| To solve the two problems of marine corrosion and construction material cost in marine and coastal engineering structures,the spirally reinforced seawater sea-sand concrete-filled aluminum alloy tube column（ASSC）is proposed innovatively.In this new type of column,the external aluminum alloy tube can not only resist marine corrosion,but also provide a closed confinement environment to protect the internal spiral reinforcement cage from chloride ion corrosion.Moreover,the embedded reinforcement cage can form a secondary constraint on concrete,so as to make up for the disadvantage that the restraint effect provided by aluminum alloy tube is weaker than that of steel tube.Therefore,this member has the advantages of corrosion resistance,economy and aesthetics,so it is expected to have a good application prospect in marine and coastal engineering structures.In this paper,the axial compression behavior of these columns is studied by combined with experiments,numerical simulation and theoretical analysis.The main work and achievements are as follows:（1）The axial compression loading test of 16 ASSC specimens and 1seawater sea-sand concrete-filled aluminum alloy tube column（ASC0）was completed,and the results show that the addition of spiral reinforcement cage with a total reinforcement ratio of 3%has little effect on the failure mode and ultimate bearing capacity,but has significant effects on the ductility and energy absorption characteristics.The axial compression behavior of ASSC increased first and then decreased with the increase of the ratio of spiral stirrup to longitudinal reinforcement(rhv).The contribution of spiral stirrup to axial compression is greater than that of longitudinal reinforcement.The axial compressive behavior of specimens in rhv=2.2 group and with thin and dense spiral stirrup or few and thick longitudinal reinforcement is the best.（2）The corresponding finite element model is established and the longitudinal stress of concrete,the strain of each component and the stress of aluminum alloy tube are analyzed by combining the experimental and simulation results.The results show that the longitudinal stress of concrete increases significantly after the reinforcement cage is added,and spiral stirrup improves the constraint of aluminum alloy tube on the central concrete.The aluminum alloy tube and spiral stirrup exert restraint after elastic-plastic stage.When the spacing of spiral stirrup is 40～100mm,the aluminum alloy tube,spiral stirrup and longitudinal reinforcement can work together and yield before the peak point.Moreover,the average longitudinal and tangential stresses of aluminum alloy tubes under peak load are 0.87f0.2 and 0.24f0.2,respectively.（3）Eighty models were established to systematically analyze the influence of various parameters on the axial compression behavior of ASSC column.The results indicate that adding spiral reinforcement cage is more beneficial to improve the axial compression behavior than increasing the thickness of aluminum alloy tube when the steel content is the same.The improvement effect of increasing aluminum alloy tube strength on bearing capacity decreases as concrete strength increases.With the decrease of concrete strength or the increase of aluminum alloy tube thickness,the improvement effect of increasing reinforcement strength on axial compression behavior increases slightly.The decrease of ductility coefficient caused by increasing concrete strength is greater than the increase of bearing capacity.The yield time of spiral stirrup is delayed with the increase of spacing.In addition,the size effect of ASSC column is not significant,and the size effect disappears when the nominal confinement factor is greater than 0.78.（4）Three calculation formulas for axial compression capacity of ASSC column are proposed.The verification results show that the formula derived based on the characteristics of composite restraint has the highest accuracy and the least discreteness.The average calculation error of this formula is less than3%,so it can accurately predict the axial bearing capacity of such columns.Finally,some suggestions are put forward for the configuration parameters of spiral stirrup,longitudinal reinforcement and concrete.The research results of this paper can provide a new idea for the construction of marine and coastal engineering structures,provide a reasonable reference for the design of spirally reinforced seawater sea-sand concrete-filled aluminum alloy tube column,and enrich the relevant theories of composite structures. |
