The seismic behavior of coupling beams and walls constructed with tensile strain-hardening, high-performance fiber-reinforced concrete (HPFRC) was studied through tests of large-scale precast coupling beams and coupled walls. A precast coupling beam design was developed to speed up construction and minimize interference with wall reinforcement. Three isolated precast coupling beam specimens with a span-to-depth ratio of 1.75 were tested under large displacement reversals. Test results indicate the use of HPFRC allows a reduction of the reinforcement required to achieve a stable coupling beam response by providing confinement and contributing to beam shear strength. A concrete design shear stress capacity of 0.41√fc', [MPa] (5√fc', [psi]), where fc' is the compressive strength of the concrete, was found to be appropriate. In addition to the coupling beam tests, two four-story coupled wall specimens with precast HPFRC and regular concrete coupling beams were tested under lateral displacement reversals. Besides allowing the evaluation of seismic behavior of coupled walls with HPFRC coupling beams, the use of HPFRC in the plastic hinge regions of the walls as a means of relaxing transverse wall reinforcement was evaluated. The two coupled wall specimens exhibited drift capacities of at least 2.5%. The HPFRC coupling beams were more ductile and damage tolerant than the regular concrete beams. The incorporation of an HPFRC material in the wall allowed the use of a concrete design shear stress capacity of 0.33√fc', [MPa] (4√fc', [psi]) and a wider spacing of transverse reinforcement confining the wall boundary regions.

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...

Results are reported from reversed cyclic tests of five large-scale squat wall specimens reinforced with steel bars having a specified yield strength of either 60 or 115 ksi (413 or 792 MPa). Two specimens were designed for a shear stress of 5√f c ′ psi (0.42√f c ′ MPa) and the other three 9√f c ′ psi (0.75√f c ′ MPa). Boundary element confining reinforcement complied with the requirements of Chapter 18 of ACI 318-14 in all but one specimen, which had 50% of the required transverse boundary element reinforcement. Specimens constructed with Grade 115 steel had similar strength and exhibited 20% greater drift capacity than those with Grade 60 steel. Use of Grade 115 steel tended to control the softening effect of sliding at the base of the wall and to increase the component of drift due to reinforcement strain penetration into the foundation.

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