SEISMIC RESPONSE OF LONG-SPAN ARCH BRIDGES UNDER BHUJ GROUND MOTION: STRUCTURAL-FORM, SPAN, AND TOPOGRAPHY-ORIENTED ASSESSMENT

This study assessed the seismic behaviour of straight and arch bridge configurations under the Bhuj 2001 ground-motion record and established a validated analytical basis for later topography-sensitive modelling. Three-dimensional STAAD.Pro models were prepared using consistent concrete properties, bridge geometry, support conditions, dead load, IRC Class AA moving load, and time-history input. The numerical idealisation was checked against manual bending-moment and shear-force calculations for an 80 m validation sub-model; the inner-girder moment differed by only 27 kN-m, approximately 0.80%, between the manual value of 3360 kN-m and the STAAD.Pro value of 3387 kN-m. For the principal 168 m comparison, the arch bridge reduced maximum displacement from 21.8 to 13.8 mm, acceleration from 7.68 to 4.61 mm/s², velocity from 14.72 to 8.83 mm/s, and maximum shear from 9.92 to 5.952 kN. These changes represent reductions of approximately 36.70%, 39.97%, 40.01%, and 40.00%, respectively, making the 168 m arch configuration the better-performing structural form under the reported conditions. Span sensitivity was pronounced: arch displacement increased from 13.1 mm at 20 m to 29.3 mm at 30 m and 30.5 mm at 40 m, while acceleration and velocity also increased. The objectives concerning model development, validation, dynamic comparison, and governing response trends were achieved. The results confirm that arch action limits global seismic response, demonstrate the flexibility penalty of longer spans, and provide a practical framework for evaluating valley geometry, unequal supports, foundation stiffness, and spatially varying excitation in future bridge studies.

[1] L. Geli, P.-Y. Bard, and B. Jullien, “The effect of topography on earthquake ground motion: A review and new results,” Bulletin of the Seismological Society of America, vol. 78, no. 1, pp. 42–63, 1988. [2] R. K. Dahal et al., “Topographic effects on seismic ground-motion amplification and structural response: Recent advances and engineering implications,” 2024. [3] R. S. Harichandran et al., “Response of long-span bridges to spatially varying ground motion,” 1996. [4] X. Lu et al., “Effects of nonuniform support excitation on the seismic response of large-span arch bridges,” 2022. [5] I. Mohseni et al., “Dynamic response of a long-span reinforced-concrete arch bridge subjected to near-field and far-field ground motions,” 2018. [6] X. Duan et al., “Seismic damage assessment of a high-speed railway long-span arch bridge–track system using an improved interlayer area-damage model,” 2024. [7] Y. Zhao et al., “Seismic damage patterns of long-span deck-type concrete-filled steel-tube arch bridges under different viscous-damper configuration strategies,” 2025. [8] S. N. Krishnakanth et al., “Design and analysis of bridge design using STAAD.Pro,” International Journal of Research Sciences and Advanced Engineering, vol. 2, no. 12, pp. 211–224, 2015. [9] M. P. Singh, “Post-earthquake observations and performance of the Rudramata Bridge, Bhuj, Gujarat,” Earthquake Engineering Research Institute, 2002. [10] Bureau of Indian Standards, IS 1893 (Part 1):2002, Criteria for Earthquake Resistant Design of Structures, New Delhi, India, 2002.