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.

The century-old Harvard bridge spans the Charles River between Boston and Cambridge. About half of the 23 spans are suspended by wrought iron eyebars. Recent failures of some of these eyebars were examined. The primary cause of failure was the seizure of the joints at the eyebar pin locations as a result of the intrusion of water and salt, and the consequent heavy corrosion of the joint. The seizure of these joints led to high edgewise bending stress in the bars as the bridge underwent thermal movement. The cracking was enhanced by the presence of the corrosive medium so that the cracks were initiated and caused to grow by some combination of corrosion fatigue and stress-corrosion cracking, the former probably being predominant.

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.

During construction of a river bridge with 80 twisted cables, one or more fractures were found in each of 21 wires of 18 cables before assembly. All were located at the outside wrapping whose Z-profile wires were galvanically zinc-coated. It was suspected that hydrogen played a role during crack formation, and that it penetrated during pickling or galvanizing. This supposition was confirmed also by the fact that the wire fractures were not observed during cable winding, but only subsequently to it, and therefore seemed to have appeared only after a certain delay.

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.

On 23 Dec 1997, a portion of the main ore conveyor at a large mine collapsed onto a highway and shut down mine operations. The conveyor structure that collapsed was supported by a steel truss spanning 185 ft. Truss failure occurred just as the conveyor transport rate was increased to 8,260 tph. Under this total loading, which was only slightly above the regular operating condition, a poorly designed and fabricated transition joint in the west lower chord failed, thereby overloading other key structural members and causing the entire truss to collapse. Another contributing cause of the collapse was the transition joint welds, where the fracture originated. They were made with undersized fillet welds, 20% smaller than specified on the original fabrication drawing. Because of the poorly designed joint detail and the deficient welds, both of which concentrated stress and strain in the low ductility direction of the transition joint plate, lamellar tearing of plate material occurred at the boxed I-beam fillet weld attachment. Brittle fracture of this joint precipitated global collapse of the truss structure.

A catastrophic brittle fracture occurred in a welded steel (ASTM A517 grade H) trapezoidal cross-section box girder while the concrete deck of a large bridge was being poured. The failure occurred across the full width of a 57 mm (2 1 4 in.) thick, 760 mm (30 in.) wide flange and arrested 100 mm (4 in.) down the slant web. Failure analysis revealed a major deficiency in fracture toughness. The failure occurred as a brittle fracture after the formation of a welding hot crack and approximately 40 mm (1 1 2 in.) of slow crack growth. It was recommended that bridges fabricated from this grade of steel undergo frequent inspection and that stringent test requirements be imposed as a condition of use in non-redundant main load-carrying components.

An I-beam of IS-226 specification—I-section dimensions of 450 x l50 x 10 mm (17.7 x 5.9 x 0.4 in.) and a length of 12.41 m (40.7ft)—was flame cut into two section in an open yard near these a coast under normal weather conditions. After approximately 112h, the shorter section of he I-beam split catastrophically along the entire length through the web. Detailed investigation revealed segregation of high levels of carbon, sulfur and phosphorus in the middle of the web and high residual stresses attributed to rolling during fabrication. Flame cutting caused a change in the distribution of the residual stresses, which, aided by low fracture toughness due to the poor quality of the beam, resulted in failure. It was recommended that segregation be avoided in cast ingots used for I-beam manufacture by implementing a better quality-control procedure.