EVALUATION OF THE LEVER-TYPE MULTIPLE TUNED MASS DAMPERS FOR MITIGATING HARMONICALLY FORCED VIBRATION

2005 ◽  
Vol 05 (04) ◽  
pp. 641-664 ◽  
Author(s):  
CHUNXIANG LI ◽  
Q. S. LI
Keyword(s):  
Damping Ratio ◽  
Static Stretching ◽  
Tuned Mass Dampers ◽  
Optimum Frequency ◽  
Long Span Bridges ◽  
Long Span ◽  
Magnification Factors ◽  
Tuning Frequency ◽  
Stiffness And Damping ◽  
Multiple Tuned Mass Dampers

The lever-type multiple tuned mass dampers (LT-MTMD), consisting of several lever-type tuned mass dampers (LT-TMDs) with a uniform distribution of natural frequencies, are proposed for the vibration control of long-span bridges. Using the analytical expressions for the dynamic magnification factors (DMF) of the LT-MTMD structure system, an evaluation, with inclusion of the LT-MTMD stroke, is conducted on the performance of the LT-MTMD with identical stiffness and damping coefficients but unequal masses for mitigating harmonically forced vibrations. The LT-MTMD is found to possess the near-zero optimum average damping ratio regimen when the total number of dampers exceeds a certain value. In comparison, the LT-MTMD without the near-zero optimum average damping ratio and the traditional hanging-type multiple tuned mass dampers (HT-MTMD) without the near-zero optimum average damping ratio can achieve approximately the same optimum frequency spacing (an indicator for robustness), effectiveness, and stroke. Compared with the HT-MTMD, the LT-MTMD needs lesser optimum average damping ratio but significantly higher optimum tuning frequency ratio. Its main advantage is that the static stretching of the spring may be adjusted to meet the practical requirements through the support movement, while maintaining the same robustness, effectiveness, and stroke. Consequently, the LT-MTMD is a better choice for suppressing the vibration of long-span bridges as the static stretching of the spring required is not large.

An Improved Flutter Analytical Method for Bridge

2014 ◽  
Vol 587-589 ◽  
pp. 1468-1472
Author(s):  
Guo Fang Chen ◽  
Wei Xu ◽  
Bao Chu Yu
Keyword(s):  
Wind Velocity ◽  
Damping Ratio ◽  
Classical Case ◽  
Pulse Load ◽  
Fe Model ◽  
Transient Dynamic Analysis ◽  
Long Span Bridges ◽  
Long Span ◽  
Stiffness And Damping

With the help of the commercial FE package ANSYS, this paper presents a finite element (FE) model for analyzing coupled flutter of long-span bridges. This model models the aero-elastic forces acting on the bridge utilizing a specific user-defined element Matrix27 in ANSYS, by which stiffness and damping matrices can be expressed in terms of the reduced wind velocity and flutter derivatives. Taking advantage of this FE model, Transient dynamic analysis is carried out to determine the dynamic response of a structure under the action of pulse load, of which the damping ratio can be obtained by considering response peaks which are several cycles apart. The condition for onset of flutter instability turns into that, at a certain wind velocity, the structural system incorporating fictitious Matrix27 elements does simple harmonic vibration with zero damping ratios or near zero one. The damping ratio is completely calculated in post-analysis of ANSYS and the initial frequency is given by any value and the last frequency can be got by iterating several times. In order to validate the developed procedure, a classical case study on three hundred meter simple supported beam is provided.

OPTIMUM MULTIPLE TUNED MASS DAMPERS FOR BASE-EXCITED DAMPED MAIN SYSTEM

2004 ◽  
Vol 04 (04) ◽  
pp. 527-542 ◽  
Author(s):  
S. V. BAKRE ◽  
R. S. JANGID
Keyword(s):  
Damping Ratio ◽  
Tuned Mass Damper ◽  
Frequency Bandwidth ◽  
Tuned Mass Dampers ◽  
Explicit Formulas ◽  
Optimum Parameters ◽  
Main System ◽  
Mass Damper ◽  
Tuning Frequency ◽  
Multiple Tuned Mass Dampers

The optimum parameters of multiple tuned mass dampers (MTMD) for suppressing the dynamic response of a base-excited damped main system are investigated by a numerical searching technique. The criterion selected for the optimality is the minimization of the steady state displacement of the main system under harmonic base acceleration. The parameters of the MTMD that are optimized include: the damping ratio, the tuning frequency ratio and the frequency bandwidth. The optimum parameters of the MTMD system and corresponding displacement are obtained for different damping ratios of the main system and different mass ratios of the MTMD system. The explicit formulas for the optimum parameters of the MTMD (i.e. damping ratio, bandwidth and tuning frequency) are then derived using a curve-fitting scheme that can readily be used in engineering applications. The error in the proposed explicit expressions is investigated and found to be negligible. The effectiveness of the optimally designed MTMD system is also compared with that of the optimum single tuned mass damper. It is observed that the optimally designed MTMD system is more effective for vibration control than the single tuned mass damper. Further, the damping in the main system significantly influences the optimum parameters and the effectiveness of the MTMD system.

Flutter mitigation of a superlong-span suspension bridge with a double-deck truss girder through wind tunnel tests

2020 ◽  
pp. 107754632094615
Author(s):  
Yanguo Sun ◽  
Yongfu Lei ◽  
Ming Li ◽  
Haili Liao ◽  
Mingshui Li
Keyword(s):  
Wind Tunnel ◽  
Damping Ratio ◽  
Suspension Bridge ◽  
Wind Tunnel Tests ◽  
Long Span Bridges ◽  
Long Span ◽  
Upper Deck ◽  
Torsional Damping ◽  
And Control ◽  
Wind Induced Vibration

As flutter is a very dangerous wind-induced vibration phenomenon, the mitigation and control of flutter are crucial for the design of long-span bridges. In the present study, via a large number of section model wind tunnel tests, the flutter performance of a superlong-span suspension bridge with a double-deck truss girder was studied, and a series of aerodynamic and structural measures were used to mitigate and control its flutter instability. The results show that soft flutter characterized by a lack of an evident divergent point occurred for the double-deck truss girder. Upper central stabilizers on the upper deck, lower stabilizers below the lower deck, and horizontal flaps installed beside the bottoms of the sidewalks are all effective in suppressing flutter for this kind of truss girder. By combining the structural design with aerodynamic optimizations, a redesigned truss girder with widened upper carriers and sidewalks, and double lower stabilizers combined with the inspection vehicle rails is identified as the optimal flutter mitigation scheme. It was also found that the critical flutter wind speed increases with the torsional damping ratio, indicating that the dampers may be efficient in controlling soft flutter characterized by single-degree-of-freedom torsional vibration. This study aims to provide a useful reference and guidance for the flutter design optimization of long-span bridges with double-deck truss girders.

PERFORMANCE OF DUAL-LAYER MULTIPLE TUNED MASS DAMPERS FOR STRUCTURES UNDER GROUND EXCITATIONS

2006 ◽  
Vol 06 (04) ◽  
pp. 541-557 ◽  
Author(s):  
CHUNXIANG LI
Keyword(s):  
Natural Frequencies ◽  
Vibration Mode ◽  
Frequency Tuning ◽  
Tuned Mass Damper ◽  
Tuned Mass Dampers ◽  
Optimum Parameters ◽  
Generalized System ◽  
Magnification Factors ◽  
Mass Damper ◽  
Multiple Tuned Mass Dampers

The dual-layer multiple tuned mass dampers (DL-MTMD) with a uniform distribution of natural frequencies are proposed, which consist of one large tuned mass damper (L-TMD) and an arbitrary number of small tuned mass dampers (S-TMD). The structure is represented by a generalized system corresponding to the specific vibration mode to be controlled. The criterion for assessing the optimum parameters and effectiveness of the DL-MTMD is based on the minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure installed with the DL-MTMD. Also considered is the stroke of the DL-MTMD. The proposed DL-MTMD system is demonstrated to show higher effectiveness and robustness to the change in frequency tuning, in comparison to the multiple tuned mass dampers (MTMD) with equal total mass ratios. It is also demonstrated to be more effective than the dual tuned mass dampers (DTMD) with one large and one small tuned mass damper, but they maintain the same level of robustness to the change in frequency tuning. The DL-MTMD system can be easily manufactured as the optimum value for the linking dashpots between the structure and L-TMD is shown to be zero.

Effects of Soil-Structure Interaction on the Response of a Structure With Tuned Mass Dampers

2015 ◽  
Author(s):  
Chong-Shien Tsai ◽  
Hui-Chen Chen
Keyword(s):  
Soil Structure ◽  
Damping Ratio ◽  
Excitation Frequency ◽  
Soil Structure Interaction ◽  
Entire System ◽  
Mass Ratio ◽  
Tuned Mass Dampers ◽  
Soil Layers ◽  
Structure Interaction ◽  
Multiple Tuned Mass Dampers

This paper aims at examining the effects of soil-structure interaction (SSI) on the response of a structure which is equipped with multiple tuned mass dampers (MTMD) and founded on multiple soil layers overlying bedrock. Closed-form solutions have been obtained for the entire system, which consists of a shear beam type superstructure, multiple tuned mass dampers, and multiple soil layers overlying bedrock, while subjected to ground motion. The proposed formulations simplify the problem in terms of well-known frequency ratios, mechanical impedance and mass ratio, which can take into account the effects of SSI, mass ratio of the MTMD at each excitation frequency and damping ratio in the entire system. These formulations are capable of explicitly interpreting the major dynamic behavior of a structure equipped with multiple tuned mass dampers and interacting with the multiple soil layers overlying bed rock. The SSI effects on the dynamic response of a tuned-mass-damped structure as a result of multiple soil layers overlying bedrock were extensively investigated through a series of parametric studies.

scholarly journals Parametric Study of Tuned Mass Dampers for Long Span Transmission Tower-Line System under Wind Loads

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Li Tian ◽  
Yujie Zeng
Keyword(s):  
Frequency Ratio ◽  
Damping Ratio ◽  
Vibration Reduction ◽  
Tuned Mass Damper ◽  
Reduction Ratio ◽  
Transmission Tower ◽  
Tuned Mass Dampers ◽  
Line System ◽  
Long Span ◽  
Mass Damper

A parametric study of tuned mass dampers for a long span transmission tower-line system under wind loads is done in this paper. A three-dimensional finite element model of transmission tower-line system is established by SAP2000 software to numerically verify the effectiveness of the tuned mass damper device. The wind load time history is simulated based on Kaimal spectrum by the harmony superposition method. The equations of motion of a system with tuned mass damper under wind load excitation are proposed, and the schematic of tuned mass damper is introduced. The effects of mass ratio, frequency ratio, damping ratio, the change of the sag of transmission line, and the robustness of TMD are investigated, respectively. Results show that(1)the change of mass ratio has a greater effect on the vibration reduction ratio than those of frequency ratio and damping ratio, and the best vibration reduction ratio of TMD is not the frequency ratio of 1;(2)the sag-span ratio has an insignificant effect on the vibration reduction ratio of transmission tower when the change of sag-span ratio is not large; and(3)the effect of ice should be considered when the robustness study of TMD is carried out.

Research on Simplifying the Buffeting Response Spectrum of Suspension Bridge

2013 ◽  
Vol 791-793 ◽  
pp. 370-373
Author(s):  
Hua Bai ◽  
Yue Zhang
Keyword(s):  
Response Spectrum ◽  
Damping Ratio ◽  
Suspension Bridge ◽  
Concrete Bridges ◽  
Main Beam ◽  
Response Analysis ◽  
Long Span Bridges ◽  
Buffeting Response ◽  
Long Span ◽  
The Impact

In order to solve the problem of traditional buffeting analysis method is complex, the paper summarizes a calculation method of simplifying the suspension bridge buffeting response spectrum which considers the background response by simplifying the vibration mode function. Examples calculation shows that this function is efficient and accurate. With this method the paper analyzes the impact of parameters including structural damping ratio, aerodynamic admittance function, pneumatic self-excited forces, the main beam span and so on on the suspension bridge buffeting response. Results show that: First, the impact of the background response on concrete bridges with larger damping ratio cannot be ignored. Second, when aerodynamic admittance takes Sears function, the buffeting response analysis results may be partial dangerous. Third, the role of the background response on large long-span bridges of more than 2000 m can be ignored.

A hybrid approach for parameter optimization of multiple tuned mass dampers in reducing floor vibrations due to occupant walking: Theory and parametric studies

2017 ◽  
Vol 20 (8) ◽  
pp. 1232-1246 ◽  
Author(s):  
Ruotian Xu ◽  
Jun Chen ◽  
Xinqun Zhu
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Hybrid Approach ◽  
Tuned Mass Damper ◽  
Dynamic Responses ◽  
Optimization Approach ◽  
Tuned Mass Dampers ◽  
Mass Damper ◽  
Floor Vibrations ◽  
Multiple Tuned Mass Dampers

This article presents a hybrid approach for determining optimal parameters of multiple tuned mass dampers to reduce the floor vibration due to human walking. The proposed approach consists of two parts. The first one is a partial mode decomposition algorithm to efficiently calculate dynamic responses of the coupled floor–multiple tuned mass damper system subjected to moving walking loads. The second one is an adaptive genetic simulated annealing method for the optimization of multiple tuned mass damper parameters. To establish optimization, certain variables must be considered. These include the mass, natural frequency, and damping ratio of each tuned mass damper in a multiple tuned mass damper system. The objective is to minimize floor responses and remove unreasonable requirements, such as uniform mass distribution and symmetric distribution of the tuned mass damper frequency. The proposed hybrid approach has successfully been applied to optimize the multiple tuned mass damper system to reduce the vibration of a long-span floor with closely spaced modes. By the hybrid approach, an extensive parametric study has been carried out. The results show that different walking load models and uncertainties in the dynamic properties of the floor and each tuned mass damper itself can affect the overall performance of the multiple tuned mass damper system. The proposed hybrid optimization approach is very effective and the resulting multiple tuned mass damper system is robust in reducing floor vibrations under various conditions.

Sign in / Sign up

Export Citation Format

Share Document