Seismic Control Of TMD For Multi-story And High-rise Buildings Considering Bending Effects

Tuned mass damper(TMD),plays an important role in the vibration control system of structures.TMD does well in wind vibration control,but when used to control structural vibration caused by earthquakes,TMD exhibits some defects,which limit its seismic application.In order to make TMD behave better in earthquakes,we need to overcome these defects,which depends on further study of TMD.In the study of TMDs,researchers often use the single degree of freedom model and the lumped mass story shear model.The story shear model is a simplified model used in the field of building structure,however,it ignores the bending effect of the structure as a whole.Considering the sensitivity of TMDs to frequencies,another simplified model,the story bending-shear model,can be more suitable for the study of TMD.The story bending-shear model takes into account the bending effect of the whole structure,depicts the frequency characteristics of the structure more accurately than the shear model,while the increase of the degree of freedom and calculation is not much.In this paper,the influence of bending effect on the vibration reduction effect of TMD is studied.The main research work and results are as follows.(1)Different models are established for the same structure,including a shear model,a bending-shear model,and a beam-column finite element model,and the linear time history analyses under the same ground motions are carried out to compare the differences between the three.The results show that the structure periods,the time history trends,the maximum values and the root mean square values of the bending shear model and the beam-column finite element model are similar,but the results of the shear model are obviously different from those of the other two.This shows that the bending shear model is a simplified model with higher precision.(2)3 TMDs are designed respectively according to the calculation of a shear model,a bending-shear model,and a beam-column finite element model,and then the vibration reduction effects of the 3 TMDs are compared.In order to study the seismic effect of the TMDs,two kinds of analyses are carried out,i.e.,the linear time history analyses of the structure subject to 6 different ground motions with different predominant periods,and the power spectrum analyses of the structure subject to different filtered white noises corresponding to different site classifications.For the multiple structural responses considered,the TMD designed by the bending-shear model behaves similarly as the one designed by the beam-column finite element model and is obviously better than the one designed by the shear model.So we can come to our conclusion that it is necessary to consider the bending effect of the structure for the study of TMD,i.e.,the bending-shear model is a simplified model which is more suitable for the study of TMD.(3)Finally,the influences of the bending effect of structure on the vibration reduction efficiency of TMD are studied via the bending shear model with different structural height to width ratios and simple harmonic ground motions with a variation of frequencies.The results show that,although the influences of bending effect on the displacement of the top floor increase with the structural height-to-width ratio and the influences of bending effect on the vibration reduction efficiency of TMD are always obvious with different structural height-to-width ratio,the influences of bending effect on the vibration reduction efficiency of TMD don't increase with the increase of structural height-to-width ratio as expected.The other way around,the vibration reduction efficiency of TMD is most related to the ratio of load frequency to structural frequency.