Fatigue Evaluation of Structural Composite Lumber (SCL) T-beam Bridge Girders

摘要

Structural Composite Lumber (SCL) was designed to achieve maximum strength, stiffness and efficient use of wood. Product variations of SCL are currently being used in transportation sector, especially for rural and other low traffic volume roads. Commercially available pre-built SCL bridge girders are gaining increased popularity. As these girders are repeatedly subjected to numerous cycles of wheel loads, their fatigue behavior becomes a serious concern. The current study tests 12 newly procured, 20 ft long SCL T-beam bridge girders for flexural fatigue under a stress controlled test setup. AASHTO LRFD loading was applied on the girders. The number of load application cycles was consistent with expected traffic volume for a sixty year time span. Transverse post-tension was applied to the girders to simulate the stress laminated deck effect as in an in-service girder. Results from the study indicate that the SCL T-beam bridge girders are capable of withstanding the repetitive loads. Most of the beams did not suffer any severe physical damage. Some girders experienced cracking and separation at the SCL-epoxy interface. The girders without any significant damage due to fatigue were loaded statically up to failure. The residual strengths of the fatigued girders were compared to the ultimate flexural strengths of fresh beams of similar material type.