Figures 6,7 and 8 present detailed findings on life-threatening parameters outlined in Fig. 4 for all 179 RCC buildings. Among them, Fig. 6 highlights that 14 buildings are situated on a creeping riverbed, 30 possess heavy upper storeys, 20 feature large unanchored projections, and 21 have open stories with slender columns. Additionally, Fig. 7 reveals that 12 buildings exhibit floating columns, 28 have slender columns with stiff beams, and 24 have flat slabs lacking structural walls, classifying them as high-risk structures warranting red tagging and rendering them unusable. Furthermore, Fig. 7 illustrates that 48 buildings lack gaps with adjoining structures, while 19 have heavy parapet walls susceptible to earthquake damage. Moreover, Fig. 8 indicates that 30 buildings boast heavy balconies, 63 have large story heights or expansive room sizes, 69 feature sizable window openings comprising over 50% of the wall area, and 45 possess unanchored water tanks. These structures fall under the yellow-tag category as per NDMA guidelines, necessitating structural interventions to enhance their seismic resilience.
Figures 9 through 12 provide detailed insights into the life-threatening parameters outlined in Fig. 5 for all 120 masonry buildings. Among these structures, Fig. 9 reveals that 9 are adjacent to deteriorated buildings, 15 feature heavier upper storeys, 19 possess large unanchored overhangs, and 11 exhibit a plan aspect ratio exceeding 4.0. Furthermore, Fig. 10 illustrates that out of the 120 buildings, 49 lack continuous lintel bands, 50 have door/window openings positioned close to wall corners, 19 boast thick walls or traverse stones, and 18 have stiff upper storeys with walls that are not interconnected at corners. In addition, Fig. 11 highlights that 10 masonry buildings have heavy cantilever balconies, 15 showcase separations in walls and roofs, and 28 display cracks in the walls. Notably, from the same figure, it is evident that 58 masonry buildings lack gaps, 13 feature heavy parapet walls, 11 rest on sloped ground, and 12 lack connections to the sloped ground they occupy. Lastly, Fig. 12 underscores that 50 masonry buildings have unanchored water tanks on the roof, 27 exhibit vertical cracks in the walls, 29 possess poor-quality construction materials, and 23 boast large room sizes and expansive window openings covering more than 50% of the wall area.
Out of a total of 179 RCC buildings, 102 (57.3%) have been labeled as red or deemed unusable owing to extent of vulnerability to earthquakes, while 40 (22.5%) are tagged as yellow, indicating that they can be made usable through temporary interventions or seismic retrofitting techniques. Additionally, 36 (20.2%) buildings have been classified as green and are deemed safe for use. Additionally, among the 120 masonry buildings, 91 (75.8%) have received a red tag or are deemed unusable, 14 (11.7%) require temporary intervention, and 15 (12.5%) have been found to be usable in terms of earthquake safety. These details are depicted in Fig. 13 provided below.
Analysis of Figs. 4 and 14 reveals that the predominant cause of red tags is attributed to factors such as heavier upper storeys (resulting in mass irregularities), slender columns with stiff beams (representing a soft or weak storey), and flat slabs lacking structural walls, which signify a deficiency in strength within that particular storey. Previous earthquake findings have highlighted these factors as key contributors to building failures during seismic events11. Similarly, Figs. 4 and 15 indicate that the primary reasons for yellow tags include large room sizes and expansive windows covering more than 50% of the wall area. Other significant contributors to yellow tagging are the absence of gaps between adjacent buildings and unanchored water tanks at the roof level. These factors have been identified as significant causes of structural damage during past earthquakes. 10, 11
Based on the analysis of Figs. 5 and 16, it is evident that the primary cause of red tags among masonry buildings is the absence of continuous lintel bands and the positioning of door and window openings close to wall corners. These factors were identified as significant contributors to the extensive damage witnessed during the Bhuj earthquake of 2001 in India. Furthermore, Figs. 5 and 17 highlight that the majority of yellow tags are attributed to insufficient gaps between buildings and unanchored water tanks at the roof level. Additional factors leading to yellow tagging include vertical cracks in the walls and the use of poor-quality construction materials. These factors have been implicated in structural damage during earthquakes in Nepal and Bhuj, where similar building typology, construction practices, and similar construction materials were observed. 10, 11