Field Tests of Two Prestressed-Concrete Girder Bridges for Live-Load Distribution and Moment Continuity

Two similar bridges constructed with a live-load continuous connection were tested for live-load distribution and joint continuity. Girder distribution factors (GDFs) were compared with AASHTO equivalent values. For positive moments on all girders as for negative moments on interior girders, results using AASHTO equivalent GDFs were found to be generally conservative. However, for negative moments on exterior girders, test results exceeded AASHTO values, significantly so with two-lane results. GDF results were verified with a finite-element analysis (FEA) model, which produced behavior similar to the field tests. With respect to joint continuity, it is estimated that a simple span would produce a maximum positive moment about 7% higher than the actual structure, whereas a completely continuous structure would produce a maximum positive moment about 16% lower than that of the actual structure. For negative moments, the actual structure experienced about 28% of that of a continuous structure. Shear reactions were also investigated. Recommendations are proposed for evaluating transverse distribution of live load as well as the longitudinal distribution of live load, accounting for the effect of joint continuity.