Assessment of structural response under extreme loading through advanced Finite Element analysis is very important. However, capturing the accurate response of Reinforced Concrete (RC) structures requires careful consideration of geometry, boundary conditions, and material characteristics. Despite well-established material models available for concrete and steel, the prediction of realistic structural response remains uncertain. Tests on uniaxial compression yield material parameters for concrete in compression, while establishing the parameters for concrete in tension through direct tension tests is quite challenging. Thus, inverse analysis and tests like three-point bend test, compact tension test etc., are being adopted to obtain softening parameters of concrete. An inverse approach through finite element modelling has been employed to optimize the softening parameters, emphasising Load-CMOD (crack mouth opening displacement) response on notched beams. The sensitivity of Load-CMOD response on \(\sigma \left(w\right) vs. w\) (cohesive stress-crack opening displacement) relationship to understand the efficacy of the proposed inverse analytical methodology in generating optimal \(\sigma \left(w\right) vs. w\) relation is focused. This work advances the understanding and modelling nonlinearity of concrete, thereby improving the accuracy of structural analyses.