Keywords: anchorage; beam-column joints; bond and development; highstrength concrete; high-strength steel; hooks; reinforced concrete; reinforcement. INTRODUCTIONProvisions for calculating the development length of hooked bars in U.S. design codes, such as the ACI 318-14, "Building Code Requirements for Structural Concrete"; ACI 349-06, "Code Requirements for Nuclear Safety-Related Concrete Structures"; and the "AASHTO LRFD Bridge Design Specifications" (AASHTO 2012) are based primarily on studies performed in the 1970s by Minor and Jirsa (1975), Marques and Jirsa (1975), and Pinc et al. (1977). These studies included only a small number of specimens containing standard hooks and a limited range of material properties (Grade 60 [420] reinforcing steel with yield strengths of 64 and 68 ksi [441 and 469 MPa] and concrete compressive strengths between 3750 and 5400 psi [26 and 37 MPa]). Neither high-strength steel bars nor high-strength concrete, now commonly available in construction practice, were included in these studies.The main objective of this paper is to present the results of a study of key parameters affecting the anchorage strength of standard hooked bars with a much wider range of material properties. For the purpose of this study, standard hooked bars are defined according to the provisions in Section 25.3 of ACI 318-14. Due to the magnitude of the study, the results are presented in a series of papers. The specific objectives of this paper are to describe the experimental program, provide detailed information about the observed mode of failure of the specimens, and present an evaluation of the experimental results in the context of the development length provisions for hooked bars in ACI 318-14. A second paper will present a statistical analysis of the test results and formulate equations to characterize hooked bar anchorage strength for normal and high-strength materials. Subsequent papers will evaluate specific parameters affecting hooked bar anchorage strength and develop code change proposals. RESEARCH SIGNIFICANCEThe use of high-strength steel and concrete is becoming more common in the construction industry due to benefits such as lower congestion, smaller member dimensions, and increased useable floor area. Current provisions in ACI 318-14 for hooked bar anchorage are based on limited test results that include a single grade of reinforcement and a narrow range of concrete compressive strengths. An experimental program with an expanded range of material properties was necessary to develop a better understanding of the main parameters that affect anchorage strength and to formulate code provisions applicable to the full range of material strengths available in present-day reinforced concrete construction. EXPERIMENTAL PROGRAMA total of 337 beam-column joint specimens-276 with two hooked bars and 61 with three or more hooked barswere tested to investigate the anchorage strength of hooked bars (Searle et al. 2014; Sperry et al. 2015a,b). The parameters of the study were bar size, bar stress a...

The effect of close spacing on the anchorage strength of standard hooks is investigated. Sixty-seven simulated beam-column joint specimens were tested, each containing three, four, or six No. 5, 8, or 11 (No. 16, 25, or 36)

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XM-28 (UNS S24100) and 2304 (UNS S32304)