Ultimate Bearing Capacity Analysis Of Steel Reinforced Concrete Pier Based On The Improved Elastic Compensation Method

Steel reinforced concrete piers are a new type of pier structure proposed in recent years to improve the application of reinforced concrete piers in high-head drain structures.Preliminary research shows that it has obvious advantages in bearing capacity compared with reinforced concrete piers.However,the current research on the bearing capacity of steel-reinforced concrete piers is based on the finite element overload method or the Elasto-Plastic Incremental Analysis.Such solution methods are relatively simple and have some shortcomings in calculation efficiency and convergence control.Therefore,it is necessary to seek a new,more convenient and efficient method to calculate the ultimate bearing capacity of steel reinforced concrete pier.According to the lower bound theorem of structural plastic limit analysis and the basic theory of elastic compensation method raised by Mackenzie,this paper introduces the calculation method of yield strength and equivalent stress of concrete materials based on Drucker-Prager yield criterion.Defining the concept of failure strength and the constant λ associated with it to reflect the characteristics of the concrete material that has not been unstable after entering the yield.On this basis,the concept of unit bearing ratio,bearing ratio uniformity and reference bearing ratio is added to the traditional elastic compensation method to improve the elastic modulus adjustment strategy and the ultimate bearing capacity solving method,which make the elastic compensation method suitable for the calculation of ultimate bearing capacity of steel reinforced concrete structures.Then the improved elastic compensation method is verified through the test of steel reinforced concrete short column under different compression conditions and the bending performance test of steel reinforced concrete beams.With the verifications,the improved elastic compensation method is used to calculate and study the ultimate bearing capacity of steel reinforced concrete piers.The results show:(1)The lower limit form elastic compensation method based on Drucker-Prager yield criterion for the ultimate bearing capacity analysis of steel reinforced concrete structures improved in this paper can be effectively used for calculating the ultimate bearing capacity of steel reinforced concrete piers under different working conditions,steel reinforced concrete short columns and bent steel under different compression conditions and flexural steel reinforced concrete beam,which provides a new way to solve the ultimate bearing capacity of steel reinforced concrete structures.(2)Using the improved elastic compensation method to solve the ultimate bearing capacity of steel reinforced concrete piers under different working conditions,steel reinforced concrete short columns and bent steel reinforced concrete beams under different compression conditions,the solution results are relatively close to the results of experimental values and elastoplastic incremental method with higher computational efficiency and better iterative stability.(3)The fracture strength σ’0 of the concrete material in the steel reinforced concrete structure defined in this paper has the following linear relationship with the yield strength σ0:σ’0=λσ0 Among them,the constant λ related to the failure strength reflects the bearing capacity space of the concrete material in the steel reinforced concrete structures after entering the plastic yielding until the instability failure.The correspondingλ values of different steel reinforced concrete structures under different loading conditions are also different.When using the elastic compensation method improved in this paper to solve the ultimate bearing capacity of steel-reinforced concrete piers under different working conditions,the value of λ is recommended to be 1.0 from the perspective of engineering safety,which is considered that the bearing capacity of the piers when entering plastic yield is its ultimate bearing capacity.(4)When the elastic compensation method improved in this paper is used to solve the ultimate bearing capacity of steel reinforced concrete structures,the convergence control and solution accuracy are determined by the parameter ε.When the elastic load compensation method is used to solve the ultimate bearing capacity of steel reinforced concrete piers under different working conditions,the convergence control condition ε is recommended to be 0.01 in the premise of ensuring the accuracy and computational efficiency.