Prestressing Strand Bond Characteristics Under Reversed Cyclic Loading

Abstract

U ntensioned, bonded prestressing strand is used in a variety of ways during construction of precast prestressed concrete structures, Untensioned strands can he used to reinforce the connection of precast elements. Hanson and Burnett' and Burnett and Anise dicussed the use of untensioned strands to connect floor slabs and elements of large-panel structures. Salmons and McCrate 3 considered the bond characteristics of untensioned bonded prestressing strands similar to those which extend from the ends of precast prestressed beams used in bridges. In response to seismic loads or pattern loading of structures, untensioned, bonded strands that reinforce the connection of precast elements and pass through supports can experience loads that cause repeated slip of the strands relative to concrete within the support. Loss of bond in this region may result in severe reduction of lateral stiffness of the structure and in loss of stiffness under certain gravity loadings. The objective of the test program was to study the effects of different variables on the cyclic pullout behavior of initially unstressed, bonded strands.