Pull-out and push-in tests of bonded steel strands

Abstract

The objective of this study was to analyse the behaviour of prestress strand anchorages by bonding with an epoxy adhesive for structural strengthening use. Pull-out and push-in tests were carried out on 15·2 mm diameter prestress steel strands sealed in 18 mm diameter holes with several embedment lengths, complemented by long-term tests. Experimental results are presented and compared with theoretical results regarding maximum pull-out and transmittable loads and also draw-in results. Theoretical results are obtained by solving the governing equation of the bond phenomenon adopting a non-linear local bond/slip law derived from pull-out tests with short embedment length. The study shows that it is reasonable to assume an average constant bond stress for anchorage design with the studied epoxy adhesive in the range of the studied values of anchor embedment length and diameter. The average values for bond stress to be used for determining the maximum pull-out and transmittable loads were found to be 12·0 and 5·2 MPa, respectively. Experimental draw-in values show a great variability, and so determining transmission length based on draw-in values may lead to a false perception that the transmission length is very variable.