Damage avoidance solution to mitigate wind-induced fatigue in steel traffic support structures

Abstract

Non-redundant, cantilevered traffic signal support structures undergo frequent wind-induced excitation; the subsequent vibrations result in stress reversals that lead to fatigue, and possibly fracture, particularly at the welded connections. To accommodate more lanes and reduce roadside hazards, spans continue to increase—as do the number of connection failures. Presented herein is a low-cost damage avoidance approach to mitigate wind-induced fatigue effects for cantilevered traffic support structures. Load-balancing is provided to relieve the dead load tensile stresses in the tube-to-transverse plate connections, thereby increasing fatigue capacity. The proposed damage avoidance system adds a beneficial fail-safe, load-balancing redundancy for cantilevered traffic signal structures. The benefit of the proposed system is quantified using a probabilistic fatigue assessment framework. Full-scale prototype testing is conducted in an ambient wind environment to serve as input and statistically describe response. Fatigue performance is modeled as mean stress dependent from which a dependable service life is derived. The efficacy of the proposed damage avoidance technique is assessed for a variety of wind environments where it is shown the dependable service life increases by an order of magnitude.