12-441, SPR RB19-014, SPR RB07-013
Iowa Department of Transportation
Brent Pharesbphares@iastate.edu email >
Bridge Research Engineer, BEC
About the research
As accelerated bridge construction (ABC) has gained the attention of the bridge community, certain bridge types, such as integral abutment bridges, have seen limited use. Integral abutments eliminate the expansion joint from the bridge superstructure by rigidly connecting the superstructure and foundation. The integral abutment is therefore often large and heavily reinforced, which presents challenges for ABC projects.
This research investigated integral abutment details for use in ABC projects through mechanical splicing of the integral diaphragm and the pile cap. Two ABC details, the grouted reinforcing bar coupler detail and the pile coupler detail, were evaluated in the laboratory for constructability, strength, and durability. A typical cast-in-place detail was also constructed and tested as a baseline.
For the grouted reinforcing bar coupler detail, a plywood template was used to “match cast” the pile cap and the integral diaphragm. The template was simple to construct and resulted in the successful alignment of 17 spliced steel bars and grouted couplers over an 8 foot specimen. Though the grouting of two couplers was obstructed, more than adequate strength was created by the connection, and the crack width at the precast joint was comparable to that of the cast-in-place specimen.
The pile coupler reduced the number of spliced connections between the pile cap and integral diaphragm sufficiently to facilitate adequate construction tolerances. The splicing system worked well during construction, but the detail’s strength and durability was less than ideal. Several lessons were learned from these tests that could improve the structural performance of the pile coupler detail.