Post-Installed Metal Anchors Behavior In Cyclically Cracked Concrete

Abstract

The mechanical behavior of post - installed metal anchors is well known under quasi - static loads but is mostly unknown in seismic loading conditions. Particularly, the loadbearing capacity of such construction products is greatly influenced by the presence of cracksin concrete, especially when the anchor is fixed along a crack.In seismic conditions, fasteners are expected to transfer cyclic actions as reliably aspossible, from the fixture to the concrete. At the same time, the cracks system of the concrete structure will be subjected to a variation of their width.Actually, post -installed metal anchors are covered by two codes in Europe: ETAG - 001 Guideline 6 and Eurocode 2.2 These codes require anchors testing in cracked concrete with static crack opening of 0,3 mm. A Working Group EOTA, involving a number of writers, iscurrently working on a revised version of ETAG - 001 Guideline 6 covering the seismic behavior too.Today, the only one code that cover the seismic behavior of these products is ACI 3551 which provides an experimental test with cyclic loading applied to the anchor installed in anopened crack having constant width.In this paper the results of a recent experimental test on a torque -controlled expansion anchors (bolt - type) installed in cracked concrete specimens are presented. The originality ofthese tests is that the anchors are installed along a concrete crack, which undergoes to opening and closing cycles, while the design axial load is applied to the anchor and remains constant during the test. This approach could be interpreted as complementary to the one followed by ACI 3551 code.The testing apparatus allows the monitoring of the anchor slip during theopening/closing crack cycles. Furthermore, the effects of increasing damage in the concrete and in the anchor on the residual pull - out capacity of the anchors could be estimated.