A modified liquid column damper (TLCD), of which the space inside the tube filled with liquid material is applied to structure, for damping purpose. Installed with the tuned liquid column damper, the vibration of structure system caused by external force may be mitigated by the TLCD device due to the sloshing motion of, the liquid in the tube. The traditional TLCD was modified into a multi-directional TLCD, which is a damper of arc-shaped circular, tube. The horizontal part was designed into a ring that may connect to dampers of other directions while, the vertical part was modified into an arc shape that may function similar to traditional vertical TLCD but provide a wider space between the arc columns. The study on multi-directional tuned liquid column dampers mainly focused on basic characteristics of the damper and the behavior of structures equipped with the new developed dampers subjected to dynamic forces. Based on the theorem of TLCD, the governing equation of multi-directional TLCD was re-derived. The parameters related to damping ratio were measured in the experiment, where a model of free vibration was performed. A multi-directional TLCD system with various damping ratio was designed in harmony with optimal damping ratio. In the experimental results, it was found that during a resonant excitation with the structure, a multi-directional TLCD can have good damping effect, particularly when the, orifice opening is 18%.

In this study, a tension leg platform (TLP) incorporated with the TLCD (Tuned liquid column damper) is tested experimentally. The advantages of TLP with TLCD devices are as follows¡G1.When the TLCD devices use on the TLP, the columns under the platform could provide the buoyant force. 2. When the TLCD devices are injected into water, the vibration of the platform could be mitigated by the water sloshing power. 3. It can change the natural frequency within limits by changing the liquid length. In this thesis, a scaled-down model is tested in the laboratory to verify the analytical results. When the experiment tested, the total mass of the system should be the same no matter if the TLCD devices are applied or not. We used the accelerometers to obtained the acceleration of the platform including the surge, heave and pitch motions. The tendon force is obtained by the strain gage. Can be found from the experiment course, after the structure adds the TLCD devices, the responses of three motion can be effective reduced. So what reducing shaking to disappear and can be designed and discussed best by this text under various kinds of situations of finding out.

In this thesis , the response of tension leg platform¡]TLP¡^subjected to wave force is studied by means of an analytical stochastic technique. The effectiveness of tuned liquid column damper¡]TLCD¡^and the effectiveness of various parameters to the TLP is discussed. Also an experiment study is used to check the analytical solution. Analytical solution show that all the parameters including the mass of the platform, the diameter of the floating barrel, the draft of the platform and the dimension of the platform will affect the TLP¡¦s resonant frequency and amplitude. When the TLCD is applied, the peak value is reduced for the surge and heave response spectrum generally, but the peak value of the pitch response spectrum is sometimes increased. The effectiveness of TLCD becomes more significant when the width-length ratio is increased. If the mass of TLCD is constant, the effectiveness of TLCD will be the same no matter water or mercury is injected into. Comparing the analytical solution with that from experiments, the results show reasonable consistence in trend.

Abstract In this study, a model of typical tension-leg type of floating platform incorporated with the upgraded TLCD (Tuned liquid column damper) devices is tested experimentally. The advantages of upgraded TLCD are as follows: 1. When the TLCD devices are applied, the columns under the platform could provide the buoyant force. 2. When the TLCD devices are injected into water, the vibration of the platform could be mitigated by the water sloshing power. 3. The force of tension-leg could be adjusted by the quantity of water which is injected into the columns. In this thesis, a scaled-down model is tested in the laboratory to verify the analytical results. When the experiment is tested, the total mass of system should be controlled no matter if the TLCD devices are applied or not. Both the acceleration and tendon force are recorded. The acceleration of the platform is obtained in the accelerometers including the surge, heave and pitch motions. The tendon force is obtained by the strain gage. According to the results of experimental testing the platform system incorporated with TLCD devices has smaller response during the different cases. The amplitude reduction effect can be observed in the response of time history including the surge, heave and pitch motions while the energy reduction effect can be observed in the response spectra for the surge, heave and pitch motion. Additionally, the tendon force reduces obviously. Thus, this study may verify that the application of TLCDs to the offshore system is found valuable.

With the progress of civilization, buildings and residential constructions become taller and taller. Seismic design for buildings to resist earthquakes also attracts more attentions. The common vibration energy dissipation devices such as TMD, TLD, etc. have been popular but they have limitations such as requirement for large space to install and difficult to be installed after the building is finished. TLCD as an alternative may improve these defects. The new developed MR-TLCD system has the advantages of real-time control and is reversible. Based on the theorem of TLCD, the control equation of MR-TLCD considered the fluid viscosity. The parameters of external control magnetic force and properties of MR-fluid inside the tube needed in damping ratio calculation were measured in the experiment, where a model free vibration experiment was performed. A MR-TLCD system of which the damping ratio was designed in harmony with optimal damping ratio. The comparison was also made for the damping effect of traditional TLCD, MR-TLCD(uncontrolled), MR-TLCD(passive controlled) under dynamic loadings of various frequencies and amplitudes. The experimental results showed that MR-TLCD is more suitable in large amplitude external force. TLCD plays the best vibration mitigation effect when the external force is resonant to the structure, but MR-TLCD is better in other frequency range. It is encouraging that the application of MR-TLCD can have larger scope than TLCD. Keyword: vibration mitigation, experiment, TLCD, MR-TLCD