| For many years,China has been a major graphite mining and use country,in the process of graphite mining left a large number of tailings,these tailings are harmful to the environment and there are no perfect treatment measures,the current research on the recycling of graphite tailings,especially its application as building materials in the field of engineering is still in the development period,so it is necessary to explore in depth.In this paper,the best replacement rate of graphite tailings concrete was obtained by replacing sand with graphite tailings of different contents,configuring graphite tailings concrete with different replacement rates,and testing the mechanical properties of the concrete after standard curing.A set of graphite tailings concrete columns with the optimum replacement rate was also designed based on the current code in China,and a proposed static test was conducted to investigate the difference in hysteresis performance betw een them and ordinary concrete columns under low circumferential reciprocal loading.Based on the OpenSees finite element software and using the measured strength values obtained from the material property tests and the design parameters of the column specimens,the columns were modeled and analyzed,and the simulation results were compared with the test results to verify the accuracy of the model,and the specific research of this paper is as follows:(1)Exploring the best replacement rate of graphite tailings concrete from the perspective of mechanical properties:Concrete with different replacement rates of graphite tailings under the same ratio was designed according to the Ordinary Concrete Proportioning Design Regulations(JGJ55-2011),and after standard curing,the concrete was subjected to compressive strength test,splitting tensile strength test and static compressive elastic modulus test,and evaluated according to the results of the three types of tests The best replacement rate of graphite tailings,the results show that the concrete prepared by replacing 30%sand with graphite tailings has the highest tensile strength and compressive strength,and the elastic modulus is higher than that of graphite tailings concrete under other replacement rates and close to that of ordinary concrete,therefore,the best mechanical replacement rate of graphite tailings is considered to be 30%in this paper.(2)To investigate the main damage patterns and hysteresis performance differences between graphite tailings concrete columns and ordinary concrete columns under low circumferential reciprocal loading at different axial pressure ratios:two groups of concrete columns were designed according to the Code for Seismic Design of Buildings(GB50011-2010),one group was ordinary concrete columns and the other group was graphite tailings concrete columns with the best mechanical replacement rate.The proposed static tests were conducted on the two sets of columns at 0.3 and 0.6 axial pressure ratios,respectively,to observe their damage patterns and analyze their hysteresis curves.The results showed that the hysteresis curves and skeleton curves of graphite tailing concrete columns under low circumferential reciprocal loading were similar to those of ordinary concrete columns,and the differences in seismic performance evaluation indexes such as stiffness,ductility and energy dissipation were not significant;while the specimens differed greatly under different axial pressure ratio loading,and the bearing capacity of the specimens was improved when loaded at high axial pressure ratio compared with low axial pressure ratio,but the ductility was decreased.(3)Based on the design parameters of the column specimen and the results of the material property test,the model was established and numerically analyzed by OpenSees finite element simulation software,and then the differences between the simulation results and the test results were compared in terms of the hysteresis curve and the characteristic parameter values of the bearing capacity to verify the accuracy of the model.Then the loading axial pressure ratio was extended and seven axial pressure ratios from 0.3 to 0.9 were used for the finite element simulation of graphite tailing concrete columns.The results show that the hysteresis curves of the simulation and the test are in good agreement,and the differences in the values of the bearing capacity characteristic parameters are small,indicating that the OpenSees model constructed in this paper is accurate and can be used for the finite element simulation of reinforced concrete columns.In addition,according to the results of the finite element extended simulation,it can be known that the axial compression ratio has a great influence on the hysteretic properties such as the skeleton curve and the bearing capacity parameters of graphite tailing concrete. |
