There has been an increase in the design of bridge substructures using precast elements in order to accelerate construction. Often, these designs require innovative connection methods, such as reinforcing bars spliced in closure pours between precast pieces. Making these splices using large-sized bars for the flexural reinforcement can be challenging because the development length of straight reinforcement, particularly Class B tension lap splices that must be 1.3 times the ordinary development length, can make closure pours quite large. Furthermore, failures of these connections tend to be brittle, thus adequate development is important.
One strategy for reducing the closure pour length is to lap splice hooked bars in a non-contact fashion, which enables easier fit-up of members during construction. While AASHTO does provide limits for lap-spliced straight longitudinal bars in flexural members, there is no guidance on the maximum offset distance between hooked bars serving as a lap splice. There is also little data for non-contact lap splices or the development length of hooked bars that are larger than #6 bars. Additionally, multiple layers of spliced reinforcement in tension is not explicitly covered in AASHTO.
The objective of this work will be the development of recommendations for designing non-contact, hooked bar lap splices in precast substructure elements. The scope will include large-scale structural tests to assess the need for modification factors based on: bar size, hook type, distance between lapped bars, side cover, transverse tie reinforcement, multiple layers of reinforcing, reinforcement yield strength, and concrete strength. The analysis will assess the cracking at service level stresses and the conditions of the elements at strength level and incipient failure.