Search

In seismic areas, the application of structural dampers becomes compulsory in the design of buildings. There are various types of dampers, such as viscous elastic dampers, viscous fluid dampers, friction dampers, tune mass dampers, yielding/ metallic dampers, and magnetic dampers. All damper systems are designed to protect structural integrities, control damages, prevent injuries by absorbing earthquake energy, and reduce deformation. This paper is a part of research investigating the behaviour of the U-shaped steel damper (as one type of metallic damper) that can be applied to the buildings in seismic areas. The dampers are used as connections between the roof and supporting structure, with the two general purposes. The first is to control the displacement of roof under an earthquake, and the second is to absorb seismic energy through the plasticity of some parts in dampers. If a strong earthquake occurs, the plasticity will absorb the seismic energy; therefore, heavy damage could be avoided from the roof’s mainframes. In this paper, several models of U-shaped steel dampers are introduced. Several parameters, such as elastic stiffness, maximum strength, and energy dissipation, are determined under two conditions. Firstly, static analysis of the proposed damper under variation of U-steel plate configurations, searching the model with more significant energy dissipation. Secondly, static analysis of the unsymmetrical and symmetrical damper under different loading directions. An in-house finite element program that involves both geometrical and material nonlinearities is developed as a problem solver. A quasi-static lateral loading is given to each model until one cycle of the hysteresis curve is reached (in the displacement range between -20 mm to +20 mm). The above parameters are calculated from the hysteresis curve. From the results, the behaviour of the U-steel damper can be described as follows. Firstly, increasing the energy dissipation in the lateral direction can be done by increasing the lateral stiffness of the damper. However, it can reduce the maximum elastic deformation of the damper. Secondly, under the random direction of loading, a symmetrical shape can increase the energy dissipation of the damper.

This research proposes a new method for boat impact vibration attenuation using the exchange of momentum principle with a pre-straining spring mechanism. The boat dynamic is modeled using a hinged-supported beam structure. The wave excitation on the boat hull is expressed using one degree of freedom spring-mass system. The simulation study is performed to evaluate the impact damper performance in reducing the boat shock response. Two kinds of momentum exchange impact damper i.e., without and with pre-straining spring mechanism, are evaluated. The simulation results show that the impact damper with pre-straining spring mechanism (PSMEID) is better than the passive momentum exchange impact damper (PMEID) in reducing the boat shock vibration response

Crack is a problem that frequently found in a structure. Identification of crack is a crucial aspect in decision making about structure condition. Structural Health monitoring has become a solution to detect the crack. Basically, if a crack initiates and propagates in a structure, the natural frequencies of the structure will change because of decreasing stiffness and abrupt curvature of mode shapes will occur. This research is developed from before research and aimed to identify the crack position in a free free cantilever beam experimentally by analytically using finite element model (FEM) and experimental modal analysis (EMA). First, a perfect cantilever beam without any cracks is modeled by FEM and identified by EMA. Then artificial cracks are created to the beam with single and two cracks, and FEA model and EMA identification is developed. The position of the crack then is identified by the change of mode shape curvature using curvature change index that obtained from the difference in mode shape curvature between the damage and the undamaged cases, and mode shape curvature based on curvature sensitifity caused by decreasing stiffness caused by cracks.The result shows that mode shape curvature has better sensitifty to detect the position of cracks, and results of experiment show good corelation with results of finite element analysis.

This research proposes a novel landing gear system using a four-bar linkage mechanism. The mathematical model of the landing gear system is calculated analytically. A simulation study is performed to investigate the landing gear performance in reducing the impact vibration response of the main system. It is found from the simulation study that nonlinear characteristic of the landing gear stiffness improves its impact vibration response. The simulation results show that rebound displacement and acceleration response of the main system using the proposed technique is smaller than that of using a conventional landing gear system.

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.

A Tuned Liquid column Damper (TLCD) performance depends on the TLCD natural frequency and damping ratio. Theoretically, the TLCD natural frequency is determined by its dimension and the length of fluid inside TLCD column. The damping ratio of TLCD is influenced by several factors such as friction between the fluid and TLCD column, TLCD junction angle and a built-in orifice plate with a small opening. In this research, the effect of TLCD junction angle to its performance in reducing the structural response is evaluated by varying the TLCD angle from 30° to 90°. An experimental model of two DOF shear structure with TLCD is governed to evaluate the TLCD performance. The experimental results show that a TLCD with junction angle 60° filled with 325 ml water is better than others in reducing the vibration response of a two DOF shear structure.

This paper investigates one type of metallic dampers used in many large buildings in seismic areas. The previous studies have shown a possibility of the introduced damper to act as a damper as well as energy absorber through yielding on some parts of the damper. However, the occurred yielding caused a plastic deformation after unloading. The study aims to substitute the previous critical area to another part which is considerably uncritical during loading. Therefore, an additional part in the form of a slender column is inserted into the damper. The bottom part of the column is clamped to the base plate of the damper. There is a restoring moment acting on the column which was able to restore a large displacement of the damper to at least a small residual plastic displacement after unloading. A stiffness, strength and energy dissipation of the modified damper is determined by a nonlinear finite element technique which involves both geometrically and materially nonlinearities. The model was subjected by a monotonic increasing load which is applied horizontally through the method of displacement control until one cycle of hysteresis is formed. The final result is in a term of comparison of hysteresis curves between a full model of hysteresis damper with and without a slender column.

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.

This research is aimed to design and analyze the performance of double dynamic vibration absorber (DVA) using a pendulum and a spring-mass type absorber for reducing vibration of two-DOF vibration system. The conventional fixed-points method and genetics algorithm (GA) optimization procedure are utilized in designing the optimal parameter of DVA. The frequency and damping ratio are optimized to determine the optimal absorber parameters. The simulation results show that GA optimization procedure is more effective in designing the double DVA in comparison to the fixed-points method. The experimental study is conducted to verify the numerical result.

One of the important consideration in designing an unmanned aerial vehicle (UAV) is the dynamics characteristic of UAV structure. The dynamics characteristic of UAV structure can be evaluated from its dynamic parameters such as : natural frequencies and mode shape. These parameters play an important role in determining the system’s dynamic response. In general, a low stiffness structure is more sensitive to the dynamic load in comparison with a high stiffness structure. In this research, modification UAV structural stiffness is conducted by varying rib and spar number and configuration on UAV wing. Evaluation of rib and spar number and configuration effect to the natural frequency and mode shape of UAV structure is conducted numerically and experimentally. The simulation results show that the natural frequencies increases with increasing of the number of spar and decreases with decreasing of the number of rib.

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.

This paper proposes an active control type of momentum exchange impact damper (AMEID) and its application to reducing shock vibration of the floor. The floor is modeled as a one-degree-of-freedom system. The active component of AMEID is realized by using a linear motor. The controller design of AMEID is based on the LQR optimal control theory. The simulation results show that the performance of AMEID is not affected by the mass ratio. In addition, the performance of AMEID is compared with the conventional passive momentum exchange impact damper (PMEID), the active mass damper (AMD) and the conventional active control method in reducing the floor shock vibration. It is shown that the shock reduction performance obtained by AMEID is larger than that obtained by PMEID. The power consumption and the stroke of the actuator for AMEID are lower than those of AMD. Furthermore, the transmitted force obtained by AMEID is smaller than that of the conventional active control.

This paper deals with reducing floor impact vibration and sound by using a momentum exchange impact damper. The impact damper consists of a spring and a mass that is contact with the floor. When a falling object collides with the floor, the floor interacts with the damper mass, and the momentum of the falling object is transferred to the damper. In this works a computational model is formulated to simulate dynamic floor vibration induced by impact. The floor vibration is simulated for various sized damper masses. A proof-of-concept experimental apparatus was fabricated to represent a floor with an impact damper. This example system consists of an acrylic plate, a ball for falling object, and an impact damper. A comparison between simulated and experimental results were in good agreement in suggesting that the proposed impact damper is effective at reducing floor impact vibration and sound by 25% and 63%, respectively.

This research discusses the static analysis of the kiln girth gear at Indarung cement Factory V PTSP due to replacement of the oldest girth gear with the newest one. The newest version of girth gear system has a smaller number of supporting spring (spring plate) in comparison with the previous one. Therefore, it is necessary to analyze the effect of the spring plate number to the strength and stiffness of the girth gear system to assure the kiln can work properly. In this research the effect of the spring plate number to the linear and torsional stiffness of the girth gear is evaluated. Based on the simulation results, decreasing of the spring plate number from 16 to 12, significantly affect the total stiffness of the supporting spring. Furthermore, it was found from the simulation that the total stiffness of the supporting spring much affected by the axial stiffness of the spring plate comparing to its lateral stiffness.

The authors' previous study proposed a novel shock vibration control using the active momentum exchange impact damper (AMEID) in simulations. By using this method, the shock vibration of the vibratory system is greatly reduced by transferring a part of its momentum to the damper mass. This feature is effective for suppressing the first large peak value of the acceleration response due to a shock load. In this paper, the active control of shock vibration using AMEID in actual conditions is evaluated by experiments. A one-degree-of-freedom vibratory system is used as the controlled object. The controller is designed by using the discrete-time LQR optimal control theory. The effectiveness of the AMEID approach is verified experimentally.

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.