Study On Behavior Of High Performance Concrete Under Triaxial Compression

High performance concrete has the characteristics of high strength,high durability and high fluidity,and has a wider application range.With the popularization of new structures such as concrete filled steel tubular,concrete under triaxial compression is becoming more and more common.However,there are few studies on high performance concrete under triaxial compression,which limits the development and application of high performance concrete.Therefore,the mechanical properties,strength relationship and damage model of high performance concrete under triaxial compression are studied in this paper.The main research contents and results are as follows:1.Taking lateral confining pressure and concrete strength as variable parameters,60 high performance concrete cylinder specimens were designed and manufactured for conventional triaxial tests.The failure modes,stress-strain curves,peak stress,peak strain,initial elastic modulus,energy dissipation performance and damage development of high performance concrete under triaxial compression were analyzed.Research shows:When the confining pressure of HPC changes from no confining pressure to confining pressure,the failure mode changes from longitudinal splitting to oblique splitting.The stress-strain curve has four stages:elastic rising stage;plastic rising stage,softening falling stage and failure stage,but the softening falling stage is not obvious in high confining pressure state(σw≥32 MPa);With the increase of lateral confining pressure,the peak stress,peak strain,initial modulus of elasticity and energy dissipation performance increase with the increase of lateral confining pressure;With the increase of concrete strength,peak stress and initial modulus of elasticity increase,peak strain decreases,and energy dissipation performance decreases,increases and decreases;Damage evolution curve can be divided into non-damage stage,slow development stage,rapid development stage and failure stage.The existence of confining pressure reduces the development speed of damage.2.Based on the conventional triaxial test results,the applicability of Drucker-Prager criterion and four-parameter criterion with triaxial isobaric failure points is discussed.The results show that Drucker-Prager criterion can be used as strength criterion of high performance concrete under triaxial compression,and the method of solving relevant parameters is put forward based on Morku’s ethics theory.The four-parameter criterion with triaxial isobaric failure point can well reflect the yield stress of high performance concrete when its coarse aggregate is rigidly crushed under high hydrostatic pressure and meet the safety requirements in structural design.3.Based on Najar damage theory,a uniaxial damage model of high performance concrete is proposed.The damage model is extended to triaxial compression by using equivalent uniaxial method.