INFLUENCE OF RAILING STIFFNESS ON SINGLE-SPAN TWO-LANE STEEL GIRDER BRIDGES

The presence of railings or parapets acting integrally with the concrete deck placed on steel girders has the effect of stiffening and therefore altering the lateral wheel load distribution on highway bridges. The American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges and AASHTO LRFD Bridge Design Specifications procedures do not account for the presence of railings when evaluating the load-carrying capacity of highway bridges. This paper presents a parametric study using 3D finite element analysis to investigate the influence of railing stiffness on one-span, two-lane steel girder bridges. Railings of different sizes were placed on one or both sides of the bridge deck, in combination with various span lengths and girders spacing. AASHTO HS20 design trucks were placed longitudinally and transversally in order to produce maximum longitudinal bending moments in the steel girders. The wheel load distribution obtained from finite element analysis at the critical section of each bridge were compared with the AASHTO procedures and with reference cases for bridges without railing. This study confirmed that the presence of concrete railings modeled and built integrally with the deck tends to stiffen the bridge superstructure. Further, the study quantified the effect of railing in increasing the load-carrying capacity of steel bridges. The results of this research will therefore assist structural engineers in better designing new steel girder bridges and/or evaluating more precisely the load-carrying capacity of existing bridges with railings of different sizes. Bridge engineers can consider adding or stiffening railings/parapets as a practical method for strengthening existing steel girder bridges.