Study On Mechanical Properties And Constitutive Relations Of ECO Concrete For Steel Bridge Deck Pavement

Asphalt concrete is widely used in steel bridge deck pavement,which is prone to pit,crack,steel structure corrosion and other diseases.These diseases will increase the maintenance cost and reduce the durability of the bridge.In recent years,a new type of modified polyurethane concrete,being a bridge deck pavement material,called ecological conservation optimization concrete(ECO concrete for short),developed in China,has the characteristics of high strength and good toughness.The ECO concrete,having the advantages of convenient construction,energy saving,environmental protection,high bonding strength,wear resistance,waterproof and anti-corrosion performance can improve the service life of bridge deck pavement.At present,the ECO concrete has been applied to many bridges in China.However,there are few reports on the constitutive relationship of ECO concrete,especially the temperature-related mechanical properties and constitutive relationship,which restricts the development of ECO concrete engineering applications.The Tongzi River Bridge(TRB),located in the mountains where are a big temperature difference,whose deck pavement will first time uses the ECO concrete in Guizhou province,is a large suspension bridge.There are many mechanical problems with ECO concrete need to be solved urgently.Therefore,taking the TRB as the engineering background,combined with the climatic characteristics of the Guizhou mountainous,this paper study on the mechanical properties and constitutive relationship of ECO concrete under the influence of the temperature by the method of experiment,theory and simulation.The main research work and results are as follows:(1)The theoretical calculation formulas of the change of compression strength and splitting tensile strength of cubic ECO concrete with temperature changing,and the conversion formulas between compression strength and splitting tensile strength are established respectively.The 30 cubic ECO concrete specimens are designed and fabricated.According to the climatic characteristics of mountainous areas in Guizhou,five different temperatures of-10°C,0°C,15°C,40°C and 60°C are selected to complete the cube compression test and splitting tensile tests of ECO concrete.The results show that the compressive strength and splitting tensile strength of ECO concrete decrease with the temperature increase.(2)The temperature-dependent constitutive relationships of ECO concrete under uniaxial compression and uniaxial tension are established.The 15 ECO concrete prism specimens and 15 ECO concrete bone rod specimens are designed and fabricated,and axial compression and axial tensile experiments at different temperatures are carried out.The results show that the peak strain increase with the increase of temperature.The axial compressive strength and modulus of elasticity decrease with the increase of temperature.Through the experiments,the influence law of temperature on the mechanical properties of the material,such as compression failure mode,axial compressive strength,peak strain,compressive elastic modulus and Poisson’s ratio,is discovered.(3)A special fixture for the concrete uniaxial tensile experiment is developed,which effectively solves the problem that the experiment is to fail due to stress concentration.The specimens of ECO concrete uniaxial tensile experiments are bone rods.Based on ABAQUS finite element software,the finite element model of the specimen is established to analyze the influence of specimen shape and fixture structure on the stress distribution of the specimen.By using the new fixture,the success rate of the experiment is greatly improved.(4)Relying on the bridge deck pavement project of TRB in Guizhou Province,using MIDAS finite element software,the full-bridge models with ECO concrete and asphalt concrete as bridge deck pavement materials are established respectively.Under the three working conditions of temperature load,vehicle load and load combination of temperature and vehicle,the mechanical properties of ECO concrete and asphalt concrete bridge deck pavement at different temperatures are studied and analyzed respectively.The results show that the maximum tensile stress of ECO concrete bridge deck pavement is significantly less than that of asphalt concrete under three working conditions.The increase in temperature can homogenize the tensile stress of bridge deck pavement and reduce the concentration of tensile stress.(5)Using the temperature-dependent material parameter system and bond-slip constitutive relationship,the local finite element models of steelECO concrete interface and steel-asphalt concrete interface are established by using ABAQUS finite element software.The simulation results show that at 15 ℃ and 60 ℃,the shear failure strength of the steel-asphalt concrete interface is only 12.6% and 5.0% of that of the steel-ECO concrete interface.The shear capacity of the steel-ECO concrete interface is better than that of steel asphalt concrete.The constitutive relations and the basic material parameters of ECO concrete(including material density,tensile strength and compressive strength at different temperatures,elastic modulus,linear expansion coefficient,Poisson’s ratio,etc.)are obtained for the first time.The engineering modeling parameter system of ECO concrete is constructed,which lays a foundation for finite element analysis.