PSI - Issue 70

Pradeep Ushakumari Abhinand et al. / Procedia Structural Integrity 70 (2025) 129–136

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investigation is specifically on the seismic performance and design considerations of a representative exterior perimeter SMRF as marked in Figure 2. The SMRF considered in this study has been designed in accordance with the latest Indian seismic design provisions. Specifically, the seismic design follows the guidelines prescribed in IS 1893 (Part 1): 2016 for earthquake resistant design of structures, IS 800: 2007 for general construction in steel, and IS 18168: 2023 for ductile detailing of steel structures, ensuring comprehensive compliance with current national standards (IS 800, 2007; IS1893(1), 2016; IS 18168, 2023). The SMRF is considered to be situated on hard soil, classified as Type II per the IS soil classification system. The factor of importance for the building ( I ) is taken as 1.0, consistent with a standard occupancy category, while the seismic zone is taken as Zone V, representing the highest level of seismic hazard in the Indian seismic zoning map. The response reduction R -factor and Ω d are adopted as 5.0 and 3.0, respectively, as recommended for ductile SMRFs. The design needed first mode natural period of the structure is estimated using empirical expressions, which are based on the height of the structure. The resulting approximate fundamental period of the frame is noted as 0.73 seconds. Using this and other relevant seismic parameters, the seismic base shear coefficient ( A h ) is determined to be 0.049. Accordingly, the total design associated base shear for the study SMRF is obtained as 582 kN. To determine the lateral seismic forces distribution along the frame height, both the equivalent static lateral force (ELF) method and the modal response spectrum (MRS) method are employed. The base shear derived from the MRS analysis is scaled up to meet the base shear value obtained from the ELF approach, ensuring consistency in seismic demand estimation. The final design base shear or V d and its corresponding distribution are then applied across the height of the frame. Additionally, an accidental torsional eccentricity of 5% with respect to the building plan geometry is considered to account for unforeseen asymmetries and to ensure a conservative design approach. The structural members are designed for the governing load combinations involving both gravity and seismic loads, as stipulated in IS codes. The column and beam cross-sections are adopted such that they fulfil the strong column – weak beam capacity limit criterion, which is essential to promote ductile failure mechanisms and to ensure adequate energy dissipation during seismic events. For all steel components, the Poisson’s ratio and Youngs modulus of elasticity are assumed to be 0.3 and 200 GPa, respectively. The design yield strength ( f y ) of steel is taken as 250 MPa, and a yield overstrength factor ( R y ) of 1.1 is considered to account for the inherent material overstrength (IBC SEAOC, 2021; Pandikkadavath & Sahoo, 2016a; Pandikkadavath & Sahoo, 2016b, Pandikkadavath & Sahoo, 2017). The selected cross-sections are further verified to ensure compliance with the width-to-thickness ratio limits recommended for highly ductile as well as plastic cross-sectioned members. Both the flange and web components of the sections are checked against the limiting slenderness criteria prescribed in relevant standards to ensure that local buckling does not precede yielding, thereby enabling the members to exhibit stable and ductile behaviour under seismic loading (Pandikkadavath & Sahoo, 2019; Shaijal et al ., 2022, Pandikkadavath et al ., 2022). It is worth noting that the final cross-sections adopted for the SMRF members are built-up I-sections fabricated using plate elements, as detailed in Table 1. For instance, the designation 400×12W_130×25F refers to an I-section composed of a web plate with a depth of 400 mm and an effective thickness of 12 mm, along with flange plates that are 130 mm wide and 25 mm thick. Such plate constructed built-up sections are commonly employed to meet the required strength and ductility while offering flexibility in optimizing the member dimensions based on design demands. For the numerical investigation of the 4-storey SMRF, an idealized two-dimensional model is developed using the OpenSees framework (Mazzoni et al., 2006). Both columns and beams are created as elastic segments with zero length rotational springs at either ends. These springs can facilitate the near end plastic hinge formation and can represent the validated inelastic flexural response of the structural segments, as per the recommended modelling approach (Ibarra et al ., 2005; Lignose & Krawingler, 2011; Krawingler, 1978). That is, these zero-length rotational springs are capable of manoeuvring the multilinear backbone curves to capture the nonlinear hysteretic response of Table 1. The final column and beam cross-section details of the study frame. Storey Beam Column 4 400X12W_130X25F 500X12W_150X25F 3 450X12W_160X25F 550X16W_180X25F 2 480X12W_190X25F 600X16W_200X25F 1 500X12W_200X25F 650X16W_240X25F