Estimation of design axial stiffness of reinforcing piles in vertical extension remodelling process using numerical computation

摘要

In this study, optimal design axial stiffness of piles of the piled-raft in a vertical extension remodelled building will be estimated through theoretical and numerical approach. The range of the axial stiffness of existing piles (K-ve) were displayed and the upper limit of the deteriorated existing piles were proposed by using the formula by Randolph and Wroth (1978), along with 38 cases of field data. In addition, the required axial stiffness of reinforcing piles (K-vr) in vertical extended building will be estimated based on the proposed axial stiffness of existing piles, and through computer-based method, PLAXIS 3D and Yonsei Piled-Raft (YSPR). After the validation of both numerical models used in this study, the calculation was first carried out to estimate the reference axial stiffness by using PLAXIS 3D. After the evaluation of the reference value, the required axial stiffness of reinforcing pile to rehabilitate the structural stability will be estimated by substituting the existing piles with axial stiffness of deteriorated existing piles using YSPR. The required axial stiffness of reinforcing pile will be displayed by three different slenderness ratio (L/D) and two different end-bearing condition. As a result, it was found that the axial stiffness of end-bearing reinforcing pile requires significant degree of increase to compensate with the deterioration of existing piles of the vertical extension remodelling.