Predicting load-deflection behavior in reinforced concrete beams via the Schnobrich analytical framework

The Schnobrich model used to predict the load-deflection behavior of reinforced concrete (RC) beams under monotonic loads is improved in this study. The accuracy of these improvements is validated by applying the model to two composite beams that had previously been tested and the results compared to theory. Comparisons are made with code limit state design approaches (ACI 318-19; AISC, 2017). The Schnobrich model utilizes a combination of non-associated plasticity, smeared cracking, and other incremental constitutive laws, and in each case exceeds the predictability of both codes, with AA% of 97.62% and 93.03%, as compared to 95.36% and 92.87% respectively. Key statistical results (e.g., RMSE: 2.43 kN Vs 4.46 kN; R²: 0.9977 Vs 0.9922) indicate the model’s ability to capture highly nonlinear phenomena such as stiffness degradation, and behavior after yielding. The modified model thus is considered highly effective in achieving feasible, reliable, and accurate predictions, thereby validating its adoption and enhancing its potential applicability to real-life RC beam design problems, thus providing a better link between code-based approaches and more complicated numerical approaches.