Browsing by Author "Wu, Jong-Cheng"

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Design tables and charts for uniform and non-uniform tuned liquid column dampers in harmonic pitching motion
(2012-02-01)
Wu, Jong-Cheng
;
Wang, Yen-Po
;
Chen, Yi-Hsuan
;
土木工程學系
;
Department of Civil Engineering
In the first part of the paper, the optimal design parameters for tuned liquid column dampers (TLCD) in harmonic pitching motion were investigated. The configurations in design tables include uniform and non-uniform TLCDs with cross-sectional ratios of 0.3, 0.6, 1, 2 and 3 for the design in different situations. A closed-form solution of the structural response was used for performing numerical optimization. The results from optimization indicate that the optimal structural response always occurs when the two resonant peaks along the frequency axis are equal. The optimal frequency tuning ratio, optimal head loss coefficient, the corresponding response and other useful quantities are constructed in design tables as a guideline for practitioners. As the value of the head loss coefficient is only available through experiments, in the second part of the paper, the prediction of head loss coefficients in the form of a design chart are proposed based on a series of large scale tests in pitching base motions, aiming to ease the predicament of lacking the information of head loss for those who wishes to make designs without going through experimentation. A large extent of TLCDs with cross-sectional ratios of 0.3, 0.6, 1, 2 and 3 and orifice blocking ratios ranging from 0%, 20%, 40%, 60% to 80% were inspected by means of a closed-form solution under harmonic base motion for identification. For the convenience of practical use, the corresponding empirical formulas for predicting head loss coefficients of TLCDs in relation to the cross-sectional ratio and the orifice blocking ratio were also proposed. For supplemental information to horizontal base motion, the relation of head loss values versus blocking ratios and the corresponding empirical formulas were also presented in the end.
Wind-induced interaction of a non-uniform tuned liquid column damper and a structure in pitching motion
(2008-12-01)
Wu, Jong-Cheng
;
Wang, Yen-Po
;
Lee, Chien-Liang
;
Liao, Pei-Hsuan
;
Chen, Yi-Hsuan
Wind-induced interaction between a tuned liquid column damper (TLCD) and a structure (bridge deck) in pitching motion is investigated both theoretically and experimentally. Non-uniform cross-sections in TLCDs are considered in general. Theoretically, the interacted equations of motion under wind excitation were derived for a single-degree-of-freedom rotational structure equipped with a TLCD based on energy principles. An addition term, which had never been revealed in existing literature, was discovered. The second part in this study was to demonstrate the existence of this additional term through experimental verification. This task was carried out by conducting large scale tests on the system of a TLCD on a rotational structure (which is a spring-constrained steel beam pivoted at mid-span) and by making comparisons between the experimental and analytical responses of the interacted structure subjected to harmonic loading. To obtain all necessary parameters for computing the analytical responses in the interaction, the individual identification of the properties of the TLCD and structure using free vibration and forced vibration techniques was also performed. Comparison results show that analytical responses with the additional term included can represent the actual interaction more closely than those without the additional term. Therefore, the inclusion of the additional term in pitching interaction equations is essential. (C) 2008 Elsevier Ltd. All rights reserved.