The use of tuned liquid dampers to enhance the seismic performance of concrete rigid frame buildings

A tuned liquid damper (TLD) is a passive energy dissipation device that has been used successfully in suppressing the vibration of tall structures under strong wind load events. It consists of one or multiple tanks, partially filled with water and rigidly attached to the structures. During a dynamic loading event, the vibration of the structure leads to the development of a sloshing motion for the liquid inside the tank. If the frequency of the sloshing motion is properly tuned to the natural frequency of a dominant mode of vibration of the structure, the sloshing motion imparts an inertia force that acts against the structural vibration. This effect leads to a reduction in the structural response, and, consequently an increase in the effective damping of the structure. Many studies were conducted during the last two decades to investigate the response of TLDs and structure-TLD systems under narrow band excitations simulating wind loads. The focus was to assess the use of TLDs in improving the serviceability of the structures.;An experimental program conducted on a single degree of freedom system simulating a structure with a TLD attached and subjected to transient loading. The test results reveal that the TLD is capable of responding quickly to transient loading and can increase the damping characteristics of the structure under earthquake loading. A numerical model, in which the structure-TLD system, is simulated as a two degree of freedom systems is then developed and validated using the experimental results. While this model captures the non-linear behaviour of the TLD, it is restricted to a linear structural behaviour only.;A non-linear material model simulating the behaviour of reinforced concrete rigid frame elements under cyclic loading is then developed and validated using experimental results available in the literature. This material model together with the non-linear model simulating the sloshing behaviour of a TLD are incorporated together into a multi-degree (MDOF) finite element simulation. The MDOF model is validated by comparing its performance to the previously validated two degree of freedom model.;An eight-story reinforced concrete rigid frame building is designed using the seismic provision specified in the National Building Code of Canada, NBCC. Various earthquake records are developed to match the uniform hazard spectra of the recent NBCC code. A tuned liquid damper is designed to match the cracked fundamental frequency of the reinforced concrete building which is modeled using the developed MDOF numerical model. The response of the structure with and without TLDs is evaluated using the numerical model. The study considers also the use of multiple tuned liquid dampers (MTLD) that are tuned for a certain range of frequencies around the cracked fundamental frequency of the building. The results of the analysis indicate that the use of MDOF leads to a better structural performance and to a large reduction in the structural vibration. For the MTLD case, the reduction of the structural response has varied between 21% and 50% for the six time history records used in the analyses. A significant reduction in the ductility demand of the reinforced concrete members is also achieved when MTLDs are used.;The current study involves an assessment for the use of TLDs as auxiliary damping devices for buildings in order to enhance their behaviour under seismic loading. Specifically, the study focuses on reinforced concrete rigid frame buildings.;Keywords. Tuned liquid dampers (TLD), transient loading, seismic excitation, RC beam/column joint, fluid structure interaction, fluid sloshing, structural response.