PSI - Issue 70

Vivek Kumar C et al. / Procedia Structural Integrity 70 (2025) 97–104

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2. Model Configurations A G+15 multi-storey structural steel building with X bracings was designed using ETABS 21 software. The study compared steel structures with and without X bracing systems across zones. An SMRF modelled a 25 m x 22.5 m G+15 building on Type 2 soil in seismic zone IV. To evaluate seismic loading, ten scenarios were modelled, resulting in four models with X bracing. a. Case 1 – Steel Structure without bracing system located in Zone IV. b. Case 2 – Steel Structure with bracing system with X Bracing at centre position c. Case 3 – Steel Structure with bracing system with X Bracing at corner/end position d. Case 4 – Steel Structure with bracing system with X Bracing at alternate position of each floor. The IS codal provisions IS 875: 2015 (Part 3) and IS 1893:2016 (Part 1) were used in seismic evaluation. The study compared steel structures with and without X bracing systems across different zones. To evaluate seismic loading, three X bracing positions were developed. The seismic and wind loading patterns were given in tables 1 and 2.

Fig.2. Model’s (a) Plan view (b) 3 -Dimensional view

Fig.3(a). Unbraced structure

Fig.3(b). X Bracing system in centre

Fig.3(c). X Bracing system in corners

Fig.3(d). X Bracing in alternate floor system

3. Structural Configurations

Base Shear (V B ) is measured using the formula given as: V B = A h . W -- (1) --- (2) IS 1893:2016 (Part 1), Table 2 displays factors used in structural design calculations. Z represented the zone factor, I indicate importance factor, and R is for response reduction factor. The average response acceleration coefficient for rock and soil sites, as detailed in IS 1893:2016 (part 1), is expressed as S a /g. with 5% structural damping. = ℎ 2 ∑ ℎ 2 = 1 --- (3) Table 1. Seismic and Wind Load Coefficients as per IS 1893 : 2016 and IS 875 (Part 3) : 2015 Configurations Value Zone Factor -Z 0.24 Basic Wind Speed - V b 44 m/s Structural Importance factor -I 1.5 Terrain Category – k 1 1 Soil type - S 1 Building Importance Factor – k 2 1.02 Response reduction factor - R 5 Topography factor – k 3 1.0 Damping Ratio 0.05 Cyclonic region importance factor – k 4 1.0 (1) ℎ = 2 R g