Post-failure Capacity of Built-up Steel Members

Mechanically fastened built-up steel members have long been known to possess internal member redundancy and, as a result, multiple load paths which can be exploited to increase their functional life. Internal redundancy provides the ability to resist total member failure in the event of a fracture of an individual component. However, there is little experimental data in the literature regarding post-fracture capacity in terms of strength and subsequent fatigue life. The experimental study currently underway will provide needed information on parameters that affect the ability of built- up members to arrest a fracture as well as the available remaining fatigue life. Additionally, further information concerning load redistribution and energy release during a fracture is being studied. Test specimens consist of both existing riveted and new high-strength bolted large-scale built-up plate girders. The results from this study will be used to develop recommended design and assessment procedures for both types of members in the as-fractured condition. The potential exists to remove the fracture critical classification from existing and new bridges in which built-up members are utilized. In cases where sufficient capacity exists and the fracture critical designation can be removed, rational in- service inspection procedures will also be developed. This presentation will report on the research results obtained to date. Considering the large number of riveted fracture critical bridges in the inventory, many agencies will benefit through implementation of more rational based inspection frequencies resulting from this study. Further, new members utilizing high-strength bolted built-up members could also be used without the penalty of being classified as fracture critical in terms of inspection

Member-Level Redundancy of Built-Up Steel Girders Subjected to Flexure

The purpose of this research was to describe the behavior of mechanically fastened built-up girders in a partially failed condition. This was achieved by testing large-scale riveted and high-strength bolted built-up specimens to determine their fracture resilience at low temperatures and their fatigue capacity after a single component was failed. Additionally, a finite element parametric study was performed to understand the behavior of built-up girders and to better describe the load distribution that occurs locally in the region adjacent to a failed component

Bonding Behaviors of GFRP/Steel Bonded Joints after Wet–Dry Cyclic and Hygrothermal Curing

This paper presents the outcomes of a research program that tested and examined the behaviors of glass fiber-reinforced polymer (GFRP) bonded steel double-strap joints after being cured in a variety of harsh curing conditions. Nineteen specimens were manufactured, cured in an air environment (the reference specimen), treated with different wet–dry cyclic curing or hygrothermal pretreatment, and then tested under quasi-static loading. Based on the experimental studies, mixed failure modes, rather than the cohesive failure of the adhesive, were found in the harsh environmental cured specimens. Additionally, an approximately linear relationship of load–displacement curves was observed for all the GFRP/steel bonded specimens from which the tensile capacities and stiffness were discussed. By analyzing the strain development of the bonded specimens during quasi-static tensile testing, the fracture mechanism analysis focused on the threshold value of the strain curves for different cured specimens. Finally, based on the studies of interfacial fracture energy, Gf, the effects of harsh environmental curing were assessed. The results showed that the failure modes, joint tensile capacities, stiffness, and interfacial fracture energy Gf were highly dependent on the curing conditions, and a significant degradation of bonding performance could be introduced by the investigated harsh environments