Research On The Application Of Fabricated Steel Tube Restrained Concrete Reinforced Columns

Fabricated Steel Tube Confined Concrete(FSCCC)reinforced column is a semi-finished product of fabricated steel tube in the factory,which is installed into a finished product on site.The expansive grout is poured between steel tube and concrete to form a steel tube confined concrete.It reinforced existing concrete columns.During its entire life cycle,the characteristics of a building's safety,durability,and applicability will change with changes in various factors.The negligence and mistakes of the building during the construction phase and the accumulation of damage during the normal use phase make it unable to meet the functional and use requirements of the structure,which requires us to strengthen the structure.Reinforcement technology,especially environmentally friendly and efficient reinforcement technology,has become an important area for scholars at home and abroad.We need to develop a new type of reinforcement technology that can meet the requirements of modern buildings on space,time,beauty,environmental protection,and special construction.Fabricated Steel Tube Confined Concrete reinforced column is such an environmentally friendly and efficient reinforcement technology.The theory of Fabricated Steel Tube Confined Concrete reinforced column is derived from concrete-filled steel tube.This paper analyzed the basic concept,stress principle,calculation of normal section bearing capacity,structure,and secondary stress principle of steel tube confined concrete.It provides a theoretical basis for the following design analysis.In this paper,the reinforced concrete columns with fabricated steel tube confined are studied from the following aspects:(1)Under the condition of proper unloading as possible,the wall thickness change of reinforced column steel pipe has influence on its axial compression ratio.We conclude that as the wall thickness of the steel pipe increasing,the axial compression ratio of reinforced column cannot be effectively changed.Therefore,a new method was proposed in this paper,which is to change the axial compression ratio of the column by changing the equivalent section of the concrete.Through calculating and analyzing,we can see that although the axial pressure ratio decreasing with the continuous increase of the depth of cut,the decrease is very slow.Compared with the method of increasing the wall thickness of the steel tube which let the axial pressure ratio of the original column to only decrease to 0.55,the original column axial compression ratio can be reduced to less than 0.5 by changing equivalent section of the concrete.Finally,the axial compression ratio can be reduced to the limit required by the code.We can see changing equivalent section is feasible.(2)Considering the secondary load,the reinforced column stress-strain curve is synthesized from the curve of ordinary concrete and steel tube confined concrete.We conclude that although the stress of the initial composite curve being lower than the confined concrete curve,the confined concrete is quickly realized effect.Finally,the two curves basically coincide.Therefore,the overall effect of composite curve is similar as the confined concrete curve.In the strain range of 0.0008 ? 0.0033,the axial compression ratio of reinforced columns is smaller than that of ordinary columns.From the perspective of reinforced column stress and strain,the axial compression ratio exceeding the limit was controlled to the limit value through fabricated steel tube confined reinforcement,which significantly improved the ductility of the overall structure.(3)Based on the above methods,an example of the engineering reinforcement of the first underground layer and the eleventh layer above ground was designed and analyzed from the parameters of the thickness of the steel tube and the depth of the concrete cut.The new construction technology of fabricated steel tube reinforcement is described in detail.The new construction method was realized by assembly makes it have obvious advantages in engineering rescue and disaster relief.After comparing the reinforced concrete with the newly confined concrete,the load was applied again.After the new and old structures worked together,the stress and strain of reinforced columns and the bearing capacity was analyzed.The following conclusions are promoted: As long as parameters of section D,parameters t wall thickness of steel tube,and parameters of number of steel tube sections n are same,the relationship between the compressive strain and the bearing capacity of the concrete before and after the reinforcement is the same,the limit of the reinforced columns is same,and the bearing capacity is basically same.After the reinforcement of each frame column,the ultimate bearing capacity is significantly increased.All of them meet the requirements of the column to be subject to axial pressure.Compared with columns on the same axis position on different layer,the bearing capacity of the reinforced column gradually decreases with the rise of the layer.The ultimate bearing capacity of each layer of columns has not met their axial pressure requirements,and far exceeded their axial pressure requirements.