Renovation techniques for rib to deckplate fatigue cracking in orthotropic bridge decks

Abstract

Steel orthotropic bridge decks possess 5 fatigue critical points. One of these is the longitudinal rib to deckplate weld. At that connection, a combination of large transverse bending stresses caused by concentrated wheel loads and residual stresses in local plasticized zones due to the welding procedure may initiate fatigue cracking at the weld root or toe. For new bridges, the normative documents provide minimum plate thicknesses, in combination with maximum rib spacings in order to avoid fatigue problems. However, a large number of these decks have been built around the world since the 1950's, which do not comply to these recommendations, many of them showing fatigue cracks. For these bridges, renovation solutions are required since the deck system cannot be separated from the main structural system. A first part of this paper reviews the current state of the art of renovation techniques for poorly designed rib to deckplate connections including peening, stress relieving and overlaying. In a second part the results of a full scale fatigue test carried out at Ghent University College are presented and discussed. In this test, an epoxy bonded connection between the original steel plate and a repair plate is tested under fatigue loading conditions at 5000000 cycles. The test indicates no signs of crack initiation or debonding, confirming this method as a valid alternative.