Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...

894.5 Fatigue Test ResultsTo develop a better understanding of the fatigue behavior of wrought iron foundin many historic bridges, some limited fatigue testing was completed during this study.Four un-notched smooth tensile coupon specimens, from the Adams Mill bridge, werecycled at a constant-amplitude stress range (R=0.05) until either failure or three millioncycles occurred.The first specimen was cycled at a stress range of 20 ksi. It never failed and thetest was considered a run-out when the specimen reached three million cycles. Thesecond specimen was cycled at a stress range of 30 ksi and it also never failed and the testwas stopped at three million cycles. Two additional fatigue tests were completed at astress range of 35 ksi. These specimens failed at 639,200 cycles and 713,900 cycles,respectively. Although the database is very limited, this may suggest that the endurancelimit for smooth wrought iron specimens is somewhere between 30 and 35 ksi.Other fatigue testing that was reported during the literature search consisted oftesting completed on certain truss members such as eyebars (Elleby, 1976). Since thesemembers were not smooth specimens and have localized notch and stress effects theirfatigue lives were much lower than the fatigue lives found during experimental testingreported herein.4.6 Charpy Impact Test ResultsTo evaluate the notch toughness of the wrought iron material, the Charpy impacttest was performed on specimens from both the Bell Ford Bridge and the bridge nearDelphi, IN. The Charpy impact test determines the impact energy needed to fracture anotched specimen of the material. The greater the impact energy, the greater the fracture