual data,the proposed design load exhibited a consistent trend with the actual jacking load variations.It was observed that the simulated maximum jacking force exceeded the maximum jacking force during the jacking process,providing valuable insights for the design of jacking load for underpinning joints.