Estimation of Framed Building Response to the Induced Settlements of Shallow Tunneling

Induced ground surface settlement due to tunneling causes damages to the adjacent structures. Relative stiffness approach is a well-known method of estimation of these probable damages based on soil to building stiffness ratio. Importance of calculation of the structural stiffness in an accurate way necessitates a comparison between the results of different available methods. In this study, the numerical analysis is performed to recognize the most suitable method of the calculation of the bending stiffness of the buildings. The obtained modification factors are then plotted versus the calculated relative stiffness. The numerical results show that the amounts of the settlement that are underestimated by conventional methods. Therefore, in this paper a correction factor is proposed to improve previous modification factors. The proposed approach maintains the simplicity in the calculation process besides of its more accurate results.   In conventional methods, the ground settlement of the greenfield condition is evaluated, and then, applied to the investigated building. The induced deformation to the building is affected by its stiffness. Therefore, estimating an accurate value of the stiffness leads to the results for better understanding of the response of the building. Various approaches such as the parallel axes, Lambe and Meyerhof methods are available to calculate the bending stiffness of a building. However, selection of an efficient method for calculation of the building stiffness is important. The problem is analyzed by finite element method based PLAXIS2D software considering different geometries. It includes buildings with variable numbers of stories and different widths of footings. Settlement trough is obtained for each condition and bending stiffness of each building is calculated based on the length of the hogging and the sagging part of the building. The deflection ratio and the modification factors are then calculated. The obtained modification factors versus the relative stiffness are plotted in a semi-logarithmic domain. The obtained results from this research work indicate that the conventional methods of estimation of the building deformation due to tunneling predict underestimated values in the sagging part of the settlement where the majority of the building is damaged. Therefore, this study has been made to look into this problem by introducing a new correction factor. By using this factor, the damage can accurately be determined.