A Review Design of Box Culvert with Comparative Study with and Without Cushion Loading with Different Height to Width Ration

Box culverts and box-type bridges play a pivotal role in transportation infrastructure by enabling uninterrupted water flow beneath road and railway embankments while supporting traffic loads. Their structural design must account for a variety of complex loading conditions, including earth pressure, traffic-induced live loads, and water surcharge. Over the years, numerous studies have analyzed these structures using both traditional manual methods and modern software tools like STAAD Pro, focusing on optimizing parameters such as span, shape, material use, and load dispersion to ensure safety and cost-effectiveness. Despite the extensive research in this domain, a significant gap remains in understanding the impact of varying cushion depth—the layer of material provided above the top slab—on the structural performance of box culverts and bridges. Cushion depth plays a crucial role in distributing loads, reducing stress concentrations, and influencing the overall behavior of these monolithic structures under service conditions. Surprisingly, this parameter has received limited attention in existing literature. This review aims to consolidate and critically assess previous works on the design and analysis of box culverts and box-type bridges, with a special focus on highlighting the overlooked influence of cushion depth. By identifying this gap, the paper advocates for future research that systematically investigates the role of cushion variation in enhancing structural performance and durability, ultimately contributing to more resilient and efficient infrastructure design.