This paper outlines the theory, development, validation, and some results of a quadratic strip theory method to predict the global structural response of the KRISO hull geometry due to regular waves in the time-domain. The method attempts to capture nonlinear effects of the dynamic problem due to time-varying underwater hull volume imparted by waves and vessel motions. These effects are formulated by drawing a relationship between the coefficients, 𝐴33, 𝐵33, and 𝐶33 and the sectional draft, 𝑇𝑠. Additional nonlinearities are introduced by allowing for a flexible hull girder, and the inclusion of structural damping. Validation is facilitated by running test computations and comparing the linear and nonlinear results to segmented model test data. It is found that the predicted results are validated by the model data, and that nonlinear effects account for a significant increase in predicted bending moment.