Design of reinforced concrete bridges

The shortest span reinforced concrete decks are built as solid slabs. These may be supported on bearings although, due to durability issues with expansion joints and bearings, it is usually preferable to cast them integral with in-situ abutments or place them as part of pre cast box culverts. As the span increases, the optimum form of construction changes to voided slab or beam and slab then box girder bridges. Open spandrel arches enable relatively long spans, more commonly built in steel or prestressed concrete, to be built efficiently in reinforced concrete. Reinforced concrete is also used for deck slabs and substructures for bridges with main elements of steel or prestressed concrete. The key design criteria and checks required by codes are the same regardless of the form of construction. These are for ultimate strength in flexure, shear and torsion and for serviceability issues including crack widths and service stresses. For elements with significant live load ratios, reinforcement fatigue may sometimes also have to be checked.