冷軋I型斷面構材之撓曲行為研究

The Study of Flexural Behavior of Cold-Formed I-Shape Section Member

陳景鴻(Ching-Hung Chen)

指導教授 ： 潘吉齡

朝陽科技大學/理工學院/營建工程系/碩士(2015年)

摘要

針對一體成形彎折而成之冷軋I型斷面，先前研究已進行了四點載重撓曲實驗，本研究乃透過有限元素分析軟體之模型建立、材料性質、邊界條件、側撐條件模擬(角鋼與橫撐構件)與網格鋪設分析所得之結果，比較兩者結果之差異性，包含中點位移量和載重變形圖。另外本研究亦嘗試使用AISI規範運算之結果與實驗值互相比較。實驗結果發現原設計之格柵梁破壞的模式均為局部挫屈造成上翼板肢材的分離，因此另外製做改良型式之格柵梁，此格柵梁在翼板末端增加突唇，且以摺縫方式將突唇與腹板接合，實驗結果顯示此方法是有效防止翼板肢材的分離，且大部份之試體破壞則改變為腹板摺曲破壞。試體模型分析過程中，證明使用線性彈簧可有效模擬以橫撐構件為側撐系統之格柵梁載重變形，研究發現有限元素模型與實驗試體的中點位移量仍有些許差異，其中因素可能為邊界條件或材料性質參數的設定不妥當，比較實驗試體之最大彎矩值與規範計算所得之標稱撓曲強度，觀察出實驗值大於規範的計算值，而規範計算之腹板摺曲強度與實驗結果比較後，建議規範運算之結果可用於預測以橫撐構件做為側撐系統之改良型冷軋型鋼I型梁。另嘗試以等效厚度之觀念，根據試體模型翼板厚度之變化情形進行分析，結果發現原翼板厚度1.4倍之試體模型與實驗結果最為接近。

關鍵字

撓曲行為 ； 冷軋型鋼

並列摘要

In the study of integral I-shaped cold-formed steel section, four-points loading bending tests were conducted in previous research. The numerical analysis was achieved by using finite element analysis software to establish structure model, build boundary conditions, simulate bracing supports (angle bracing and member blocking), and create mesh. Both test and analysis results including the displacement at midpoint of beam and the deformation shape under ultimate load were studied to compare the differences. In addition, the predicted values computed according to AISI specification were also adopted in the comparison of tested values. The separation phenomenon of compressive flange due to local buckling was observed for the prototype I-shaped beam test. The section was redesigned and improved by applying folding mechanism on the edge stiffener of flange into web of section. As a result, the separation of flange was found to be prevented effectively, and the failure mode of flexural test turned into web crippling located at loading points. Some discrepancies were found between the analytical values and test values for the displacements at midpoint of beam under ultimate loads, it is probably due to the incorrect setting of boundary conditions and material parameters utilized in the finite element analysis. The predictions computed based on specification were less than the test ultimate flexural strengths. However, it is observed that the web crippling strength calculated according to specification provide a good agreement with the ultimate strength of test. It is suggested that the computed value from specification can be adopted to predict the failure strength of integral I-shaped cold-formed steel section in this study. The concept of equivalent thickness was adopted in the ABAQUS analysis. By change of flange's thickness for finite element mpdel, the output of analysis by choosing 1.4 times the thickness of sheet steel agrees well with the results of experiment.

並列關鍵字

Flexural Behavior ； Cold-Formed Steel

參考文獻

1. 潘吉齡、林明毅，「冷軋I型鋼斷面在撓曲強度上的探討」，朝陽科技大學營建工程系碩士論文，台中，2013。

4. Cheng Yu, “Cold-Formed Steel Flexural Member with Egde Stiffend Holes: Behavior, Optimization, and Design.” Journal of Constructional Steel Research. 2012.71:210-218.

5. Cheng Yu and Benjiamin W. Schafer, “Simulation of cold-formed steel beams in local and distortional buckling with Applications to The Direct Strength Method.” Journal of Constructional Steel Research. 2007.63:581-590.

6. Mohammad Reza Haidarali and David A. Nethercot, “Finite Element Modeling of Cold-Formed Steel Beams Under Local Buckling or Combined Local or Distortional buckling, ” Thin-Walled Structures. 2011.49:1554-1562.

7. Mohammad Reza Haidarali and David A. Nethercot, “Local and Distortional Buckling of Cold-Formed Steel Beams with Both Edge and Intermediate Stiffeners in Their Compression Flanges, ” Thin-Walled Structures. 2012.54:106-112.