Experimental analysis of a modified two-step corbel for precast concrete system

Abstract

Concrete corbels are the most common component used in connections of precast concrete structures. The industrial production system is especially difficult when multi-planar corbels with different shapes are used. To overcome this problem, the column may be cast without corbels, which are instead cast in a second stage after the column has been stripped from the mould. This system can improve the industrial production and reduce the openings and cut-outs in the formwork. In the two-step corbel system analysed in this paper, fully anchored threaded couplers are placed in the column mould and used in a second stage to splice the main reinforcement of the corbels. Different treatments of the column–corbel interface and two applied load eccentricities are analysed. Thirty-four specimens with a monolithic corbel or a two-step corbel are tested. The corbel strength and crack width of the column–corbel interface are measured by experimental tests. Alternatives are suggested to the two-step corbel system; that is, the use of a loop reinforcement crossing the interface to reduce the interface crack width and the use of 80 kg/m3 steel fibres to replace the secondary reinforcement of the corbel. This solution showed the same strength and interface crack width as monolithic corbels under the service limit state. The addition of steel fibres to the corbel did not have a significant influence on its strength. However, the steel fibres were necessary to guarantee a ductile failure of the compression strut in the absence of secondary reinforcement in the corbel.