Frequently-occurred fire incidents are always considered hazardous due to its potential to inflict severe building damages, heavy casualties and huge financial losses. In order to estimate the reinforced concrete (RC) building’s possibility of being reused after fire, it is necessary to take into account fire consequences to calculate the post-fire resistance of RC structures. However, there are limited instructions for such calculations in the current design provisions in Vietnam. Hence, the authors introduce the Vietnam national technical regulation on fire safety for buildings and constructions and the recently-drafted design standard for ensuring fire resistance and post-fire resistance of concrete and reinforced concrete structures, which specifies post-fire materials’ mechanical properties and structural calculation at ultimate limit states to determine residual strength of RC structures in general and columns in particular. Then, a number of case studies that have already been successfully applied for assessing RC columns in real buildings influenced by fire will be performed. It is shown that the proposed calculation approach is straight forward and can be practically applied in reality. Furthermore, a sufficient strengthening method for fire-affected RC columns will also be introduced in the latter part of the article.