Energy Absorption Characteristics Of Fiber Reinforced Cementitious Composites Tubes Under Transverse Compression

The research of energy absorbing structure or component is always an important topic that people pay special attention to.Due to the low tensile strength and poor toughness of concrete,traditional energy-absorbing structures generally use metal materials ranther than concrete.Recent studies have shown that Fiber Reinforced Cementitious Composites(FRCC)have excellent ductility and energy absorption capacity,being expected to be energy-absorbing material used in harsh environments and inconvenient maintenance.Based on the background aboved,this paper studies the energy absorption characteristics of FRCC tube components under quasi-static transverse compression.The main works can be summarized as follows:(1)The mechanical properties of FRCC materials are studied.The FRCC materials with different fiber types and vloume fraction were designed,specimens for axial compression and axial tensile were prepared,and the tensile and compressive stress-strain curves of FRCC were obtained.The mechanical properties of FRCC were analyzed,including stress,strain,poisson's ratio,elastic modulus and fracture energy.The results showed that the peak stress and strain of FRCC under uniaxial compression remain at the same or similar level,while the peak stress and fracture toughness of axial tension increase by the increase of fiber content.(2)The energy absorption characteristics of FRCC tubes under transverse compression are analyzed.The transverse compression test of FRCC tubes with different fiber types,volume fraction and tube size was carried out and rational indexes were selected to evaluate the energy absorption capacity of tubes.The results show that FRCC tubes present a four-hinge failure mode.The total energy absorption and stroke efficiency of FRCC tubes can be increased by 60 times and 37 times respectively in the most ideal circumstances.Moreover,the larger the diameter ratio,the larger the volume specific energy absorption and the correlation is approximately linear.(3)Based on Extended Finite Element Method(XFEM),the compression of tubes was simulated,and the influence of mesh size was analyzed.The simulation results were basically consistent with test phenomenon.Based on the numerical simulation,it is found that the deformation process forms three stages: elastic deformation,nonlinea r reinforcement and softening,and residual deformation.In the elastic stage,the stress distribution of tube section is approximately satisfied with hyperbolic distribution.When the tensile strain on the inner tensile zone of the tube exceeds the elastic limit,the tube go into non-linearity.And the load displacement curve of the tube reaches the inflection point of softening section and residual deformation section when the outside edge of danger area of the tube is completely destroyed.(4)On the basis of experiment and simulation,a theoretical analysis model of FRCC tubes under transverse compression based on nonlinear hinge model is presented.The results show that the nonlinear hinge model can well describe the mechanical behavior of the crack segment after FRCC cracking,and the load displacement curve can be derived accurately.The theoretical study shows that larger fracture energy of materials and more fracture surface are good for higher total energy absorption of the energy-absorbing components.And increasing the thick-diameter ratio can improve the stroke efficiency.