Investigation of Reinforcement Anchorages with Large Diameter Bars: Fid-Bau Portal

Investigation of Reinforcement Anchorages with Large Diameter Bars

Schoening, Janna / Hegger, Josef

Abstract Bond zones in heavily reinforced concrete details are highly utilized. Bar spacing and concrete cover are small, while bar diameters are large. The anchorage of the large diameter bars leads to high rebar-forces to be developed, and substantial concrete stress. The bond between reinforcement and concrete matrix results in hoop stress around the bar and longitudinal cracks occur subsequently. Anchorages of reinforcement in structural concrete were tested in bond tests with short bond lengths or lapped splices by many authors. In contrast, tests of the end anchorage at beam supports have hardly been conducted. Since the bond stress distribution is not constant over the bond length, an extended anchorage length does not necessarily lead to increasing bearing capacity. Eurocode 2 however simplifies the bond strength to be constant over the bond length, which leads to higher resistance with increasing anchorage length. For confinement by stirrups or concrete cover, Eurocode 2 allows for a reduction of anchorage length. The structural behaviour of concrete elements reinforced with large diameter bars was investigated by beam-end tests and lapped splices at RWTH Aachen University. The test results were published at the fib Symposium 2015. An additional test series comprising 12 test specimens analyses the anchorage behaviour at supports of elements subjected to bending. To investigate the required anchorage length for large diameter bars, the confinement by concrete cover and transverse reinforcement is varied. The aim of the investigation is a reduction of the anchorage length for large diameter bars and a quantification of the required transverse reinforcement allowing for ductile behaviour. This paper presents the tests and a potential anchorage length reduction for the confinement of heavily reinforced anchorages.