Dam Engineering Vol XX Issue 1 77 Shape optimisation of concrete arch dams for dynamic load using mesh design velocity Jalal Akbari (formerly a graduate student at the Tarbiat Modares University) Assistant Professor Department of Engineering Malayer University Malayer Iran Email: akbari@malayeru.ac.ir or jalal.akbari@gmail Mohammad Taghi Ahmadi Professor Department of Civil Engineering Tarbiat Modares University Tehran Iran Email: mahmadi@modares.ac.ir Summary The main contribution of this paper is an efficient shape optimization algorithm for com- plex concrete arch dam based on shape sensitivity formulations for design-dependent loads, such as body forces, surface tractions and earthquake loadings. In literature the applied forces are often assumed to be conservative or design-independent. However, in shape design problems applied loads are often functions of design variables. Also, for practical shape definition in the optimisation of large arch dams, a high number of design variables and numerous non-linear constraints are needed. Therefore, for efficient sensitivity design, the concept of mesh design velocity of finite element nodes is employed. It also enables a fast estimation of the gradients needed for each optimisation cycle. The relevant optimisation sub-problem is solved with the SQP method. These pro- cedures have been implemented in a special purpose software, along with an efficient definition of seismic loads suitable for optimisation purposes. The method is successful- ly applied to an existing Iranian arch dam, and has enabled a dramatic reduction of com- putational efforts when compared to classical methods. Keywords: Concrete arch dam, mesh design velocity, sensitivity design, finite element, optimisation.