Accurate estimation of blast loads on structures is essential for reliable predictions of structural response and damage. Current practice in blast effect analysis and design estimates blast loads primarily based on empirical formulae obtained from field blast tests. Due to the limited availability of test data, those empirical formulae are usually applicable to the case that the reflection surface of the structure is big enough so that no wave diffraction around the structure exists. They will overestimate the blast loads on structure columns without infill walls around them, which are very common in the modern buildings, especially for the ground floor columns. For a standalone column, the initial reflected pressure may be quickly relieved at the edge of the column, and the column will be engulfed with the blast wave due to diffraction. Therefore, the interaction between the blast wave and structure is important for such columns. The blast loads on such columns will be different from those obtained in field blasting tests on walls. There is no method in the open literature to estimate blast loads on standalone columns. In the present study, interactions between blast waves and structure columns are simulated using AUTODYN 3D. The influence of the scaled distance of the blast, column stiffness, ratio of the supported mass to the column mass, and column dimension and geometry, on the blast wave-column interaction is investigated. Based on the numerical simulation results, some formulae are proposed to estimate the blast pressure, impulse, and the reflected pressure time history on standalone structure columns.