Development of a Load Test
for the Evaluation and Rating of Short-Span Reinforced Concrete Slab Bridges
Nathan Capaldi, Graduate Student (nxc14@po.cwru.edu)
and
Arthur Huckelbridge, Associate Professor (aah4@po.cwru.edu)
Department of Civil Engineering
Case Western Reserve University
Cleveland, OH 44106-7201
After the creation of the National Bridge Inspection Standards (NBIS), all states were required to inspect, inventory and evaluate those bridges which are located on federal aid routes. A bridge is normally inspected and its structural strength is estimated. A load rating is then calculated, and if it indicates a reduced capacity, the bridge is posted for a proper weight limit. This practice allows a prolonged, yet limited use of bridges for which the rating analysis indicates the presence of a safety problem. (Imbsen, NCHRP Report 108)
There exists in the state of Ohio a large inventory of short-span reinforced concrete slab bridges, particularly on rural secondary highways, whose actual structural reliability cannot be accurately ascertained. Quite often little or even no design documentation exists to assist the responsible local jurisdictions in assessing the ability of these bridges to carry modern truck loadings or to establish a proper load rating.
Visual inspection alone, while valuable in assessing a bridge’s general condition and state of maintenance, cannot accurately predict load carrying capacity. Conventional load testing, which typically requires extensive electronic instrumentation, complex data acquisition equipment, and specialized expertise in structural testing procedures and data interpretation, is not feasible for such a large inventory of bridges.
A need definitely exists for quantitative bridge evaluation procedures that can be utilized by local jurisdictions in the load rating of such under-documented structures. These procedures must be of such a nature that the requirement for specialized expertise in structural testing and data interpretation is minimized, while still producing meaningful quantitative data, directly applicable to the rating process.
A previously conducted feasibility study has demonstrated the potential of utilizing simplified load testing as an aid in the evaluation and load rating of such structures. A quantitative database of structural response information for this category of structures is needed, however, in order to develop an actual test-based evaluation procedure, suitable for use by regular bridge inspection personnel. The investigation is directed toward developing that database by field-testing an ensemble of twenty short-span slab bridges.