Stay-In-Place Deck Panels - Horizontal Shear Strength of Bridge Deck Panels - Part 2

摘要

One of the most economic methods of bridge deck construction consists of prestressed concrete deck panels used in stay-in-place forms in conjunction with the cast-in-place concrete topping instead of the traditional monolithic roadway deck slabs. The performance of this type of deck as a composite unit is only possible if the horizontal shear stress resulting from bending of the deck if effectively transferred across the interface of the two elements. It is assumed that horizontal shear stresses are transmitted across the interface due to bond between the precast panel and cast-in-place concrete acting in conjunction with the horizontal shear connectors provided across the interface. Presently the Indiana Department of Transportation requires a minimum of 20 shear connectors in (1.27 to 1.91 mm) total amplitude deformations is specified instead of a raked finish with a total amplitude of 0.25 in. (6.35 mm) because of the reduced 2.5 in (63.5 mm) thickness of the panels used in Indiana. This study focuses on the evaluation of the horizontal shear strength across a broom finished interface. Experiments were undertaken on six precast prestressed deck panels with composite cast-in-place concrete topping. All the specimens were 8 ft. x 3ft. (2.4 m x 2.4 m) and 2.5 in. (63.5 mm) thick precast prestressed panels were 5.5 in (140 mm) topping slab. Specimens 1 and 5 had no shear connectors and specimens 2, 3 and 6 had four shear connectors across the interface. Specimen 4 had four shear connectors and the top of the precast panel was sprayed with a bond breaking agent (form oil) to eliminate chemical bonding between the precast panel and cast-in-place concrete topping. The test results indicated that shear connectors are not required to achieve adequate composite action at service and ultimate load levels in panels with broom finished top surface. This finding is limited to situations where the nominal average shear stress does not exceed 115 psi. A minimum of 4 shear connectors will likely be provided for handling purposes. A comparison of the performance of the specimens in this study with and without shear connectors indicates that specimens with four shear connectors were stiffer near failure load. The minimum of 4 connectors did not significantly increase the load carrying capacity of the panels tested. Lubrication of the interface in specimen 4 resulted in a 10% decrease in ultimate capacity as compared to that of companion specimen 3. But the failure load in specimen 4 was 82% high than the predicted value based on development length requirements (stand slip criteria).