| China's economy has developed rapidly these years,the economic structure has gradually changed from extensive to intensive,people's life has been greatly improved as the result of rapid development of urban construction and industrial development.But at the same time,the hidden problems are gradually revealed,such as too many non-renewable resources was consumed by the booming construction,and the exploit of sand or aggregates can not be unscrupulous as before.The urbanization and the frequent occurrence of earthquakes have created countless construction wastes,it will cause many problems such as pollution of the environment and waste of land no matter what how to deal with those wastes,as a result,the environmental protection is getting increasing attention these years.Nature aggregate in concrete partially or completely replaced by recycled aggregate forms recycled concrete,and recycled aggregate is formed by the wasted concrete through crushing or other processing.By this way,we can realize the recycling and reuse of construction wastes,and greatly save nature aggregate to solve various environmental problems,which has significant environmental,economic and social benefits.But in the crushing process of recycled aggregate,some internal cracks will appear,affecting the performance of the recycled aggregate.Because of the particularity of those materials,the importance of research on its constitutive model and seismic performance has gradually become apparent.The current research of recycled aggregate concrete performance is mainly divided into two aspects,one of which is mainly focused on material properties,in this way,the mechanical properties of recycled concrete are improved through carbonization or soaking nano-solutions;on the other hand,it is mainly focused on the structural form.By adding steel pipe or section steel into the recycled concrete structure to improve the working conditions of the recycled concrete and change therecycled concrete to a three-way stress state,thereby improving the mechanical properties of it.Due to the addition of steel pipe or section steel,a stronger restraint effect is provided by those rolled steel,the work conditions of recycled concrete has been changed,which improves the stiffness and ductility of the members,and is conducive to improving the mechanical properties of the structure or members.This article considers from the aspect of members,and has carried out related research work on the axial pressure performance of H-section-steel-reinforced recycled aggregate concrete filled circular steel tube stub columns.The following research results have been achieved:Firstly,Combined with the researches of domestic and foreign experts and scholars in recent years,the current research status is described from the aspects of recycled concrete,steel tube recycled concrete and section steel recycled concrete,and the ABAQUS nonlinear finite element software is used to H-section-steel-reinforced recycled aggregate concrete filled circular steel tube stub columns,H-section-steel-reinforced recycled aggregate concrete filled square steel tube stub columns under the axial compression.The modeling process of three kinds of finite element models is described in details,and the veracity and effectiveness of these three models is proved based on relevant test results.Secondly,The bearing capacity analysis method of H-section-steel-reinforced recycled aggregate concrete filled circular steel tube stub columns and H-section-steel-reinforced recycled aggregate concrete filled square steel tube stub columns was deduced,Based on limit analysis,twin shear unified strength theory,mean time given the different confining pressure between highly confined recycled aggregate concrete and medium confined recycled aggregate concrete,the bearing capacity of these two parts are analysis respectively.ultimate bearing capacity calculation formulas of steel-reinforced recycled aggregate concrete filled circular steel tube stub columns and H-section-steel-reinforced recycled aggregate concrete filled square steel tube stub columns are proposed.According to the comparison of results between values of formulas and data of others' test,the effectiveness ofbearing capacity calculation formula is proved.Meantime,the bearing capacity calculation formulas are also suitable for those stub columns which without steel-reinforced.Thirdly,Non-linear finite element simulation analysis was performed on the axial compression process of H-section-steel-reinforced recycled aggregate concrete filled circular steel tube stub columns and H-section-steel-reinforced recycled aggregate concrete filled square steel tube stub columns,respectively,to extract the load(N)-strain(?)curve,and the parameters such as the replacement percentage of recycled coarse aggregate,steel reinforced ratio,diameter-to-thickness ratio,length-to-thinness ratio of short column are analyzed.Based on the nonlinear finite element analysis,the calculated value of the bearing capacity formula was verified.The calculated results of the formula are in good agreement with the peak loads obtained by the finite element analysis,and the validity of the formula is verified to a certain extent.Fourthly,The derivation of the bearing capacity calculation formulas of the steel-reinforced recycled aggregate concrete filled circular steel tube stub columns and H-section-steel-reinforced recycled aggregate concrete filled square steel tube stub columns have some similarities,section of RAC-filled square steel tube is equivalent to the section of RAC-filled circular steel tube with the same sectional area and steel reinforced ratio in this paper for the purpose of simplifying the analysis.This simplification is verified by nonlinear finite element analysis.Under the condition that the simplified relationship between the members of those two sections is consistent,the axial compressive bearing capacity is consistent Well,to some extent,the effectiveness of the equivalent process is proved. |
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