Mesoscopic Simulation And Mechanical Properties Of Cracked Concrete

When crowded rebar and unexpected load occurred in concrete members,the plastic damage and invisible cracks could be generated.Local cracking of concrete structures is a common phenomenon in engineering,and national structural design codes allow concrete structures to be worked with cracks.However,in the past,the main objective of research on the mechanical properties of concrete was uncracked concrete,and the influence of local cracking on the mechanical properties of concrete had not been clearly understood.Therefore,the fracture morphology and mechanical properties of cracked concrete were studied,and the quantitative relationship between fracture morphology and mechanical properties was attempted to be determined,which had important engineering significance and scientific value for the design and evaluation of reinforced concrete structures.In this paper,laboratory tests and numerical simulations were carried out to investigate the loss of mechanical properties of concrete after local cracking.The laboratory test was carried out to test the mechanical parameters of mortar,aggregate and the interface(type I fracture energy and tensile strength).According to the test results,the calculation formula of mortar-aggregate interface parameters was proposed,and accurate material parameters was provided for numerical study.Finally,a quantitative relationship was established between the crack width of the concrete and the loss rate of the mechanical index.The main research results obtained are as follows.(1)Based on ABAQUS-PYTHON joint simulation,a set of simulation analysis methods for cracked concrete was designed.In the numerical simulation study,the concrete random aggregate model of meso-level was established.The cohesive element was inserted globally to simulate the random cracking characteristics of concrete under tensile force,and the concrete cracking model under specific crack width was extracted to further analyze its uniaxial tensile and compressive mechanical properties.(2)A calculation model of cement mortar-aggregate interface parameters was established.The I-type fracture energy and tensile strength of the three types of cement mortar and two kinds of stone and the bonding interface between them were tested.The fracture energy(or strength)of the cement mortar was set as the independent variable.The energy(or strength)was set as the dependent variable,and a non-linear fitting was performed to establish a universal cement mortar-aggregate interface parameter model.(3)A numerical analysis model of local cracking concrete under tension and compression was established.Axial tensile or compressive force was applied to concrete specimens with average crack widths of 0mm,0.1mm,0.3mm,0.5mm,1mm,and 2mm,respectively.The change law of tensile and compressive strength of concrete loss rates with increasing crack width was analyzed.The research showed that when the crack width of the concrete was controlled within 0.3mm,the elastic modulus and strength basically did not change;as the crack width continued to increase,the ultimate strengthdecreased continuously,but the elastic modulus did not change.The research in this paper provides a mesoscopic simulation analysis method for the performance loss of reinforced concrete members due to local cracking.It provides a new model based on crack morphology for the local cracking mechanical properties of reinforced concrete members.It has certain guiding significance for the design and evaluation of reinforced concrete structures.