BEHAVIOR OF BONDED ANCHORS IN UNCRACKED AND CRACKED CONCRETE AT HIGH TEMPERATURE

International audiencePost-installed bonded anchors are commonly used in steel-to-concrete connections that demand high load-carrying capacities and flexible and/or unplanned anchoring locations. While formulations of polymer-based bonded anchors have continued to advance in their temperature-resistant properties, all polymers possess an inherent sensitivity in load-carrying capacity to temperatures near and above glass transition. Protocols for determining fire performance of post-installed bonded fastening products are described in EOTA TR 020 for bonded fasteners and EAD 330087 (2018) for post-installed reinforcement (PIR). No fire criteria are currently provided in EAD 330499 (2019) for bonded fasteners or in any American anchor assessment documents. Beyond the limitation that TR 020 (2005) cannot be used as the basis for a European Technical Assessment, descriptions in TR 020 permit a degree of interpretation that can significantly influence the evaluated performance of bonded anchors under fire conditions. Therefore, there is a need to improve the fire assessment of bonded anchors in uncracked and cracked concrete by recommending clearer and more specific criteria that can be placed into anchor assessment documents. This paper presents an experimental study on bonded anchors using an epoxy resin in cracked concrete exposed to high temperature. Reference confined pull-out tests were conducted on bonded anchors in cracked (0.3 mm crack width) and uncracked concrete at ambient temperatures in accordance with existing European guidelines. Tests were then conducted on bonded anchors in cracked and uncracked concrete exposed to high temperature with an electrical heating system. The results were analysed to understand the thermal and mechanical influence of a crack running along the embedment depth of the anchors at ambient and elevated temperatures. This experimental study provides a database for future development of testing and assessment requirements for bonded anchors exposed to hightemperature fire conditions