Experimental Study On Seismic Performance Of PE Fiber Cementitious Composite Frame Joints

Polyethylene (PE) fiber has ultra-high elastic modulus and tensile strength.Adding PE fiber into cementitious composites can make PE fiber cementitious composites, a kind of construction material with high toughness, multiple cracking failure characteristics and high compressive strength, well meeting the requirements of building developing tends of high-rise and large span structure. This article studied the effects of volume content of PE fiber on basic mechanical properties of PE fiber cementitious composites, determined the optimum proportion. Then applied this material into beam-column joint, designed and finished low-cyclic loading tests of six PE fiber cementitious composites joints and one concrete joints with two factors that stirrup ratio in core area and pouring range of PE fiber cementitious composites, this article finished the following works:(1) Finish experimental study that the influence of volume content of PE fiber on the basic mechanical properties of PE fiber cementitious composites. The study shows PE fiber's optimum proportion is 2%,the ultimate tensile strain can reach 3% under tensile load. This material has extreme deformation capability and toughness characteristics under flexural load. The failure of PE fiber cementitious composites is multiple cracking modes, and it has good capability of controlling crack.(2) Describe the crack propagation and failure process of each specimen, the results show that all joints experienced incipient crack, the penetrating crack, limit state and failure stage, multiple micro cracks appeared in core area and beam-end area of all PE fiber cementitious composites beam-column joints, and application the of PE fiber cementitious composites in beam-column joint would change the failure mode from he joint core shear failure to the beam flexural failure.(3) Analyze seismic performance such as hysteretic curves, skeleton curves, load carrying capacity, degradation of strength and stiffness,energy dissipation and shear deformation in joint core of each specimen. The results show replacing concrete in joint core and around beam and column with PE fiber cementitious composite can efficiently enhance seismic performance of joint, and reducing stirrup in core area has no effect on the seismic performance of joint, but has large effect on shear deformation in joint core. This article also make reasonable suggestion on pouring range of PE fiber cementitious composites in frame joint.(4) Analyze strain of all reinforcement in beam and column area, the results show that PE fiber cementitious composites joint can reduce deformation and slip of reinforcement, enhance anti-share capacity of beam, column and core area of joints.