12 research outputs found
Report on Phase 2.3, Investigation of Welded Highway Bridges. Project IHR-64
The object of this investigation was to study the effect of internal flaws
on the fatigue behavior of butt-welded connections in mild structural steel, the
initiation of fatigue cracks from these flaws and the propagation rates of these
cracks in the connections. Since internal flaws occur in many welds it is essential
to obtain a better understanding of the behavior of flawed connections so that adequate,
yet realistic, code requirements can be established.
The study is limited to two major types of defects, porosity and incomplete
penetration. The porosity was further subdivided into two categories based on
the severity of the defect. The specimens with incomplete penetration were made
with an initial 3/16" centrally located crack the full width of the- specimen.
The fatigue behavior of the connections with the defects is compared with
that of sound welds to observe the effects of the defects on the fatigue strength
of the connections. The data are compared with result~ of similar studies found in
the literature and also with the AASHO 1970 Specification design requirements.
Three of the specimens with incomplete penetration were examined radiographically
during the fatigue testing to determine when initiation of the fatigue
cracks occurred, and how rapidly they propagated. The results of the crack propagation
tests are compared with similar relationships developed for high strength
steels. A relationship that better fits the data for mild steel has been developed
in a manner similar to that used for the high strength steels.State of Illinois. Department of Transportation. Division of HighwaysU.S. Department of Transportation. Federal Highway Administratio