Analysis and Design of Box Culvert for Durability against Varying Thickness of Cushion

Abstract: This study presents the structural analysis of a reinforced concrete (RCC) box culvert with dimensions 1m x 2m x 1.5m, subjected to varying cushion loadings of 0.770m, 1.010m, and 1.200m, using STAAD.Pro software. The analysis focuses on both Ultimate Limit State (ULS) and Serviceability Limit State (SLS) criteria to ensure the structural integrity and durability of the culvert. For ULS, load combinations include dead load, live load, earth pressure, and cushion load, assessing the culvert's capacity to withstand maximum expected loads without failure. The study evaluates bending moments, shear forces, and ensures that the flexural and shear strengths of the culvert are within permissible limits. Results indicate that even under the highest cushion loading, the culvert design remains robust with appropriate reinforcement. For SLS, the analysis incorporates quasipermanent load combinations to evaluate deflections and crack widths, ensuring the structure's functionality and aesthetic durability under normal service conditions. Deflections and crack widths for all cushion depths were found to be within acceptable limits, demonstrating the culvert's ability to maintain serviceability and resist long-term degradation. Overall, the analysis confirms that the RCC box culvert, when designed according to the principles of ULS and SLS, achieves a balance between safety, functionality, and durability, ensuring reliable performance over its service life.