Experimental Investigations of the Effects of Multiple Heat Straightening Repair on the Structural Properties of Bridge Steels (05-1186)**
Keith Joseph Kowalkowski, Ruby and Associates, P.C.
Amit Hariom Varma, Purdue University

Experimental investigations were conducted to evaluate the effects of multiple damage-heat straightening repair cycles, i.e., multiple cycles of damage followed by heat straightening repair on the fundamental structural properties of typical bridge steels ASTM A36, A588, and A7. The damage and repair parameters considered in the study are the damage strain , the restraining stress , and number of multiple damage-repair cycles (Nr). The effects of these parameters are evaluated on the following structural properties: (a) elastic modulus, (b) yield stress, (c) ultimate stress, (d) percent elongation, (e) surface hardness, and (e) fracture toughness. A total of seventy-five laboratory-scale specimens made from A36, A588, or A7 steel were subjected to multiple damage-repair cycles, and their effects on the structural properties were evaluated. The results from the experimental investigations indicate that multiple damage-repair cycles have a small influence (± 15%) on the elastic modulus, yield stress, and ultimate stress. However, the percent elongation and fracture toughness of the damaged-repaired steel are influenced significantly. Based on reductions in the percent elongation and fracture toughness, it is recommended that A7 and A36 steel be limited to three damage-heat straightening repair cycles. A588 steel can be subjected up to five damage-heat straightening repair cycles.