Seismic Fragility Assessment of Columns in a Piloti-Type Building Retrofitted with Additional Shear Walls

Hoang Dang-Vu,Kihak Lee,Jiuk Shin

doi:10.3390/su12166530

Abstract

This study evaluated the influence of additional shear walls, constructed on the first floor, as strengthening methods for a piloti-type building subjected to earthquake loadings. Piloti-type buildings are commonly designed as urban structures in many cities of South Korea. The existence of just columns on the first floor of the building is a feature that is advantageous from an architectural viewpoint, and yet has potential structural disadvantages. Such columns usually exhibit shear–axial failure, due to inherent vertical and horizontal irregularities and insufficient seismic reinforcements. Among several retrofitting methods, including additional braces, carbon fiber reinforced polymers, dampers, and so forth, this research considered reinforced concrete shear walls to improve the seismic responses of piloti buildings. A parametric analysis of the location of the retrofitted shear walls in a typical piloti building was implemented using the Zeus-NL program. Nonlinear time history analysis and incremental dynamic analysis were performed to comparatively evaluate the structure’s seismic responses and fragility curves before and after retrofit.

Highlights

Seismic response evaluations have been conducted on existing structures and their retrofitted versions
Choudhury and Kaushik [12] assessed the vulnerability of reinforced concrete (RC) buildings with open ground stories, considering wall openings
The research clarified the misperception that using openings in upper stories to reduce structure stiffness offsets the soft story effect, which is the main reason for the collapse of open ground story RC buildings

Summary

Introduction

Seismic response evaluations have been conducted on existing structures and their retrofitted versions. Motivated by the mentioned research, this study conducted a fragility assessment of a piloti-type building before and after being retrofitted with shear walls on the first floor. In the target piloti building, it is worth noting the core wall in the corner of the ffiirst fflloor, which increases the vulnerability of the columns, especiallllyy corrnneerr ccoolluummnnss,, dduuee ttoo tthhee ttoorrssiioonnaall eeffffeecctt. Besides their practical advantage and simplicity, shear walls were intentionally used to mitigate the torsional effffect existing in the target piloti building due to the corner core wall, rather than other retrofifittttiinngg mmeetthhooddss. Yield ddiisspplalcaecmeemnte.nFtm. :FMm:axMimauxmimsturemngsthtr. eδnmg:tDh.ispδlmac:eDmiesnpt laatcmemaxeimnutmatstmrenagxtihm. um strength. k: Initial stiffness

Input Ground Motions and Design Spectrum

Hysteretic Curves

Column Fragility Curves

Findings

Conclusions