預鑄五螺箍矩形SRC柱之軸壓與反覆載重試驗

Abstract

本研究旨在探討新型的「五螺箍」應用於矩形鋼骨鋼筋混凝土(Steel Reinforced Concrete，SRC)柱之可行性。本研究的五螺箍是以自動化機械加工製造，因此具有高度經濟效益，很適合用於預鑄工法。再者，由於SRC柱中之鋼骨能對SRC柱核心之混凝土提供有效的圍束，因此有助於提升SRC柱之韌性並可降低箍筋之用量，達到更經濟的設計結果。本論文包含兩項研究課題，其一為五螺箍SRC短柱之軸壓實驗；其二則是五螺箍SRC長柱之反復載重實驗。 第一個主題中，本研究進行22支實尺寸之短柱軸壓試驗。主要參數包括箍筋之型式與間距、鋼骨之型式與用量、圍束箍筋用量設計法等。整體而言，採用五螺箍之試體其韌性皆優於採用傳統橫箍筋者。五螺箍除了圍束混凝土的能力比傳統橫箍筋好之外，亦沒有橫箍筋在角隅處可能發生彎鉤脫落之問題，因此能夠發揮較佳的韌性。本研究發現，在相同的斷面尺寸與縱向總用鋼量之情況下，五螺箍SRC柱之韌性明顯的比配置傳統橫箍筋的SRC柱好很多，亦優於同樣配置五螺箍之RC柱。 第二個主題中，本研究進行4支實尺寸之長柱反復載重耐震試驗。主要參數包括鋼骨用量、箍筋用量（間距）等。試驗結果發現，SRC柱之反復載重遲滯迴圈均相當飽滿，四組試體所發揮的層間變位角均高達5.7% 弧度以上，且SRC柱之強度可以持續且穩定的維持在高檔，並無明顯下降的趨勢。此一現象顯示，在高達5.7% 弧度的大變形狀況之下，五螺箍SRC柱仍然具備十分穩定的強度，可以有效的抵抗強震所引致之水平剪力，而不致於發生結構體快速崩塌之現象。此外，由試驗中發現，五螺箍SRC柱底部之塑鉸區發揮了良好的韌性，該區之混凝土僅有表面的保護層剝落，五螺箍內部所圍束之混凝土大致保持完好，且SRC柱之主筋並無挫屈現象，箍筋亦未發生斷裂之情形。

This study explores the feasibility of a new type of “5-spirals” applied in rectangular SRC columns. The 5-spirals in this study are processed and produced by automatic machinery, highly cost effective, and suitable for precast construction. In addition, the steel in the SRC column works effectively in confining the reinforced concrete at the core of the SRC column and therefore is helpful in reducing usage of confinement hoops for more economical design result. This thesis consists of two topics, the axial compression test on the 5-spirals SRC short columns and lateral cyclic loading test on the 5-spirals SRC long columns. For the first topic, the axial compression test on 22 full-size columns was carried out in this research. Primary parameters include the type and spacing of hoops, the steel ratio, the volume ratio of the design for confinement hoops, etc. Generally speaking, the ductility of the test specimens, the 5-spirals, was better than that of traditional rectangular hoops. Besides working better in confining reinforced concrete than rectangular hoops, the 5-spirals were free of the problem of possible hook loosening at corners that is typical of rectangular hoops. This study found that with the same section size and total steel volume, the ductility of 5-spirals SRC columns were obviously superior to that of traditional rectangular –hoop SRC columns and better than that of 5-spirals RC columns with the same configuration, too. For the second topic, the cyclic seismic load test was carried out on 4 full-size long columns. Test results showed that the cyclic loading hysteretic loops of the SRC columns were all very stable, with the interstory drift angle of all the four test specimens as high as 5.7% radians and the strength of the SRC columns could last and be maintained steadily at a high level without any obvious sign of decline. This phenomenon showed that under large deformation as high as 5.7% radians, 5-spirals SRC columns continued to possess very stable strength and can effectively withstand the lateral force caused by a major earthquake so as not to result in the quick collapse of the main structure. The tests showed that plastic hinges at the bottom of the 5-spirals SRC columns had exercised outstanding ductility. Only the protection layer on the surface of the concrete in the area had spalled off. The concrete confined inside the 5-spirals had generally remained in a good condition and the main reinforcing bar of SRC columns had shown no sign of buckling.