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EC2 Confined

The EC2 confined model is a variant on the parabola-rectangle. In this case the confining stress σ\sigma increases the compressive strength and the plateau and failure strains.

fc,c={fc(1+5σ/fc)σ≤0.05fcfc(1.125+2.5σ/fc)σ>0.05fcεc,c=εc(fc,s/fc)2εcu,c=εcu+0.2σ/fc\begin{aligned} & f_{c, c}= \begin{cases}f_c\left(1+5 \sigma / f_c\right) & \sigma \leq 0.05 f_c \\ f_c\left(1.125+2.5 \sigma / f_c\right) & \sigma>0.05 f_c\end{cases} \\ \\ & \varepsilon_{c, c}=\varepsilon_c\left(f_{c, s} / f_c\right)^2 \\ & \varepsilon_{c u, c}=\varepsilon_{c u}+0.2 \sigma / f_c \end{aligned}