Bond Behavior of Strands in UHPC: Fid-Bau Portal

Bond Behavior of Strands in UHPC

Vojvodic, Goran / Hadl, Philipp / Tue, NguyenViet

Abstract UHPC-Elements are highly suitable for prestressing due to material properties, such as high strength, matrix density und durability. From a structural and economic point of view especially thin-walled members are of interest. Further elements casted in the prestressing bed with pre-tensioning have advantages regarding production, transport and assembly. For this application an early strength development is required and brittle behavior needs to be avoided. Early strength can be reached by using proper concrete mixtures and ductility can be increased by adding steel fibers. Particularly important is also the knowledge of the bond properties, which are required for global and local structural design. As part of the current research project Substitution of steel by UHPC the bond behavior of prestressing strands in UHPC has been investigated. In high strength concrete the bond length of the strands in the matrix is relatively short. This results in higher splitting forces due to tensile stresses. The aim of the research was to determine the fiber content necessary for taking up the required restraining force and additional concrete cover without using conventional reinforcement. Secondly the bond behavior was described by characterizing the transfer zone. A self-developed UHPC mixture with self-compacting properties and a compressive strength higher than 180 MPa after 28 days without heat treatment and a high amount of steel fibers was used. The bond behavior is going to be presented in detail by theoretical basics, results of experimental tests and their comparison to results from literature.