Numerical Analysis Of Multi-scale Basalt Fiber Reinforced Concret

Basalt fiber is a kind of continuous fiber which is made of basalt material and drawn at high speed by drawing drain plate after high temperature melting.It has excellent properties such as high strength,corrosion resistance,high temperature resistance and electrical insulation,basalt fiber is one of the four important fibers in China because of its low pollution to the environment.It has been widely used in the field of civil engineering.Although it has been proved that basalt fiber can strengthen concrete,but it is mainly about the appearance of the phenomenon and rule summary,without in-depth connection between the fiber and the strengthening mechanism of concrete.As a composite material,the heterogeneity of basalt fiber concrete will affect the performance of concrete at Micro,meso and macro scales,from the microscale of fiber-mortar interface,the mesoscale of random fiber-aggregate concrete and the macroscale of fiber reinforced concrete beam-column joints,the influence of fiber on the mechanical properties of the research carrier is analyzed by different scale evaluation indexes,and then the strengthening mechanism of basalt fiber on concrete is summarized.The main contents of this article are as follows:(1)The microscale model of fiber-mortar interface considering bond and friction is established from the pull-out load-displacement curve and energy analysis,the influence factors of fiber diameter,interfacial stress and pull-out angle on interfacial properties were analyzed.The results show that the interfacial properties of the fibers are mainly divided into two types.In the interface dominated by bonding,the increase of interfacial stress does not have much effect on pull-out load and debonding displacement,the pull-out load,debonding displacement,debonding energy and friction energy all increase with the increase of fiber diameter.In the interface dominated by friction,the pull-out load and friction energy are increased by increasing the fiber diameter and interface stress,but the bond toughness is decreased.The pull-out load of the fiber will be reduced if the fiber is pulled out obliquely,and there is no obvious rule for the bond toughness.(2)Through the secondary development of Python,a 3-D random fiber-aggregate concrete mesoscale model is established with Abaqus,which considers the influence of fiber diameter,fiber length and fiber content on concrete,the meso concrete evolution state is related to macro phenomena,and the reliability of the model is verified by experiments.The results show that the damage of the cubic compressive specimens originates from the weak interface transition zone in the middle of the concrete,and extends to join under the load,forming the "X" shape of failure.The damage of split and flexural specimen occurs in the area of the tension area and the midline of the bottom area with the largest tensile stress respectively,and extends to the failure of the specimen in the area under the action of load.The interaction of fiber-mortar interface makes the fiber restrain the mortar and slow down the damage development of the concrete matrix.Within the study parameters,increasing the diameter,length and content of fiber can enhance the mechanical properties of concrete materials such as cube compressive,splitting tensile and flexural.(3)A macroscale model of fiber-reinforced concrete beam-column joints is established to compare the effect of fiber reinforced concrete on the seismic behavior of the joints in the core zone and the plastic hinge zone,the effects of fiber content,diameter,length and feeding area on properties were analyzed.The results show that under the action of reciprocating load,the concrete in the core area is damaged rapidly and develops to failure,and the damage spreads to the end of the beam,and the plastic strain accumulates to form plastic hinge.The material properties of fiber reinforced concrete,which in turn enhances the seismic behavior of joints.Within the study parameters,increasing fiber content,diameter,length and drop area can slow down the damage development and stiffness degradation of joints,and generally enhance the bearing capacity,stiffness,yield displacement,ultimate displacement and energy dissipation capacity of joints,but the energy dissipation efficiency and ductility will be reduced to a certain extent.