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Title: Field Testing to Failure of a Skewed Solid Concrete Slab Bridge

Author(s): Fabien Lagier, Bruno Massicotte, David Conciatori, Jean-François Laflamme

Publication: Symposium Paper

Volume: 342


Appears on pages(s): 40-59

Keywords: solid slab bridges, field testing, load rating, shear failure, nonlinear finite element analysis

DOI: 10.14359/51725936

Date: 6/1/2020

In 2006 in Quebec, a skewed cantilever solid concrete slab bridge without shear reinforcement collapsed due to a shear failure, which highlighted the need to improve the assessment of this type of structure. A large experimental program was carried out to test three decommissioned solid slab bridges to failure. In parallel, an extensive nonlinear finite element analysis study was performed with the aim of better understanding the failure mechanisms, the degree of load redistribution, and to gain insight into the ultimate shear capacity of these structures. A beam shear failure mode was expected for the first two bridge tests, but a flexural failure mode was observed. This paper focusses mainly on the last field test of a simply supported solid slab bridge having a 40 degree skew. The load position and the loading protocol were established with the objective of causing a shear failure at the obtuse corner of the slab where high shear forces develop. The main test motivation was to illustrate that simply supported solid slab bridges would normally not be prone to shear failure due to an intrinsic redundancy. The paper presents experimental techniques that could help bridge owners in assessing the performance of their bridges. The test results also provide valuable information for calibrating nonlinear element models that can be used for assessing the carrying capacity of existing concrete bridges. Although the actual bridge conditions were worse than anticipated, a global shear failure mode occurred near the obtuse corner at a maximum load of 1400 kN, which significantly exceeded the factored shear force due to the maximum traffic load. The failure was followed by a gradual load redistribution toward undamaged portions of the slab. This field test confirmed the assumption of non-fragility for this type of bridge, where support conditions enable development of an intrinsic redundancy. Despite these observations, nonlinear analyses carried out in parallel to the testing program indicated that this beneficial effect diminishes with an increase of slab thickness.