Bolted connections have many benefits and are popular for connecting precast structures. They can be used for several different configurations, allow fast and easy installations, and are reversible in their nature. By maximizing the use of precast technology together with bolted connections, workload is shifted from sites to prefabrication facilities, which results in higher precision and consistent quality.
Even if precast concrete structures can be manufactured with higher precision than on-site constructions, their connections must still have sufficient amount of installation tolerances to allow efficient installations. With bolted connections, this is realized by using oversized bolt holes. Additionally, a joint gap is left between structures to allow positioning after the installation. The gap must be filled with cement-based grout to secure the load-transfer through the joint in the final stage.
When bolted connections are finalized by grouting the gap and/or tightening the nuts, they are typically subjected to shear and normal forces or their combination. In general, shear forces may be resisted by frictional forces acting at the joint faces, if the joint is subjected to simultaneous compressive normal forces. Nevertheless, such compressive forces do not exist in all applications, and shear forces must be transferred by other means.
When loading the structures and their connections, they must retain adequate performance both in serviceability and ultimate limit states. Considering shear transfer in serviceability limit states, aesthetics and durability of structures and their connections cannot be endangered by excessive deformations (cracking or yielding) or displacements (slip between structures). In bolted connections for precast structures, this would mean cracking of joint grout, yielding of anchor bolts or slip due to oversized bolt holes.
The current code methods must be reviewed for their suitability in assessing the maximum shear force in serviceability limit states. This can be done by comparing the results from experimental investigations with calculated values.
Read the White Paper - Shear transfer in Peikko bolted connections
