Civil Insight: A Technical Magazine Volume 2 | Page 19

CIVIL INSIGHT 2018 TEACHERS’ SECTION 19 A Study of Evaluation of Transverse Racking Response of Underground Rectangular Structure Er. Kameshwar Sahani Lecturer Department of Civil and Geomatics Engineering, Kathmandu University, Nepal [email protected] Abstract The brief study of seismic analysis of underground rectangular structure is presented in this paper. Underground Substructure facilities are the important part of the modern society constructions. The use of underground facilities and infrastructures is the result of lack of space for those facilities above ground and the requirement of having that infrastructure below grade. The seismic performance of shallow cut- and-cover box tunnel has been relatively poor in comparison to the performance of bored mined tunnels. Road tunnels are very practical alternatives to cross physical obstruction or transverse through physical barriers such as mountains or snow bound areas. The evaluation procedures for transverse response of tunnel structures is based on the simplifi ed analytical method. An effort has been made in the present study to fi nd racking deformation of underground structure by analytical method using Nepal earthquake data (25th April 2015). Keywords: Soil-Structure interaction;Free-fi eld deformation; Flexibility ratio; Racking deformation. INTRODUCTION Underground rectangular structures undergo racking deformation during seismic shaking. The racking deformation is caused primarily by seismic waves propagating perpendicular to the tunnel along longitudinal axis, causing deformations in the plane of the tunnel cross section (Wang, 1993; Owen and Scholl, 1981). Vertically propagating shear waves are generally considered the most critical type of waves for this mode of deformation. Figure 1: Ovaling/Racking deformation of structure (Source: Wang et al., 1993)