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斜張橋ケーブルにおける空力振動現象の解明のため，筆者らは2000年から大型傾斜ケーブル模型による屋外観測を行っている。これまで，風洞実験において振動応答の類似性を確認し，その発生メカニズムについての解明が進められているものの，傾斜ケーブル周りの流れ場は3次元性が強く，模型端部の条件に振動応答が敏感であることや，降雨の状況の再現性，自然風の乱れによる応答評価の問題など，風洞実験に基づいた研究手法では解明が困難な要素が残されている。そこで，実際の気象条件のもとで観測された振動現象について考察を行った。さらに風洞実験によって，剛体ケーブル模型を用いて静的空気力を測定し，傾斜ケーブルのギャロッピングの発現について考察を加え，斜張橋ケーブルの空力振動現象について考察を行った。, Authors have been conducted the field observation of large-scale inclined cable model at the Shionomisaki Wind Effect Laboratory of Disaster Prevention Research Institute since 2000. Using a few types of the cable models, their responses have been measured and analyzed especially under seasonal wind of winter and typhoon wind of summer. Then, the rain-wind induced vibration and the galloping like vibration was observed. The mechanism of the second vibration was not completely proved as galloping. However, this result might show the possibility of divergent type vibration at the stay cables. Also, the steady wind force coefficients for inclined cables were investigated using wind tunnel tests.

本研究では, 斜張橋ケーブルで観測されるレインバイブレーションなどの高風速渦励振の発生メカニズムを解明するために, 屋外に大型ケーブル模型を設置して, その挙動を観測した。その結果, 降雨の有無により強風時の大型ケーブル模型の応答特性に大きな違いが見られ, レインバイブレーションと考えられる振動応答も得られた。また, 、風洞内において傾斜ケーブル模型を用いた自由振動実験を行い, 屋外観測との対応を調べた。, A single full-scale cable model using 30m long polyethylene pipe for cable-stayed bridges was exposed to natural wind in order to investigate the 3-D wind-induced behavior and to clarify the mechanism of rain-wind induced vibration. Consequently the rainfall induced the rivulet on the cable surface, which makes the cable model more sensitive aerodynamically.

本稿は, 1998年9月下旬に近畿地方を中心に, 東海, 北陸, 東北地方におよぶ広範囲に被害をもたらした台風7号の奈良盆地周辺の被害状況を, 上空撮影, 現地調査, アンケート調査により明らかにするとともに, 海岸から離れた内陸部で発生した強風の特性を, 地形が強風に及ぼす影響に焦点を当て, 考察するものである.アンケート調査および気象官署の観測データをもとに, 奈良盆地周辺の強風域と風向の時間変化が明らかになり, さらに台風周辺の気流を模擬した風洞実験により, 地表面付近の流れが谷の走向や山地の位置によって複雑に歪められることが明かとなった。, Strong wind disaster in Kansai area due to Typhoon 9807 in September, 1998 was investigated by taking pictures from airplane, field survey and questionnaire.Mechanism of strong wind with the influence of topography is also discussed by flow visualization of air flow over 3 dimensional topographic model in the specially designed typhoon wind tunnel.

On February 22, 1994 a strong extratropical cyclone passed over the Pacific Ocean along the east coast of Tohoku and Hokkaido districts of Japan. During the passage of this cyclone, three accidents were caused in transport facilities by high winds. A field survey as conducted just after the accidents to collect data of the accidents and of weather conditions. These data were analyzed to deduce the wind speed at the site of accident. Two wind tunnel experiments were performed associated with the accident of JR Nemuro line.It is revealed that the critical wind speed to cause the derailment of the train is lower than expected when the wind blows diagonally to the train. By the inspection of surface weather charts it was revealed that the high wind aera distributed widely around the center of the extratropical cyclone.

Increasing of span length of suspension bridges, it has become more important how to evaluate the stability of flutter phenomina than before. Recent investigations have paid, in consequence, a lot of considerations on identification of aerodynamic derivatives.This study is concerned with identification of aerodynamic derivatives of structual sections of 2-D rectangler and truss girder sections.In order to identify them by wind tunnel tests, two different system identification methods, forced vibration method and free vibration method, are used. The result of identification of aerodynamic derivatives were mainly disscussed from the point of superposition of unsteady aerodynamic force corresponding to different mode.

The mechanism of vortex-induced oscillation of bluff section is closely related with the instability of separated shear around its body. The shear layer can be easily stimulated by self-movement of the body or external disturbance such as flow perturbation, applied sound with a specified frequency fluctuation and so on.In this study, the investigation of vortex-induced oscillation for 2-D rectangular section was performed by the way of shear layer instability stimulation by applying sound. Furthermore, geometrical shape effect on the response characteristics of the vortex-induced oscillation of edge girder bridge section was also investigated on the basis of applied sound technique.Additionally, the effect of turbulence on vortex-induced oscillation was fundamentally investigated by use of applied sound technique from the turbulent frequency effect point of view.

This study aims the clarification of torsional flutter characteristics of H-section with variousslenderness ratio B/D. Its dynamic response is classified into three types in dependence onslenderness ratio, that is, restricted oscillation type, divergent oscillation type and stable type.Effect of turbulence is drastically affected by slenderness ratio. For example the restrictedoscillation tends to change to divergent one. In the case of divergent oscillation, flutter onsetvelocity increases with turbulence.

In this paper, the aerodynamic admittance or the dynamic lift function of long spannedbridges with plate like structural section are discussed, and the deflectional response of afew sectional models due to random vertical gust is analized by numerical calculationmethod evaluating Duhamel's integral and by analog simulation method.Experimental results of dynamic lift function in wind tunnel test are simulated approxi-mately by the modified quasi-steady theory or the Sears function.By using with these dynamic lift functions, the calculating results of numerical analysisand analog analysis for the deflectional response due to vertical gust show the goodagreement with the experimental results.

This study purposes the clarification of cable-aerodynamics of a cable-stayed bridge, which isone of recent majoring subjects in bridge aerodynamics. The response characteristics of cablewith various materials, rain conditions, various diameters and various atittudes against wind havebeen measured in wind tunnel.As a conclusion, a cable shows an aerodynamic instability more or less when wind blowsskewly a cable with certain angle, and the role of rain in "cable rain vibration" is merely to acual-ize the hidden aerodynamic instability characteristics of cable.

In connection with flexible long spanned bridge structures it is called for to disclose the vortexshedding excitations of flat box type cross sections which commonly are induced in rather lowwind velocity.In this paper an attention is particularly placed on three themes, namely (I) the effect of pitchingangle, (ii) the effect of turbulence incident to natural strong winds and (iii) consequent treatmentfor improvement of aerodynamic stability. In addition to these the effect of solidity ratio of trussgirders on vortex induced excitations is also discussed based on the wind tunnel tests.

In this study, the effects of turbulence on galloping were investigted from the frequencyeffect of turbulence point of view. Two 2-D rectangular cylinders with slenderness ratios 1 (B/D=1, B: chord length, D: height of section) and 2 (B/D=2) were used and the steady lift forceand an aerodynamic response were measured in grid-turbulent flow and a pulsating sinusoidalflow. As a result, it is sujested that the higher frequency fluctuating components of turbulenceintensifies the entrainment effect of separated shear layer around the body, and the comparativelylow frequency fluctuating components of turbulence which is correspponeding to "shear layer in-stability enhancement frequency region" which would generate a vortices on a body side surfacewhich sometimes interact with Karman vortices, have few significant effect on steady lift forceand galloping response.

In order to evaluate aerodynamic responses of various types of cross sections applied for long-span suspension bridges, an approximate form of aerodynamic system functions is presented inthis paper.The aerodynamic system function is defined here as a generalized form of frequency dependenttransformation function between fluctuating gust and resulting aerodynamic forces of lift andpitching moment. An advantage is particularly illustrated to employ the time history analysisfor wind-induced buffeting responses subjected to strong natural gusts, which is considered tofeature non-stationary characteristics. Experimental results are also illustrated and compared withnumerically evaluated responses of typical cross sections of long-span suspension bridges.

This study aims the clarification of aerodynamic characteristics of an inclined cable inrelation with "rain-wind induced vibration". Inclined cables were cleared to be essentiallyunstable in wind tunnel test. Axial flow observed in the near wake plays an extremelyimportant role for this aerodynamic instability. In almost cases of prototype cable-stayedbridges, the instability seems to be sensitively stabilized by the turbulence of the natural wind, high Scruton number and so on. When it rains, the hidden instability sometimes appearsagain by forming water rivulet on cable surface.

In this study, human-response against bridge vibration was investigated in the frequencyrange 0.2 Hz-1.0 Hz and in the amplitude range 1.0 cm-10.0 cm in order to evaluate serviceabilitylevel for pedestrian to the bridge vibration. Approximately 100 persons were tested on OhshimaBridge and vertically oscillating stage.Furthermore, the evaluation procedure of the extreme distribution of wind speed in considera-tion of Typhoon effect in various wind directions was developed and failure probability of severallong span suspension bridges due to strong wind were calculated. Finally the conceptional prob-abilistic approach of bridge design method against strong wind was shown in standing on a fai-lure probability.

This study is concerned with the induced mechanism of torsional buffeting oscillation of thebasic structural H-shape section due to turbulent flow, which generally tends to generate typicaltorsional flutter phenomenum. The aerodynamic pitching moment for H-shaped cross section isalso measured in sinusoidally fluctuating flow to obtain the equivalent Kussner function experi-mentally. This function indicates fairly good agreement with the equivalent Wagner function asthe result of comparison of indicial response curves and of time history response analysis. Subse-quently the torsional buffeting characteristics can be said to be evaluated to large extent from thetorsional unsteady force characteristics in smooth flow.

This study aims to clarify the aerodynamic effects of the "corner cut" for the sake of themitigation of aerodynamic instability of the tower like structure. Two-dimensional rectangularcylinders with various cutting of their corners were tested in a wind tunnel, and their re-sponse, stationary pressure and stationary aerostatic force were measured in smooth flow. Be-sides flow visualization in water flume was carried out in order to visualize the effect of "cor-ner cut" to the flow pattern.Finally, the optimum size of corner cut was discussed by use of the elastic full scalemodel of tower of a long spanned cable-stayed bridge.

In this study, the strong wind caused by typhoon has been statistically investigated by useof wind data measured at the local meteorological observatories, especially being targeted therelationship between the strong wind and the location of eyes of typhoon.Furthermore, the probabilistic property of annual maximum wind speed caused by typhoonat Osaka has been analyzed from the point of specified route of typhoon. The strong windmechanism in Kinki Prefecture due to the second Muroto typhoon has been fundamentallystudied by use of topolographical models in a circulated flow generated by special typhoon simu-lation device.

In this study, in order to evaluate the expected extreme wind speed in Japan in con-sideration of Typhoon effect, the "Typhoon factor" was induced into the extreme wind speedexpected from parent distribution characteristic obtained from usual wind-speed measurementat local meteorological observatories in Japan.Furthermore, the evaluation method of failure probability of a long span bridge due tostrong wind was discussed in taking the assumed joint probability density of expected extremewind, wind direction and its incident angle, both aerostatic and aerodynamic response char-acteristics of the bridge into account.

This study is concerned with the vortex-induced oscillations of blluff bodies. A series of windtunnel tests was conducted for some basic bridge deck sections and for some simply modified modelsof suspension bridge towers in order to obtain the aerodynamically improved structural sections.The mechanism of interaction between bodies and fluid around bodies is studied by means of theflow visualization in water flume. Consequently experimental results obtained here indicate thatthe response characteristics of bridge deck sections are strongly governed by the depth/width ratioand the shape of leading edge and both of factors and furthermore vortex-induced oscillations oftower of suspension bridge are sensitively dependent on the lateral distance between two struts.

This paper presents the method of flexural-torsional response characteristics of stiffeninggirder of suspension bridge subjected to randomly fluctuating gusty wind. The flexual-tor-sional response of stiffening girder is numerically calculated in course of time, based ondata of fluctuating wind velocities, to evaluate the power spectral densities by convertingthe time-history of response. The results obtained by this indirect method accord with theexperimental results, while the results obtained by the customary method, namely thedirect method, tend to overestimate the frequency dependent response characteristics. Inconnection with the above method of analysis, the transfer lift function, viz. the frequencydependent relation between lift force and wind velocity, is studied by the wind tunnel testsfor a few typical structural cross section.

On the aeroelastic response of long-spanned suspension bridges due to the random gust, afew kinds of model tests are performed in turbulent shear flow generated in the wind tunnel. Inturbulent flow comparatively large oscillations are observed for low wind speed region below thecritical flutter velocity. The power spectrum of this response is in good agreement with thetheoretical predictions, obtained by the modified quasi-steady theory in which the dynamic effects ofstructures are considered. Besides, as its applications to real structures, some numerical evaluationsare made for estimating the aerodynamic random response of Honsho-Shikoko connecting suspen-sion Bridge (Akashi Strait Bridge) due to the random gust.

Wake Galloping is defined as cross flow oscillation of leeward cylinder in higher wind velocitydue to Karman vortex shedding when two cylinders are suitably arranged in series with approach-ing flow.In this study, in order to discuss the physical mechanism of Wake Galloping, some windtunnel experiments were carried out, like static and dynamic pressure measurements on the surfaceof leeward cylinder, flow visualization by smoke wire method. On the basis of these measure-ments, some characteristics concerning the relationship between the flow pattern around twocircular cylinders with the unsteady pressure are investigated.

This study is concerned with the vortex-induced oscillation and galloping of bluff bodies.For some basic cross sections the mechanisms of vortex-induced oscillations was classifiedto three different types by the characteristics of velocity fluctuations in wake in relation tothe occurrence of vortex-induced oscillations. Furthermore the effect of mass-damping para-meter and some attachments like deflector on the responsive amplitude of vortex-inducedoscillations was investigated for cable-stayed bridge deck sections. On the othet hand theproperties of galloping oscillation were examined for some bluff sections and some commentsof applicability of quasi-steady theory to galloping oscillation were briefly shown.

In this study, three kinds of aero-statical or dynamical unsteadinesses are experimentallyinvestigated and are compared with each others for some basic structural sections. Theseunsteadinesses are characterized by equivalent Wagner function, equivalent Kussner and theunsteady indicial function. Especially the last function is defined as the aerostatical indicialfunction when the square value of mean wind velocity, U2 is given to be time step function.Finally, the turning over accident of subway train on the Nakagawa Bridge crossingthe Arakawa River by TASTUMAKI in Tokyo area in 1978 is fundamentally discussed byapplication of the unsteady properties of lift force obtained here.

This study is concerned with the bluff body aerodynamics, I.e. the vortex-induced oscillationand galloping.Aerodynamic effects of separated vortices generated by body movement to torsional vortex-induced oscillation has been investigated by changing rotational axis of two dimensional rect-angular cylinder. Furthermore, the Karman vortex effect to these self-movement vortex-in-duced oscillation has been experimentally clarified by arrangement of splitter plate in a wakeof cylinder.The galloping investigation for simplified box girder section and the fundamental considera-tion of its aerodynamically stabilizing mechanism have been done by pressure measurement, static force measurement and flow visualization.

This paper presents timely varying aerodynamic responses of plate-like structures due torasdom gusts. The aerodynamic admittance or the dynamic lift functions for a few typicalstructural sections, which are considered indispensable in determination of aerodynamic forcesdue to fluctuation of wind velocities in lateral and longitudinal directions, are examinedby use of wind tunnel tests and are compared with the Sears function and the Horlockfunction for thin plate. Based on these aerodynamic lift function, aerodanamic lift function, aerodynamic responses of thin airfoil (NACA-0012) and of long-spanned suspension bridgeare numerically calculated, the results of which indicate a fairly good agreement with theexperimental results.

In this study the aerodynamic improvement for the coupled flutter oscillation of the bridgeroad deck box section of super long-spanned suspension bridge was experimentally investigated.The mitigation of the aerodynamic instability by installing "air gap" on the deck was target-ed here, besides the effects of the geometry shape of the edge fairing of the box girder werebliefly discussed. The unsteady pressure distribution on the box girder in a state of coupledflutter oscillation was measured, then it was clarified the pressure difference between upperand lower flange near the leading edge was significantly mitigated by the installment of "airgap", consequently this could sufficiently and aerodynamically stabilize the box girder.

Experimental investigations are performed by wind tunnel tests on aeroelastic characteristicsof long-spanned truss bridge in connection with the design of the Nanko Bridge in Osaka, Japan.Based on previous contributions by number of former researchers a few cases of shear flows aresimulated so that the variation of wind profile may be taken into an account in model tests. Resultsindicate that, though the bridge is aerodynamically stiff enough, the induced drag and side forcesdepend remarkably on the solidity ratio and the angel of yaw and experimental results on thesetake an important role on design of this kind of structures.