Abstract: For the layout and size optimization of tower crane booms， a two-stage topology and size optimization method was proposed. In the first stage， a periodic plate-beam topology optimization model of the boom was established， and the continuum topology optimization of the web plate was performed by using the periodic SKO method. After getting the optimized topology of web plate， the optimized web topology was transformed into a discrete web layout through the extraction of the principal stress path. In the second stage， the size optimization mathematical model was established with the web radius taken as the design variable， the boom compliance as the objective function and the material volume of the boom as the constraint. The size optimization criterion was deduced by the Lagrange multiplier method and Kuhn-Tucker condition. In addition， the stability constraints of the webs were proposed to ensure the boom stability during the size optimization process based on the Euler formula. By comparing the original boom with the optimal booms， the optimization method can effectively reduce the mass of the boom， increase the rigidity of the boom， and reduce the deformation and structural stress level.

Key words: crane boom, topology optimization, size optimization, periodicity, SKO(soft kill option), optimization criterion