Effect of deterioration of integral railings on one-span multilane concrete slab bridges

Abstract

The American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges (2002) or LRFD Bridge Design Specifications (2012) empirical equations fail to take into consideration the effect of railings as being integral parts of the bridges. In addition, the effect of railing stiffness is overlooked in the design stage. Such integrally-built railings possess the effect of stiffening and attracting the load to the slab edge thus inducing an alteration of the wheel-load distribution on concrete slab highway bridges. Past research has presented and computed the increase in the load-carrying capacities of bridges with integrally-built railings, and this increase is significant and varies with the railing size and bridge geometry. Preliminary studies have shown that high stress or moment concentration in the slab edges may be induced due to accidental or long-term deterioration of the railings, and such concentrations may even, at times, exceed the moments in cases whereby no railings were present at all. This research will aim at studying and quantifying the effect of railing deterioration, taking into account various levels of full breakage at multiple locations along the bridge railing’s extent. Typical one-span, simply-supported, multilane (three or four lanes) straight reinforced concrete slab bridges with standard railings on either or both slab edges are taken into account. The finite-element method is utilized to investigate the railing deterioration’s effect occurring on one side of the slab edge. The railing’s deterioration is investigated parametrically through the variation of the location and length, and the extent is modelled by assuming distinct full breakage or deterioration of the railings. Having selected bridges with no railings and bridges with full non-deteriorated railings as reference cases, the wheel-load distribution and bridge moments at the critical sections are evaluated. AASHTO design truck loads are inserted transversely a