| Building materials industry development planning(2016～2020)promulgated by Ministry of Industry and Information put forward" On the premise of guarantee product quality and the ecological security,improve the ability of given industrial waste of cement,concrete,wall materials and the mechanism of sandstone and other products,gradually increase the varieties of disposing solid waste.Produce green building materials based on the construction garbage." Working hard on developing heat retaining recycled concrete,on the one hand,it contributes to solve the problems of waste seriously,pollute the environment of construction waste;on the other hand,it contributes to solve the problems of building energy efficiency.Based on the research results of vitrified micro bubbles which is a new sort of environment-friendly and inorganic lightweight insulation materials have been made by Taiyuan university of technology and our school,and combine with CFDST.Firstly,this paper develops lightweight and heat retaining recycled concrete whose strength meets the construction requirements and thermal conductivity is lower,secondly,does axial compression experiment studies and theoretical analysis on thin-wall square double skin steel tube short columns filled with VMB recycled concrete.And carries out the following preliminary work:(1)By the experimental study on the content of fly ash is 20%,content of calcined diatomite is 3%,and contents of vitrified micro bubbles(VMB)are from 0%to 120%of concrete of 100%recycled coarse aggregate replacement ratio.The results show that:With the increasing of contents of VMB,apparent density、elastic modulus and coefficient of thermal conductivity of recycled concrete reduce significantly;When the content of VMB is 100%,cube compressive strength of VMB recycled concrete can reach 32.55 MPa,apparent density is 1943 kg/m~3,which is 22.9%lower than 2387kg/m~3 of normal concrete,coefficient of thermal conductivity is 0.3243W/(m·K),which is 74.6%lower than 1.3153W/(m·K)of normal concrete;and work out the linear relation between fc and fcu is fc=0.81fcu.(2)By the axial compression experimental study on twelve thin-wall square double skin steel tube short columns filled with recycled concrete.The results show that:Specimens mainly present drum-shaped crushed,because of the setting of inside steel pipe,hollow specimens can effectively delay the local buckling,enhance the capacity of resistance capacity to deformation,and make the load distribute more uniformly and transit more smoothly;Ultimate bearing capacities of content of 100%VMB recycled concrete hollow specimens that width-to-thickness ratios are 64 and 88 increase by 4.2%and 12.9%than those of solid specimens;Axial compression bearing capacity increase coefficient and ductility coefficient of solid specimens and hollow specimens affected by the coefficient of restraint effect are different remarkably,ductility coefficient of hollow specimens increase by 24.4%than that of solid specimens.(3)Considering large generous than steel pipe and local buckling of the negative impact of the ultimate bearing capacity,this paper use the effective width method and analyze the regression analysis of experimental data,work out the relationship between concrete axial compression strength increase coefficient of specimens and coefficient of restraint effect is rectilinear,then get out axial compression bearing capacity calculating expression of CFST and CFDST in this paper which have higher calculation accuracy can provide theoretical reference for the engineering practice concerned.(4)By using the finite element ANSYS to analyze 12 specimens for the nonlinear analysis of axial compression,this paper work out The stress,strain and displacement change characteristics and limit bearing capacity of axial compression of the specimens.The results show that:Working mechanism,deformation characteristics and bearing capacity of axial compression of the specimens are agreement with the experimental results. |
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