Economic Design Comparison of Pre-Stressed Concrete Slab & Box-Girder Railway Bridges

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Addis Ababa University


An investigation has been undertaken to study the design comparison of pre-stressed concrete Slab and Box-girder railway bridges based on economy of the structure. Though, the Prestress concrete bridges are the most widely used bridges types, nowadays it’s an alternative solution for reducing the dead load of the structure and allows the possibility to build longer span bridges and to carry heavy loads. The condition survey site visit during this study also reveals that railway bridges structure has to be built properly and the contractors have to carry about economy, efficiency of the structures without forgetting maintainability. Slab bridges are to be employed for span less than 15m, though not considered in the actual practice so far. The objective of this study is to develop a reliable engineering Computer program using excel spread sheets template for analysis, design and cost estimate of superstructures of pre-stressed Slab and Box-girder railway bridges. Hence, identifying a clear demarcation of span length for selecting between Slab and Box-girder bridges on the basis of economy, happens to be found indispensable. For the design of superstructure pre-tensioned system is used for Voided Slab bridges and post-tensioned for Box-girder bridges. A comparative study on the basis of cost of materials is conducted to select and identify the economical span range of Voided Slab and Box-Girder bridges. The developed program is illustrated using particular example of both Slab and Box-girder bridges. The analysis results show that precast pre-stressed Voided Slab bridge is economical up to 15m and that of the Box-girder is economical beyond 15m.



Voided, Slab, Box-girder, Economy, Excel, Pre-stressed, Bridge, Railway, Precast