Load Distribution of Existing Solid Slab Bridges Based on Field Tests

The load-carrying capacity of existing slab bridges is commonly calculated based on the equivalent width recommended by the American Association of State Highway and Transportation Officials (AASHTO). Interest in the field load testing of highway bridges has increased significantly in recent years. Load capacity of a bridge based on field testing is generally greater than that determined from standard rating calculations. The main parameters affecting the equivalent width were identified using the grillage analogy method. The results suggest that edge beam size should be considered in the equivalent width calculation. A simplified equation for the equivalent width is proposed for solid slab bridges with or without edge beams. The equivalent widths based on the AASHTO and LRFD cores was compared with those based on the field tests and analyses. The equivalent widths based on the grillage analogy and field tests are higher than those based on the AASHTO and LRFD codes, which indicates that the codes give a conservative estimate of the equivalent width. In the absence of field tests, the grillage analogy provides an accurate estimate for the equivalent width and bridge rating.