Structural behaviour of bolted end-plated reinforced concrete beams

摘要

The paper reports a study on the flexural strength and deformation characteristics of concrete beams reinforced with threaded steel bars that were tensioned against steel plates bearing on the concrete ends by means of tightening nuts. Stressing of the beams was achieved when the nuts were turned until finger tight. Six beams were subjected to monotonic loading and 4-20 cycles of loading. Four control beams were also cast using normal non-tensioned bars. Cracking loads for the prestressed beams averaged 280% of the control beams. For the two series of beams, the ratio of cracking load P_(cr) to the failure load P_(ult) was almost the same, averaging 0.25 and 0.22 for the prestressed and control beams, respectively. Cyclic loading of the prestressed beams was characterized by complete crack closure on the removal of the applied load, but for the unstressed beams, cracks remained open throughout the full load cycles. Failure loads for the stressed beams averaged 244% of the unstressed beams, even though the span-to-depth ratio was larger for the former. Failure loads for the stressed beams averaged 219% of the theoretical failure load (based on an assumed unstressed beam). At failure the maximum crack width in the beams ranged from 0.03 to 0.2 mm for the prestressed beams, and 2.9-3.5 mm for the unstressed control beams.