填充型與未填充型鋼骨箱型柱鋼板剪力牆耐震行為研究

Abstract

鋼板剪力牆系統為一種新型抗側力系統，具有高側向勁度與韌性之系統，近年於美加地區已漸受採用，但此系統在國內工程實例上的應用仍不多見，主要原因可能是：一、邊界梁柱之容量設計要透過複雜的板條模型來完成，二、根據美國AISC規範，邊界柱塑鉸只能產生於柱底，柱尺寸設計過於不經濟，三、國內多採用箱型柱來當作鋼結構之柱構件，此與過去研究及國外採用之H型寬翼柱完全不同。若鋼板剪力牆之邊界柱構件採用填充型與未填充型箱型柱，柱腹板位於柱斷面兩側，柱翼板面內之局部勁度較大，而柱翼板之面外勁度小，卻在中心線與鋼牆板相接，須承受拉力場作用，並同時須承受構架側位移時柱軸力與彎矩行為。 有鑑於此，本研究針對箱型柱翼面外受拉行為提出採淨寬兩端固端梁及門形構架簡化材料力學模型，分別分析填充型及未填充型箱型邊界柱內側柱翼面外受拉之受力變形行為。並以von Mises平面應力降伏法則來探討箱型邊界柱同時受軸力與彎矩及內側柱翼面外受拉之內外表面應力行為。 為了探討填充型與未填充型鋼骨箱型柱鋼板剪力牆構架之耐震行為能力，並驗證本研究提出箱型邊界柱內側翼板面外額外受拉效應之耐震設計的適用性，並探討過去提出之邊界柱容量設計(在最大考量地震階段下放寬柱底塑鉸至四分之一底層高，但限制柱頂無塑鉸行為)是否適用，本研究於國家地震工程研究中心完成三座實尺寸雙層單跨鋼板剪力牆構架之反覆側推試驗，並進行試體的ABAQUS有限元素模型及SAP2000板條模型分析。試體跨距為3.42米，每層樓高為3.82米，寬高比0.9，三座試體鋼牆板均使用2.6公厘厚的低降伏強度鋼板，邊界梁尺寸設計相同，並以內側柱翼面外受拉考慮是否會降伏來決定三座之邊界柱板厚，其中試體NCB及WCB採填充型邊界柱，試體NSB採未填充邊界柱。 試驗與有限元素模型結果證實，本研究提出之採淨寬兩端固端梁及門形構架簡化材料力學模型可分別保守地預測填充型及未填充型箱型邊界柱內側柱翼面外受拉之受力變形行為。過去提出之邊界柱容量設計亦適用於採填充型與未填充型箱型柱之鋼板剪力牆構架，如事前設計所預測，試體內側柱翼面外受拉表面降伏及塑鉸產生於柱1/4柱高的鋼板剪力牆構架仍有相當飽滿的遲滯迴圈反應，且內填混凝土對邊界柱抗壓強度、牽制鋼管局部挫屈有明顯幫助，更可節省鋼料用量。另外，以箱型邊界柱內側翼板面外受拉劇烈降伏為設計目標之試體WCB，可觀察到較嚴重的面外永久變形，是工程應用該避免之設計限制。

Steel Plate Shear Walls(SPSWs) have evolved into an effective lateral force resisting system in recent years. However, it is still not widely adopted in Taiwan construction practice. This may be due to the following three reasons: 1) The capacity design of the boundary elements must be checked by using the strip model, which may be complicated and time-consuming. 2) According to the AISC seismic building provisions, the column plastic hinge should be designed to form only at 1st story column bottom end. Therefore the design result for the 1st story column may not be economical. 3) In Taiwan, built-up box columns are commonly adopted. However, most of the past studies of SPSWs focused on wide flange boundary columns. If the boundary columns in the SPSWs are concrete filled steel box column or bare steel box column, the inner column flanges connected to the steel panel would be subjected to the out-of-plane pull-out forces when the tension field action develops. These vertical boundary members also have to resist the axial force and the in-plane bending moment at the same time. Allowing the inner column flange to go into minor yielding under the pull-out effects, this study proposes the column flange capacity design methods. It considers two simplified models, fixed clear-span beam and flat-portal frame for steel box column with and without infill concrete respectively, and the full tension field pull-out effects to design the inner column flanges. The Von Mises yielding criterion of plane stress is used to estimate stress distribution of inner column flange subjected to column axial force, in-plane moment and column flange out-of-plane pull-out moment. In order to investigate the seismic responses of SPSWs using box columns with and without infill concrete, and to verify the effectiveness of the proposed column flange capacity design requirements that prevent the plastic hinge from forming at top end of bottom column under maximum considered earthquake, three full-scale two-story SPSW specimens were tested in National Center for Research on Earthquake Engineering. Each specimen is 3.42-meter wide and 7.64-meter tall. The 2.6mm-thick low yield strength steel plates and the same boundary beams were adopted. Three different column sizes were designed for the three specimens considering the column inner flange out-of-plane flexural requirements. They were named NSB, NCB and WCB in which Specimen NCB and WCB used concrete filled box column, and Specimen NSB used bare steel box column without infill concrete. Results of the ABAQUS pushover analyses and the cyclic tests up to a roof drift of 0.04 radians confirm that the proposed column flange flexural requirements and column capacity design are suitable for seismic SPSW using box columns with or without infill concrete. It could achieve both good seismic performance and economy. The specimen NCB having minor yielding in inner column flanges and the 1st story column plastic deformations spreading over the mid-high of the column still possessed rather good load-carrying capacity. In addition, infill concrete for steel box column enhances the compression capacity and local buckle resistance. However, under the steel panel pull-out forces major yielding of the inner column flanges in Specimen WCB was observed. This design should be avoided as significant permanent plastic deformations could develop.