Seismic behaviour of connections between precast concrete elements

Abstract

Several precast concrete systems have been in use in New Zealand in the construction of moment resisting frames designed for earthquake resistance, despite the lack of code design guidelines. The two design codes for buildings, NZS 4203 (1984) and NZS 3101 (1982), deal only with the design of monolithic concrete construction. The use of precast concrete in moment resisting frames in New Zealand assumes that this method of construction behaves the same as monolithic reinforced concrete structures. A test programme was devised to provided experimental evidence on the seismic behaviour of the most commonly used precast concrete arrangements. Six full-scale subassemblages were quasi-statically tested under reverse load conditions with increasing displacements to failure. Four tests were conducted in H-shaped specimens connected at the beam midspan. The remaining two specimens were cruciform-shaped and had the connection detail in the critical region at the beam-column joint. It was found that neither of the connection detail nor the construction joints have a detrimental effect on the seismic performance. Hence, the assumption of designing these systems as if monolithic is adequate. Theoretical work was undertaken to give simple design recommendations for the design of different connecting details, including the design of interior beam-column joints. Truss models and the concept of shear friction were extensively used. This report also discusses in some detail the stress-strain behaviour of the two grades of New Zealand manufactured reinforcing steel. Test results on the effects of bar deformations, strain ageing and strain rate on the cyclic behaviour of reinforcing steel are presented. An analytical model based on test results is postulated