A non-classical elasticity-based beam deformation framework experimentally verified by plain concrete beams

Accurate prediction of concrete beam deflection is essential for structural analysis and design. Conventional Euler–Bernoulli beam theory describes flexural stiffness based on the EI relationship; however, this formulation may not fully represent the actual deformation behavior of concrete members due to complex internal stress-transfer mechanisms. This study experimentally examines a non-zero point-moment-based moment deflection theory for predicting the flexural response of plain concrete beams. Third-point bending tests were conducted on beams with different concrete strength grades and cross-sectional configurations, and the experimental results were compared with predictions from the classical deflection theory and the proposed moment deflection theory. The results show that the classical theory consistently underestimates the measured deflections, with larger discrepancies observed for hollow-section beams. In contrast, the proposed theory provides closer predictions for all tested specimens. The average mean absolute percentage error (MAPE) of the classical theory is reduced from 17.7% to 5.3% by the proposed theory. The findings demonstrate that the non-zero point-moment-based moment deflection theory can serve as a complementary approach for describing the deformation behavior of plain concrete beams beyond the conventional EI-based stiffness framework.