Analysis of Design Wind Speed Variation above the Gradient Height for Large City Terrain (II)

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Project title

Code/計畫編號

NSC102-2221-E019-043

Translated Name/計畫中文名

都會地況設計風速於梯度高度以上風速變化情形之探討(II)

Project Coordinator/計畫主持人

Jing-Jong Jang

Funding Organization/主管機關

National Science and Technology Council

Co-Investigator(s)/共同執行人

林博雄

Department/Unit

Department of Harbor and River Engineering

Website

https://www.grb.gov.tw/search/planDetail?id=3091125

Year

2013

Start date/計畫起

01-08-2013

Expected Completion/計畫迄

31-07-2014

Bugetid/研究經費

488千元

ResearchField/研究領域

土木水利工程

近來幾年，隨著現代建築技術的進步和都市經濟發展，世界各大都市超高樓建築林立，如台北 101大樓、日本東京天空樹、中東杜拜的哈里發塔，其建物高度分別達到 510m、634m、828m，然而臺灣現行風力設計規範所訂定的風速梯度高度與設計風壓最高只到 500m。實際上，真實自然風場的風速垂直分佈狀態常與理論和規範假設不同；一般而言，實場風速變化並非在到達梯度高度以後保持均勻，反而是會產生內縮或外張的現象。由於目前國內超高層(>300m)風速剖面相關研究不多，也尚無初步具體結論，因此本計畫將針對此主題持續深入研究探討，相信研究成果將有助於未來高樓結構耐風安全設計。台灣地區位處於太平洋颱風盛行的地區，夏秋之際常遭受到颱風的侵襲，建築物也常損壞。由於颱風時實際的風速剖面與梯度高度，可能不同於現行規範設定的大都會地況Ａ的 500公尺以上風速等速不再變化；實際上，超高層以及梯度高度以上之風速變化難以預測，因此利用風速壓計算式所得之風壓，透過風壓係數 Cp 、風力係數 Cr 與陣風反應因子G，計算所得之風力來設計超高樓結構，對結構之安全性與經濟性將有完全不同的影響。本研究結合主持人之土木結構風工程專長與共同主持人之大氣科學專長，首先將利用中央氣象局所屬氣象觀測站和台大大氣科學系之探空氣球觀測資料，取得台灣近年來颱風時期台北都會區之風速資料，利用地面高度 3000m以下的風速觀測資料進行分析，主要針對高度500m ~1000m的風速剖面進行模擬分析，以及風速壓的模擬分析，並對台灣現行的設計風壓進行探討。由於去年台北 101 上架設了微型氣象站，將透過與共同主持人與台大大氣科學系之合作，取得相關風速量測資料，對台北 101 大樓的風速剖面進行模擬分析，並於未來擴大到其他之超高樓(如高雄 85大樓)之風速量測做更進一步之探討。就本研究進行一年來之初步資料分析，風速剖面分佈在梯度高度以上並非定值，常有的內縮現象，大致上可分為四種情況(標準內縮現象、多點內縮現象、內縮現象不明確、內縮點產生停滯)其中以多點內縮現象最多。台灣現行規範於 2007年剛修定施行，也有參照台灣的地理、氣候等條件，出修正的 α 及 Zg 值，然而對於超高樓結構仍然未有適合的 α 及 Zg 值和風速剖面，希望經由本計畫持續研究的成果，提高超高結構物耐風安全設計之可靠度，以及提供未來超高樓結構的耐風設計規範條文修訂之參考。 There are many super-tall structures were built in recent years, due to the rapid development of building technology and economic growth. Such as the Taipei 101 (509m)、Tokyo Sky-tree Tower (634m) and the Dubai Burj Khalifa Tower (828m). The wind speed is the most important factor for building wind resist design. ( 20.5q V ) However, the wind speed profile of the current building design code is constant for the height above gradient height which is about 500m. Therefore, it is very important to have the accurate wind speed profile distribution for the safety design of super tall buildings with more than 500 meters. Taiwan is a subtropical island and located at the Pacific Ocean Rim where typhoons occurred frequently and lots of tall buildings and structures were damaged every year. The current Taiwan building code for wind resistant design was revised and published in 2007. The wind pressure is function of wind speed V(Z) with parameters α and Zg. The wind speed profile coefficients introduction into the current building code for wind resistant design is based on the codes of USA and Japan. Up to today, there are few data or researches about the natural wind filed of Taiwan. Thus, this research will focus on the wind speed profile especially for the characteristic of wind speed profile above gradient height in Taiwan large city area during typhoon. This research will continue collect the wind speed data from the National Weather Bureau and wind speed data of Taipei 101 building from National Taiwan University. We will study the effect of the gradient height wind speed which is varied with height during typhoon. At last, a wind speed profile model will be proposed and a tall building example will be set up. Structural analysis and simulation will be performed to study the effect of different wind sped profile models. The results and conclusions or suggestions of this research will be helpful for future super tall structure wind resistant design code with revised gradient height effect. It will also be useful for the future building design codes revision and benefit the whole structure engineering society.

Keyword(s)

風速剖面
耐風設計
梯度高度
都會地況
wind speed profile
wind resistant design
gradient height
large city terrain

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Analysis of Design Wind Speed Variation above the Gradient Height for Large City Terrain (II)

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