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Bond of deformed bars in steel fiber-reinforced concrete under cyclic loading

University of British Columbia

The influence of reversed cyclic loading on the anchorage bond behaviour of deformed bars in plain and steel fiber reinforced concrete was studied. The intent was to examine the feasibility of using steel fibrous concrete to improve anchorage bond performance in beam-column joints in moment resisting frame structures for seismic resistance. Twenty-four specimens were tested, in which a single bar was simultaneously pulled at one end and pushed in at the other; the load was reversed cyclically to simulate the loading of a bar passing through an interior beam-column joint under seismic loading. The important variables were the size of steel fibers and the pattern of loading. The results indicate that the loading history has a significant influence on the bond deterioration. A significant reduction in stiffness and resistance capacity is observed for specimens under reversed cyclic loading as compared to those under monotonic loading, and this was primarily due to a deterioration in the stress transfer mechanism. The addition of steel fibers improved the anchorage bond capacity by 20 to 26 percent and retarded the rate of bond deterioration under reversed cyclic loading. The steel fibers were also found to make a definite contribution to crack control and thus better serviceability. From a study of the geometric characteristics of the applied stress displacement curves, a trilinear model was proposed to predict the response of a specimen under reversed cyclic loading of incrementally increasing nature. Finally, an elastic axisymmetric finite element analysis was carried out as a supplement to the information obtained from the experimental study. It was found useful in formulating a theory on the bond deterioration mechanism.

Text

2010-06-12

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http://hdl.handle.net/2429/25597

Civil Engineering

University of British Columbia

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