Suppression of pedestrian bridge vibration by multiple tuned mass dampers | |
| Author | Kittipoom Rodsin |
| Call Number | AIT Thesis no. ST-99-33 |
| Subject(s) | Damping (Mechanics) Bridges--Vibration Damping (Mechanics) Bridges--Vibration |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering. |
| Publisher | Asian Institute of Technology |
| Abstract | The performance of both multiple tuned mass dampers (MTMD) and single tuned mass damper (STMD) in suppressing pedestrian bridge vibration is investigated. The study is separated into two parts. In the first part, the actual vibration characteristics under normal usage of pedestrian bridge are simulated by a computer program based on numerical approach. In reality, there are many pedestrians walking across the bridge. Therefore, the multipedestrian load is considered in finding bridge responses. To obtain the actual multi-pedestrian load, the random pedestrian characteristics based on the actual pedestrian properties are simulated in a completely random manner. The Poisson distribution of arrival rate and normal distribution of pacing rate and pedestrian weight are assumed in modeling of multi-pedestrian load. The accuracy of simulated bridge responses is confirmed by actual bridge test. From the simulated results, it is found that the multi-pedestrian load has the characteristic of narrow band excitation. Thus, in the second part, the performance of both MTMD and STMD in suppressing bridge vibration from narrow band excitation is investigated. The index that delineates the effectiveness of TMD is RMS response ratio expressed by the ratio of root mean square (RMS) response of structure with TMD to corresponding response without TMD. A parametric study is conducted to illustrate the influence of various parameters on the effectiveness and robustness of TMD. The important parameters are modal mass ratio, tuning ratio, damping ratio, frequency range ratio, and number ofTMD. In this study, the modal mass ratio of TMD is fixed to 1 percent. It is found that MTMD with uniformly distributed natural frequency yields the best performance based on practical condition. Therefore, this frequency arrangement type is adopted. The evidently advantage of MTMD compared with STMD is the effectiveness. The MTMD at the optimal parameters provides higher effectiveness than the optimal STMD. Moreover, in the optimal frequency range ratio, the effectiveness of MTMD is higher than STMD in wider range of damping ratio. In the optimal parameters, damping ratio of MTMD is apparently lower than that of STMD while the optimal tuning ratio of both systems are not different. It is also noticed that, the effectiveness of MTMD tends to be increased when the number of TMD is increased. However, when the number of TMD exceeds 11 , only slightly effectiveness increment is observed. In comparison with other types of excitation, e.g. harmonic and wide band excitation, the optimal parameters ofMTMD under narrow band excitation are approximately the same while the optimal parameters are different in case of STMD. The another important benefit of MTMD is the robustness of the system due to the possible error in optimal ttming condition. Although the robustness of MTMD at the optimal parameters is not different from the optimal STMD, the robustness of MTMD can be improved by widening frequency range ratio and increasing in damping ratio. However, when the robustness increases, the effectiveness tends to reduce. Neve1theless, the MTMD is more both effective and robust than a conventional STMD when the appropriate parameters are selected. Moreover, in practice, the portability and ease of installation are also the advantage of MTMD. However, rather high vibration amplitude of small TMDs in MTMD system compared with STMD tends to be the only drawback ofMTMD. |
| Year | 1999 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pennung Warnitchai |
| Examination Committee(s) | Worsak Kanok- Nukulchai;Gupta, Satyendra P.; |
| Scholarship Donor(s) | Asian Institute of Technology Partial Scholarship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1999 |