Considering the need to search for optimal solutions in the field of Civil Structural Engineering, this book aims to evaluate the efficiency of the Genetic Algorithm when used as an auxiliary tool for preliminary structural design. This is pertinent because, in this context, the codes are more simplified due to the use of a small number of variables, facilitating the integration of the method into the technical design routines. Two Genetic Algorithms were developed: one to optimize a post-tensioned concrete pedestrian bridge with a "T" cross-section, and another to optimize roof beams with an "I" cross-section for a prefabricated warehouse. To assess the efficiency of the optimization method, the solutions found by the algorithms were compared with actual implemented solutions of both elements.