About design and testing of the load transfer zone on concrete in prestressed structures

Abstract

Design the load transfer zone on concrete in prestressed structures is a time-consuming and nontrivial task. To confirm the design assumptions, it is necessary to conduct appropriate tests using kits of the prestressing systems. The authors have analyzed the new Russian national standard for prestressing systems and compared its requirements with other Russian and international standards.  The purpose of the research is to experimentally verify the methodology for design the load transfer zone in prestressed concrete structures, as well as to prepare recommendations for designers based on the current and previous research by the authors. The article presents the results of testing the load transfer zone on concrete from an anchorage with a bearing cup for 19 strands (OS-19) manufactured by STS LLC, which is the most commonly used anchor in bridges in the Russian Federation. The article includes drawings of the test specimen, photographs of the specimen before and after concreting, and diagrams of the location of indicators on the faces and strain gauges on the reinforcement. The test specimen was used to measure the deformations of the concrete on the faces and the reinforcement bars using strain gauges. The article analyzes the type of the specimen's failure during the testing process. The article provides a brief description of the test specimen's finite-element model and compares the experimental data on concrete deformations and reinforcement stresses with the theoretical values.  The analysis of the results shows a sufficient convergence of the measured values, indicating the reliability of the design assumptions. However, the authors have discovered a previously unknown effect of reducing the stresses in the longitudinal reinforcement of the specimen. Based on this work and the authors' practical experience, the article provides recommendations for designers of prestressed structures that are not included in existing Russian standards.