Numerical Analysis of Causes and Cures of Longitudinal Reflection Cracking on Side-by-Side PC Box-Girder Bridge Deck

摘要

Finite element analysis, based on various construction and service stages, of a genetic bridge was carried out to find the potential reasons causing longitudinal reflection cracking on top of bridge deck as well as the cures for solving this problem. Meanwhile, the effect of applied transverse posttensioning magnitude and tendon location as well as bearing pads' supporting restraint was modeled in the FEA to investigate their effect on the distribution of transverse posttensioning force along the joints between adjacent box-girders. Results show that (1) transverse posttensioning and diaphragms reduce efficiently the tensile stress on top of deck; but this efficiency slows down significantly in bridge corner area, where exists still relatively higher tensile stress than other locations; (2) In some cases of loading combination, most locations on top of deck along the joints exist transverse tensile stresses, but the magnitude is less than 0.7Mpa, which could not cause the cracking if the decking concrete cover and keyway grout are properly selected and cast to the designated specifications; (3)Two patterns of transverse posttensioning output almost same result in the clamping stress along the joints for this proposed particular bridge model; (4)The vertical spacing between two tendon locations (upper and low level)should be farther spaced than the currently specified 1/3 girder depth so that less tensile stress or compressive stress is expected on top of deck; (5) The restrain from bearing pads modeled in this FEA has little effect on the stress distribution along joints between box girders.