PSI - Issue 70

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 70 (2025) 129–136

Structural Integrity and Interactions of Materials in Civil Engineering Structures (SIIMCES-2025) Seismic Response Reduction Factor Assessment of a 4-Storey Special Steel Moment Resisting Frame Pradeep Ushakumari Abhinand a , Muhamed Safeer Pandikkadavath b,*

a Post Graduate Scholar in Structural Engineering, Department of Civil Engineering, National Institute of Technology, Kozhikode, India b Assistant Professor, Department of Civil Engineering, National Institute of Technology, Kozhikode, India

Abstract The seismic design of special moment resisting frames (SMRFs) fundamentally depends on the seismic response reduction factor ( R ), which accounts for structural ductility ( R μ ), redundancy, and material overstrength ( Ω d ) to reduce the elastic base shear to a design-level force. The Indian seismic code IS 1893 specifies empirical R values based solely on the type of lateral force-resisting system, without explicitly addressing structural parameters such as storey height and geometric configuration. This study investigates the R -factor for a 4-storey SMRF designed according to IS 1893 using the modal response spectrum method. A detailed nonlinear model is developed in OpenSees incorporating appropriate inelastic material properties. Nonlinear incremental dynamic analysis (IDA) is conducted using a suite of far-field ground motions. The inter-storey drift ratio (IDR) and peak ground acceleration (PGA) are employed as the engineering demand parameter (EDP) and intensity measure (IM), respectively. The fully developed seismic base shear ( V y ) corresponding to a target drift level is extracted and compared with the elastic base shear ( V e ) from linear dynamic analysis to estimate the system’s R -factor. The computed R -factor is then contrasted with the code-specified value. Results indicate that the evaluated R -factor exceeds the IS 1893 recommendation by 25%, and the Ω -factor is 62% higher for the examined frame. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of International Conference on Structural Integrity Organizers

Keywords: Seismic response reduction factor; Special steel moment resisting frame; Inter-storey drift ratio; Incremental dynamic analysis.

* Corresponding author. Tel.: +91-9895599785. E-mail address: msafeerpk@nitc.ac.in

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of International Conference on Structural Integrity Organizers 10.1016/j.prostr.2025.07.035