複合式星形與圓形螺箍應用於矩形SRC柱之可行性研究

Abstract

本研究主要在探討一種新型的「複合式螺旋箍筋」應用於矩形鋼骨鋼筋混凝土(Steel Reinforced Concrete，SRC)柱的可行性。這種新型的複合螺箍是由一組星形螺箍(Star Spiral)與一組圓形螺箍(Circular Spiral)共同交織而成，它可以對矩形SRC柱之混凝土提供良好的圍束。本研究的複合式螺旋箍筋可以採用自動化加工製造，有助於大幅降低箍筋綁紮之人力及縮短工期，很適合應用於預鑄工法(Precast Construction)。論文中主要包含兩項研究課題，其一為複合式螺箍SRC短柱之軸壓載重實驗；其二則是複合式螺箍SRC長柱之反復載重實驗。 第一個主題中，本論文進行八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，複合式螺旋箍筋之短柱試體可以使用較少的箍筋量，達到強度與韌性皆優於採用傳統橫箍筋者的效果。複合式螺旋箍筋除了圍束混凝土的能力優於傳統橫箍筋之外，亦沒有傳統橫箍筋可能發生角隅彎鉤脫落之問題，因此能夠發揮較佳的韌性。實驗結果顯示，在相同的縱向總用鋼量之情況下，複合螺箍SRC柱之韌性明顯優於配置傳統橫箍筋的RC柱，亦優於同樣配置複合螺箍之RC柱。 第二個主題中，本論文進行兩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，在層間變位角（Drift Angle）高達5.6% 弧度下，兩支SRC柱之強度均可以穩定的維持在高檔，並無強度明顯下降的趨勢。另一方面，複合螺箍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，複合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。

A series of full-scale rectangular steel reinforced concrete (SRC) columns confined with a new type of multiple spiral cage were tested under monotonic axial compression and cyclic lateral load. The multiple spiral cage is a device of two interwoven spirals including a circular spiral at the center and a star-shaped spiral surrounding the perimeter of the column. The innovation of applying the star spiral to rectangular SRC columns is to take its advantage in concrete confinement at the four corners of the rectangular cross-section. The multiple spiral cage can be easily produced by automatic processing, which will dramatically reduce labor force and is suitable for precast construction. The major parameters of this study included the cost effectiveness of the multiple spirals, and the axial strength and seismic performance of the spirally confined SRC columns. As compared to the reinforced concrete column tied with traditional rectangular hoops, the test results revealed that, with significant saving of the consumption of the confinement steel, the SRC columns confined with the multiple spiral cage demonstrated excellent performances in both strength and ductility.