Experimental Study On Mechanical Properties And Constitutive Relationship Of Self Compacting-hybrid Fiber Reinforced Concrete

Concrete materials are widely used in current construction projects.Traditional concrete has the disadvantages of large brittleness and low tensile strength,which results in poor ductility of the structure and brittle failure.Adding fibers to concrete can limit the development of concrete cracks.Self Compacting-Hybrid Fiber Reinforced Concrete not only has good ductility,but its vibration-free features save a lot of human and financial resources,speed up the construction progress,and meet the concept of energy conservation and environmental protection in today's society.At present,this kind of high-performance concrete mechanical property research theory has not been perfected,especially for the constitutive equation of concrete.Based on domestic and foreign research,this paper analyzes the working performance,compression performance and constitutive equation of Self Compacting Steel-PVA Hybrid Fiber Reinforced Concrete.The main research contents are as follows:(1)Based on the test of working performance of 21 groups of newly mixed concrete,the effects of fiber content,type and aspect ratio on the filling,interstitial permeability and segregation resistance of the newly mixed concrete are analyzed,and the calculation of the working performance with the fiber content formula;An analytical model for the relationship between slump expansion and residual height was established based on rheological theory.Studies have shown that the fluidity of concrete decreases with the addition of fibers;the viscosity-related shape factor of ordinary self compacting concrete is higher than that of Self Compacting-Hybrid Fiber Reinforced Concrete.(2)Based on concrete cube compression and prism axial compression tests,the effects of single steel fiber and steel-PVA hybrid fiber on the failure shape,strength,and peak strain of concrete are analyzed.The mechanical properties of concrete with steel fiber calculation formula.The compression curves of ordinary self compacting concrete and self compacting-fiber reinforced concrete are compared.Calculate the equivalent compressive toughness index of self compacting-hybrid fiber reinforced concrete,give the calculation formula of the change of toughness index with the amount of fiber,and analyze the influence of different fibers on the toughness index.Studies have shown that fibers have little effect on the strength of concrete and can slightly increase the peak strain of concrete.Compared with ordinary self compacting concrete,fibers can delay the rapid breaking of test blocks and significantly increase the toughness of concrete.A steel-PVA fiber hybrid effect function based on the quadratic fitted surface is proposed,and calculation formulas for the influence of different mixed fiber contents on the mechanical properties of concrete are given.(3)According to the measured characteristics of the stress-strain curve of the concrete compressive axis of the concrete prism,a constitutive equation suitable for Self Compacting Steel-PVA Hybrid Fiber Reinforced Concrete under uniaxial compression is proposed,and the formula for calculating the parameters is given.The measured curve is in good agreement with the calculated curve.Analysis of highperformance concrete structures and components provides material basis.(4)The OpenSees finite element analysis software was used to simulate the mechanical properties of ordinary self compacting concrete columns and self compacting-fiber reinforced concrete columns under low-axis reciprocating loads,and the hysteresis curve and the skeleton curve were compared and analyzed.Research shows that the addition of fibers significantly increases the energy consumption of concrete.