半圓頂型屋蓋結構物表面擾動風壓交相關頻譜之分析與擬合

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Title:	半圓頂型屋蓋結構物表面擾動風壓交相關頻譜之分析與擬合
Other Titles:	Approximation of cross spectra of fluctuating pressures on dome-like structure's surface
Authors:	林香伶;Lin, Hsiang-Ling
Contributors:	淡江大學土木工程學系碩士班羅元隆;Lo, Yuan-Lung
Keywords:	半圓頂型屋蓋;擾動風壓;雷諾數;紊流強度;屋蓋曲率;Domed Roofs;Wind Pressure Fluctuations;Reynolds number;turbulence intensity;Roof Curvature
Date:	2016
Issue Date:	2017-08-24 23:48:20 (UTC+8)
Abstract:	當休閒娛樂活動與大量儲存空間的需求與日俱增，使得大跨度結構也越來越多，大跨度結構的特性為跨度大且材質較輕，故此類結構物受風力作用的敏感程度亦無可避免地增加。風力作用對於大跨度結構物所造成的反應成為設計大跨度結構物最重要的一環。大跨度結構的相關研究在以往已有若干學者針對表面風壓特性進行探討，但大部分均為定性探討；此外，大跨度結構表面風壓分布深受雷諾數、紊流強度以及其屋蓋曲度影響，因此進行風洞實驗時，均需將這些因素考慮進去。本研究以Lo and Kanda [1]的實驗資料中不同曲率的半圓頂型結構物作為研究對象。經由風洞實驗，以過往曾被提出的眾多經驗公式與本研究新提出的擬合公式，針對屋蓋子午線上，兩鄰近擾動風壓之Root-coherence與Phase function進行交頻譜分析與擬合，探討半圓頂型屋蓋結構表面擾動風壓交相關頻譜之結果與趨勢變化，根據不同曲率與風壓孔間距提出對擬合公式係數影響的迴歸公式，並與實驗比較其差異性，作為日後風力載重計算與數值模擬之依據。由擬合結果得知，不同屋蓋曲率的交頻譜變化趨勢相同，因此可以使用 f/D=0.5的交相關頻譜擬合結果取代 f/D=0.2~0.4的擬合結果。以Root-coherence與Phase function擬合公式係數進行迴歸後再進行Co-coherence擬合，可以發現對於f/D=0.5的擬合結果最好，隨著f/D愈小擬合結果的誤差愈大。 When the demands for leisure activities and a large number of storage spaces are increasing, there are more and more large-span structures being constructed. The unique features of large-span structures are their large span roofs and lighter materials, which make them sensitive to wind loads. Therefore wind effect on large-span roofs have become the most important issue in the whole design procedure. Related researches about large-span structures in the past have been explored by a number of scholars. Reynolds number, turbulence intensity and roof curvature dominate the estimation of the wind loads. However, most conclusions were given in qualitative discussion. This present study adopts several different curvatures for hemispherical dome structures in Lo and Kanda’s experiments. By comparing proposed empirical formulas and the one proposed in the present study, cross spectrum of any two neighboring fluctuating pressures along the roof meridian have been well approximated. From fitting results, cross spectra with different roof’s curvature have similar trends. Therefore the case of rise/span ratio (f / D) equals 0.5 can be used instead of other three (f / D = 0.2, 0.3, 0.4) in conveneince. By separately regressing the fitted coefficients of root-coherence and phase functions, the cross spectra can be approximated well in a quantitative way.
Appears in Collections:	[Graduate Institute & Department of Civil Engineering] Thesis

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