Tensile Behavior of Single Cast-in Anchors in Plastic Hinge Zones

Abstract

Cast-in concrete anchors and headed studs, embedded in concrete, are used to connect structural steel members and concrete. Typical embedded connections include brace-column connections and girder-wall connections. Such connections are a critical component in composite construction between steel and concrete members, affecting structural performance during earthquake events. For example, shake table tests of structure models have shown that the embedded connections are susceptible to damage in earthquakes, which in turn disturbs the desired structural performance [1,2]. Typical failure modes for cast-in anchors in tension are anchor steel failure and concrete breakout failure. Anchor steel failure is caused by fracture of an anchor shaft in tension while concrete breakout failure is marked by a concrete cone broken away from the base concrete, in which the connection is located. Concrete breakout failure occurs when anchors are located close to an edge or with a small embedment depth. Concrete breakout is a brittle failure mode and thus not preferred for anchor connections in seismic zones [3]. The well-established design procedures for concrete anchors, such as those stipulated in ACI 318-11, do not apply to the anchors installed in plastic hinge zones. This is because the concrete in plastic hinge zones likely develops substantial damaged during an earthquake while the design procedures are based on experimental tests of anchors in concrete that is not stressed/cracked.