Experimental And Theoretical Research On Bearing Capacity Of Coral-concrete Filled Steel Tube

With marine development and the competition of maritime rights andinterests, including military protection engineering, marine construction isincreasing. For isolated reef engineering, all the required materials are distantfrom the mainland transport; and the transportation costs are very expensive.Coral-CFST has become the first choice of marine development projects, for theadvantage of its easily obtained raw material, high early strength and convenientconstruction. However, due to the structure and living environment of coral,whose’s surface attaches a large number of chloride ion. Chlorine ion corrosionbecomes the primary problem to restrict its application. This paper is on the basisof theoretical analysis, through which proved the feasibility of application ofcoral concrete in steel pipe concrete. To facilitate the practical application ofengineering, the paper studies through the method of experiment, theory andfinite element analysis, focusing on the bearing capacity and ductilityperformance of coral-CFST, through a lot of numberical analysis, gives thebearing capacity formula of coral-CFST under axial compression and calculatesthe bending member displacement ductility factor.It includes the following research work:On the basis of corrosion mechanism of concrete in steel, it can beconcluded that corrosion reaction rate is controlled by the oxygen content in steeltube through the theoretical analysis, and calculate the corrosion thickness limitof different cross section forms of coral-CFST under different types of corrosionby limit analysis method, and the calculated results with the existingexperimental results are compared.With the strength grade of30MPa concrete for the reference concrete, usingcoral reefs and sand to replace concrete coarse and fine aggregate completely,and then, do the material tests and axial compression short column experimentfor3groups of9coral-CFST respectively, and the experimental phenomena andresults are analyzed.The coral-CFST axial comoression process was simulated by the finiteelement software ABAQUS and the experiment results are verified by comparing the simulation results. According to the unified theory of ordinary CFST,combining with coral special-CFST short columns bearing capacity tests andfinite element analysis resluts, the paper ultimately gives the coral special-CFSTcapacity calculation formula based on ordinary CFST design method, which isprovided to practical engineering.The hysteretic behavior of the coral concrete filled steel tubularcompressive-bending member is analyzed by using Rayleigh-Ritz method and thelimit equilibrium theory. A curve model is provided, the calculation of thedisplacement ductility factor is given, and the reason of ductile differencesbetween coral-CFST and common-CFST is analyzed.