Performance-Based Seismic Assessment of a Steel Moment-Resisting Frame Designed as per IS 18168:2023 Using Incremental Dynamic Analysis

Steel moment-resisting frames (SMRFs) are widely used for multi-storey buildings, yet code-based design checks the structure at one design-level force and says little about how often a given performance limit would be exceeded as shaking becomes stronger. This project carries out a performance-based seismic assessment of a G+7 steel SMRF of 20.1 m × 20.1 m plan, located in Seismic Zone III (Mumbai), using Incremental Dynamic Analysis (IDA). The building was modelled in ETABS with Fe 350 steel, 150 mm interior and 250 mm exterior walls and a live load of 3 kN/m².Five ground-motion records from the Chamoli (1999), India–Burma (1988) and Uttarkashi (1991) earthquakes were chosen following the selection criteria of FEMA P695. The fundamental period obtained from modal analysis was used to read the spectral acceleration Sa(T1) of each record, and each record was normalised by 1/Sa(T1). The normalised records were then scaled in steps of 2 and applied as time histories under the service load combinations DL+LL ± THAX/THAY and DL ± THAX/THAY. The maximum storey drift was recorded for every scale factor until it exceeded 0.4 % (and further for each record), and the scale factor producing exactly 0.4 % drift was found by linear interpolation for each record. The five scale factors were arranged in ascending order, and a lognormal fragility curve was built from the mean and standard deviation of their natural logarithms.The fundamental period of the model from modal analysis was T1 = 2.379 s. The scale factors that produce a maximum storey drift of 0.4 % were 6.65, 12.60, 18.58, 28.32 and 28.34 for the five records. The lognormal fit gave λ = 2.8075 and β = 0.6119, so the scale factor at 50% probability (the median) is 16.57.The structure was finally designed according to IS 800:2007 and the ductile-detailing provisions of IS 18168:2023 using the scale factor corresponding to 50 % probability. The report also reviews published IDA studies on steel, composite and concrete frames to place the work in context.Layout of the report. Chapter 1 introduces the problem, aim and scope. Chapter 2 reviews the literature on performance-based design, IDA, ground-motion selection and fragility. Chapter 3 describes the methodology. Chapter 4 describes the structural model, loadsand design data. Chapter 5 presents the results and discussion. Chapter 6 gives the conclusions and the scope for future work..