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. Key words: Fatigue, orthotropic deck, rib to deckplate weld, epoxy bonded overlay.
Highlights
Steel orthotropic bridge decks contain at least 5 fatigue critical locations (Figure 1) (Uchida et al, 2008)
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
From the late 1970’s up to today many cases of fatigue cracking at this location have been described
Summary
Steel orthotropic bridge decks contain at least 5 fatigue critical locations (Figure 1) (Uchida et al, 2008). Eurocode 1993-1-9 defines fatigue detail categories for the rib to deckplate connection, based on tests carried out in the 1980’s (Figure 2) (CEN, 2007) These detail categories are rather conservative of nature, especially for the partial penetration welds as commonly used in modern practice. Many such cases have been found in practice, and there is need for a fatigue detail for this type of fatigue failure as well Impressive work in this field has been done by Kolstein, who has thoroughly analysed huge amounts of fatigue testing data from the 1980’s, 1990’s, and early 2000’s (Kolstein, 2007). His conclusions have lead to a comprehensive and more detailed proposal for classifycation of rib to deckplate weld details (Figure 3).
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