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Degraded Gerber Saddles in RC Bridges


Sudden failure of reinforced concrete (RC) or prestressed concrete (PC) Gerber saddles of bridges and viaducts has occurred all around in the word in the last few years due to corrosion of steel bars. The danger of sudden and brittle failure is often due to general and pitting corrosion of steel bars, concrete crushing, and loss of bond in steel bars. In this paper, the flexural response of reinforced concrete Gerber supports under their self-weight with or without service loads was investigated through determination of the load-deflection response of beams, with the focus on the consequences of pitting corrosion and loss of bond in steel bars. A simplified strut-and-tie model was developed to predict the flexural response of Gerber supports in terms of load-deflection curves, deduced analytically in a closed form. The model includes the effects of corrosion of steel bars, loss of bond, and concrete crushing due to the biaxial state of stresses. Several experimental laboratory studies regarding the flexural behavior of RC beams with Gerber supports were collected to validate the proposed model. In addition, numerical analyses were performed through a nonlinear finite-element code for comparison with the experimental and analytical results.