The optimal design of near-periodic structures to minimize vibration transmission and stress levels

This work is concerned with the optimal design of a near-periodic beam system to minimize vibration transmission and also maximum stress levels. Both narrow-band and wide-band excitation are considered, and two sets of design parameters are investigated; namely, the individual bay lengths and the individual bay damping values. It is found that very significant reductions in the selected objective functions can be achieved with relatively minor design changes. In the case of the system bay lengths, it is found that a near-optimum design can usually be found by employing a ''bound search'' algorithm, which obviates the need for a full optimization routine. Furthermore, it is shown that vibration transmission cannot readily be reduced by changing the damping distribution in the system (while maintaining the same amount of ''total'' damping), although significant reductions in the maximum stress levels can be obtained through this means. The findings of the work have application to more general engineering structures which an of near-periodic construction. (C) 1997 Academic Press Limited.