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Non-elastic responses of tall steel buildings subjected to across-wind forces
Tamura, Yukio,Yasui, Hachinori,Marukawa, Hisao Techno-Press 2001 Wind and Structures, An International Journal (WAS Vol.4 No.2
This paper presents an analytical method which takes into account the non-linearity of individual members, and discusses some case study results. It also discusses the relationship between member non-elastic behavior and excitation duration, and the relationship between member fracture and overall structure behavior. It is clearly demonstrated that the frame already shows almost unstable behavior due to long-columnization just before the occurrence of a column fracture. Then, a column fracture immediately induces a structural collapse mechanism.
Aspects of the dynamic wind-induced response of structures and codification
Tamura, Yukio,Kareem, Ahsan,Solari, Giovanni,Kwok, Kenny C.S.,Holmes, John D.,Melbourne, William H. Techno-Press 2005 Wind and Structures, An International Journal (WAS Vol.8 No.4
This paper describes the work of the International Association for Wind Engineering Working Group E -Dynamic Response, one of the International Codification Working Groups set up at the Tenth International Conference on Wind Engineering in Copenhagen. Comparisons of gust loading factors and wind-induced responses of major codes and standards are first reviewed, and recent new proposals on 3-D gust loading factor techniques are introduced. Then, the combined effects of along-wind, crosswind and torsional wind load components are discussed, as well as the dynamic characteristics of buildings. Finally, the mathematical forms of along-wind velocity spectra for along-wind response calculation and codification of acceleration criteria are discussed.
Amplitude Dependency of Damping in Buildings and Critical Tip Drift Ratio
Tamura, Yukio Council on Tall Building and Urban Habitat Korea 2012 International journal of high-rise buildings Vol.1 No.1
The importance of appropriate use of damping evaluation techniques and points to note for accurate evaluation of damping are first discussed. Then, the variation of damping ratio with amplitude is discussed, especially in the amplitude range relevant to wind-resistant design of buildings, i.e. within the elastic limit. The general belief is that damping increases with amplitude, but it is emphasized that there is no evidence of increasing damping ratio in the very high amplitude range within the elastic limit of main frames, unless there is damage to secondary members or architectural finishings. The damping ratio rather decreases with amplitude from a certain tip drift ratio defined as "critical tip drift ratio," after all friction surfaces between primary/structural and secondary/non-structural members have been mobilized.
Wind load combinations and extreme pressure distributions on low-rise buildings
Tamura, Yukio,Kikuchi, Hirotoshi,Hibi, Kazuki Techno-Press 2000 Wind and Structures, An International Journal (WAS Vol.3 No.4
The main purpose of this paper is to demonstrate the necessity of considering wind load combinations even for low-rise buildings. It first discusses the overall quasi-static wind load effects and their combinations to be considered in structural design of low-rise buildings. It was found that the maximum torsional moment closely correlates with the maximum along-wind base shear. It was also found that the instantaneous pressure distribution causing the maximum along-wind base shear was quite similar to that causing the maximum torsional moment, and that this asymmetric pressure pattern simultaneously accompanies considerable across-wind and torsional components. Secondly, the actual wind pressure distributions causing maximum quasi-static internal forces in the structural frames are conditionally sampled and their typical pressure patterns are presented.
Effect of taper on fundamental aeroelastic behaviors of super-tall buildings
김용철,Yukio Tamura,윤성원 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.4
Aeroelastic wind tunnel experiments were conducted for conventional and tapered supertallbuilding models to investigate the effect of taper on fundamental aeroelastic behaviors in variousincident flows. Three incident flows were simulated: a turbulent boundary-layer flow representingurban area; a low-turbulent flow; and a grid-generated flow. Results were summarized focusing on theeffect of taper and the effect of incident flows. The suppression of responses by introducing taper wasprofound in the low-turbulence flow and boundary-layer flow, but in the grid-generated flow, theresponse becomes larger than that of the square model when the wind is applied normal to the surface. The effects of taper and incident flows were clearly shown on the normalized responses, power spectra,stability diagrams and probability functions.
조강표,타무라 유키오,이토 타카요시 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)
Wind-tunnel experiments of a communication steel tower were conducted for the wind-induced response using a rocking model. A turbulent wind flow (II of AIJ Recommendation on Loads on Buildings) was generated to closely simulate full scale wind environments. Two different damping levels (0.4% and 1.0% critical damping), which were adjusted by a silicon damping device, were selected as target damping ratios to estimate wind-induced vibration of the prototype structure with and without a tuned mass damper (TMD). Wind-excited motions of the prototype structure (K Tower in Japan) recorded in a video type were also analyzed and compared with the results of the wind-tunnel tests. The experimental results have a reasonable agreement with the analyzed result of video images.
Aerodynamic and Flow Characteristics of Tall Buildings with Various Unconventional Configurations
Tanaka, Hideyuki,Tamura, Yukio,Ohtake, Kazuo,Nakai, Masayoshi,Kim, Yong Chul,Bandi, Eswara Kumar Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.3
Tall buildings have been traditionally designed to be symmetric rectangular, triangular or circular in plan, in order to avoid excessive seismic-induced torsional vibrations due to eccentricity, especially in seismic-prone regions like Japan. However, recent tall building design has been released from the spell of compulsory symmetric shape design, and free-style design is increasing. This is mainly due to architects' and structural designers' challenging demands for novel and unconventional expressions. Another important aspect is that rather complicated sectional shapes are basically good with regard to aerodynamic properties for crosswind excitations, which are a key issue in tall-building wind-resistant design. A series of wind tunnel experiments and numerical simulation have been carried out to determine aerodynamic forces and wind pressures acting on tall building models with various configurations: corner cut, setbacks, helical and so on. Dynamic wind-induced response analyses of these models have also been conducted. The results of these experiments have led to comprehensive understanding of the aerodynamic characteristics of tall buildings with various configurations.
Field Measurement and Modal Identification of Various Structures for Structural Health Monitoring
Yoshida, Akihiko,Tamura, Yukio Council on Tall Building and Urban Habitat Korea 2015 International journal of high-rise buildings Vol.4 No.1
Field measurements of various structures have been conducted for many purposes. Measurement data obtained by field measurement is very useful to determine vibration characteristics including dynamic characteristics such as the damping ratio, natural frequency, and mode shape of a structure. In addition, results of field measurements and modal identification can be used for modal updating of FEM analysis, for checking the efficiency of damping devices and so on. This paper shows some examples of field measurements and modal identification for structural health monitoring. As the first example, changes of dynamic characteristics of a 15-story office building in four construction stages from the foundation stage to completion are described. The dynamic characteristics of each construction stage were modeled as accurately as possible by FEM, and the stiffness of the main structural frame was evaluated and the FEM results were compared with measurements performed on non-load-bearing elements. Simple FEM modal updating was also applied. As the next example, full-scale measurements were also carried out on a high-rise chimney, and the efficiency of the tuned mass damper was investigated by using two kinds of modal identification techniques. Good correspondence was shown with vibration characteristics obtained by the 2DOF-RD technique and the Frequency Domain Decomposition method. As the last example, the wind-induced response using RTK-GPS and the feasibility of hybrid use of FEM analysis and RTK-GPS for confirming the integrity of structures during strong typhoons were shown. The member stresses obtained by hybrid use of FEM analysis and RTK-GPS were close to the member stresses measured by strain gauges.