Influence of stiffness of railings on one-span multi-lane steel girder bridges -

Abstract

The conventional analysis and design of highway bridges ignore the contribution of railings in a bridge deck when calculating the flexural strength of superstructures. In fact, the presence of railings acting integrally with the bridge deck has the effect of stiffening and therefore altering the lateral wheel load distribution on highway bridges . The current research presents a parametric study to investigate the influence of stiffness of railings on load distribution and load-carrying capacity of multi-span multi-lane steel girder bridges. The finite-element method is used to investigate the effect of span length, slab width, girder spacing on one-span simply supported, two-lane, three-lane, and four-lane steel girder bridges. The finite element program SAP2000 (2013) is selected for the analysis. American Association of State Highway and Transportation Officials (AASHTO) HS20 design trucks were positioned on the bridges to produce the maximum moments. Various stiffnesses of railings on either or both edges of the slab are considered. Bridges without railings served as reference cases. The wheel load distribution factor for the reference cases and for cases with railings are calculated and compared. The finite-element analysis results were also compared with AASHTO procedures. The AASHTO load and resistance factor design (LRFD) wheel load distribution formula correlated conservatively with the finite-element results and all were less than the typical AASHTO Standard formula (S-5.5). Increasing the stiffness of railings has shown to increase the load-carrying capacity when included in the strength evaluation of highway bridges. The research will therefore assist structural engineers in better designing new steel girder bridges, or evaluating more precisely the load-carrying capacity of existing bridges, in the presence of railings. Such can also be considered as an adequate and practical method for strengthening and rehabilitating steel girder bridges.