Experimental Research And Numerical Simulation Of Behavior Variation For Early-Age Concrete

Behavior of early concrete have important influence on crack, bearing capacity, durability of stucture. Behavior of early concrete changes drastically, which has significant difference compared with after curing concrete, and the existing research methods are not enough to disclose the characteristics of temperature、humidity and deformation for the early concrete. Based on the indoor model test, this paper studies the change laws of temperature and strain of early concrete; Based on the secondary development platform of ABAQUS, this paper develops the coupling of temperature, humidity, stress field in the early concrete sticky elastic-plastic deformation characteristics. The specific contents and research results are as follows:(1) The early concrete temperature, humidity and stress analysis of the basic theory are introduced; Based on the secondary development platform of ABAQUS, and using FORTRAN language, the thermal field subroutine UMATHT which takes the degree of hydration theory and the change of thermal parameters into account is developed; And based on the theory of maturity, a viscoelastic-plastic structure field calculation subroutine which is based on Double exponential creep function(Double Power Law, DPL) and Drucker Prager yield criterion is composed. The validity and rationality of the developed subroutines are demonstrated through various numerical examples.(2) The change of temperature and strain for the early concrete was studied by indoor test. The suitable for condition monitoring of early concrete test device is developed, and concrete temperature and strain were monitored used the high precision of vibrating wire sensor during the first 140 hours, and then the changing rule of the temperature and strain were determined.(3) Writing a Python program based on genetic algorithm, and combined with the indoor test results, the adiabatic temperature rise equation of control parameters are acquired. In this paper, the development trend of the early concrete thermal parameters is studied by indoor simulation test of concrete temperature field accurately.(4) According to the actual data of the indoor test of temperature and strain, the change trend of early thermal expansion coefficient of concrete is studied. Tsinghua university, hohai ding, Bjontegaard O and Jeong early concrete thermal expansion coefficient formula are fitted, which is compared with the measured strain, it is found that the change law of thermal expansion coefficient of exponential decline more accurately reflect the early concrete.(5) Using multi-field sequential coupling method, the subroutines developed in this paper have been applied to practical engineering, and a numerical simulation research of early stress and plastic cracking of a concrete column structurehas been carried out. The specific heat, thermal conductivity, creep, drying shrinkage, elastic modulus, tensile strength and plastic have been considered synthetically in the calculation. The results show that early age stage has a great influence on drying shrinkage deformation mainly on surface stress, structure surface cracks appear, should be paid attention to in the practical engineering.