# Stressing State Analysis of SRC Column with Modeling Test and Finite Element Model Data
## 1 Introduction  
Reinforced concrete structures are widely used in various engineering structures all over the world. Spiral reinforcement concrete (SRC) columns have apparent nonlinear behavior during the loading process due to the restraint effect of stirrups on the core concrete. Therefore, it is very typical among reinforced concrete structures. Moreover, SRC columns are widely used in engineering due to their high bearing capacity, deformation capacity, and energy consumption capacity [1, 2]. Since the beginning of the twentieth century, many scholars worldwide have studied the bearing capacity of SRC columns from the perspective of constitutive models of confined concrete and concrete strength criteria [3, 4]. Taking the Chinese code for concrete structures GB 50010-2010 [5] as an example, three contributions are considered when calculating the axial bearing capacity of SRC columns: core concrete, vertical bar, and stirrups' restraint effect. Moreover, the three parts' contributions to the SRC column's bearing capacity are linearly superimposed, as shown in Equation (1):  
\[N\leq 0.9(f_{c}A_{\text{cor}}+f_{y}^{\prime}A_{s}^{\prime}+2\pi f_{\text{yv}}A_ {\text{sso}}) \tag{1}\]  
\[A_{\text{sso}}=\frac{\pi d_{\text{cor}}A_{\text{ssl}}}{s} \tag{2}\]  
Most of the world's concrete structure codes [5, 6, 7] have similar ideas when calculating the ultimate bearing capacity of SRC columns or design calculations. Therefore, the problem of calculating the ultimate bearing capacity of SRC columns is transformed into the process of establishing the constitutive relationship of concrete confined by stirrups and determining the peak stress/strain. There are many classic and well-known constrained concrete constitutive models, including the [PERSON] model [1], [PERSON] model [8], [PERSON] model [9], and Hoshikuma model [10], etc. Tables 1 and 2 are the peak stress/strain improvement coefficients of the classic confined concrete constitutive model and the expressions of the rising section, falling section, and softening coefficient of the constitutive model. It can be seen from Tables 1 and 2 that even for the classical confined concrete constitutive model, there is a huge difference in form between the peak stress/strain and the expression of the constitutive model. In addition, the constitutive model has a more significant gap in the mechanism. For example, the Mander model does not consider the softening coefficient in the expression; for the [PERSON] constitutive model, the softening coefficient is mainly affected by the peak stress/strain: For the [PERSON] constitutive model, the influencing factor of the softening coefficient is the structure of the SRC column. The fundamental reason for the considerable difference in the form of these expressions is that the working behavior of concrete is difficult to describe accurately; the ultimate state of concrete has substantial uncertainties. There are still many studies on the ultimate bearing capacity of SRC columns based on the constitutive model of concrete confined by stirrups and the ultimate state. For example, [PERSON] [11], [PERSON] [12], [PERSON] [13], [PERSON] [14], [PERSON] [15], and others proposed various constitutive models and peak stresses of concrete confined by stirrups from 1992 to 2018. These models and coefficients can often only better predict the working behavior of partially constructed stirrup-constrained concrete. Therefore, the peak bearing capacity of SRC columns was obtained based on these constitutive models, and the peak stress/strain improvement factor has the characteristics of substantial uncertainty. In addition, there is relatively little research on SRC columns based on numerical simulation, but the essence of numerical simulation from concrete structures is the selection of constitutive models and the determination of ultimate states. Therefore, the peak bearing capacity of SRC columns was obtained based on these constitutive models' uncertainty.