A Review: Cost Analysis of RC Buildings in Differ-ent Seismic Zones

Abstract

Seismic zone variations across India from [Zone II to V], significantly influence RC building costs through base shear amplification, member reinforcement increases and ductility detailing requirements per IS 1893:2016 with Zone V structures costing 25 to 40% more than Zone II equivalents for identical G+10 configurations. This review synthesizes 20 studies (2015 to 2025) analysing cost implications of seismic coefficients (Z=0.10 to 0.36), response reduction factors (R=3 to 5) and importance factors (I=1.0 to 1.5) across building heights, materials (M25 to M40) and analysis methods (ETABS static/RSM). Zone III to IV transitions add 15 to 25% to concrete/rebar volumes; soft storey irregularities amplify costs 20 to 30% through stiffness upgrades. Quantity estimation reveals 12 to 18% steel increase per zone increment, while P-Delta effects in tall buildings add 8 to 12% to lateral systems. Findings establish cost-index relationships (?/sqm vs Z-factor) enabling economic Zone V design through optimized R-factors and regular geometry. Gaps identified include lifecycle costing, hybrid material optimizations and Zone V field validations.

Introduction

Rapid urbanization in India has increased mid-rise reinforced concrete (RC) residential construction (typically G+6 to G+10), where seismic design as per IS 1893:2016 significantly influences construction cost. Seismic zone factors (Z = 0.10 in Zone II to 0.36 in Zone V) amplify base shear by up to 3.6 times, leading to higher reinforcement (25–40%), increased concrete volume (10–20%), and overall cost escalation of ?1,400–2,500 per sqm. While low-seismic Zone II allows economical designs using M25 concrete and Fe415 steel, high-seismic Zone V requires M30–M40 concrete, Fe500 steel, and ductile detailing per IS 13920, increasing costs by 30–35% for identical building layouts.

Using ETABS, seismic analysis (Equivalent Static / Response Spectrum) shows progressive member up-sizing from Zone II to V: columns increase from 450×450 mm to 600×600 mm, beams from 300×550 mm to 350×650 mm, and reinforcement rises by 20–30%. Cost penalties are concentrated mainly in perimeter columns and beams, where support reactions increase by 40–65%, while gravity loads remain constant (IS 456, IS 875), confirming seismic coefficients as the primary cost driver.

Cost estimation based on CPWD Schedule of Rates 2023 indicates Zone V adds ?800–1,100/sqm due to higher steel quantities, concrete grades, formwork, and labor for ductile detailing. Literature consistently reports 25–35% cost premiums in Zone V, driven mainly by steel consumption (65–85 kg/sqm). Studies also show that regular building configurations, higher response reduction factors (R = 5), and hybrid systems (frames with shear walls) can reduce seismic cost premiums by 10–20%.

The present study focuses on a G+6 RC residential building (20 m × 15 m plan) analyzed across Zones II to V using ETABS, with quantities validated via IS 1200 and costs computed using CPWD SOR 2023. The objectives are to quantify material escalation, evaluate percentage cost variation from Zone II to V, and develop cost-index curves (?/sqm vs Z-factor). Results confirm that seismic zone escalation leads to about 36% higher total cost in Zone V, dominated by reinforcement and ductile detailing, while optimization through structural regularity and efficient seismic design can significantly mitigate these increases while maintaining IS 1893 compliance.

Conclusion

Review confirms seismic zoning fundamentally alters G+6 RC building economics through 3.4x base shear progression Zone II to V demanding 29% steel escalation (28 to 36T), 4.7% concrete increase and IS 13920 ductile premiums yielding ?1,650 to ?2,250/sqm (+36%) via CPWD SOR 2023 rates. Perimeter systems absorb maximum impact: exterior columns +42% reactions necessitate 6.2% Ast vs 4% baseline, beam rebar +50% (4 to 6#16mm). Zone III to IV marks design transition requiring M30/Fe500, column up-sizing (450 to 550mm), stirrup intensification (150 to 100mm c/c) where ?24% cost rise concentrates. Zone V full ductility doubles transverse steel, P-Delta demands 600mm columns maintaining drifts ?0.004h. R=5 SMRF optimization caps escalation vs irregular +45%; shear wall hybrids offer 12 to 15% steel savings though M40 offsets partially. IS 1893 conservatism overdesigns Zone II 12% steel vs gravity, suggesting tiered R-factors. Lifecycle justifies ?36L Zone V pre-mium vs disaster losses. CPWD labor +8% unconservative for semi-urban; regularity maximizes economy. G+6 (20m×15m) estab-lishes ?/sqm-Z curves guiding developers through material progression, geometry control, hybrid systems ensuring IS compliance with minimized 36% premiums across India\'s seismic spectrum.

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Copyright

Copyright © 2026 Yogesh K. Tarare, Mr. Aaquib Ansari. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.