開口煙囪之應力分析

Abstract

本文簡單地介紹美國的煙囪設計規範—ACI 307-88， 包括風力載重部份與強度設計 法。選取具有處理薄膜 伸張與抗撓曲能力的平板元素來分析煙囪之應力行為。 首先分 析單開口煙囪與無開口煙囪應力分佈之行為，然 後固定開口角度而改變同斷面上兩開口 之相鄰角度，來 研究這些斷面上應力之行為且比較與無開口時的差異。 同時我們將同 斷面相鄰之開口合併成一個大開口，找到 一個相鄰夾角的臨界角，當相鄰夾角小於此臨 界角時可 使得此大開分析之最大應力小於以兩開口分析時之最大 應力。最後改變小開 口角度並根據上述分析過程找到一 個對應之臨界角。 The main purpose of the paper is to investigate the stress concent ration effect of chimney structure with openings . Plate element is em ployed to build models for analysis of chimney with no opening, single op ening and two openings. The commercial F.E.M. Package, ANSYS 5.1, is used to analyze these models in this research.First, the stresses of chimneys w ith no opening and single opening are studied. Second, the chimneys with di fferent angle between two openings are analyzed in order to compare the s tresses with that of the chimney with no opening. Finally, the two openings and the shell between the two openings are treated as a big opening by eli minate the shell, and then the stress concentration factor is compared to that with two openings in order to obtain the corresponding critical angle b etween the two openings. The correspondent critical angle is found for vary ing opening angle. Hence , some modifications for designing chimney shell are recommended in accordance with the results.