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Report No.: CCEER-04-7

Title: Cyclic Response and Low Cycle Fatigue Characteristics of Plate Steels

Authors: Peter Dusicka, Ahmad Itani and Ian Buckle

Date: November 2004

Sponsoring Agency: California Department of Transportation (CalTrans) and Federal Highway Administration (FHWA)

Performing Organization:
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557

Abstract:

An experimental evaluation of the stress-strain behavior and the low cycle fatigue life was conducted on five grades of plate steel to determine their suitability for use in earthquake structural engineering applications. The steel grades ranged from high performance steel HPS 485 MPa (70 ksi) to low yield point steel LYP Grade 100 MPa (14.5 ksi). The coupons were tested to failure using complete reverse cyclic axial strains of primarily constant strain amplitude between 1% and 7% strain and at constant strain rate of 0.1%/sec. The cyclic stress increased with strain amplitude for all of the steels, but the experimental results also indicated a strong dependency on the steel grade. The cyclic stress-strain response was idealized by a power law relationship and cyclic hardening was evident in specific cases when compared to the monotonic response. The cyclic stress was nearly 2 times the yield stress for A709 Grade 345 MPa (50 ksi) and nearly 5 times the yield stress for low yield point steels LYP Grade 100 MPa (14.5 ksi). In all cases the majority of the cyclic hardening occurred within the first several reversals. From the limited number of dynamic test results, the dynamic strain rate had negligible effect on the yield strength, cyclic stress-strain response as well as the fatigue life. The low cycle fatigue life of the different steels did vary, but overall the fatigue life was relatively similar for all grades. The experiments showed that all of the steels would be suitable for earthquake engineering applications, although the effects of welding or multi-axial stresses were not considered.

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