42 research outputs found
Evaluation of TLCD Damping Factor from FRF Measurement Due to Variation of the Fluid Viscosity
Tuned Liquid Column Damper (TLCD) has become an alternative solution for reducing low frequency vibration response of machines and structures. This is not surprisingly that the damper has simply structure and low maintenance cost. The main disadvantage of using TLCD is the complexity in controlling TLCD damping factor experimentally. Theoretically, damping factor can be controlled by adjusting the orifice dimension. However, this method is time consuming and not appropriate conducted in the real application. A more simply method for adjusting TLCD damping factor is by varying the fluid viscosity. This research is aimed to evaluate the effect of fluid viscosity to the damper performance. Two DOF shear structure with TLCD is used as the experimental model. Several TLCD fluids with different viscosity are evaluated. Evaluation of TLCD damping factor due to variation of the fluid viscosity is conducted by comparing the Frequency Response Function (FRF) obtained from the experimental data
Empirical Evaluation of Variation of Orifice Blocking Ratio in a Tuned Liquid Column Damper using Frequency Response Function Measurement
Tuned liquid column damper (TLCD) is a simple technique used to increase the structure resistance to the external load. This type of damper can effectively decrease the structure response when the TLCD parameters such as the natural frequency and damping factor are well selected. Even though several TLCD models have been proposed and many algorithms to optimize the TLCD parameters have been developed. However, it is very little research has been conducted to evaluate the TLCD damping factor experimentally. A simple method for adjusting the TLCD damping factor empirically is by varying the orifice blocking ratio. In this research, 5 types of blocking ratio were trialled in the TLCD. They were without orifice and with 2, 4, 6 and 8 18 mm diameter orifices. The TLCD is positioned at the second floor of a Two-DOF shear structure. A frequency response function showing the ratio between the response magnitude and the excitation force on the structure in the frequency domain was recorded for each trial. The results show that the TLCDs with orifices damped vibrations more effectively than the one without orifice. The larger the blocking ratio, the larger the TLCD damping factor. Two 18 mm orifices were insufficient to damp the vibration as the blocking ratio is too large and TLCD is less responsive to the vibrations. The optimum condition of a U-Shaped TLCD blocking ratio was found to be 70.77% which corresponded to 4 holes of 18 mm orifice diameter. This type of TLCD dampened up to 80.04% of the vibration magnitude
Vibration Response Suppression of Space Structure using Two U-Shaped Water Container
Nowadays, a passive vibration control technique using dynamic vibration absorbers (DVA) has drawn many researchers’ attention in the structural dynamic field. The reason is that this technique is simple and it can work effectively in reducing the vibration response when its parameters are optimally designed. The DVA fundamental concept is the addition of a new vibration system to the primary system. This new system addition causes reduction of the vibration response of the primary system during excited by a dynamic load. One simple technique to realize the DVA for structural application is by using water vibration. This research is aimed to develop one type of dynamic vibration absorber using the water vibration system in a U-shaped container for a two-story building structure model. Besides being used as the dynamic absorber, this U-shaped container is also functioned as the water storage tank in the building. Regarding reduce the first bending mode response of the structure in x-z and y-z plane, two U-shaped water storage tanks are placed on the upper floor of the building. The dimensions of the water storage tanks are designed so that the natural frequency of moving water in the tank is the same as the natural frequency of the first bending mode of the structure in x-z and y-z plane. The performance of dynamic absorber is evaluated by applying the impulsive and seismic loads on the building. The simulation results show that the U-shaped water storage tank placed on the upper floor of the building can reduce the response amplitude of the structure under impulsive loads. Meanwhile, for the seismic load case, the performance of dynamic absorber is clearly seen when the excitation frequency is close to the natural frequency of the building structure
Static and Dynamic Analysis of Steel U-Damper for Space Structures
This paper is a part of research in searching an appropriate damper for space structures constructed in seismic areas. The study investigates a stiffness, strength and energy dissipation of the damper under loading. For this purpose, a U-shaped hysteresis steel damper is modeled and analyzed by a nonlinear finite element technique which involves both geometrical and material nonlinearities. The model is subjected to a monotonic increasing load which is applied horizontally until one cycle of hysteresis is formed. The stiffness, strength, and energy dissipation of the damper is directly determined from the graph of load–displacement. Feasibility of the hysteresis damper is investigated further for application on building construction. The damper is placed on the roof and supporting structure of the building. A 2-DOF spring-mass model, as a simple modelling of the building is introduced with damper’s properties are taken from the results of the first study. A seismic load is applied to see the response of the model. The static numerical analysis showed that the properties of the introduced damper, such as stiffness, strength and energy dissipation, are depending on the geometry of the damper. The results show that reducing the length of lower plate or height of the damper will increase stiffness, strength and energy absorption. In contrary, reducing the width of the damper will decrease all properties. Moreover, the results of the dynamic analysis show the feasibility of damper to reduce to reduce the amplitudes of the response of the roof under seismic load
PERALATAN PEREDAM GETARAN DINAMIK PADA BANGUNAN BERTINGKAT
Dua pasang peredam dinamik TMD dan TLCD diusulkan dalan invensi ini untuk meningkatkan ketahanan struktur bangunan terhadap beban gempa. Kedua pasang peredam dinamik TMD dan TLCD tersebut dipasangkan secara bersilangan pada atap bangunan sehingga mampu mengurangi respon bangunan akibat beban gempa terutama jika gangguan gempa berada di dekat frekuensi pribadi pertama dari struktur. Parameter peredam dinamik berupa massa dan dimensi TMD dan TLCD dipilih sesuai dengan kapasitas ruangan serta rasio massa yang diinginkan. Parameter dinamik berupa kekakuan pegas TMD dan ketinggian air pada TLCD diperoleh secara analitik. Harga redaman pada TMD dan TLCD diperoleh secara empirik
Robust Optimal Design of TMD and TLD Parameters in Reducing the Seismic Response of a Two DOF Shear Structure
This research proposes a technique for reducing the seismic response of a vibration system using
TMD and TLD absorbers. Application of the proposed method to the dynamic model of a two DOF
shear structure is evaluated. The equation of motion of the system is calculated by considering the
nonlinear behavior of the fluid motion inside the TLD container. The nonlinear characteristic of the
TLD absorber is modeled using a nonlinear stiffness and dashpot. Robust optimum design of the
absorber parameters using Genetic Algorithm (GA) is conducted base on the mean value and the
variance of the performance function, which calculated from the ratio between the system response
and its excitation signal. The simulation results shown that a combination of TMD and TLD
absorbers can effectively reduce the seismic response of a two DOF vibration systems
Low Speed Orientation Control Using Variable Mass System: Application In Solar Panel
This study offers a mechanism to control low-speed orientation using semi-active control. The semi-active system consists of a variable mass system and a torsional spring. The torque generated by a variable mass system controls the platform’s orientation. An evaluation of the control system’s effectiveness is tested on a solar panel. The variable mass was represented by moving the water from one reservoir to another located at the left and right sides of the panel using an electrical pump. A solenoid valve controls the flow. The test results indicate that the energy consumption of electrical pump as actuators is reduced. Based on several references, the actuator energy consumption for controlling the orientation of solar panels was generally 2% - 3%, while in this study 0.79%.
A new concept for UAV landing gear shock vibration control using pre-straining spring momentum exchange impact damper
This study proposes a new method for reducing the shock vibration response of an Unmanned Aerial Vehicle (UAV)
during the landing process by means of the momentum exchange principle (MEID). The performance of the impact
damper is improved by adding a pre-straining spring to the damper system. This research discusses the theoretical
application of the damper to the UAV landing gear system. The UAV dynamics is first modeled as a simple lumped mass
translational vibration system. Then we analyze a more complex two-dimensional model of UAV dynamics. This model
consists of the main wheel, nose wheel and main body. Three cases of UAV landing gear mechanisms: without damper,
with passive MEID (PMEID) and with pre-straining spring MEID (PSMEID) are simulated. The damper performance is
evaluated from the maximum acceleration and force transmission to the main body. The energy balance calculation
is conducted to investigate the performance of PSMEID. The simulation results show that the proposed PSMEID method is
the most effective method for reducing the maximum acceleration and force transmission of UAV during impact landing
Dynamic Vibration Absorber for Squeal Noise Suppression in Simple Model Structures
In recent research it was found that squeal noise caused by friction-induced vibration can result
in mode coupling instability. Presently, there is no method that can be reliably used to eliminate
this kind of noise. This paper is focused on the use of dynamic vibration absorbers (DVAs) to
suppress the generation of squeal noise. The performance of the DVA is investigated numerically
for two simple cases, i.e. a simple two-degree of freedom model, and an L-shape space
frame. It is found that the DVA can be applied to shifting or reducing the unstable region of
mode coupling, by which the unstable region is removed from the operating condition. Particularly,
the addition of the DVA in horizontal direction on the near-point-of-friction can
possibly avoid unstable mode coupling. However, the addition in vertical direction will increase
the possibility of squeal noise incident. Moreover, a high frequency DVA in horizontal direction
at the near-point-of-friction shifts the unstable region into higher normal contact sti®ness and
higher friction coe±cient. Consequently, addition of a mass with very sti® spring or a rigid mass
in the horizontal direction can prevent the occurrence of unstable mode coupling, as long as it is
not coupled with the vertical direction. If the added mass a®ects the dynamic behaviors in both
vertical and horizontal directions, squeal noise in the original normal contact sti®ness can still
occur
Response Reduction of Two DOF Shear Structure Using TMD and TLCD by Considering Absorber Space Limit and Fluid Motion
A Combination of dynamic vibration absorbers (DVAs) consist of Tuned Mass Damper
(TMD) and Tuned Liquid Column Damper (TLCD) for reducing vibration response of a two-DOF
shear structure model is proposed. The absorber parameters are optimized using Genetic Algorithm
(GA). The cost function is derived from the ratio between structure response and the excitation signal.
The limitation in absorber space and fluid motion are considered during optimization process. The
simulation results show that GA optimization procedure is effective to get the optimal absorber
parameters in the case of limited absorber size and motion