Stress distribution and bearing stiffeners details related to fatigue and fracture of steel girders with corrugated webs

The use of corrugated webs in steel girders has been shown to be an innovative, economical and structurally adequate solution to premature web stability failure. It allows relatively thin webs without the need for welded stiffeners. The elimination of welded stiffeners reduces the fabrication cost and increases the fatigue life of the beams. A reasonable number of investigations have been carried out to study beams with corrugated webs under static loads, however minimum work has been done to describe the behavior of this type of beams under repeated cyclic loads. These limited results clearly showed that beams with corrugated webs sustain longer fatigue lives than conventionally stiffened beams. A need, therefore exists for conducting experimental and analytical studies that would demonstrate the potential of beams with corrugated webs under fatigue loads. This thesis investigates the fatigue life of these beams analytically and experimentally. A total of six girders with trapezoidal corrugation were tested under cyclic loads the main parameters were the stress range at the top of the bottom flange, the stiffener type and location. The experimental program showed that, from the fatigue standpoint, the best stiffener detail is a single plate stiffeners on both sides of the inclined fold, welded to the top flange and web and cut short from the bottom flange. More importantly, the experimental results exhibited a fatigue life 2.6 times longer than the one calculated for a conventionally stiffened beam under the same stress range. Finite Element Methods were used to analyze the state of stresses in beams with corrugated webs. This analysis showed two critical areas susceptible to fatigue failure: (a) the bottom flange at the web fold line and (b) the center region of the inclined fold. In addition, Fracture Mechanics in conjunction with Finite Element Models were used to develop logarithmic equation that would approximate the fatigue life of beams with corrugated webs good agreement between the experimental results and this formulation was observed.