無梁版構架系統需避免穿透剪力破壞，此破壞模式不但無預警，且容易造成大規模連續倒塌。過去研究顯示版柱接合部穿透剪力強度與樓版局部轉角相關，轉角變形越大則剪力強度越低(剪力衰減)，若能限制接合部樓版變形，應可有效提升接合部穿透剪力強度。據此，本研究針對無梁版構架系統提議強版弱柱的新構想，發展一新型柱使接合部變形能集中在柱端，要滿足此條件此柱應具有低勁度，且在大變形下能維持其設計軸力強度的特性。鋼管圍束鋼筋混凝土柱，將主筋集中在斷面中心應可滿足上述特性，藉由大尺寸構件實驗，本研究主要目的欲探討此設計之可行性。

本研究總共測試六組試體，主要測試變數包含：(1)斷面尺寸、(2)軸壓比、與(3)鋼管端部切削與否，所有試體在固定軸壓下承受往復水平載重，實驗結果發現所有試體均可維持軸力與彎矩強度超過層間位移角8%，實驗主要因安全考量而停止，試體變形量主要集中在柱端。就試體強度而言以ACI 318-19 (2019)計算之彎矩強度明顯低估試體之最大強度，因此本研究提出一強度預測模型，以合理評估試體強度。另外，試體撓曲剛度分佈約在0.5EcIe ~ 0.7EcIe間，變化主要與軸力大小有關，本研究因此提出一剛度模型以考量軸力變化對撓曲剛度之影響。

整體而言，在相同斷面與主筋比的情況下，新型柱強度較一般鋼筋混凝土柱高。撓曲剛度略低，惟試體在高軸壓下具有相當優異之變形能力，在相同軸力作用下，新型柱應可大幅縮小其斷面大小而不會影響其往復載重行為。

Slab-column connection is succeptible to punching shear failure. This type of failure has to be prevented due to its brittle failure mode and tendency to trigger progressive collapse. Previous studies have shown that punching shear capacity of slab-column connection decays as the connection rotation increases. Based on this, this study proposes a new idea for slab-column framed system-strong slab weak column. In this sytem, deformation is expected to be primarily absorbed at the column ends and thus reduce the connection rotation to sustain the connection punching shear capacity. The proposed column then needs to have lower lateral stiffness to absorb the connection rotation and sustain the designed axial load under larger lateral deformation. Those required charateristics may be achieved by using the steel tube confined reinforced concrete column with longitudinal reinforcement concentrated at the center of the cross section. A test program is conducted to investigate the potential of this new column.

A total of six specimens were tested in this study. The main test variables include: (1) section size, (2) axial compression ratio, and (3) whether the end of the steel tube is cut or not. All specimens are subjected to cyclic lateral load under fixed axial compression. Experimental results indicate that all test specimens sustain the designed axial force and peak lateral road to more than 8% drift. Tests are terminated due to safety concerns. Deformation appears to be concentrated at the end of column. The nominal flexural strength calculated by ACI 318-19 (2019) significantly underestimates specimen peak strength. A strength model is developed in this study to reasonably evaluate the strength of the specimen. The range of specimen flexural stiffness is between 0.5EcIe ~ 0.7EcIe. The increase of flexural stiffness appears to primarily associated with the axial force. A stiffness model is then proposed based on test results.

On the whole, the peak strength of the proposed column is higher than that of the typical reinforced concrete column with the same cross section and reinforcement ratio. Flexural stiffness of the proposed column is slightly lower. Considering that the proposed specimen has superior deformability under high axial load, the cross section of the proposed column can be further reduced without adversely impacting its cyclic behavior.

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