Size Effect on Strand Bond and Concrete Strains at Prestress Transfer

Abstract

[EN] The size-effect phenomenon has been analyzed with pretensioned prestressed concrete prismatic specimens at prestress transfer. An experimental program that includes variables such as concrete mixture design, specimen cross section size, and concrete age, has been conducted. Several series of specimens with different embedment lengths have been made and tested using a testing technique based on the bond behavior analysis by measuring prestressing strand force. In addition, some specimens have been instrumented to determine longitudinal concrete strain profiles. The tests have provided data on concrete strains, transfer length, effective prestressing force, bond stress, and concrete modulus of elasticity. Relationships between measured prestressing strand forces and effective prestressing forces obtained from concrete compressive strains have been found. A coefficient to account for the specimen crosssection size-effect on the concrete modulus of elasticity has been proposed. Comparisons between test results and theoretical predictions from pre-existing equations in the codes have been made.