Simple Design Details using Precast Concrete Panels at Skewed Expansion Joints

The Texas Department of Transportation (TxDOT) has developed a new design detail that uses precast concrete panels as stay-in-place formwork adjacent to expansion joints in prestressed concrete bridges; however, skewed bridges present a unique challenge to the use of the precast panel system immediately adjacent to the expansion joint.

The objective of this research project was to investigate the response of trapezoidal precast panels used immediately adjacent to the expansion joint in skewed bridge decks. Five representative test specimens were constructed comprising two skew angles: 30o and 45o. Trapezoidal, precast panels for the 45o specimens were fabricated at Ferguson Structural Engineering Laboratory (FSEL) by project personnel. Trapezoidal, precast panels for the 30o specimens were manufactured by an independent precast concrete supplier. Four of the specimens were subjected to statically applied loads on the ends of the skewed panels, and one of the panels was subjected to fatigue loading on the skewed end before being loaded monotonically to failure.

All test specimens containing the 45o precast panels fabricated at FSEL failed in diagonal shear at the short side of the trapezoidal panel when load was applied at midspan of the skewed end of the slab. All test specimens containing the 30o precast panels fabricated by an independent precast supplier failed by delamination due to horizontal shear between the panel and the cast-in-place topping slab when load was applied at midspan of the skewed end of the slab. Regardless of the failure mode for load applied at midspan of the skewed end of the specimen, all specimens failed in punching shear when load was applied at midspan of the square end of the trapezoidal panel.

Fatigue of the skewed panels did not limit the strength or stiffness of the panels along the skewed end. However, the maximum load carrying capacity along the skewed end may be limited if delamination occurs between the skewed panels and the topping slab. Current TxDOT specifications do not quantify levels of panel surface roughness for precast panels; therefore, additional testing is scheduled to take place in the summer of 2008 to further investigate the effect of panel surface roughness on the horizontal shear capacity between the trapezoidal panel and the cast-in-place topping slab.

The research team concluded that trapezoidal panels exhibit adequate strength and stiffness for current design loads if delamination is avoided.