鋼梁與箱型柱接合內橫隔板耐震設計研究

Seismic Design of Diaphragm Plate in Steel Beam-to-Box Column Joints

謝欣倫(Hsin-Lun Hsieh)

指導教授 ： 蔡克銓

國立臺灣大學/工學院/土木工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.03021

摘要

箱型柱由四片鋼板銲接而成具有雙強軸特性，在國內鋼造建築結構中廣泛使用，柱內於梁上下翼板之接合位置處有兩塊水平隔板以利傳遞力量。國內梁柱接頭研究中，曾有探討箱型柱之橫隔板之彈性變形，近年來更有研究發現在橫隔板與柱板間銲道破壞機率高。常見的梁接箱型柱接頭實驗都以單梁單柱的形式居多，雙梁與柱接合是否會使箱型柱內橫隔板承受更大的受力變形的問題值得探討，因此本研究進行箱型柱內橫隔板有關之研究，期望能進一步了解橫隔板對於前述兩種鋼梁箱型柱接頭在梁彎矩荷載下之力學行為，並進一步提出耐震設計之建議。
　　本研究先利用ABAQUS有限元素模型分析相同柱面彎矩下兩種鋼梁與箱型柱接頭之橫隔板內應力分布，結果顯示兩者柱內橫隔板接近受拉柱翼板的正向拉應力分布趨勢與大小都相似，且會達到降伏拉應力。然而雙梁之柱內橫隔板接近柱腹板會達到剪應力降伏，習見實驗採單梁形式時卻不會。將橫隔板受力需求依較大的應力分布種類分成正向力與剪力兩種，在柱面彎矩達相同狀態下，考慮較大的剪力作為橫隔板的設計受力需求。
　　本研究並將相對柔度特性用來計算H型柱連續板之受力需求方法運用在箱型柱內橫膈板，推導預測箱型柱內橫隔板的柔度特性公式，針對梁翼板與橫隔板之寬度比、厚度比和柱翼板寬厚比用ABAQUS有限元素模型分析進行參數研究，利用參數研究方式及迴歸方法得到柔度特性公式，精算前述兩種接頭形式的箱型柱內橫隔板的受力需求，研究結果顯示也可保守簡算單梁柱內橫隔板的剪力需求為梁彎矩拉力的一半，而雙梁內橫隔板剪力等於梁彎矩拉力，因而提出橫隔板的設計建議。
　　本研究亦舉不同橫隔板厚度之分析實例來比較習見與本研究建議的橫隔板設計，藉著相同受力或變形條件，並配合試體實驗數據觀察其局部行為，比較模型中關鍵位置之塑性變形的發展。分析結果顯示，雙梁之橫隔板在柱面彎矩達非線性時，無論是橫隔板的von Mises應力、橫隔板變形、梁翼邊緣的等價塑性應變指數以及破裂指數都比採同橫隔板厚度的單梁形式更趨嚴重，因此本研究建議進一步進行雙梁抗彎接頭實驗，並考慮加厚橫隔板設計，使這些局部應力或應變反應降低。

關鍵字

箱型柱 ； 橫隔板 ； 有限元素分析 ； 柔度特性公式 ； 橫隔板受力需求 ； 耐震設計 ； 橫隔板厚度

並列摘要

Built-up box columns are widely used for steel structures in Taiwan because of its bi-axial strength and stiffness. In the welded beam-to-column moment connections, welded internal diaphragms in the column at the beam flange elevations play an important role in transferring the beam flange forces into the column. For an interior column, two beams are connected to the opposite flanges of the box column, while only one beam for an exterior column. In common practice, the thickness of the diaphragm plate is the same as the beam flange thickness in either interior or exterior column. Most of the tests on welded beam to box column moment connections have been conducted for exterior columns. Under the severe earthquake loads, the diaphragm plates having a thickness identical to the beam flange may go into severe inelastic responses when both two beams develop plastic hinge adjacent to an interior column. This research investigates the deformations and stress distributions, quantifies the force demand, and proposes the seismic design method for diaphragm plates in box columns.
First, this paper presents the difference on stress responses in diaphragms between the exterior and interior connections using finite element (FE) software, ABAQUS. The shell element model was calibrated first using a beam-to-exterior box column connection specimen. Then extensive FE analysis results show that diaphragm peak shear stresses near the column web in the interior column is almost twice of those of in an exterior column. However, diaphragm peak normal stresses near the column flange are similar in both two types of connections. In order to allow designers to efficiently size the diaphragm thickness, this paper proposes two approaches to quantifying the seismic force demand on the diaphragm. One is based on the relative flexibilities of the column flange and diaphragm. The other is based on the simplified free body diagram. The simplified approach is convenient and conservative.
The FE analysis results indicate that the deformation and von Mises stress in the interior column diaphragm are much larger when the diaphragm thickness is the same as the beam flange. The diaphragm plate, thickness determined from the proposed method reduces the peak diaphragm deformation by 75% and allows the diaphragm to remain elastic when plastic hinges form on both two beams. The FE analysis results also indicate that the equivalent cumulative plastic strain and rupture index on beam flange edge caused by diaphragm yielding are much higher in an interior connection than those in the exterior connection. The paper concludes that further experimental tests are desired in order to gain insights into the effects of diaphragm plate responses on rotational capacity of welded beam to interior box column moment connections.

並列關鍵字

welded moment connection ； box column ； diaphragm ； finite element analysis ； seismic design

參考文獻

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