en Optimal design Optimal design پژوهشي Research Water cycle algorithm (WCA) is a new metaheuristic algorithm which the fundamental concepts of WCA are derived from nature and are based on the observation of water cycle process and how rivers and streams flow to sea in the real world. In this paper, the task of sizing optimization of truss structures including discrete and continues variables carried out using WCA, and the optimization results were compared with other well-known optimizers. The obtained statistical results show that the WCA is able to provide faster convergence rate and also manages to achieve better optimal solutions compared to other efficient optimizers. water cycle algorithm; truss structures, sizing optimization; metaheuristics; constraint optimization 115 129 http://ijoce.iust.ac.ir/browse.php?a_code=A-10-1-96&slc_lang=en&sid=1 H. Eskandar 18003194753284600467 18003194753284600467 No A. Sadollah 18003194753284600468 18003194753284600468 No A. Bahreininejad bahreininejad@um.edu.my 18003194753284600469 18003194753284600469 Yes