About the research
For this project, an innovative wide joint was designed with a roughened interface surface, shrinkage-compensating concrete, and reinforcement steel. The researchers built and tested a specimen that consisted of two box beams and one innovative intermediate joint under early-age thermal loading and cyclic live loading in the laboratory. During these tests, no cracking was found in the joint and no trend of increasing differential displacement was found between the two beams over the course of millions of live load and thermal cycles.
Based on the results of the literature review and laboratory tests, this wide joint between the roughened interface surface, filled with shrinkage-compensating concrete and reinforced by reinforcement steel, can create a crack-free joint without the utilization of a shear key or transverse post-tensioning.
This joint is as functional as the traditional cement grout-filled narrow joint with respect to the transfer of the moment and shear between the girders, while also performing better than the traditional joint in resisting joint cracks in both early-age loading and the long-term service life of the bridge. At the same time, the test results for the new innovative joint detail appear to compare very well with the ultra-high performance concrete (UHPC) based joint detail developed and tested previously by the Federal Highway Administration (FHWA). However, the UHPC joint may have greater durability due to the very low material permeability
To further investigate the performance of this joint detail, the researchers recommend that a field trial be completed. During this field trial, the bridge should be monitored and evaluated during early-age concrete curing as well as for a period of at least two years following construction.