Effects of traffic vibration on curing concrete stitch: Part II—cracking, debonding and strength reduction

In bridge widening projects, the possible damaging effects of traffic vibration on curing concrete stitch have been causing concern, and design engineers have to consider what traffic restrictions or mitigation measures are necessary. However, different researchers, using different test methods, have obtained widely different results for the threshold vibration causing damage. To resolve this problem, a new vibration test method that can more closely simulate the actual loading conditions of the curing concrete stitch has been developed as presented in Part I [Kwan AKH, Ng PL. Effects of traffic vibration on curing concrete stitch: Part I—test method and control program. Engineering Structures 2007; 29(11):2871–80]. Herein, the results of an experimental program, in which a total of 24 specimens have been tested using the new method, are presented. In the experimental program, the specimens were subjected to different amplitudes of vibration and the damages so caused to each specimen were assessed in terms of cracking, reduction in bond strength, reduction in contraflexural strength and slackness at the construction joints. The results revealed that whilst the threshold curvature causing cracking or slackness is relatively small, the threshold curvature causing significant reduction in bond or contraflexural strength is relatively large, and in fact larger than expected.