Protection technology and 3D finite element analysis for exterior walls of historic buildings subjected to underground addition and core-replacement renovation

Against the backdrop of the coordinated development of urban renewal and heritage building conservation, taking the 42C plot of Block 42 in Shanghai Suhe Bay as a case study, this paper addresses the stability challenges of historical building facades induced by deep foundation pit construction disturbances. An active protection scheme integrating “anchor static-pressed steel pipe pile underpinning and back-braced steel frame strengthening” was proposed. The mechanical reliability of this scheme was verified through single pile bearing capacity calculations and raft punching shear verifications. To systematically evaluate the impact of construction on the retained building and the surrounding environment, a three-dimensional finite element model was established using Midas GTS NX software. The entire process, from mixing pile construction and diaphragm wall trenching to foundation pit excavation, was simulated to analyze structural deformation and internal force responses. Additionally, a specialized analysis of the temporary strengthening system was conducted using Midas Gen 2020 software. The results indicate that the proposed underpinning and strengthening scheme can effectively control the deformation and structural internal forces of the retained historical facade and its foundation, with all indicators meeting current code requirements. Meanwhile, the deformation of the adjacent subway tunnel is strictly controlled, and the tunnel response remains well below the engineering safety control limits. This study can provide valuable technical references for similar projects.