For complex and bulky bridge crashworthy devices, accurate finite element (FE) simulation and impact testing both have significant limitations in verifying their protective performance. The simplified single macro-element method has demonstrated its efficiency in assessing ship-bridge collisions, and this study aims to extend the application of this method to the rapid assessment crashworthy devices performance. To accomplish this objective, the accurate determination of the crush curve for the crashworthy device is essential. Furthermore, the single macro-element approach encounters difficulties in accurately capturing the local deformation of a crashworthy device. This study introduced a discretized macro-element (DME) method aimed at rapidly evaluating the crushing behavior and protective performance of crashworthy devices during ship collisions by employing a comprehensive approach that combines experimental, numerical, and analytical techniques. The combination of theoretical analysis and FE simulations indicated that, based on the principles of similarity laws, the crush curve of large crashworthy devices can be deduced through experiments on scaled specimens. By utilizing the derived crush curve for both the ship and crashworthy device, the DME method accurately captured the local deformation of the crashworthy device. The accuracy of the DME method in assessing the performance of crashworthy devices was verified through an illustrative example. A parametric study has demonstrated the potential of the DME method for optimizing the structure of crashworthy device, owing to a significant increase in computational efficiency.