INFLUENCE OF RAILING STIFFNESS ON SINGLE-SPAN TWOLANE STEEL GIRDER BRIDGES

Abstract

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.