Finite-Element Analysis of Steel Girder Highway Bridges

This paper compares the performance of four finite-element modeling techniques reported in the literature used in evaluating the wheel load distribution factors of steel girder bridges. A typical one-span, simply supported, two-lane, composite bridge superstructure was selected for this study. American Association of State Highway and Transportation Officials (AASHTO) HS20-44 design truck loads were positioned to produce maximum moments in the girder. Two finite-element programs, SAP90 and ICES-STRUDL, were used to perform the analysis along with their preand postprocessing capabilities. The results of these modeling techniques were compared with AASHTO wheel load distribution factors (in 1996 and in 1994) and published experimental results. The four finite-element modeling techniques yielded similar load distribution factors. Further parametric study, varying the span length and girder spacing, was conducted and the distribution factors obtained using two of the four finite-element modeling techniques correlated well with AASHTO's 1994 load and resistant factor design (LRFD) based formula, but not with AASHTO's 1996 simple formula (S/5.5). The AASHTO LRFD formula also correlated well with prototype experimental results reported in the literature by various researchers. This paper will assist bridge engineers in gaining confidence using the new AASHTO wheel load distribution factors and adopting a finite-element modeling technique when analyzing new bridges or evaluating the load carrying capacity of existing bridges.