Study On Verticle Vibration Control Of Pedestrian-bridge With Novel Tuned Mass Dampers

With the lower natural frequency and damping ratio,the long span pedestrian-bridge may cause excessive human-induced vibration.It brought some problems to daily such as,vibration serviceability,fatigue damage,et al.As an available energy absorber,traditional tuned mass damper(TMD)were well applied in practical projects.But there were still some shortages with traditional TMD.For example,the frequency range was too narrow to modify for post maintenance,the spring elongation was limited by installation space and the effect was mainly depended on the mass ratio(μ),etc.The research of novel TMDs have been a hot topic in engineering and academia.As such,relies on the project of the National Natural Science Foundation of China“The theory and technology of three-element passive mitigation of structural vibration and its performance improvement for vibration control of stay cables"(51878274).Lever mechanism and inerter were introduced and this paper carried out the optimization design of the lever-type tuned mass damper(LT-TMD)and tuned mass damper-inerter(TMDI).Taking a two-degree-of-freedom simplified pedestrian bridge-TMD model as the research object,the vertical vibration control of two novel TMDs were studied.The main contents and conclusions of this paper were as follows:(1)Vertical vibration control of pedestrian-bridge with traditional tuned mass damper.The effect of optimization design by considering main structural damping was studied.The results showed that the fixed-point theory was not suitable when considering main structural damping.When the main structural damping within 0～5%,the results in optimum parameter and vibration control by considering the main structural damping were similar to the results with ignoring the main structural damping.(2)Vertical vibration control of pedestrian-bridge with lever-type tuned mass damper.The LT-TMD mechanism modal was carried out for obtaining its equivalent parameters.The influence of the mass adjustment coefficient(the ratio of the distance between the mass and the supporting spring to the lever fulcrum)to vibration control effect on the pedestrian bridge was evaluated.The results showed that the frequency range of LT-TMD was widened and the the elongation of the spring can be changed.Meanwhile the mass amplification effect and the modification can be made easily by the leverage mechanism.When theμ was constant and the mass adjustment coefficient was smaller than 1,the vibration control effect equipped with the LT-TMD was lower than traditional TMD.When the μ was constant and the mass adjustment coefficient was bigger than 1,vibration control effect equipped with the LT-TMD was better than traditional TMD.(3)Vertical vibration control of pedestrian-bridge with tuned mass damper-inerter.The TMDI mechanism models equipped two different inerter connections(grounded or not)were carried out for obtaining its optimum parameter.The influence of the inertial mass ratio β(the ratio between the inertial mass and structural modal mass)to vibration control effect on the pedestrian bridge was evaluated.The results showed that the inerter can enhance the mass amplification effect and widening the frequency range.When the μ was constant,vibration control effect equipped with the TMDI(inerter grounded)was much better than traditional TMD.With the increasing β,the TMDI with grounded inerter was better than the TMDI without ground inerter on pedestrian bridge vibration control effect.