過去討論鋼筋混凝土柱-基礎接合部強度的相關文獻相當有限，惟近期研究(Worsfold and Moehle, 2019)顯示受彎矩主控之柱-基礎接合部在強度評估上還有許多研究空間，本研究延續去年的測試計畫(陳玠宏，2021)，設計、製作、並測試另外十組大型鋼筋混凝土柱-基礎試體，進一步探討不同設計參數下，以彎矩主控之鋼筋混凝土柱-基礎其接合部強度。

本研究十組試體主要測試變數包含：(1) 柱主筋錨定方式、(2) 基礎主筋量、以及(3) 基礎剪力鋼筋型式與配置。實驗結果顯示，在基礎版內無配置棒棒糖式繫筋或180-90彎鉤繫筋的五組試體其力量損失與接合部內產生錐形破壞面有關，此錐形破壞面應為錨栓群混凝土拉破造成，相較柱主筋以90度標準彎鉤且彎鉤向內錨定，柱主筋使用擴頭錨定可以傳遞較大的彎矩強度。以錨栓強度模型去評估這些試體最大側力發現ACI 318-19混凝土拉破強度、彎鉤錨定之單根錨栓拔出強度、以及混凝土剪破強度相當保守，應有合理提高的空間。本研究所建議之混凝土拉破強度提升係數，可以適當地評估去年六組試體測試結果。

另一方面，在基礎版內配置配置繫筋(棒棒糖式繫筋或180-90彎鉤繫筋)的情況下，另外五組試體其最大側力均達到柱底降伏強度，而側力損失主要因為柱主筋握裹破壞，這些試體在測試過程中可以聽到基礎版底有混凝土剝落之聲音，其中柱主筋使用擴頭錨定可以提供較佳錨定拉力、維持最大側力至較大位移，而彎鉤錨定鋼筋則因為延續端承載於基礎主筋上所以提供較佳壓力、其緊縮(pinching)情況較為緩和。

Existing researches on strength of the reinforced concrete (RC) column-foundation connection are limited. A recent study (Worsfold and Moehle, 2019) indicated that there is still some room for research on this subject. This research, as an extension of the study conducted last year (Chieh-Hung Chen, 2021), designed, constructed, and tested another 10 large-scale column-foundation specimens to further investigate the strength of RC column-foundation connection governed by moment transfer.

The key test parameters of the 10 specimens tested in this study included: (1) anchorage types of the column flexural reinforcement, (2) amount of foundation flexural reinforcement, and (3) shear reinforcement scheme in the connection. Test results showed that specimens without the use of candy-cane or 180-90 crossties failed due to the formation of cone-shape failure surface in the connection. Compared to the specimens anchored by 90 degree standard hooked bar with the tail bent inside, specimens anchored by T-head was able to transfer larger moment. Based on the maximum strength of these specimens, analytical results showed that concrete breakout strength in tension, pullout strength of a single bar, and concrete breakout strength in shear as per ACI 318-19 appeared to have room to increase. The proposed amplification factor for concrete breakout strength in tension appeared to be applicable to the six specimens tested last year.

For specimens with candy-cane or 180-90 crossties, on the other hand, maximum lateral strength of the rest of five specimens appeared to be limited by yielding of the column longitudinal reinforcement at the column base. The loss of lateral force was associated with the bond deterioration. The sound of concrete pieces falling on the ground was heard during the test of these specimens. Specimens anchored by T-head sustain the tension better to a larger deformation. Specimen anchored by hooked bar with the tail bend outside was able to distribute the compression force to the bottom foundation flexural reinforcement and thus alleviated the pinching behavior.

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