Cyclic Behavior of Concrete Beams with Unstressed Steel Strands as Longitudinal Reinforcement

• Main Authors: Meng-Yi Hsieh, 謝孟益
• Other Authors: Yu-Chen Ou
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/669s99

碩士 === 國立臺灣大學 === 土木工程學研究所 === 107 === This study mainly discusses the structural behavior of the unstressed steel strands replacing the traditional steel bars as the longitudinal reinforccement of the beam, and provides a new steel strand anchoring method for the joints. The method can effectively improve the steel strands with different kind of surface texture. Five real-size beam-column joint specimens are designed for testing how unstressed steel strands work in beam-column joint. According to the different replacement rate of steel strands, they can be divided into three grades, B grade (full reinforcement), BSR grade (mixed reinforcement), BST grade. (All steel strand reinforcement).3 seats are the T-shaped test pieces, covering the three grades described above; 2 seats are cross-shaped test pieces, only BSR grade and BST grade. The test method is to perform the cyclic loading on the beam end, and the upper and lower ends of the column are fixed by prestressed steel bars to simulate the true structural behavior of the moment-resisting frame against the lateral force. The loading duration is in accordance with the provisions of ACI 374.1, in order to benefit other beams in the future and help database established. In addition, this paper also discusses the crack control and displacement control of beams with unstressed steel strands under working load. According to Chen''s test results and analysis, it can be understood that using ACI 318-14 can effectively control crack developing on the specimens of B grade and BSR grade. Speaking of displacement control of beam, if the effective moment of inertia method in current code is used, the instantaneous deflection of specimens of B grade and BSR grade can be conservatively evaluated. Furthermore, if the B grade and BSR grade specimens increase their beam depth by 12% and 40% respectively, they have the same deflection control ability as the conventional reinforced concrete beams. In terms of strength design, according to the results of the beam-colum joint test and the test results of Chen Yuming''s beam, it is pointed out that no matter the amount of replacement of the strand, the nominal calculated bending moment according to the current specification are conservative. Although the energy dissipation status of all specimens are similar, the difference is mainly the toughness capacity. Among them, the B grade specimen and BSR grade specimen have significant toughness capacity. At the end of the text, a design method for replacing traditional steel bars will be proposed, including three parts, one is the control of cracks and displacement under working load, another is the design of unstressed steel strands member under ultimate strength, and the other is the design of sectional detailing.