Experimental study of aerodynamic damping of a twisted supertall building

Kim, Wonsul,Yoshida, Akihito,Tamura, Yukio,Yi, Jin-Hak Elsevier 2018 Journal of wind engineering and industrial aerodyn Vol.176 No.-

<P><B>Abstract</B></P> <P>The aerodynamic damping ratios and aeroelastic instability of a 180° helical supertall building with good aerodynamic behavior in both the along-wind and across-wind responses were investigated using an aeroelastic model test (rocking vibration model test). The aerodynamic damping ratios for the 180° helical and square models were evaluated using the random decrement technique. Furthermore, the effect of the triggering level and number of time segments on the evaluation of the aerodynamic damping ratio was also investigated. It was found that both the mean and fluctuating displacement responses of the 180° helical model in the along- and across-wind directions showed better aerodynamic behaviors than those of the square model. Aeroelastic instability of the 180° helical model was not observed at any of the reduced velocities considered in the study. In the along-wind direction, the aerodynamic damping ratios of the 180° helical model exhibit similar trends to those of the square model. However, in the across-wind direction, the aerodynamic damping ratios of the 180° helical model show significantly different trends than those of the square model. Furthermore, there was no effect of the variation in the wind direction on the aerodynamic damping ratio of the 180° helical model. We found that in the evaluation of the aerodynamic damping ratio, it is possible to adopt the triggering level at the value of the standard deviation or √2 times of the standard deviation of the displacement responses if the random decrement signature has a high number of triggering points.</P> <P><B>Highlights</B></P> <P>Characteristics of aerodynamic damping ratio and aeroelastic instability of a 180° helical supertall building were studied through wind tunnel experiments using the rocking vibration model test.<UL> <LI> For the 180° helical model, both the mean and fluctuating displacement responses in the along-wind and across-wind directions show better aerodynamic behavior than those of the square model. </LI> <LI> Aeroelastic instability for the 180° helical model is not observed for any of the reduced velocities. </LI> <LI> In the across-wind direction, the aerodynamic damping ratios of the 180° helical model at different wind directions show a similar distribution regardless of the change in the wind direction, i.e., the effect of the aerodynamic damping force on the 180° helical model in the across-wind direction can be neglected. </LI> <LI> It might be possible to obtain a reliable aerodynamic damping ratio if the RD signature with the number of time segments over 2000 is used in the evaluation of the aerodynamic damping ratio through the rocking vibration model test. </LI> <LI> These results may be help practical designer in preliminary design of supertall buildings. </LI> </UL> </P>

Wind-induced Aerodynamic Instability of Super-tall Buildings with Various Cross-sectional Shapes

Kim, Wonsul,Yoshida, Akihito,Tamura, Yukio Council on Tall Building and Urban Habitat Korea 2019 International journal of high-rise buildings Vol.8 No.4

The effectiveness of aerodynamic modification to reduce wind loadings has been widely reported. However, most of previous studies have been investigated dynamic forces and pressure distributions on tall buildings with various unconventional configurations. This study was investigated dynamic characteristics and aerodynamic instability of super-tall buildings with unconventional configurations through extensive aeroelastic model experiments. Seventeen types of supertall building models were considered such as basic and corner modification with corner cut, chamfered, oblique opening, tapered, inversely tapered, bulged, helical with twist angles of $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, $360^{\circ}$ and composite with $360^{\circ}$ helical & corner cut, 4-tapered & $360^{\circ}$ helical & corner cut, setback & corner cut, setback & $45^{\circ}$ rotate. As a result, aerodynamic characteristics of helical models with single modification are superior to those of other models with single modification. However, effect of twist angle for helical model is negligible. Further, the 4-tapered & $360^{\circ}$helical & corner cut model is most effective in reducing the along- and across-wind fluctuating displacement responses in all of experimental models.

풍직각방향과 비틀림방향의 응답상관을 고려한 풍하중 조합

김원술(Kim, Wonsul),김용철(Kim, Yong Chul) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.4

The wind tunnel test was conducted to investigate characteristics of fluctuating wind forces acting on tall buildings for various side ratios (D/B=1.0, 1.1, 1.2, 1.3, 2.0 and 3.0) and different terrain roughnesses. Further, the wind load combination was examined by the correlation of the displacement response between acrosswind and torsional directions through Spectral Modal Analysis Method and Time History Analysis Method. As a result, there was no significant effect of the changing of terrain roughnesses on fluctuating moment coefficients for acrosswind and torsional directions, but they were varied with the changing of wind directions. Acrosswind overturning moment coefficients were highly correlated with the torsional moment coefficient with the increase in wind directions. The response and correlation obtained by Time History Analysis were good agreement with those of Spectral Modal Analysis. Also, the response correlation between acrosswind and torsional directions was highly affected by natural frequency ratios. Hence, the wind load combination for acrosswind and torsional directions shall be considered that when the natural frequencies between acrosswind and torsional directions are close to each other.

다양한 풍환경에 노출된 초고층건물의 공력진동 특성

김원술(Kim, Wonsul),김용철(Kim, Yong Chul) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.8

Using the conventional and tapered super-tall buildings, aeroelastic wind tunnel experiments were conducted to investigate the effect of taper on fundamental aeroelastic behaviors in various incident flows. Three different wind environmental conditions were simulated: a turbulent boundary-layer flow representing urban area; a grid-generated flow; and a low-turbulent flow. Results were summarized focusing on the effect of taper and the effect of wind environmental conditions. By using the tapered building shape, the suppressions of responses were profound in the boundary-layer flow and low-turbulence flow, but in the grid-generated flow, the response becomes larger than that of the conventional square model when the wind is applied normal to the surface. The pros and cons of the tapered building shape in various wind environmental conditions were clearly seen.

방음벽의 공기역학적 성능 향상에 관한 연구

김원술 ( Kim Wonsul ),정일원 ( Jung Il Won ),남우석 ( Nam Woo-suk ),신철식 ( Shin Cheol-shik ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.2

지난 2016년 12월 발표된 제1차 기후변화대응 기본계획(2017∼2036)에 따르면 우리나라는 효율적 기후변화 대응을 통한 저탄소 사회 구현을 목표로, 저탄소 에너지의 보편화, 기후산업의 주류화 등의 다양한 정책을 수립하여 국가 기후변화대응을 위한 지속적인 노력을 기울이고 있다. 이러한 노력으로 태양광 발전 관련 산업이 발전하고 있으며, 구조공학 분야에서도 태양광 방음벽 등의 설치가 증가하고 있는 추세이다. 그러나 최근 국지적인 돌풍에 의한 산업시설물의 외장재 및 방음벽 피해가 빈번히 발생하고 있는 추세이다. 본 연구에서는 과거 40년 이상의 기상관측자료를 이용하여 기후변화에 따른 풍속의 특성을 조사하였고, 풍동실험을 통해 방음벽의 모서리 형상 변화에 따른 풍하중의 특성을 조사하였다.

상시진동을 이용한 가거초 해양과학기지의 동특성 추정

김원술(Kim, Wonsul),이진학(Yi, Jin-Hak),민인기(Min, In Ki),심재설(Shim, Jae Seo) 한국연안방재학회 2017 한국연안방재학회 학술발표대회 논문집 Vol.2017 No.-

종합해양과학기지는 해양물리, 해양기후, 해양환경, 해양생물 등의 장기관측을 통해 다양한 연구지원이 가능한 종합 해양학 연구실 기능을 가지고 있다. 이러한 해양관측시스템을 안정적으로 운영하기 위해서는 해양 과학기지 구조물에 대한 구조성능 확보 또한 매우 중요하다. 본 연구에서는 지난 2011년 태풍 무이파에 의해 피해를 입은 후, 구조물의 높이를 5m 증고하여 재시공된 가거초 해양과학기지 구조물에 대하여 동적응답 계측시스템을 구축하고, 계측된 데이터를 이용하여 구조물의 동특성을 분석하였다. 향후에는 장기 계측된 데이터를 이용하여 파랑-구조물 및 바람-구조물 응답 간의 분석 등의 좀 더 심도 있는 연구가 수행되어야 할 것이다. 또한 이러한 결과는 재킷식 해양플랫폼에 대한 다양한 연구를 가능하게 하는 테스트베드 역할을 할 수 있을 뿐만 아니라, 해양구조물 해석 등의 연구결과의 신뢰성 향상에 기여할 수 있을 것으로 사료된다.

건축물의 공간스케일을 고려한 내압의 평가 방법

김원술(Kim, Wonsul),김용철(Kim, Yong-Chul) 대한건축학회 2020 대한건축학회 학술발표대회 논문집 Vol.40 No.2

건축물 해체공사의 허가제도 소개 및 발전 방향

김원술(Kim, Wonsul),지명호(Ji, Myoung-Ho),최승민(Choi, Seung-Min),안충원(Ahn, Choong-Weon) 대한건축학회 2020 대한건축학회 학술발표대회 논문집 Vol.40 No.1

장기 계측 데이터를 이용한 가거초 해양과학기지의 동특성 평가

김원술(Wonsul Kim),이진학(Jin-Hak Yi),민인기(In Ki Min),심재설(Jae Seol Shim) 한국연안방재학회 2017 한국연안방재학회지 Vol.4 No.5

In order to study ocean and meteorological changes related to the global climate change and global warming, Korea is operating several ocean research stations (ORS) including Ieodo ORS, Gageocho ORS and Sochengcho ORS in remote ocean area. In 2011, the Gageocho ORS was attacked by Typhoon Muifa and was damaged to its structural members and various observation equipments. After that, the Gageocho ORS was reconstructed with increased height by 5m and then dynamic response measurement system has been built to assess the structural integrity of Gageocho ORS whether it is healthy or not. Using the measured dynamic response data including acceleration and tilt, the structural dynamic characteristics of the Gageocho ORS were investigated. As a result, three natural frequencies of the first two bending modes and the first torsional mode were estimated as 1.79 Hz, 1.82 Hz and 2.65 Hz, respectively, and the difference between natural frequencies for two bending modes is not significant because is almost symmetrical shape. It is also found that, when the acceleration response is larger, the damping ratios in first mode can be obtained more consistently with lower irregular fluctuations. The averaged damping ratio was about 0.7%. The present results and those obtained from long term monitoring can be used to identify and to assess the structural integrity of the Gageocho ORS, and can be useful in preliminary design of offshore structures.

형상이 복잡한 초고층건물의 진동응답 특성

김원술 ( Kim Wonsul ),이진학 ( Yi Jin-hak ) 한국구조물진단유지관리공학회 2017 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.21 No.1

In this paper, characteristics of wind-induced vibration responses of supertall buildings with unconventional configurations were investigated through extensive aeroelastic model tests. As a result, it was found that helical and composite models were most effective in reducing the wind-induced vibration responses in both along- and across-wind directions.