International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 08 Issue: 09 | Sep 2021 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 915 Influence of Angle of Incidence in Inelastic Response of an Idealized Single-Story R/C Structural System due to Bi-Directional Ground Motion Krishnendu Chowdhury 1 , Utsha Chowdhury 2 , Abhishek Hazra 3 1,2 Assistant Professor, Department of Civil Engineering, K K College of Engineering & Management, Jharkhand, India 3 Assistant Professor, Department of Civil Engineering, Narula Institute of Technology, West Bengal, India ----------------------------------------------------------------------***--------------------------------------------------------------------- Abstract – This study examines the influence of angle of incidence in inelastic response of an idealized single-story R/C structural system subjected to bi-directional ground motions. In this work the models have various degree of inelasticity, are subjected to a set of near-fault and far-field ground motion pairs with different characteristics for both the symmetric and asymmetric structural system. It is demonstrated that by applying the bi-directional ground motions only along the principal axis of the building that estimates the critical response of the structural elements due to the variation in any angle of incidence of ground motion in an inelastic sense. The result implies that in accurate estimation of the structural performance by the by the progressive damaging torsional effect in R/C structures. This damaging effect predicted by using the single-storied idealized model that represent the degrading behavior of the R/C load-resisting elements. In this study, the response of flexible and stiff side elements of a structure have been changed due to the variation of critical angle of orientation in an inelastic zone that obtained the maximum critical response in different angles for every 15° interval in anticlockwise sense with the entire 360° orientation of ground motions. Key Words: Seismic response, Inelastic response, Near-fault, Far-field, Angle of incidence, Bi-directional, Time period ratio. 1. INTRODUCTION The estimation of anticipated seismic damage of structures due to a specific earthquake ground motion is a prime area of research in seismic risk assessment. Generally, buildings are damaged by the dynamic load that destruct the significant life and financial losses. In that case two major requirements that the structural performance and the ground motion intensity initiate to evaluate the structural damage probable of an earthquake. The strong motion database, horizontal directional components of motions are usually applied along the principal axis of structure which are available along orientations of recording for the seismic design of structures. Ground motions deals like a vector formation. It is still unclear that in which particular direction ground motions are attacked on a structure. Therefore, the rotational components are usually neglected whereas the translational parts are given in two horizontal and one vertical direction. Generally, the recording sensors i.e., north-south (N- S) and east-west (E-W) directions are aligned on the principal axis of structure. It implicit the existing of possible different directions of seismic incidence by rotating ground motion pairs. Therefore, this incidence of seismic orientation leads to an increasing the response of structural dynamic. The estimation of maximum seismic response of structure associated to the ground motions excitation using the variation of angle of incidence is already studied by different researcher throughout the globe. One of the valuable investigations into estimated the inelastic response on several engineering demand parameters (EDPs) of single-story asymmetric structural system with the peak inelastic deformation demand due to bi-directional ground excitation displaced that there was not a particular angle of incidence for all maximum EDPs values [1]. Another investigation on a single-story torsionally-stiff symmetric and as well as torsionally-flexible asymmetric system in inelastic response owing to bi-directional near-fault (NF) ground motion makes a critical angle of incidence depending on several engineering demand parameters (EDPs). This study demonstrated that the incidence angle leads maximum displacement of structure depending on fault-normal (FN) and fault-parallel (FP) components of ground motion [2]. Furthermore, the response in nonlinear dynamic analysis of a 3D single-story R/C frames under bi-directional ground motion evaluated that the critical incidence angle of ground motion is more efficient for the design of R/C frame structure [3]. Some researchers [4] have been estimated the response of single-story asymmetric building in inelastic seismic response subjected to bi-directional ground motion