直接分析設計法應用於廠房鋼構架建築之研究

The Study of the Direct Analysis Method for Steel Factory Building Frame Design

10.6989/JN.201112.0249

華根(Ken Hwa)

直接分析設計法 ； 具椅靠柱鋼構架 ； 有效長度因數 ； 虛擬側向力 ； direct analysis method ； leaned column frames ； effective length factors ； national loads

南亞學報

31期（2011 / 12 / 01）

249 - 264

繁體中文

鋼構架的分析與設計主要是以有效長度概念來考慮構件強度，但其計算的過程卻相當繁複。為簡化設計程序，美國鋼結構協會2005版規範附錄七中提出直接分析設計法以二階彈性分析合併虛擬側向推力與折減勁度的應用，免除有效長度的使用。本文旨在探討台灣鄉間許多具倚靠柱的廠房鋼構架建築應用直接分析設計法的合理性，由於此類鋼構架結構側向穩定度較一般鋼結構為低，因此，原有的虛擬側向推力有過大之疑慮。研究數據結果發現，若梁勁度遠大於柱勁度時，虛擬側力不應施加，且無法應用原有AISC-LRFD之交互方程式，應予修正；對於一般具倚靠柱鋼構架建議在不考慮折減勁度時，取虛擬側力為樓層載重之千分之二即可。另外，柱構件的長細比與載重分佈對於分析結果的影響不大。

Effective length concept has been used to evaluate member strength in a steel frame for many years. However, the process of calculating the effective length factors is not straightforward. The current trend is to avoid the use of effective length factors in the design of steel frames. In the 2005 AISC Specification Appendix 7, for ordinary steel frames, the direct analysis method is proposed to account for nonlinearities and inelastic effects by applying notional loads and/or modified stiffness to structures. In Taiwan, there are many factory steel frame buildings with leaned columns. Since the lateral stability of these frames is lower than ordinary steel frames, the purpose of this paper is to examine the factors used in the direct analysis method for these particular steel buildings. The research data show that for the case of beam stiffness is much greater than column stiffness, notional load need not be applied and interaction equations of AISC-LRFD are not appropriate. For ordinary steel frames with leaned columns, notional load is recommended to be equal to 0.2% of total design gravity loads acting on the considered floor level. In addition, slenderness ratio of column members and loading distribution do not have great influence to the analysis results.