Sliding mass floor system for seismic response control

Abstract

A new concept of small sliding mass blocks as distributed bi-directional friction tuned mass dampers (TMD) is developed and tested for seismic response control of a framed building model. The proposed distributed TMD system can be accommodated within a depth of 10 cm at each floor of the building and does not require any specialized tools and is suitable for enhancing seismic performance of existing buildings as well. An analytical model has been developed for the modelling of distributed friction TMDs and the model has been validated by comparing predicted response with the experimental observations during a shake table test for a steel portal frame with distributed friction TMDs. It is found that the proposed distributed friction TMDs can reduce the seismic response by as much as 60% for mass ratio of 8% and tuning ratio of 0.9 with respect to the first normal mode of the building. A parametric study using different earthquake ground motions suggests that the coefficient friction of 0.2 has the most robust performance. The interface between ultra high molecular weight polyethylene (UHMWPE) and steel provides the desired coefficient of friction. This pair of sliding interfaces is also desirable from the point of view of durability as UHMWPE is highly abrasion resistant and is widely used in orthopedic implants. The proposed arrangement of distributed friction TMDs readily allows for the possibility of each mass block to be used as bi-directional TMD and tuned to different mode of vibration, if required. These distributed TMDs are also found to be very effective in greatly reducing the storey drifts in buildings on hill slopes. The results suggest that it is possible to achieve the immediate occupancy performance objectives even during extreme (MCE) level events with the help of proposed distributed friction TMDs.