Cyclic Behaviour of Beam-Column Dowel Connection in Precast Elements

Abstract

Disruption of structural continuity due to the inherent nature of the connections poses a challenge in seismic design of precast concrete structures. Seismic behaviour of portal frame systems typically used for industrial halls, is greatly influenced by the beam-column connections. Capacity design dictates that these connections should have an elastic behaviour under seismic horizontal actions to allow for the dissipation mechanisms to develop in the desired area, in this case the base of the columns. If this connection fails, the entire structure is compromised and may lead to a premature, partial, or even total collapse. Efforts are currently underway for a better understanding of the seismic response of precast structures (e.g. SAFECAST project). In this study, the test setups tried to replicate as closely as possible the behaviour of a commonly used beam-column assembly connected by steel dowels. The test specimens were designed as full scale precast concrete elements. This experimental campaign aimed to determine the failure mechanisms of the assemblies and to check if capacity design requirements were satisfied. Three setups have been tested according to the experimental protocol described in the SAFECAST report. The first test specimen was subjected to a unidirectional monotonic loading protocol with the aim of observing the maximum failure force and deformation. The resulted maximum displacement was used to determine the displacement step increment for the cyclic loading protocol of the following two specimens. In all the cases, failure has occurred in the region of the dowel connection. The failure mechanism was either because of dowel yielding, concrete spalling around the dowel, or a combination of both, consistent with results obtained by other researchers. The results have showed that the column was far from reaching its failure capacity and a premature failure has occurred in the connection area, which should be avoided in common practice. Marius G.L. Moldovan, Mihai Nedelcu and Zsolt Kovacs

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