含T字型鋼骨斷面之包覆型鋼骨鋼筋混凝土梁柱構材之耐震行為

Abstract

鋼骨鋼筋混凝土(SRC)結構經過適當的設計能兼具鋼筋混凝土結構及鋼結構的優點，然而過去的研究及相關的設計規範均較著重雙對稱斷面之梁柱構材，極少探討非對稱鋼骨斷面SRC構材之行為。由於工程實務上的使用需求，如邊柱，因此非對稱鋼骨斷面在SRC結構的領域中實有其深入研究的必要。 本研究之試驗規劃製作28組含T字型鋼骨斷面之包覆型SRC梁柱試體，以探討其耐震行為，實驗參數包括主筋數量、是否配置繫筋、箍筋間距、彎矩作用方向、軸力比及細長比。試驗結果顯示，額外配置主筋及繫筋與良好的箍筋間距將可增加SRC梁柱之極限強度及韌性，並有助於改善其承受正負彎矩遲滯迴圈的差異性。細長比大的SRC梁柱試體於極限強度及韌性上的表現均較細長比小者為差。研究結果亦顯示，ACI規範能合理且保守地預測含偏心T字型鋼骨之SRC梁柱的極限斷面彎矩值，且能準確地預測出細長柱之彎矩放大係數。

SRC beam-columns with T-shaped steel section can be arranged to connect the beams for the architectural reason. However, the eccentricity and unsymmetricity of the T-shaped steel section on the x-axis will lead to the difference of flexural strength and ductility as well as the seismic behavior in the positive and the negative moment directions when the column subjects to a cyclic lateral load. Therefore, seismic behavior of SRC beam-columns with T-shaped steel section must be investigated. Twenty-eight concrete-encased T-shaped steel section composite beam-columns were tested under constant axial load and cyclic lateral load. The variables of the specimens included the number of longitudinal bars, hoop spacing, presence of the crosstie, the magnitude of the axial load, and the slenderness ratio. The test results showed that the flexural strengths of the SRC columns in the positive and the negative moment directions about the x-axis, with respective to the unsymmetrical steel section, can be achieved to have equal amount by adding the additional longitudinal bars. Designing the hoop spacing according to the ACI seismic code and using crosstie can enhance the ductility of the SRC columns. The flexural strength of the SRC columns with high slenderness ratio was lower than those with low slenderness ratio. The flexural strength calculated according to ACI code expressions can predict the flexural strength of the tested SRC columns reasonably and conservatively with 83% accuracy. The moment magnifier also can be forecasted perfectly with 99% accuracy.