Research On Mechanical Properties Of I-shaped Axial Compression Steel Column Reinforced By External Reinforced Concrete While Under Load

As a kind of excellent structure with the characteristics of lightweight and high strength,good seismic behavior and short construction period,steel structure plays an important role in infrastructure construction in China,and it is a growing tred of possession.In response to the national sustainable development strategy and the reuse of existing resources,it is extremely important to reinforce the steel structures built in the early stage to solve the problem of insufficient bearing capacity.Reinforcement with steel-encased reinforced concrete can not only significantly improve the bearing capacity of steel columns,but also alleviate the common problems of fire prevention and corrosion prevention in steel structures,which has broad application prospects.In this paper,a new type of structure composed of reinforced concrete encased under the load of axially compressed steel columns is taken as the research object.The mechanical properties of the structure are studied by combining experimental research,theoretical analysis and finite element simulation calculation.The main contents are as follows:In order to study the mechanical properties of reinforced concrete encased in I-section steel axially compressed steel columns under load,static force loading tests were carried out on one I-section steel axially compressed steel column and four I-section steel axially compressed steel columns encased in reinforced concrete with initial load.Five additional specimens were drawn with different concrete strength grades,section steel strength and initial load as parameters.The load-displacement curve of the reinforced column shows that the ultimate bearing capacity of the specimens is significantly increased after strengthening.The influence of concrete strength grades,section steel strength grades and initial load on the ultimate bearing capacity of the reinforced column is analyzed.Based on the static loading test of reinforced columns,this paper deduces the theoretical calculation formulas of the bearing capacity of I-shaped axially compressed steel columns strengthened by encased reinforced concrete.In the process of derivation,the restraint of concrete stirrups in core area,the bond slip and stress lag between new reinforced concrete and prototype steel columns are considered.There is in good agreement that by reducing the strength of the new concrete and the new longitudinal reinforcement.The calculated value of the bearing capacity formula is compared with the experimental value,which shows that the formula in this paper has a certain reference value.In order to study the influence of bond slip on the ultimate bearing capacity of reinforced columns,establishing two finite element models,it includes bond slip and non-bond slip in ABAQUS software,which simulate the failure process of reinforced columns in the test.Comparing the results of finite element simulation with the experimental values and the calculated values of formulas,it is proved that the models are accurate and reliable.Based on the reliable finite element model,analyzing the influence of bond slip on the ultimate bearing capacity of reinforced columns in terms of concrete strength grades,section steel strength and initial load of section steel.It is concluded that the influence of bond slip on ultimate bearing capacity of reinforced columns can be restrained by increasing the strength grade and initial load of section steel in engineering practice.