MOCS-based optimum design of TMD and FTMD for tall buildings under near-field earthquakes including SSI effects

The use of TMDs is commonly discouraged for structures subjected to short-duration, pulse-like ground motions such as near-field earthquake excitations. Friction tuned mass damper (FTMD) is an innovative device compound of the traditional linear TMD with the idea of a friction damper which is still in the developmental stage for the seismic applications. The present paper investigates the performance of TMD and FTMD for seismic control of tall buildings under near-field earthquakes including soil-structure interaction (SSI) effects. A 40-story structure with a height-to-width ratio of four, a uniform mass distribution and a linear stiffness distribution in its height is considered in this study. Different conditions of the ground state are also considered for numerical studies. A design process based on a multi-objective cuckoo search (MOCS) algorithm is utilized for the optimum design of TMD and FTMD parameters. The simulation results indicate that ignoring the SSI effects may result in an inappropriate and unrealistic estimation of seismic responses and performance of TMD and FTMD in the high-rise structure. In terms of maximum displacement, acceleration, and drift of floors, it is found that the FTMD is capable of mitigating the structural responses better than the TMD. The efficiency of the FTMD is also compared with the TMD from the energy point of view for dissipation of the seismic input energy. The results show the superiority of the FTMD in the reduction of the maximum seismic input, kinetic and strain energies of the main structure, which confirm the capability of the FTMD being more than the TMD for mitigation of the seismic damages in the tall structure during near-field earthquakes. By increasing the soil softness, an increased trend is often achieved in the maximum seismic input and damage energies, thus ignoring the SSI effects may give an unrealistic result of the performance of TMD and FTMD in reducing the damage of seismic-excited tall buildings.