Seismic Fragility Analysis of Low-Rise RC Buildings with Brick Infills in High Seismic Region with Alluvial Deposits

Abstract

Most of the reinforced concrete buildings in Nepal are low-rise construction, as this type of construction is the most dominant structural form adopted to construct residential buildings in urban and semi-urban neighborhoods throughout the country. The low-rise residential constructions generally follow the guidelines recommended by the Nepal Building Code, especially the mandatory rules of thumb. Although low-rise buildings have brick infills and are randomly constructed, infill walls and soil–structure interaction effects are generally neglected in the design and assessment of such structures. To this end, bare frame models that are used to represent such structures are questionable, especially when seismic vulnerability analysis is concerned. To fulfil this gap, we performed seismic vulnerability analysis of low-rise residential RC buildings considering infill walls and soil–structure interaction effects. Considering four analysis cases, we outline comparative seismic vulnerability for various analysis cases in terms of fragility functions. The sum of observations highlights that the effects of infills, and soil–structure interaction are damage state sensitive for low-rise RC buildings. Meanwhile, the design considerations will be significantly affected since some performance parameters are more sensitive than the overall fragility. We also observed that the analytical fragility models fundamentally overestimate the actual seismic fragility in the case of low-rise RC buildings.

Seismic Fragility of Aging Elevated Water Tank with Smooth Bars Considering Soil Structure Interaction

“…A comparison of Figures 6-8, shows that the amount of water present in the tank has significant impact on seismic fragility, and the impact is higher at higher damage states. While some studies such as [33] found that soil flexibility does not significantly impact the seismic fragility of low-rise RC buildings in Kathmandu Valley, our results highlight, for similar soil conditions, its importance in special structures, such as elevated water tanks. For similar overall height, structures such as overhead water tanks are more flexible than typical RC buildings such as the one used in [33].…”

“…While some studies such as [33] found that soil flexibility does not significantly impact the seismic fragility of low-rise RC buildings in Kathmandu Valley, our results highlight, for similar soil conditions, its importance in special structures, such as elevated water tanks. For similar overall height, structures such as overhead water tanks are more flexible than typical RC buildings such as the one used in [33]. A limitation of the presented study is simplification in the modelling of fluid-and soil-structure interactions.…”

Seismic Analysis of Reinforced Concrete Building with Infill Wall and Overhead Water Tank

“…In the meanwhile, because some performance criteria are more sensitive than the total fragility, design considerations will be severely impacted. In the case of low-rise RC buildings, we also noticed that the analytical fragility models significantly overstate the real seismic fragility [1]. The findings demonstrate that infills alter the floor response spectra and peak floor accelerations.…”

The Modification of the Estimated Seismic Behaviour of R/C Low-Rise Buildings Due to SSI

“…A uniform load of 34 kN/m is applied upon the R/C horizontal beam, which accounts for the entire dead and live load of typical R/C buildings with domestic/residential and office use as well as the self-weight of perimetric masonry walls [43]. The contribution of the masonry wall infills to the frame stiffness is neglected [44,45], since the present study focuses on the effect of the relative asymmetry of the vertical R/C elements on the structural seismic response. The 2D R/C frames are dimensioned as ordinary buildings (importance factor γΙ = 1.0) according to the seismic provisions of the relevant Eurocodes [1,46] for a ductility class medium (DCM), including capacity design of joints and R/C elements in shear, and assumed to stand on a rigid soil of a site with zone ground acceleration ag = 0.36 g. The design assumptions, according to the seismic code [1], are design spectrum of type 1, viscous damping ratio of 5%, soil type C and behaviour factor estimated for each building frame by [1].…”