Strength and modes of failure of adhesive anchors in confined concrete under direct tensile loading

Bonded anchors are used in several civil engineering applications, whose performance needs to be investigated. This paper discusses some experimental investigations on the strength and failure modes of bonded anchors in concrete, without and with confinement reinforcement. The effect of strength of concrete, embedment length and diameter of anchors has been studied. The important parameters influencing the strength of anchorage system are compressive strength of concrete and the embedment depth of anchors. Three different concrete strengths of 25, 40 and 60MPa were adopted along with three embedment lengths of 150mm, 200mm and 250mm. The anchorage strength increases as the compressive strength of concrete increases. As the embedment length of anchor increases, the anchorage strength also increases. The diameter of the anchor does not show much influence on the strength of anchorage. The strength of bonded anchors was observed to coincide with the strength estimated as per both CCD design method and ACI 349 method. Bonded anchor load carrying capacity has been observed to closely match with that of the post-installed anchors. It has been observed that concrete cone failure was predominant in all the specimens without confinement reinforcement. The confinement reinforcement alters the mode of failure from concrete cone failure to ductile failure of concrete with distributed cracking.