Experimental Study On The Seismic Damage Behavior Of Aeolian Sand Concrete Columns With Different Replacement Rates

There is a large area of desert in northwest China.The reasonable development of the aeolian sand and its large-scale application in actual projects can,on the one hand,contain the process of desertification and reduce desertification losses,on the other hand,reduce the cost of collecting and transporting sand for engineering,which can bring significant environmental and economic benefits.Therefore,the aeolian sand of the Kubuqi Desert in the Inner Mongolia Autonomous Region was selected as the research object,and the feasibility of its engineering application was studied.The specific contents are as follows.(1)Study on the filling effect of Kubuqi aeolian sand on different classifications of river sand.In order to explore the influence of aeolian sand partially replacing river sand on the voidage of fine aggregate,the voidage of 9 groups of river sand with different fineness modulus replaced by aeolian sand at the edge of Kubuqi Desert was measured,and the accumulation process of fine aggregate was simulated by PFC3 D discrete element software.According to the test and simulation results,the optimal replacement rate of aeolian sand for river sand with different grades and fineness modulus is obtained.After that,the Kubuqi aeolian sand was replaced by river sand with the same gradation,and similar experiments were conducted.By co MParing with the previous results,the effect of the special particle shape of the aeolian sand in the Kubuqi Desert on the void ratio of aggregates under different fineness modulus river sands and different replacement rates was explored.(2)Study on the activity effect of Kubuqi aeolian sand in concrete.Nine groups of concrete test blocks are designed and manufactured by taking the replacement rate of aeolian sand as the variable under the condition that the gradation of fine aggregate and the void ratio of experimental concrete are kept constant.After curing for 28 days under standard conditions,the ultimate compressive strength of the blocks were measured and recorded,and the change of concrete compressive strength caused by the active effect of aeolian sand was explored on the macro level.At the same time,XRD phase analysis of cement hydration products was carried out,and the internal mechanism of the active effect was explored on the micro level.Then,the active coefficient of aeolian sand is obtained by fitting the experimental data..(3)The design idea of aeolian sand concreteBased on the above research results of aeolian sand filling effect and aeolian sand active effect,through the co MParison and difference analysis of the previous experimental data of aeolian sand concrete,the influencing factor that describe the change of compressive strength of aeolian sand concrete caused by the change of voidage of fineaggregate is defined,and a new method to determine the optimal replacement rate of aeolian sand is proposed,which considers both the filling effect and active effect of aeolian sand.(4)Experimental study on seismic damage behavior of aeolian sand concrete columnsIn order to promote the application of aeolian sand in concrete frame structure,four aeolian sand concrete columns with different replacement ratio of aeolian sand were designed and manufactured based on the previous research results on the mechanical properties and service performance of aeolian sand concrete,and the lateral cyclic loading test was carried out.The test pieces include 1 ordinary reinforced concrete column and 3aeolian sand concrete column.Then,according to the test results,the seismic damage performance is studied.In addition,the damage model of the existing column members is adjusted according to the test data,and the adjusted damage model is used for the damage analysis of the eolian sand concrete column in this paper.Finally,based on the test results,the restoring force model is established.(5)Experimental study on seismic damage behavior of steel fiber aeolian sand concrete columnsIn order to investigate the seismic damage performance of the frame structure of aeolian sand concrete mixed with steel fiber,three steel fiber reinforced concrete columns with different replacement rates of aeolian sand were designed and manufactured,and the lateral cyclic loading test was carried out.After that,the test results are co MPared with those of aeolian sand concrete columns.Finally,according to the test results,the restoring force model of steel fiber aeolian sand concrete column is established.(6)Abaqus finite element simulationThe Abaqus finite element analysis software is used to establish a model for the wind blown sand concrete column.The finite element analysis of the model is carried out,and the Abaqus analysis results are co MPared with the test results.After that,by adjusting the corresponding parameters in the model,the influence of concrete strength grade,axial compression ratio,longitudinal reinforcement ratio and stirrup reinforcement ratio on the seismic damage performance of aeolian sand concrete column is explored.