Structural Integrity Assessment of the Welded SAE/AISI 1045 Steel for Structural Use

Abstract

The anchorage of a cable-stayed bridge failed and was subsequently replaced by another anchorage made of SAE/AISI 1045 steel. The new structural component has been assessed by using different options of failure assessment diagrams. Tensile tests were performed on both the base metal and weld metal of a welded coupon composed of SAE/AISI 1045 and ASTM A572 steels. The fracture toughness was estimated from the results of Charpy tests performed on the heat-affected zone (HAZ) of SAE/AISI 1045 steel. In addition, finite element analysis was used to determine the stress state caused by four heavy vehicles (T3-S2-R4 type) localized on one side of the column. Based on two types of postulated defects, the stress state of the tie rods, and the material fracture toughness, the failure assessment diagrams were constructed to predict the critical load that can be withstood by the anchorage and the weld metal. The results indicate that both the SAE/AISI 1045 steel and the weld metal could work safely under typical operating conditions of the bridge, even when there is a detachment of one of the anchorages. The weld metal is susceptible to plastic collapse failure, while the HAZ of the steel is susceptible to a combination of fracture and plastic collapse. It is also noted that the critical stress predicted by Option 1 on the HAZ of SAE/AISI 1045 tends to be more conservative than that predicted by Option 2. The degree of conservatism ranges from 7.8% up to 12% for a superficial flaw and from 6.2% to 15.5% for an embedded flaw.