Research On The Axial Compression Properties Of Brick Columns Strengthened With Steel Tube Self-compacting Recycled Concrete

Nowadays,most of the masonry structures in our country have entered the "ageing" period.Some of these precious and memorable masonry buildings are in urgent need of reinforcement and reconstruction.The strength is greatly improved,and the reinforcement effect is good.At the same time,the use of recycled concrete can greatly reduce the problem of nowhere to pile up and difficult to dispose of construction waste,which not only saves costs and shortens the construction period,but also effectively protects the environment and saves resources.The main work and conclusions obtained in this paper are as follows:(1)In this paper,three test conditions with different substitution rates are designed.Through slump and other tests of self-prepared self-compacting recycled concrete,it has been tested that it has good working performance,indicating that it will not be used after adding recycled coarse aggregate.It will reduce the working performance of the new concrete,and the self-compacting recycled concrete can be used in this test.(2)The self-compacting recycled concrete was used to make relevant standard specimens,and the mechanical properties such as the compressive strength of the concrete cubes were tested.The final result shows that when the replacement rate increases,the mechanical properties of the self-compacting recycled concrete are all Reduced.(3)Carrying out the axial compression test of steel pipe self-compacting recycled concrete to strengthen the brick column,the main monitoring parameters are the replacement rate of recycled coarse aggregate,the intensity of self-compacting recycled concrete,and the thickness of steel pipe.The destruction patterns of different specimens are analyzed.The destruction patterns of F1～F7 columns are similar,all of which are local buckling destruction.The fracture of the internal brick-concrete structure is the main reason for the buckling of the external steel pipe.By analyzing the test results,it can be seen that the thickness of the steel pipe and the intensity of the concrete are positively correlated with the peak load of the specimen,while the substitution rate is the opposite.When the substitution rate increases,the peak load of the specimen decreases,and the steel content has the greatest impact on the peak load of the specimen.The other two have less influence on the peak load..(4)The finite element models under 11 parameters were established to further study the axial compressive behavior of the specimen.The 11 parameters include the original parameters and the additional parameters which set the replacement rates of reclaimed coarse aggregate respectively 25% and 75%,and set the grade respectively as C40 and C45.The results show that the bearing capacity of the specimens is positively correlated with the thickness of steel tubes and the strength of concrete,and decreases by the increase of the replacement rate of recycled coarse aggregate.And the thickness of steel tubes has a greater effect on the bearing capacity,while the other two have a smaller effect on the bearing capacity.The ductility and energy dissipation indexes of the specimens were compared according to the stress distribution diagram and the load-displacement curve.Analysis results show that:(a)containing steel ratio,concrete strength and bearing capacity of the specimens are positively related,and recycled coarse aggregate replacement ratio is negatively related to the bearing capacity of specimens into,among them,the steel ratio is three parameters effect on the bearing capacity of specimens in the biggest factor,the other two have less effect on the bearing capacity,this conclusion consistent with the conclusions obtained from the experiment.(b)The strength of concrete and the replacement rate of recycled coarse aggregate are positively correlated with the ductility of specimens,while the steel content is negatively correlated with the ductility of specimens.(c)The strength of the tested concrete and the replacement rate of recycled coarse aggregate are positively correlated with the energy consumption of the specimen,while the steel content is negatively correlated with the energy consumption of the specimen.