Seismic Vulnerability Assessment and Retrofit Verification of Public Service Buildings in a Himalayan Region: Rapid Visual Screening and ETABS-Based Structural Validation

Abstract

Public service buildings such as hospitals and schools are critical to community resilience in earthquake-prone Himalayan regions, yet a large proportion of this infrastructure consists of aging and non-engineered construction. This study presents a data-oriented seismic vulnerability assessment of 19 public sector buildings, comprising hospitals and educational institutions, using Rapid Visual Screening (RVS) supported by detailed field surveys. The assessed buildings include multiple structural blocks constructed between 1919 and 2015, representing unreinforced masonry: BM-brick masonry, HD-half-dressed stone masonry, RR-random rubble masonry, reinforced cement concrete (RCC), and hybrid structural systems. The assessment integrates building typology, year of construction, occupancy, observed structural and non-structural distress, and the presence or absence of seismic-resistant features, following FEMA P-154 and Indian Standards (IS 1893, IS 4326, IS 13935). Results indicate that a substantial majority of the surveyed buildings fall within moderate to high seismic vulnerability categories, with unreinforced masonry structures showing the poorest performance. Common deficiencies recorded across the dataset include the absence of seismic bands and vertical reinforcements, extensive horizontal, vertical, and diagonal cracking, severe dampness from foundation level, material degradation, and poor connectivity between structural elements. Even newer RCC and hybrid buildings demonstrated moderate vulnerability due to inadequate detailing, corrosion of reinforcement, and unanchored non-structural components. To quantitatively verify the effectiveness of the retrofit measures recommended by the RVS-based assessment, two representative structural typologies identified as high-risk in the survey- a three-storey (G+2) RC framed building with masonry infill and a two-storey (G+1) masonry building—were further evaluated through detailed linear structural modelling and analysis in ETABS, in accordance with IS 456:2000 and IS 13920:2016. The retrofit schemes evaluated (column section jacketing for the G+2 RC frame, and lateral stiffening for the G+1 masonry structure) produced substantial improvements: storey drift and displacement reduced by up to 94%, storey stiffness increased by up to about 20 times, and all previously over-stressed columns (demand/capacity ratio >1.0) were brought within safe design limits (0.33–0.74) after retrofitting. The study establishes a clear, data-based relationship between construction typology, age, observed distress, and seismic vulnerability, and demonstrates through structural analysis that the recommended retrofit interventions are effective in achieving code-compliant seismic performance. The findings confirm that RVS is an effective and scalable tool for prioritizing seismic retrofitting of public buildings, and that the proposed retrofit strategies are structurally verifiable using standard analysis software. The results underscore the urgent need for code-compliant retrofitting and maintenance interventions to reduce seismic risk and ensure life safety and post-disaster functionality of critical public infrastructure in Himalayan seismic zones.

Introduction

This study assesses the seismic vulnerability of public hospitals and schools in a Himalayan region classified as Seismic Zone IV. The region is highly earthquake-prone because of the active collision between the Indian and Eurasian tectonic plates. Since hospitals and schools are critical facilities that must remain functional during disasters, evaluating their earthquake safety is particularly important.

The research examines 19 public buildings consisting of hospitals and schools, with construction dates ranging from 1919 to 2015. The buildings include half-dressed stone masonry, random rubble masonry, brick masonry, RCC, and hybrid structures. Older buildings are mainly unreinforced masonry and commonly lack earthquake-resistant features such as seismic bands and vertical reinforcement. Newer RCC and hybrid buildings show improved structural systems but still have problems such as poor reinforcement detailing, stiffness irregularities, corrosion, and inadequate seismic compliance.

A Rapid Visual Screening (RVS) method was used to evaluate structural and environmental factors including building type, number of storeys, plan and vertical irregularities, seismic-resistant features, cracks, dampness, material deterioration, site conditions, and occupancy. Two high-risk building types were then selected for detailed ETABS structural analysis: a G+2 RCC frame with masonry infill and a G+1 masonry building. Retrofit measures were studied to determine their effectiveness in improving structural performance.

Major Findings

• Unreinforced masonry (URM) buildings were found to be the most vulnerable, particularly stone and random rubble masonry structures.
• Many masonry buildings lack plinth, lintel, and roof seismic bands and vertical reinforcement.
• Common damage indicators include diagonal, horizontal, and vertical cracks, dampness, peeling plaster, and material deterioration.
• Moisture and dampness significantly reduce material strength and increase seismic vulnerability.
• RCC buildings generally perform better but may still suffer from poor reinforcement detailing, corrosion, soft-storey conditions, and inadequate connections.
• Hybrid buildings can develop stiffness discontinuities and stress concentrations at masonry-RCC interfaces.
• High occupancy in hospitals and schools increases the potential life-safety consequences of structural failure.
• The study supports the use of RVS for prioritizing buildings for detailed assessment and retrofitting, followed by structural modelling where necessary.

Conclusion

Based on the data-oriented seismic vulnerability assessment of public hospitals and schools conducted using Rapid Visual Screening, together with ETABS-based structural verification of representative retrofit measures, the following conclusions are drawn: 1) A significant proportion of the surveyed public service buildings fall within moderate to high seismic vulnerability categories, indicating substantial seismic risk in the existing building stock of the Himalayan seismic zone. 2) Non-engineered masonry construction, including half-dressed stone masonry, random rubble masonry, and brick masonry, emerges as the most critical determinant of seismic vulnerability, primarily due to the absence of seismic bands, lack of vertical reinforcement, and poor construction practices. 3) Moisture-induced material degradation is identified as a major aggravating factor across all building typologies, leading to reduced material strength, accelerated crack propagation, and increased likelihood of brittle failure during seismic events. 4) Unreinforced masonry and hybrid buildings dominate the high-risk category, largely due to incremental development, stiffness discontinuities, and weak masonry-RCC interfaces, while reinforced cement concrete (RCC) buildings generally exhibit moderate vulnerability. 5) Although RCC structures demonstrate comparatively better global seismic performance, deficiencies in ductile detailing, soft-storey configurations, corrosion of reinforcement, and inadequate maintenance prevent many of them from achieving low-risk classifications. 6) The strong correlation between observed damage patterns, RVS classifications, and codal deficiencies confirms that construction typology is a more influential factor in seismic risk than building use or age alone. 7) The study confirms that Rapid Visual Screening is a reliable, scalable, and effective first-level tool for seismic vulnerability assessment and prioritization of buildings requiring detailed evaluation and retrofitting. 8) ETABS-based structural analysis of a representative G+2 RC framed structure confirms that column section jacketing (450x450 mm, M15 to 550x550 mm, M30) resolves all identified member-level deficiencies, reducing column demand/capacity ratios from a range of 1.002–1.067 (over-stressed) to 0.332–0.735 (safe), while storey drift remains within the IS 1893 permissible limit of 0.004 in both the existing and retrofitted configurations. 9) ETABS-based structural analysis of a representative G+1 masonry structure confirms that the proposed lateral stiffening retrofit substantially improves global seismic performance, reducing maximum storey displacement by 88–94% and storey drift by approximately an order of magnitude, while increasing storey stiffness by approximately 9–20 times; the corresponding 18% increase in base shear demand should be accounted for in the design of retrofit elements and their connections. 10) Code-compliant retrofitting in accordance with IS 13935 has the potential to significantly enhance life safety, structural performance, and post-earthquake functionality of existing public buildings, and the ETABS case studies presented here provide quantitative, code-referenced verification that such retrofit strategies are structurally effective. 11) Overall, the findings highlight the urgent need for systematic seismic retrofitting, improved maintenance practices, and strict enforcement of seismic design and construction codes to reduce earthquake risk in hospitals and schools located in seismically active regions.

References

[1] Amiraslanzadeh, F., Ikemoto, Y., & Miyajima, M. (2012). Comparative analysis of seismic retrofitting methods for unreinforced masonry buildings. Journal of Earthquake Engineering, 16(6), 1-18. [2] Bureau of Indian Standards (BIS). (1993). IS 4326: Earthquake resistant design and construction of buildings -Code of practice. New Delhi, India. [3] Bureau of Indian Standards (BIS). (2000). IS 456: Plain and reinforced concrete -Code of practice. New Delhi, India. [4] Bureau of Indian Standards (BIS). (2009). IS 13935: Seismic evaluation, repair and strengthening of masonry buildings -Guidelines. New Delhi, India. [5] Bureau of Indian Standards (BIS). (2016). IS 1893 (Part 1): Criteria for earthquake resistant design of structures. New Delhi, India. [6] Bureau of Indian Standards (BIS). (2016). IS 13920: Ductile design and detailing of reinforced concrete structures subjected to seismic forces -Code of practice. New Delhi, India. [7] Federal Emergency Management Agency (FEMA). (2015). FEMA P-154: Rapid Visual Screening of Buildings for Potential Seismic Hazards. Washington, DC, USA. [8] Middlemiss, C. S. (1910). The Kangra Earthquake of 4th April, 1905. Memoirs of the Geological Survey of India, Vol. 26. [9] Murty, C. V. R., Sinha, R., Goyal, A., Krishna, C., Meena, M., & Shinde, R. (2014). Detailed Project Report on Seismic Strengthening of Existing Buildings. IIT Bombay & IIT Madras, submitted to National Disaster Management Authority, Government of India. [10] National Disaster Management Authority (NDMA). (2014). Guidelines on Earthquake Management. Government of India, New Delhi. [11] Sawhney, A. (2014). Grand challenges for the Indian construction industry. Journal of Construction Engineering and Management, 140(12), 04014052. [12] Dritsos, S. E. (2007). Seismic strengthening of columns by adding new concrete. Bulletin of the New Zealand Society for Earthquake Engineering, 40(2), 49-72. [13] Dritsos, S. E. (2005). Seismic retrofit of buildings: A Greek perspective. Bulletin of the New Zealand Society for Earthquake Engineering, 38(3), 165-181. [14] Das, S., Sarkar, S., & Kanungo, D. P. (2023). A critical review on landslide susceptibility zonation: Recent trends, techniques, and practices in Indian Himalaya. Natural Hazards, 115, 23-72. [15] Moseley, V. J., Dritsos, S. E., & Kolaksis, D. L. (2007). Pre-earthquake fuzzy logic and neural network based rapid visual screening of buildings. Structural Engineering and Mechanics, 27(1), 77-97.

Copyright

Copyright © 2026 Vijender Singh, Dr. Sanjay Kumar Sharma. 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.