Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.Civil engineering structures such as office floors and singular footbridges may present vibration modes locally spatially distributed with closely spaced natural frequencies. A set of tuned mass dampers (TMDs) may control several vibration modes at the same time and make the control system more robust. However, under these circumstances, Den Hartog’s theory may not be applicable. In this paper, an optimum algorithm to design a set of TMDs is proposed to cancel effectively human-induced vibrations for floor structures. A comparative study is carried out in terms of the same performance indicator to find the optimum system, considering different configurations by Den Hartog’s classical approach and this optimal algorithm. This proposed algorithm will contribute to motivate future researches on passive vibration control (PVC) for floor vibrations with closely spaced natural frequencies