The bond between reinforcing bars (rebar) and concrete is one of the fundamental components governing the mechanical behavior of reinforced concrete (RC) structures. It plays a decisive role in transferring tensile and compressive stresses between the two main constituents of such structures. This bond not only prevents slippage of the rebar within the concrete but also ensures the structural integrity and proper performance of members under service and various loading conditions. One of the most common methods for achieving adequate bond strength is the use of hooks at the ends of reinforcing bars. Hooks are particularly important in critical regions of structures, splice zones, or locations where sufficient straight embedment length cannot be provided. The anchorage performance of hooked bars is influenced by a combination of parameters, including the bar diameter and type, hook angle and bend radius, concrete compressive strength, effective embedment length, concrete cover, and loading conditions.

In this paper, a systematic review of previous studies is conducted to analyze the force transfer mechanisms in the hook region and to identify the key factors affecting its anchorage capacity. Furthermore, the bond behavior under different loading scenarios—including monotonic, cyclic, and seismic loading in critical regions—is examined.

A comparison between the provisions of major design codes such as ACI 318 and Eurocode 2 with the results of experimental investigations reveals that, although significant progress has been made in this field, there remain uncertainties and challenges in accurately estimating the required development length of hooked bars. The main objective of this study is to present a comprehensive overview of past findings and to establish a scientific basis for optimizing the design of hooked bar development lengths in reinforced concrete structures