圓筒型附屬建物風載載重之探討

A Study on the Wind Loadings of the Cylindrical Tank on Buildings

台灣地區在歷次颱風中建築物之附屬構造物倒塌或毀損，皆威脅公共安全，有必要加以預防。本計畫透過蒐集國內外相關構造物之耐風設計方法、標準或規範，利用文獻整理與風洞試驗，以常見的建築物水塔等圓筒型附屬建物為例，建立參考之風壓或風力係數，供設計參考，檢討規範中關於圓筒型水塔，在不同底高的條件下，其設計風載重的表現。由研究結果顯示，對於不同筒底高度的水塔構造物而言，由規範中所建立的水平向風載重仍可涵蓋其適用範圍。本研究利用傾倒彎矩推算相當的模型頂等值靜載重，顯示提高圓筒高度，將迅速提高等值靜載重，實際設計時其對於基座桿件而言，傾倒彎矩的增加，包括基座桿件的抗拉拔及挫曲預防等均須加以特別考慮。此外採水平放置的圓筒，由於轉風攻角後並不對稱，其一般化外力係數均明顯提升。

There are lots of building components damaged by the extreme weather conditions, such as the typhoon, in Taiwan area every year. This situation will be a problem of safety of civilization lives. A suitable design criteria of wind loadings to these buildings is necessary for the designers and officers of buildings management. In this study couples of design codes and literatures are compared as the bases for the local provisions of design wind loads on buildings components and temple structures. Also a series of aerodynamics experiments about cylindrical tanks on buildings top were conducted to make up the necessary data. In experiments, the gap under the bottom of model and floor of wind tunnel was controlled as an important factor. The experimental results shown, that the gap will affect the wind force coefficients of models. But the design data provided by the code still can cover this variation. For the over turning moments of tank with different gap under the model were studied with the concept of equivalent loadings. The results shown, that the increasing of the gap under the tank will cause the equivalent loadings at the top of tank to be increased dramatically. This situation may cause the buckling of support columns under the tank and should be aware for the designer. The results also shown for the horizontal tank the change of attack angle of approaching flow, will change the project shape of tank into anti-symmetric. The generalized force of wind loadings will be increased.