Effect of deterioration of stiffening railings on reinforced 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 do not account for the presence of railings as integral parts bridges and the railings stiffness is neglected during the design stage. When built integrally with the bridge deck, these railings have the effect of stiffening and attracting load to the slab edge and therefore altering the lateral wheel load distribution on concrete slab highway bridges. Previous studies have shown and quantified the increase in the load-carrying capacity of bridge due to presence of railings, which tends to be significant depending on the railing size and bridge geometry. Preliminary studies have also shown that accidental or long-term railings local deterioration may cause high stress or moment concentration in the slab edges which could reach values that even exceed moments in cases when no railings were present. This study will therefore attempt to investigate and quantify the effect of railing deterioration, considering various levels of partial wearing or full breakage at different locations-extents along the span of the bridge railing. Typical one-span, simply-supported, multilane (one and two lanes) straight reinforced concrete bridges with railings on either or both edges of the slab are considered. The finite-element method is used to investigate the effect of railing deterioration occurring on one side of the slab edge. The deterioration is investigated parametrically by varying its location and width, and the extent is modeled by assuming different remaining depth or partial stiffness of the railing. The wheel load distribution and moments in the bridge at the critical sections are evaluated, namely at slab edges where deterioration occurred, with bridges with no railings and bridges with full railings serving as reference bounding cases. AASHTO design trucks loads are placed transversely and longitudinally to produce maxim