Anchorage of High-Strength Reinforcing Bars with Standard Hooks: Initial Tests

Abstract

This report describes the initial tests on the anchorage strength of standard hooked bars in concrete. The goal of the testing is to determine the effects embedment length, side cover, tail cover, quantity of transverse reinforcement, location of longitudinal reinforcement, concrete strength, bar size, and bar bend on the anchorage strength of hooked bars in concrete. Initial tests have been performed on No. 5 and No. 8 bars, with 90° and 180° hooks, cast in concrete with a nominal compressive strength of 5000 psi. Further testing will also include No. 11 bars and concrete strengths up to 15,000 psi. The goal of this study is to gain a firm understanding of the anchorage strength of hooked bars in concrete as a function of the key variables and use the data to establish reliability-based design expressions for development length. Thus far, the testing apparatus has been fabricated, the testing procedures have been established, and the initial specimens have been tested. The test results agree qualitatively with those in previous studies and show that hook strength increases with increased embedment length, side cover, and confining reinforcement. The results also show that hook strength is greater for hooks anchored within a column core than for hooks anchored outside of the core. The latter case is appropriate to hooks anchoring bars at the end of cantilever beams.