| China is the largest annual steel production country in the world.During the 13th Five-Year Plan period（2016-2020）,the annual output value of steel slag had exceeded 100million tons.However,the comprehensive utilization rate of these industrial wastes is less than 30%,and lots of industrial wastes stored in the open-air are causing serious harm to the environment.Steel-slag is a waste industrial emission from steel production,and its main chemical composition has great similarity with cement clinker.Therefore,it has broad market prospect and application space to use it as raw material in the production of concrete products.However,the f-Ca O and f-Ca O in the steel slag would form Ca（OH）2and Mg（OH）2 with water,which maked the poorly volume stability of steel slag concrete.Hence,steel slag concrete is difficult to be directly used in ordinary reinforced concrete members.If the steel slag concrete could be poured inside the steel tube,the steel tube can be used as a barrier to make steel slag concrete in a completely closed working environment,which ensures the long-term working performance of components.Besides,the expansive steel slag concrete filled steel tube member also can make the core concrete enter the three-way stress state in advance in the component curing stage,effectively solve the volume shrinkage problem of ordinary concrete filled steel tube,and improve the ultimate bearing capacity.A large number of researches on concrete-filled steel tube（CFST）showed that the elliptical CFST have both the excellent circumferential restraint of circular CFST and the flexible size arrangement of rectangular CFST.The elliptic members are widely used in long-span engineering projects such as highways,bridges,airports and terminals due to their unique architectural streamline shape and reasonable mechanical properties of long and short axes.Therefore,the steel slag concrete filled elliptical steel tube（SSCFEST）members can give full play to the advantages of the elliptic members and reduce the adverse effects of steel slag concrete on the structure.So far,there are few reports about the research and application of SSCFEST.In this paper,the axial and eccentric compressive mechanical properties of SSCFEST short columns were studied and designed.The specific contents are as follows:（1）The composition of steel-slag was determined by XRF,and the basic mechanical properties of concrete specimens with coarse aggregate replaced by steel-slag were tested under the same mix ratio and different substitution rates.A total of 7 groups of specimens were designed and carried out,and the influence law of steel-slag replacement rate on the compressive strength,flexural strength,elastic modulus and expansion rate of steel-slag substituted for coarse aggregate concrete was analyzed.（2）A total of 16 SSCFEST short columns under axial and eccentric loading were carried out.Several parameters were analyzed,such as replacement rate of steel-slag,ratio of the long axis to the short axis and load eccentricity,et al.Key test results such as failure modes,the curves of N-Δand N-εunder different parameters are studied.The mechanical properties and variation rules under different parameters were obtained.（3）ABAQUS finite element analysis software was used to establish the calculation and analysis model of the SSCFEST short columns.The constitutive relation of core steel slag concrete under the lateral constraint of elliptic steel tube is proposed,by considering the influence of elliptic characteristics and the strength of steel slag concrete.On the premise of fully verifying with the test results,the simulation analysis work was carried out under the parameters of steel content ratio of section,material strength,axial ratio and loading eccentricity.The mechanical mechanism,fine parameter analysis and the whole process mechanical state of the SSCFEST short columns under axial and eccentric compression were obtained.（4）Based on the research results of the SSCFEST short columns,the common material parameters in practical engineering such as component size and load eccentricity were considered.The calculational methods of axial and eccentric bearing capacity of SSCFEST short columns were put forward,by referencing the the existing domestic and international codes,and the research results of some relevant scholars.The predicted value of the design method was compared with the experimental values and the finite element analysis results in this paper,which proves the accuracy of the calculational methods proposed in this paper. |
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