Evaluation of Fatigue Strength Improvement by CFRP Laminates and Shot Peening onto the Tension Flanges Joining Corrugated SteelWebs

Abstract

Corrugated steel web with inherent high out-of-plane stiffness has a promising application in configuring large span highway bridge girders. Due to the irregularity of the configuration details, the local stress concentration poses a major fatigue problem for the welded flange plates of high strength low alloy structural steels. In this work, the methods of applying CFRP laminate and shot peening onto the surfaces of the tension flanges were employed with the purpose of improving the fatigue strength of such configuration details. The effectiveness of this method in the improvement of fatigue strength has been examined experimentally. Test results show that the shot peening significantly increases hardness and roughness in contrast to these without treatment. Also, it has beneficial effects on the fatigue strength enhancement when compared against the test data of the joints with CFRP strengthening. The stiffness degradation during the loading progress is compared with each treatment. Incorporating the stress acting on the constituent parts of the CFRP laminates, a discussion is made regarding the mechanism of the retrofit and related influencing factors such as corrosion and economic cost. This work could enhance the understanding of the CFRP and shot peening in repairing such welded details and shed light on the reinforcement design of welded joints between corrugated steel webs and flange plates.

Experimental Study on Fatigue Behaviour of Shot-Peened Open-Hole Steel Plates

“…Fatigue life results are normally expressed in terms of the relations between the stress range, Δσ, and the number of cycles to failure, N , as: where, exponent, m , is the slope of the S – N relation; C is the material constant related parameter [ 3 ]. Taking logarithm on the both sides of Equation (3), the following equation can be written as: …”

“…Shot peening has been extensively applied with the purpose of fatigue life improvement since the work-hardening and considerable compressive residual stresses can be introduced as a result of near-surface plastic deformation [ 3 , 4 ]. The effect of surface treatment on the fatigue behaviour of steel components has been highlighted by most recent studies.…”

Fatigue Property of Open-Hole Steel Plates Influenced by Bolted Clamp-up and Hole Fabrication Methods

“…Stiffness is a well-defined engineering property, easily measured, and not involved in the destruction of the test specimen [ 23 ]. During the fatigue loading, damage accumulates with the crack propagation, which in turn progressively reduces the stiffness of the test specimens.…”

“…For each class of structural components, the general equation can be expressed in relating the number of cycles to failure, N , and the applied stress range, Δ S , as: where the exponent m is the slope of the S - N relation; C is the material constant-related parameter [ 23 ]. Taking the logarithm on both sides of Equation (2), the following equation can be written as: …”

The Effect of Ultrasonic Peening Treatment on Fatigue Performance of Welded Joints

“…Usually, a welded joint has a higher stress concentration and a larger tensile residual stress at the weld toe, which will significantly reduce the fatigue life of the welded joint. Therefore, fatigue failure is one of the most important failure cases for welded joints [ 1 , 2 , 3 ]. It is well established that fatigue strength of welded joints can be enhanced by producing compressive residual stress, reducing stress concentration, increasing hardness, and forming nanocrystalline structures.…”