Experimental evaluation of partial depth precast concrete deck panels subjected to shear loading

Kintz, John Robert
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Horizontally curved girder bridges are often utilized for highway interchanges and other projects with restricted right-of-way. The large torsional demands caused by the girder geometry often require these systems to have extensive bracing, typically in the form of cross frames or diaphragms, to increase the torsional stiffness of the girder system during the construction phase. The most critical stage for the bracing is during the deck placement, when the noncomposite girders must resist the full construction load. Partial depth precast concrete panels (PCPs) are prestressed concrete panels used primarily as stay-in-place (SIP) formwork for straight girder systems. They are placed on full-length extruded bedding strips epoxied to the girder top flange, and the remaining depth of the deck is cast above. This is a time-efficient method of construction, and has become an attractive option due to ease of constructability and deck longevity. Although the panels have not been used on horizontally curved girder systems, there is a desire by bridge owners and contractors to use the forms in some curved girder applications. In addition to using the panels on curved girder applications, engaging the in-plane shear stiffness of the panels may lead to significant bracing in both straight and horizontally curved girder applications.
A research investigation focused on measuring the behavior of PCPs acting as a shear diaphragm, as well as to develop an adequate connection between the PCPs and the girders was conducted at The University of Texas at Austin. Four PCP connection details were developed and tested at two different bedding strip heights. These connections were designed for a range of capacities, and in-plane shear load was applied until failure using a frame mechanism assembly. The experimental results showed that the connected PCPs had significant shear stiffness and strength, with the panels reaching shear capacities between 91 and 154 kips before failure depending on the connection detail that was utilized. A 46 to 70 percent increase in shear stiffness was also observed when the bedding strip height was reduced from 4 inches to ½ inch. All panels greatly exceeded the design capacity using the ACI design predictions, with 7 of 8 panels eventually failing due to concrete side face breakout. The eighth PCP failed from weld rupture in which the weld connecting the WT and the girder flange began to unzip.