Prediction of development length from free-end slip in pretensioned concrete members

Abstract

Development length of prestressing strands is a significant parameter in the design of pretensioned concrete members. The adequacy of the code equations used to predict the development length needs to be verified when a new material or design parameter is introduced for precast, prestressed concrete applications. This study develops a simple and reliable technique to quantify the development length based on the premise of the slip theory, which proposes the free-end slip (FES) as an indicator of the development length. Twenty-five pretensioned concrete beams were cast with 15 mm diameter strands. FES was measured at both beam ends at prestress transfer. Development length was determined by performing bending tests at different embedment lengths. The experimental results were synthesised to revise the slip theory. The applicability of the revised-slip theory was validated by collected experimental data of pretensioned concrete members using various types of concrete, strand diameters and release techniques.