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In this paper, steel–polyethylene hybrid fiber-reinforced strain-hardening cementitious composites (HECC) are applied in beam–column external joint core region to form a novel HECC/reinforced concrete (RC) composite beam–column joint with reduced anchorage length of beam longitudinal rebar and eliminated transverse rebar, and thus to alleviate rebar congestion and simplify the construction process efficiently especially for precast RC frame structures. Five external beam–column joint specimens are constructed and tested under cyclic loading to illustrate the influences of the anchorage length of beam longitudinal rebar and longitudinal rebar ratio on the seismic performance of beam–column joint. The effects of design parameters on seismic performance, including hysteresis behavior, degradation of strength, energy dissipation capacity, and cracking patterns are discussed in detail. Experimental results indicate that the replacement of normal concrete with HECC in beam–column joint core region could apparently reduce the amount of stirrups in the joint core area while maintaining reliable seismic behavior. Remarkably, specimen with no stirrups in the core area exhibits nearly equivalent seismic behavior to that of the control RC specimen. Furthermore, the application of HECC in joint core area allows for a substantial reduction of the required anchorage length for the beam longitudinal rebar to 9d, which further simplifies the construction process considerably. [ABSTRACT FROM AUTHOR]

Engineered cementitious composites (ECC) characterizes with high strain capacity, accompanied by two notable disadvantages, i.e., low elastic modulus and severe shrinkage yet. A new type of ECC featuring relatively high tensile strain capacity, high elastic modulus as well as low shrinkage was developed by using polyethylene fiber (PE) alone (P-ECC), or hybrid combining PE fiber with steel fiber (H-ECC) in this research. The effects of sand-to-binder ratio (s/b) from 0.42 to 1.02 and fiber hybridization on compressive properties, tensile properties and shrinkage characteristics of ECC were systematically investigated. Experimental results indicated that the increase of s/b ratio could benefit the compressive strength, the elastic modulus and the shrinkage performance of ECC. The elastic modulus as well as the shrinkage properties of P/H-ECC were superior than those of traditional ECC. It is noted that H-ECC with extremely high s/b ratios (i.e., 0.72–1.02) exhibiting relatively high tensile strain capacity, comparable elastic modulus with normal strength concrete and obviously lower total shrinkage than traditional ECC, is an ideal and competitive material which can be utilized in critical structural elements characterized by deformation compatibility and desirable ductility. [ABSTRACT FROM AUTHOR]