Abstract
The influence of misalignment is investigated to improve the fatigue strength of U-type trough ribs at field welded joints in steel bridge decks. A 3-point bending fatigue test and finite element analysis were conducted on full-scale specimens. Small-scale specimens with a backing strip were also made and examined with a fatigue test and FEA to estimate the influence of misalignment. The result of the static loading test for the full-scale specimens showed that the position of maximum stress is in the bottom corners of the U-rib. It is known that fatigue cracks initiate from the inner surface of the U-rib and propagated to the outer surface, and larger misalignments contributed to a shorter fatigue life for the U-rib, based on the result of the fatigue test. The fatigue life is drastically reduced when the magnitude of misalignment is increased, as shown in the results of the fatigue test on small-scale specimens with a backing strip, and fatigue cracks usually occurred at the root of base metal. The result of stress analysis on small-scale specimens showed that the stress concentration at the root of base metal increases in proportion to larger misalignment, and the semicircular shape of the root is less subject to stress concentration than the right angle root type.