For a secondary mass damper such as tuned liquid damper (TLD) or tuned liquid column damper (TLCD), whose moving mass is liquid, it is impossible to prefabricate the damper in a factory for the identification of dynamic properties. Also, it is not easy to prefabricate a concrete tuned mass damper (TMD), whose moving mass is made of concrete, in a factory. In this article, an identification method for finding dynamic properties of secondary mass dampers based on the fullscale field test is presented. Decoupled equations of motion are derived from a coupled equation of motion of building and damper. The decoupled equations of motion are then used for system identification using the response of the damper as an input and the response of the building as an output. The proposed method is applied to numerical examples and an actual TMD and TLCD installed in buildings.
Numerous studies have reported a positive impact of acute exercise for procedural skill memory. Previous work has revealed this effect, but these findings are confounded by a potential contribution of a night of sleep to the reported exercise-mediated reduction in interference. Thus, it remains unclear if exposure to a brief bout of exercise can provide protection to a newly acquired motor memory. The primary objective of the present study was to examine if a single bout of moderate-intensity cardiovascular exercise after practice of a novel motor sequence reduces the susceptibility to retroactive interference. To address this shortcoming, 17 individuals in a control condition practiced a novel motor sequence that was followed by test after a 6-h wake-filled interval. A separate group of 17 individuals experienced practice with an interfering motor sequence 45 min after practice with the original sequence and were then administered test trials 6 h later. One additional group of 12 participants was exposed to an acute bout of exercise immediately after practice with the original motor sequence but prior to practice with the interfering motor sequence and the subsequent test. In comparison with the control condition, increased response times were revealed during the 6-h test for the individuals that were exposed to interference. The introduction of an acute bout of exercise between the practice of the two motor sequences produced a reduction in interference from practice with the second task at the time of test, however, this effect was not statistically significant. These data reinforce the hypothesis that while there may be a contribution from exercise to post-practice consolidation of procedural skills which is independent of sleep, sleep may interact with exercise to strengthen the effects of the latter on procedural memory.
In this study, a tuned liquid mass damper (TLMD) was proposed to reduce bidirectional responses of building structures, and its control performance was experimentally evaluated. The proposed TLMD with only one device body reduces bidirectional responses of building structures by behaving as a TMD and a TLCD in the weak and strong axial directions of a building fl oor plan, respectively. First, the control performance of a TLMD mounted on a scaledowned single-degree-of-freedom building model was experimentally evaluated by exciting this system with an actuator. Then, the real-time hybrid shaking table testing method (RTHSTTM) was performed to assess the control effi ciency of the total system by adopting the TLCD and the building model as the experimental and numerical parts, respectively. It was confi rmed by comparing uncontrolled and controlled testing results that the proposed TLMD can be applied to reduce the responses in both the weak and strong directions of building structures. Also, the results from RTHSTTM showed that the performance of TLMD-controlled building structure can be accurately evaluated by this method only using a TLMD as the experimental part.
Increasing heights of tall buildings often require supplementary damping system for
occupant comfort in windy condition. This paper presents a liquid column vibration absorber
(LCVA) installed in a 64-story building, which is the highest residential building with flat plate
structural system in Korea, for mitigation of wind-induced motion. LCVA is a special type of
secondary mass-type dampers relying on the motion of a column of liquid in a U-shaped container to
counteract the forces acting on the structure. Since it has different dimensions for vertical and
horizontal portions of container, it has benefits of easy tuning and wide natural frequency range. To
evaluate the control performance of LCVA, an experiment using 1/20 scaled model is performed. The
test structure is excited using a sinusoidal signal ranging 0.1 ~ 3.0Hz with 5.5mm displacement, and
acceleration and displacement of the structure, water height, and shear force are measured.
Experiment results indicate that the LCVA increase the energy dissipation capacity of the building
significantly.
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