This paper investigates the characteristics of aerodynamic forces exerted on a square cylinder under air flows which are changing their direction with time. Such air flows of time-dependent direction are generated by combining three air flows from three AC servomotor wind tunnels. The wind tunnels are aligned in radial directions with angle spacing of 45° in the horizontal plane. This wind tunnel system can generate flows which can change direction dynamically within range of 90°. The unsteady aerodynamic forces exerted on a square cylinder was measured under the air flows of constant velocity 12m/s and their rates of direction change are varied from 5 deg/s to 180 deg/s. The measured unsteady aerodynamic forces are different from the aerodynamic forces exerted by the air flows of steady direction.

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There are still some unsolved facts in the failure of old Tacoma Narrows Bridge in 1940. Especially, the onset velocity of torsional flutter has been a mystery. From this mystery, it can be considered that the effect of the heaving vortex-induced vibration could stabilize the torsional flutter instability. The aim of this paper is to clarify the existence of the aerodynamic interferences between heaving vibration and torsional vibration and try to reconsider the situation of the failure of old Tacoma Narrows Bridge.

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Wake excitation is an important problem for parallel circular cylinders. It is well known that this phenomenon is caused by the interaction between the downstream cylinder and the wake flow of the upstream cylinder. Therefore, this phenomenon is affected by the Reynolds number. In this study, to remove the effect of Re-number, some kinds of rectangular cylinders were used instead of the upstream circular cylinder. Wind tunnel test were carried out and it was found that the downstream cylinder was excited even if the width of the upstream wake was very small in comparison with the diameter of the downstream cylinder. The width and velocity defect of wake of the upstream cylinder play important role for the oscillation.

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This paper discusses the applicability of large eddy simulation (LES) to turbulent flows around a cube in an imitated atmospheric boundary layer flow. In order to generate the data of natural wind, we used the method with quasi-periodic boundary condition for the rough ground surface. The computed turbulent boundary layer, whose wind profile sets to the power law with exponent α=0.16, was compared with full-scale measurements by Silsoe Research Institute (SRI), and has good agreement. A flow around a cube in a turbulent boundary layer was computed using thus generated inflow turbulence. The pressure coefficients are more negative than full-scale results, because the mean reattachment point on the roof was difference. Unsolved problem remains for the action of the ratios of integral scales of turbulent quantities and lattice resolution which influences mean reattachment point.

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This paper describes the results of full-scale measurement of wind pressures and wind forces on roof tiles. The building used for the measurement had a gable roof and was 5.4m wide × 4.8m long × 6.7m high. The tile shapes were J type and F type. The external and internal pressures acting on roof tiles were measured, And following results were obtained. 1) The mean external pressures were almost same as the mean internal pressures. 2) The mean forces on the roof tiles were small compared to the peak forces. 3) The variation in the wind pressure coefficients with wind direction were independent of tile shape.

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Wind force on roof tiles of an experimental house with a hipped roof was measured in natural wind. The net force on the tile is given by a difference between wind force on a surface of the tile and pressure in the batten space. The suction force on the surface takes its maximum in the leeward roof when wind attacks the roof diagonally, but the pressure in the batten space of the roof becomes negative in the wind direction, then the net suction force on the roof tile is not so large in the wind direction. When wind attacks normal to the roof, the net suction on the roof tile of the windward roof takes the maximum in the mean and the peak force. The mean force on the surface is positive in the wind direction, but the pressure in the batten space is much larger than the pressure on the surface, then the mean net force is negative. The peak net suction occurs when the surface force decrease rapidly to become a large negative peak value while the pressure remains positive in the batten space The pressure on the surface of the tile is influenced greatly by local surface flow. Particularly, the pressure at the ridge of the convex surface drops greatly when the wind blow diagonally on the surface.

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This study investigates characteristics of wind pressure acting on walls of a low-rise building by full-scale measurement. It also compares local wind pressures and area-average wind pressures of 1m² involving local pressure measurement points. The results are as follows; 1) For approach flow at this site, power law exponent approximation of mean wind speed profiles is about 0.1. Turbulence intensities range from 13 to 20%. Length scale of turbulence is scattered from 75 to 90m at l0m height. 2) Local mean and rms pressure coefficients on a front-wall normal to the wind direction increase with the measurement point height. However, this tendency does not appear for peak pressure coefficients on the front wall. The pressure coefficients on a side wall parallel to the wind direction are almost constant irrespective of measurement height. 3) Peak coefficient values of local wind pressures are 1.5 times those of 1m² area average wind pressures on the side-wall. However, they are almost the same on the front-wall.

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A wind load used to design noise barriers on embankments has not been established clearly. In this study, to obtain the wind load, the coefficient of drag forces were estimated by wind tunnel tests and the maximum wind velocity according to regional conditions was obtained by a statistical analysis. Wind tunnel tests were made for some kinds of embankment (0m∼12m height) and noise barriers (2m∼4m height) with 1/50 scale models. Based on the results, we took note of the following three divisions. (1) Division by checked part of structures. (2) Division by the reproduction period of maximum wind velocity. (3) Setting of the value to decrease the wind load according to regional conditions.

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There is an inside-reinforcement method using thin shell which is one of methods to prevent collapse or deformation of concrete-covered railway tunnel. However, it is very difficult to stop the service of train, therefore, pressure variation generated by train entering and passing tunnel acts on the reinforcement structure when executing of works. The effect on the reinforcement structure of compression wave and expansion wave generated by train entering and passing tunnel were examined through model test. The test results of pressure variation on reinforcement structure were reported in 16 cases examined as to whether the train is passing each other, whether the crevice between tunnel wall and reinforcement structure is filled up and where the reinforcement structure is located from tunnel entrance.

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This paper describes the results of experimental and numerical studies on flow around various porous board fences. We examined the effects of shielding rate, hole shape and deflector of a fence on flow patterns around a fences. The velocity distributions were measured by the tandem-type hot-wire technique in a wind tunnel. The two-dimensional numerical simulation was carried out employing modified k-ε model, and the results were compared with measured results. The results of experiment and numerical simulation are in good agreement. Though there is not a recirculating cell behind the porous fences with the shielding rates of 60%, the mean velocity at the distance of x/H=10 downstream from a fence is less than 0.3 U₀. The distance of reattachment point was not affected by the direction of deflector of fence. It is found that a belt-type fence is effective in reducing velocity in the wake region.

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To consider swinging of conductor under strong wind condition is important for design of tower. Especially cost increase and harmful visual impression is caused at long span in order to increase in size of tower so that conductor may not contact each other. The authors have proposed numerical analysis method based on computer simulation “CAFSS” for calculating conductor’s swinging. Its excellent performance was confirmed the theoretically and experimentally by comparing analysis for observation swinging on test lines in a typhoon with results of “CAFSS” by using observation wind. This paper presents the comparison of conductor for swinging between “CAFSS” and observation in Miyakojima test line constructed in flat terrain.

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Precise understanding of swinging of the overhead conductor under strong wind condition is essential for the steel tower design. By considering this concurrency of the swinging, it becomes possible to reduce the weight of steel tower, and this leads to a significant cost down effect. In considering this fact, we started to study with a view of establishing a new technique for corrective grasping the relative swinging based on the observation and others of the Test Line, thus reflecting the results on the steel tower assembly design. When we investigated the data on a Shikoku Test Line in a strong wind condition that occurred in the past, we could extract the swinging phenomenon when a typhoon was passed. We then compared the observation data (wind data) obtained at that time with the analytical results obtained by numerical simulation “CAFSS”, by considering up to the variation component of blowing up angle of wind, and obtained a good coincidence between the observation and analysis, as reported in this paper.

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This paper aims to clarify the generation mechanisms of inclined cable aerodynamics, such as vortex-induced vibration at high reduced wind velocity, rain-wind induced vibration and galloping using wind tunnel tests and field observation of full-scale cable model. Consequently, Karman vortex may play an important role in the occurrence of vortex-induced vibration at high reduced wind velocity including rain-wind induced vibration. This kind of vibration may be enhanced by the non-uniform Karman vortex shedding along the cable axis.

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As previously reported, the authors have proposed two methods, the parallel member attachment method and the redundant member attachment method, aimed at reinforcing steel-tube transmission towers for wind loads. By compression strength tests and FEM analysis, it has been confirmed that the methods were able to improve the ultimate strength using simple and inexpensive construction techniques. This paper reports a vibration test and a wind response simulation, and the effects of the proposed reinforcement on the dynamic response properties of an existing transmission steel-tube tower are discussed. The results of the test and simulation showed the reinforcement brought the good performance of wind response properties.

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Wind load is dominant for designing of transmission towers and the wind direction is considered to be very influential. For these reasons, the wind direction and the line direction should be considered in the design processes. However, such a reliability design method has not been reported in the past. In this study, the probability distribution of maximum wind speed in every wind direction is calculated by using the “Estimation of Equivalent Static Wind Load” equal to dynamic analysis, which is based on the recent outcomes. Also, the probability distribution of the member axial forces regarding the line angle is obtained in the same manner. Consequently, the reliability of the current designing method is evaluated and the wind direction and the line direction are confirmed to be considerably influential in designing.

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The aim of this study is to obtain the fundamental aerodynamic characteristics of two edge girders, which would be used for the future long span cable-stayed bridge girder. Especially, the characteristics of aerodynamic interaction of various vibration mode, such as heaving vortex-induced oscillation and torsional flutter, are investigated by a series of wind tunnel tests. In addition, for the purpose of the aerodynamic stabilization of two edge girders, the aerodynamic effect of vertical and horizontal plates on this girder section was investigated by the measurement of unsteady aerodynamic forces. As one of conclusions, it was clarified that the attachments of various plates on the girder section assist the aerodynamic stability, especially from the viewpoint of the flutter onset velocity.

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This paper investigates aerodynamic study on mono-box girder with intermittent slot, windshields and inspection cart rails for super-long suspension bridge. Spring supported tests were conducted in order to make flutter performance better. The fairing, the central guard fence, windshields and the slot interval were investigated. In conclusion, The girder section combined suitable fairing shape with blocked 1.2 meters height central guard fence makes flutter performance better. In addition, windshields of 4 meters height on the shoulder have flutter performance better than that of 3 meters height. According to the 3-dimensional flutter analysis, the suitable girder section has flutter onset velocity of over 80m/s in a super-long suspension bridge with a 2800 meters center span.

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The Akashi Kaikyo Bridge is the world’s longest suspension bridge with the center span of 1,99lm. This bridge has been opened to the traffic since April 1998. The wind resistant design is one of the most important issues for the design of this bridge, and some countermeasures were taken to improve the aerodynamic stability, based on the result of the wind tunnel test with a 1/100 full-scale model and on the advanced flutter and gust response analysis. Observation system to monitor the dynamic and static behavior of the bridge is installed, and the results of the observation are used to confirm the wind resistant design. The dynamic response of the girder due to gust was compared to the gust response analysis, and the accuracy of the analysis is confirmed. Also the dynamic behavior of the tower is observed, and the effect of the tuned mass dampers installed in the tower is confirmed. In this paper, the outline of the observation system is described, and the dynamic behavior of the girder and tower is described.

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Japan Palau Friendship Bridge is a 3-span continuous hybrid extradosed bridge with the 247m main span. It has been planned that the steel girder is lifted up in one body and the period of the erection has been expected to become a few weeks because of the erection procedure in the site. The allowable amplitude is set by the limit of the shearing force of bolts in connecting plates. In wind tunnel tests, vortex-induced vibrations are observed and some effective countermeasures composed of panels are found. The amplitude of the bridge under the steel girder erection is calculated through the primary 3-dimensional analysis. It is confirmed that the 1800mm length wing takes an effect to suppress the vibration, which has been adopted in the erection stage. Consequently no vibration has been observed through the erection period in the site and the erection work has been accomplished safely.

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Recently, span length of a box girder bridge tends to become long with the innovation of bridge design. The more the span length becomes long, the more a bridge becomes flexible. And the natural frequency becomes low, so the aerodynamic instability is an important problem. To achieve safety of a box girder bridge against wind, many types of vibration control devices have been contrived. Some types of these devices are employed in actual bridges. In this paper, authors investigate about the effect of various vibration control devices in wind tunnel for the purpose to develop alternative vibration control devices those will become optional selections for various bridges.

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Wind-induced response characteristics of two main girder cross-section were studied experimentally. Because the two main girder cross-section can be thought as a combination of a channel and π cross-section, their responses were also studied and compared. For the heaving response, the vortex-induced vibration seemed to be caused by the flow separation from the windward edge and its onset wind speed agreed with the expression given by the previous studies when the representative length was taken as the whole model width. For the torsional response, for the cases with B/D=1.4∼4.1, the onset wind speed was around Vr(B)=2 for all the cases of two main girder cross-section. This onset wind speed agreed with the resonant wind speed based on the velocity fluctuation measured around the leeward edge of the model. Also from the flow visualization results, the existence of the leeward edge seemed to play an important role on the response characteristics.

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Authors have installed the hybrid type mass damper system to the control tower in Osaka international airport to reduce wind induced vibration. In 2001 summer, structural response in structural controlling condition during the typhoon was observed. This typhoon did not strike just the airport, therefore, structural response was not so huge so that the operated motion of mass dampers was also much smaller than the specification for use. Of course the motion of device includes some nonlinear frictional resistant force, the smaller its motion is, the higher the mechanical loss of device is, and structural control performance is decreased compared to the case in which the device works in greater motion. Authors analyzed the observed data in statistical manner, produced nonlinear numerical analysis, and managed to evaluate the actual performance of the mass damper system in the short stroke condition.

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A feedback control technique of vortex shedding behind a circular cylinder is investigated through two-dimensional numerical simulations. Periodic velocity excitation is applied from the cylinder surface to the separated shear flows with a time delay and feedback gain for the fluid velocity at a downstream sensor location. It is shown that the feedback excitation can suppress the vortex shedding considerably. However, the suppressing effect becomes lower if the sensor is located downstream of the formation region of the vortices behind a cylinder. This is because the change of the vortex shedding frequency resulting from the suppression of the vortices alters the phase delay between the vortex shedding and the feedback excitation.

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Various types of vibrations in consideration of motion-induced wind forces and dynamics characteristics of stuructures have been clarified by the technique of Computational Fluid Dynamics (CFD). The aim of this CFD study are to examine elastic response of a computational model in which 3-D structure of a wake region can be appropriately taken and to obtain aeroelasto-plastic behavior in wind velocities (Vr=6.0). Obtained results are as follows; 1) Delicate elastic behavior can be obtained by preparing the appropriate span ratio (H/B). 2) Aeroelasto-plastic response usually suppressed by hysteretic damping effects comparing with the elastic response. However, in spite of the effect of hysteresis damping, the response in case of small value of the yield displacement ratio (β) is larger than the elastic response for lower wind velocity (Vr<6.0) than the resonant velocity

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The purpose of this study is to investigate elasto-plastic response characteristics of a base-isolated building of small-scale and light-weight for combined wind forces. In this study, a timber house of two stories under along wind force and across wind force is subjected as a typical case. Time history response analyses are carried out for a sway model representing force-displacement relationship on horizontal plane of base-isolation story of building by MSS model. The parameters of response analyses are set by ratio of the yield displacement to the elastic maximum displacement and ratio of strengths of across wind force to along wind force. Result clarifies effects of the parameters on the behaviors of wind responses.

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Full-scale data have been used to clarify the characteristics of wind-induced vibration of the 23rd Building of Kanagawa University, a base-isolated mid-rise building. The data were recorded on August at 2001 when Typhoon 0115 passed near the measuring point. It is shown that torsional vibration cannot be ignored in evaluating wind-induced responses of a base-isolated building. The peak factors of response acceleration are from 4.5 to 5.0 on the average. The fundamental mode frequency decreases and the damping ratio increases with increment of response acceleration. When the maximum response acceleration was recorded, the damping ratio was about 10%. The isolation materials show elasto-plastic behavior in lower wind speed than the designed wind speed.

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An RTK-GPS (Leica MC1000) has a nominal accuracy of ±1cm +1ppm for horizontal displacements with a sampling rate of 10Hz. The object of this paper is to demonstrate the feasibility of RTK-GPS for wind-induced response measurements and its efficiency in measuring the displacement of a full-scale tower and to study the feasibility of hybrid use of FEM analysis and RTK-GPS for detecting the integrity of structures during strong typhoons. The efficiency of RTK-GPS is demonstrated in the full-scale measurement of an actual steel tower. According to the feasibility study of RTK-GPS for measuring wind-induced responses of buildings, the responses with amplitudes larger than 2cm and natural frequencies lower than 2Hz can be detected by RTK-GPS. Hybrid use of RTK-GPS and FEM analysis for real time monitoring of the integrity of structures is proposed and its efficiency is demonstrated.

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The characteristics of the structural frequency and damping as well as the vibration due to the wind forces of a tower supported steel stack are studied in long period field observations. And also the correlations of the vibration due to the vortex between the field observations and wind tunnel tests using 3-D rocking model are discussed. The results are summarized as follows; 1) the pattern of the wind profile above the ground level is the same as the ground surface roughness classify III, 2) the vibration due to the vortex obtains y/d=0.12 for h=0.33% and y/d=0.006 for h=0.89%, respectively (y is the maximum amplitude at the tower top, d is the duct diameter of the stack, h is the damping ratio), 3) the gust responses due to strong winds are studied by the strain data at the half of the stack height, 4) the correlation of the vibration amplitude with the field observations and the wind tunnel tests based on the Scruton number is discussed.

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This paper presents an aerodynamic design of the tower of a single span suspension bridge at the completion. The tower is relatively so high compared with its stiffness, thus ensuring the aerodynamic stability of the tower is one of the most important issues of the bridge design. In this paper, the results of the wind tunnel test, the proposed countermeasure and its effect are highlighted.

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This paper describes aerodynamic stability of the stiffening box girder of a suspension bridge with 540m main span length. A variety of aerodynamic devices (i.e., flap and fairing) are employed on box girders to suppress vortex-induced oscillation and flutter. However, we should take account of not only aerodynamic stability but also economics and esthetics. So, we examined some compact aerodynamic devices for separation control in the leading edge of the section. From the spring supported model wind tunnel tests, aerodynamic stability of the section with 50cm length horizontal plate in girder web was verified. And a drag coefficient of the section is similar to the box girder with fairings.

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The Daini-Ondo Bridge, which is planned as a Nielsen lohse type bridge with a center span of 280m, is a relatively flexible structure with a slender deck. Therefore wind tunnel tests for the bridge using 1:55 full elastic model were conducted in order to investigate its aerodynamic stability. To evaluate angle of attack variations of the approaching flow along the bridge axis due to the complex terrain at the bridge site, response tests were conducted in flows with the angle of attack distributions similar to the site, in addition to a smooth flow and boundary layer flows. In the results of wind tunnel testing, it was cleared that the bridge is sufficiently safe for aerodynamic problem.

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The Central Japan International Airport Access Roadway Bridge is planned as continuous steel box girder bridge to access the offshore airport, which is scheduled for open in 2005. The access bridges consist of two parallel roadway bridges and a railway bridge alongside. Focusing upon aerodynamic stability, there was apprehension that the bridges become unstable rather than the other same-scale steel box girder bridges, because of the complicated girder arrangement. In this study, at first, wind tunnel test employing aeroelastic model in scale 1 to 100 was carried out, and then various aerodynamic characteristics unique to the parallel structure were investigated. Next, the structural countermeasure (tuned mass damper) was proposed and designed in order to suppress the wind-induced vibration to the allowable level. Finally, safety of the bridges was verified by evaluating the effect of countermeasure, based upon the wind tunnel test results.

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This paper described the characteristics of the peak wind pressure on the wall of high rise buildings on the basis of wind tunnel tests. The experimental models were reproduced from the balconies of actual buildings, in addition to the models without balconies. The building types were regarded as the square prism, oblong plan prism, corner cutting model and corner cut off model. It was noticed how the characters of peak wind pressure coefficient were affected by building shape and roughness on wall. The main results are as follows. The negative peak wind pressure coefficients on the balcony models are smaller almost allover the surface than the model without balconies. On the model without a balcony, the negative peak wind pressure coefficients increased sharply at short evaluation time less than 1.0sec. On the other hand, the coefficients on the balcony model increased more moderately than the models without balconies. On corner cut off model and corner cutting model, they are also reduced by the balconies, in addition to corner cutting effect, except at top corner.

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Fluctuating surface pressure measurements are made for four flat roofed building models with square or rectangular plans in order to examine wind load combinations. The fluctuating pressures are integrated over all their surfaces and results are obtained of along-wind force, across-wind force, vertical force, along-wind overturning moment, across-wind overturning moment and torsional moment on their frames. The maximum wind force component and other simultaneously observed wind force components are examined, and some interesting facts regarding the wind force combinations are discussed on the basis of absolute value correlations, phase-plane expressions and so on. The maximum normal stresses in the column members of simple frame models are then examined in order to directly check the wind load combination effects.

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In order to evaluate of the wind load effect considering the wind speed directionality, wind speed probability and directional wind speed-load effect relationship should be known. Because of ‘hidden’ values problem and rareness of strong typhoons, it is difficult to evaluate the nonexceedance probability from the database of the daily maximum wind speeds with their wind directions for some decades. In this paper, the database-assisted typhoon simulation, so-called hybrid use of observed records and calculated values are proposed. Using hybrid method for typhoon winds and statistical method for non-typhoon winds, directional wind speed probabilities are evaluated. Based on the directional wind speed probabilities wind load effects of tall buildings are calculated. The wind load effects are varied according to the building orientation. The maximum of the load is slightly less than the value of non-directional evaluation. The minimum is 60 to 80% of the value of non-directional evaluation. The longer side-ratio of the building plan shows the larger variation of the load by changing the orientation.

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In this paper, LRFD formula for wind loading on claddings is improved by taking account of wind directionality effect. A method to estimate the probability distribution of extreme wind load effect on claddings is described based on the distribution of extreme wind speeds. Then, two design alternatives-non-directional basic wind speed and directional basic wind speeds-are compared. It is suggested that difference of inaccuracy inherent in design procedures should be included into LRFD formula for the consistency.

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The peak difference pressure coefficients had been analyzed by using of the data of the field measurement with the large model of an apartment. The peak factor of the internal pressure had been ealculated by subtracting the peak external pressure from the peak difference pressure. Consequently the result of 4.0 as the peak factor of internal pressure had been indicated. However, though the information related to the external pressure can get it easily, it is difficult to get the data of the internal pressure in the wind tunnel experiments. In this paper, it was examined about the way of predicting the internal pressure coefficient from the external pressure.

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This paper describes the method of developing a multi-degree-of-freedom aeroelastic model of a base-isolated mid-rise building. Several tensile springs model the horizontal stiffness of isolators and air pressure from a compressor models their vertical support. Curved lead lines and curved aluminum lines model lead dampers and steel dampers. With this model, the frequency ratio of a torsional mode vibration to sway mode vibration, and plastic displacements of isolation materials can be changed. Isolation material tests and free vibration tests show that this model provides the object performance. Wind tunnel tests show that the peak displacement factors are about 4.5 independently of wind speed, but their gust response factor decreases with increment of wind speed.

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