高強度混凝土充填箱型鋼柱於大軸力下之耐震行為

Abstract

本研究探討混凝土充填高強度箱型鋼柱（CFBC）於大軸力下之耐震行為，主要試驗參數包括寬厚比、軸力大小及斷面配置，共計有六組試體，試驗內容為施加固定軸力並進行反覆側推試驗，方形斷面寬為420、400及280 mm，寬厚比分別為13、20及22 mm，使用高強度SM 570M鋼材（降伏強度420~540 MPa）及高強度混凝土（70 MPa）。研究結果顯示寬厚比增加會小幅降低柱韌性，軸力大小對柱韌性之影響非常顯著，銲接箱型斷面內充填混凝土與否對韌性並無明顯影響，寬翼斷面相較於方形斷面而言韌性較差。 歐洲EC規範及日本AIJ規範對於混凝土充填高強度混凝土充填箱型鋼柱之強度預測較為準確，美國AISC、美國ACI及台灣規範均過於保守；各規範對於高強度鋼柱之強度預測均偏於保守，對於寬厚比較小之試體，預測誤差更大。

The cyclic load behavior of concrete filled high strength box column (high strength CFBC) under large axial load was experimentally investigated. The parameters in the study included the width-to-thickness (b/t) ratio, axial load level and section type. Total six beam-column specimens were tested under constant axial load and increasing cyclic loading. The CFBC specimens were 280 to 420 mm in width and 2000 mm in height. Nominal b/t ratios varied from 11 to 30. All the specimens were made from high strength (SM 570M, 420~540 MPa) steel, and three of them were filled with high strength (70 MPa) concrete. Experimental results indicate that the ductility decrease significantly with an increase in either the axial load level or the b/t ratio of the steel. The ductility does not change significantly whether there is concrete infill in the steel box column. Eurocode (EC 2004) and Architectural Institute of Japan (AIJ 2010) can give good accuracy in predicting the flexural strength of high strength CFBC. American Institute of Steel Construction –Load and Resistance Factor Design (AISC-LRFD 2010), American Concrete Institute (ACI 2011) and Taiwan Steel Design Code (Taiwan Code) are too conservative in predicting the flexural strength of high strength CFBC. All the design code are a bit too conservative in high strength steel column moment capacity prediction. Especially the steel column with smaller b/t ratio, the error between prediction and actual moment strength become larger.