冷軋I 型斷面在撓曲強度上的探討

The Investigation of Flexural Strength of Cold-Formed Steel I-Shaped Section

林明毅(Ming-Yi Lin)

指導教授 ： 潘吉齡

朝陽科技大學/理工學院/營建工程系/碩士(2013年)

摘要

本研究針對一體成型冷軋I 型格柵梁系統在不同連接方式下承載力進行試驗與分析，試體連接方式有使用角鋼及橫撐構件兩種，使用角鋼做為連接是為了模擬格柵梁純彎矩(Pure Bending)行為，以防止側向挫屈的現象發生，使用橫撐構件則做為實際二格柵梁之間的互相支撐，運用橫撐構件使格柵梁系統模擬成完全支撐，且提供某種程度的腹板支撐。因本研究之格柵梁皆有預先開孔，因此亦進行了使用角鋼連接之無開孔格柵梁實驗，並與預先開孔格柵梁做一比較，結果發現，橫撐構件對格柵梁腹板具有加勁之作用，使用橫撐構件做為連接的格柵梁極限承載力明顯高於使用角鋼做為連接之格柵梁系統，且開孔格柵梁之極限承載力明顯低於未開孔之格柵梁系統。

然而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為腹板摺曲破壞。本研究另以CFS軟體進行AISI 規範的構材強度預測計算，構材斷面腹板具有開孔的預測值與實驗值比較之下顯得過於保守。

關鍵字

冷軋型鋼 ； I型斷面 ； 撓曲強度 ； 格柵梁

並列摘要

This research is concentrated on the experiment and analysis study for the cold-formed steel folded I-shaped joist under flexural loading. The test specimens were formed by two different types: angle connection and horizontal bracing. The purpose of using the angle connection is to simulate the pure bending behavior which is prevented the joist specimens from the lateral-torsional buckling. The utilization of horizontal bracing for connecting two joists is to construct the actual joist system, as well as to provide an extra stiffened effect for the web of joist. Since the perforated web was adopted in the joists, the joists without web opening were also fabricated for the comparison purpose. It was observed from the test results that the ultimate strengths of test joists using angle connection are much lower than those of test joists using horizontal bracing for most of tests. And the ultimate strengths of the joists without web opening are higher than those of the joists with web openings.

The failure mode of prototype joists is the separation of top folded flange due to local buckling behavior. Therefore, improved type of joists which is amended by clipping the extended lip of flange to the web was designed and fabricated. It was found that the improved type of joists has more load carrying capacity as comparing to the prototype joist. In addition, the prediction by using the software named CFS which is based on the AISI Specification was used to compare the test values. It seems that the joist with web openings has an over conservative value computed by using AISI formulas.

並列關鍵字

Cold-Formed Steel ； I-Shaped Section ； Joist ； Flexural Strength

參考文獻

[2]. Cheng Yu and Benjamin W. Schafer, ‘‘Local Buckling Tests on Cold-Formed Steel Beams,’’ J. Struct. Eng. 2003.129:1596-1606.

[3]. Cheng Yu and Benjamin W. Schafer, ‘‘Distortional Buckling of Cold-Formed Steel Members in Bending,’’ American Iron and Steel Institute, 2005.

[4]. Cheng Yu and Benjamin W. Schafer, ‘‘Distortional Buckling Tests on Cold-Formed Steel Beams,’’ J. Struct. Eng. 2006.132:515-528.

[5]. American Iron and Steel Institute (AISI),“2007 Edition of North American Specification for the Design Cold-Formed Steel Structural Members,” CANACERO, 2007.

[6]. American Iron and Steel Institute (AISI),“2007 Edition of Commentary on North American Specification for the Design Cold-Formed Steel Structural Members,” CANACERO, 2007.