雙核心自復位消能斜撐之發展與驗證

Abstract

預力自復位斜撐是利用斜撐中之拉力構件束制斜撐中之受壓構件，並在斜撐受拉與受壓下提供自行復位之能力(在大變形下有回到零殘餘變形的能力)。而傳統自復位斜撐之變形能力受制於拉力構件之線彈性範圍之應變量，使目前自復位斜撐之極限應變量僅1.3%，對應之層間位移角為2%，而拉力構件之應變量達1.9%。線彈性應變範圍超過2%之材料鮮少，且不易取得，大部分以複合材料為主。本研究提出一新型預力自復位斜撐，增加一核心受壓構件與一組拉力構件，使斜撐之變形量在拉力構件相同應變下可達傳統自復位斜撐變形量之兩倍(或是在相同斜撐變形量下，新型斜撐之拉力構件應變量減少一半約1.0%)。本研究設計四組新型雙核心自復位斜撐與驗證其力學行為，其中四組斜撐所使用之拉力構件分別為D16鋼角線、D22玻璃纖維棒、D29玻璃纖維棒與D13碳纖維棒。實驗結果顯示雙核心自復位斜撐之力學傳力機制與理論預測相符，而對應1.2%斜撐應變與2%層間位移角之拉力構件應變量分別為0.8%、1.05%、0.9%與1.09%，皆與預測之應變量接近，並大量降低拉力構件之線彈性應變需求量。試驗中除了使用鋼角線之試體有預力損失現象，其餘三支試體皆有良好的自復位行為。本研究使用ABAQUS有限元素軟體分析四支試驗試體之行為，分析結果與預測及試驗結果符合，並對於大小預力、大小摩擦力及不同材質之拉力構件作參數研究，了解在預力大於摩擦力時才有完整之自復位行為，而摩擦力之大小決定其消逝能量之大小，但大預力會導致變形能力受限。而拉力構件之材質只影響迴圈之後勁度，並且該線彈性應變範圍影響斜撐之變形能力。

Self-Centering Energy Dissipative Brace is a kind of brace which uses tendons to constrain compression elements of the brace and provide self-centering properties under tension and compression force (restore to zero residual deformation). Traditional self-centering energy dissipative brace’s deformation capacity relies on the elastic deformation capacity of the tendons used inside the brace, and results in limitation of the braces’ deformability. Traditional SCED brace has a maximum strain of 1.3% when the tendons reach 1.9% strain and the frame reaches 2% inter-story drift. Tendons required to have large elastic strain mainly uses composite material. However, tendons having over 2% elastic strain material properties are rare and seldom used or researched. This research develops a new kind of SCED brace by adding a second core element and another group of tension elements which doubles the deformation capacity compared to traditional SCED brace while using tension elements comprised of the same material properties (or largely reduce the elastic strain demand of the tendon elements to 1% under the same brace deformation when compared to traditional SCED brace). This research designed four specimens to validate the double core SCED brace which uses different materials for its tendons. Four specimens’ tendon uses D16 steel strand, D22 glass fiber, D29 glass fiber and D13 carbon fiber respectively. The results show that the mechanism of double core SCED brace is consistent with prediction. The test results and prediction of tendon strain is close which is 0.8%, 1.05%, 0.9% and 1.09% for specimen 1 to 4 respectively while the brace has a 1.2% strain corresponding to 2% inter-story drift. The result shows that double core SCED brace can significantly reduce the demand for tendon elastic strain. Except specimen 1 due to loss of pre-tension force has poor behavior in self-centering, specimen 2 to 4 have good behavior in self-centering with no pre-tension loss. This research also uses the finite element software ABAQUS to analyze double core SCED brace behavior and compare with the testing results which is proved similar. The parametric study of double core SCED brace we choose different pre-tension force, different friction force, and different tendons to observe the difference in brace behavior. Results indicate that the lager the friction force is the larger the energy dissipation there will be, yet in order to have full self-centering behavior, the pre-tension force should be larger than friction force. However the larger the pre-tension force is the smaller the deformation capacity there is left. Unlike pre-tension force and friction force, the difference of tendons only effect the post-stiffness of the response and limits the deformation capacity due to its limitation in elastic strain.