五螺箍圍束鋼筋混凝土柱與 鋼骨鋼筋混凝土柱之軸壓行為

Abstract

本研究藉由理論解析的方法，探討五螺箍圍束方形之鋼筋混凝土（Reinforced Concrete, RC）與鋼骨鋼筋混凝土（Steel Reinforced Concrete, SRC）柱在承受軸向壓力之軸壓強度與韌性。研究方法為先探討五螺箍與傳統箍筋的差異性與特性，並建立螺箍與鋼骨圍束混凝土之材料組成律，以及定義主筋、鋼骨之應力－應變關係，最後藉由解析結果之力－應變關係，與先前之試驗結果相互比較，驗證解析模式的正確性。再用以進行參數分析，以探討螺箍間距、螺箍配置直徑、螺箍線徑、鋼骨型式與用量等，參數對軸壓強度之影響，以及參數對圍束效應在軸壓強度與韌性之影響。 研究結果顯示，參考Mander et al.、Saatcioglu and Razvi、Hoshikuma et al. 以及Légeron and Paultre圍束理論中所提出橫向箍筋之側向圍束應力，再利用理論的方法加以修正，可以合理的模擬五螺箍RC與SRC柱的參數變化，並準確的預測其極限軸壓強度、初始線彈性以及後期韌性。惟Hoshikuma et al. 理論解析值在極限軸壓強度、後期韌性有些微高估的趨勢。建議之解析模式能準確的預測試驗結果，驗證螺箍間距縮小有提升軸壓強度與圍束效果的趨勢。大小螺箍交集區配置縱向輔助筋之五螺箍RC柱，其軸壓強度與韌性提升並不明顯。因此若針對軸壓五螺箍RC柱而言，基於經濟上之考量，交集區可不配置輔助鋼筋。SRC柱試體受軸向壓力時，除了螺箍與主筋提供圍束混凝土之圍束效果之外，鋼骨亦提供對混凝土之圍束效果並提升軸壓強度與峰值後強度。本研究之解析模型能準確的預測五螺箍方形RC與SRC柱受軸向壓力之強度與軸力－應變曲線，並能反應出參數對圍束效應在軸壓強度與韌性之影響。

This study elucidates analytically the axial compressive load-carrying capacity and behavior of square reinforced concrete (RC) columns and steel reinforced concrete columns confined by five interlocking spirals. The study first investigated the differences and characteristics between five spirals and rectilinear hoops, and established the material constitution of the concrete confined by spiral and structural steel as well as the stress-strain relations of the longitudinal bar and structural steel. Finally, the force-strain relations calculated analytically were compared with previous test results to validate the analytical model. The analytical model was further used to conduct the parametric study to investigate the effects of the parameters, such as the spiral spacing, diameter of spiral layout, spiral bar diameter, and shape and amount of the structural steel section on the compressive strength and concrete confinement. Provided by the lateral tie, the lateral confined stresses proposed by Mander et al., Saatcioglu and Razvi, Hoshikuma et al., and Légeron and Paultre were modified in this study. The modified confined concrete models reasonably simulated the effects of the parameters for RC and SRC columns confined by five spirals, and accurately predicted the axial load-carrying capacity, initial linearly elastic behavior, and post-peak ductility. However, the model proposed by Hoshikuma et al. slightly overestimated the axial load-carrying capacity and post-peak ductility. Suggested models were able to accurately predict the test results, and confirmed that decreasing the spiral spacing resulted in the increase of the concrete compressive strength and concrete confinement. For five-spiral RC columns, the increases of the axial compression strength and ductility were insignificant when supplementary longitudinal bars were placed in the overlap area between large and small spirals. Thus, the supplementary longitudinal bars are not necessary for axially loaded five-spiral RC columns. In addition to the confinement contributed by the spiral and longitudinal bar, the structural steel section provided confinement effect on the concrete and enhanced the axial capacity and post-peak strength. The analytical model proposed can accurately predict the axial load-carrying capacity and the load-displacement relations of the five-spiral RC and SRC columns. The model also reflects the influences of the parameters on the confinement and further the axial compressive strength and ductility.