Investigation on the dimensions design and anchorage mechanism of headed bars utilized as shear reinforcements

Abstract

The utilization of headed bars, instead of hooked bars, as shear reinforcements in concrete structures could provide an effective solution to address the issue of reinforcement congestion during installation. Nevertheless, the method for determining anchor head dimensions based on anchorage performance remains unclear. This study proposed a method to determine reasonable anchor plate dimensions through finite element (FE) simulations, with hook pull-out performance as the fundamental basis. Firstly, based on the principle that the anchorage performance of the headed bars should not be inferior to that of the traditional hooked bars, the dimensions of the anchor plate were preliminarily determined through FE simulation. Subsequently, the rationality of the determined plate dimensions was verified through pull-out tests conducted on a total of 36 specimens. To investigate the adverse effect of seismic-induced damage on the anchorage performance of headed bars, various test variables were considered, including anchor types, loading regimes, integrity of concrete cover (intact or spalling), and existing flexural cracks. The obtained test results demonstrated the reasonability of the determined plate dimensions. Even under the conditions of cover spalling and existed flexural cracking, headed bars with the designed dimensions still exhibited better anchorage performance than that of 180-degree hooks. The results of the pull-out tests could provide a guidance for the application of headed bars as shear reinforcements in reinforced concrete (RC) structures, such as in heavily loaded walls and foundations.