A 208 cm (82 in.) ID steel aqueduct (ASTM A572, grade 42, type 2 steel) fractured circumferentially at two points 152 m (500 ft) apart in a section above ground. A year later, another fracture occurred in a buried section 6.4 km (4 mi) away. Both pipes fractured during Jan at similar temperatures and pressures. The pipe had a 24 mm wall thickness, and the hydrostatic head was 331 m (1085 ft). The air temperature was approximately -13 deg C (9 deg F), the water temperature approximately 0.6 deg C (33 deg F), and the steel temperature approximately -4 deg C (25 deg F). The pipe had been shop-fabricated in 12 m (40 ft) lengths, then shop welded into 24 m (80 ft) lengths. Field assembly was with bell-and-spigot joints. Investigation (visual inspection and Charpy V-notch testing) supported the conclusion that brittle fracture of the aqueduct pipe was attributed to a combination of stress concentrations at the toes of the fillet welds due to poor welding technique, including shop welds made without preheat, and a brittle condition of the steel at winter temperatures. Recommendations included revised welding techniques, installation of expansion joints, and the use of steel plate rolled from fully killed ingots.

In 1979, during a routine bridge inspection, a fatigue crack was discovered in the top flange plate of one tie girder in a tied arch bridge crossing the Mississippi River. Metallographic analysis indicated a banding or segregation problem in the middle of the plate, where the carbon content was twice what it should have been. Based on this and results of ultrasonic testing, which revealed that the banding occurred in 24-ft lengths, it was decided to close the bridge and replace the defective steel. The steel used in the construction of this bridge was specified as ASTM A441, commonly used in structural applications. Testing showed an increase in hardness and weight percent carbon and manganese in the banded region. Further testing revealed that the area containing the segregation and coarse grain structure had a lower than expected toughness and a transition temperature 90 deg F higher than specified by the ASTM standards. The fatigue crack growth rate through this area was much faster than expected. All of these property changes resulted from increased carbon levels, higher yield strength, and larger than normal grain size.

A large crack developed at a girder-truss joint area of the Fremont bridge in Portland, OR, on 28 Oct 1971. It occurred during a positioning procedure involving a junction piece welded to a girder, starting as a brittle fracture and terminating in plastic hinges in the girder web welds. The arch rib top plate, as it met the main girder, formed a composite beam of A588/A36 composition. Investigation showed the original design of the failed component called for an angle of high geometric stress concentration (90 deg with no radius) in a region of substantial transverse weld joints. While the material met chemical and mechanical property requirements, tests showed it had low fracture toughness and critical-sized flaws oriented normal to the principal stress in the failed junction piece. Fabrication procedures resulted in high residual stresses and a metallurgical notch at the radius in the junction piece. Stresses induced during jacking (the procedure used to raise bridge components into position) applied the stresses in the critical radius that triggered the cracking.

During the construction of a prestressed concrete viaduct, several 12.2 mm diam wires ruptured after tensioning but before the channels were grouted. They were made of heat treated prestressed concrete steel St 145/160. While the wire bundles, each containing over 100 wires, were being drawn into the channels they were repeatedly pulled over the sharp edges of square section guide blocks. The fractures were initiated at these chafe zones. It was concluded that the chafing of the wires on the edges of the guide blocks, particularly the resulting martensite formation, caused the wires to rupture.

The Rocky Point Viaduct, located near Port Orford, OR, was replaced after only 40 years of service. A beam from the original viaduct was studied in detail to determine the mechanisms contributing to severe corrosion damage to the structure. Results are presented from the delamination survey, potential and corrosion mapping, concrete chemistry, and concrete physical properties. The major cause of corrosion damage appears to have been the presence of both pre-existing and environmentally-delivered chlorides in the concrete.