混凝土桿件新型純扭力實驗—以中空鋼筋 混凝土梁扭力試驗為例

A New Pure-torsion Experiment for Concrete Members—Torsion Tests on Hollow Reinforced Concrete Beams

賴逸倫(Yi -Lun Lai)

指導教授 ： 鄭全桓

國立暨南國際大學/科技學院/土木工程學系/碩士(2012年)

https://doi.org/10.6837/NCNU.2012.00124

摘要

本論文描述四組中空鋼筋混凝土(reinforced concrete, RC)梁試體純扭力試驗。設計梁寬 50 cm、設計梁深75和71.1 cm。梁測試區長度3.5 m；含固定端及轉動端，試體縱向全長為5.76 m。四組試體之混凝土設計強度為 45 、70 、100 MPa，中空斷面設計壁厚分別為12 cm、8.5 cm、15.5 cm、8.7 cm。 以往實驗多著重在大(極限)扭矩及大扭轉角，開裂前後之扭轉角量測誤差大多相當可觀。因為，一者目前的SMMT 理論已可模擬開裂前後行為，二者開裂前後扭矩-扭轉角曲線可提供桿件線性扭轉勁度(e.g.供三維有限元素分析使用)，因此本研究針對以往實驗多不易準確量測開裂扭轉角的問題，做了若干新嘗試。以往實驗多使用鋼夾具傳遞扭轉力矩，夾具和試體間的微小滑移量很難消除，對小扭轉角量測可能造成可觀誤差。本實驗為消除微小滑移量，於扭轉端使用一體澆置的橫向RC 梁傳遞扭矩，於固定端則設計一RC block、並使用預力鋼棒施預力將其固定在下方的基座及強力地版。本實驗為使扭轉力矩有效傳遞，於轉動端上下盤間使用新型的曲盤設置，於致動器傳力元件增加新型的傳力設置。實驗量測包括開裂點在內的全程扭矩、扭轉角、剪力流有效厚度 td、鋼筋和混凝土表面應變、及試體梁縱向伸長等。本論文描述其試體製作、試驗裝置、量測設施、安裝程序、試驗過程，並呈現此四組試體之實驗結果。 關鍵字: 鋼筋混凝土，中空斷面，扭力，實驗，梁，扭矩，扭轉角

關鍵字

鋼筋混凝土 ； 中空斷面 ； 扭力 ； 實驗 ； 梁 ； 扭矩 ； 扭轉角

並列摘要

This thesis describes the tests of four full-size hollow reinforced concrete (RC) beams subjected to pure torsion. The designed width and depth of the beam specimen is 50 cm 75 cm or 71.1 cm. The length of the beam testing zone is 3.5 m; the longitudinal length of entire specimen is 5.76 m. The designed compressive strengths of concrete are 45, 70, 100 MPa, and the wall thicknesses of the hollow cross section are 12 cm, 8.5 cm, 15.5 cm, and 8.7 cm.
Most previous torsion tests of RC beams emphasized large (ultimate) torque and large twist angle, and the deviation in small-twist measurement were appreciable. Since the SMMT theory can now analyze the ranges before and after cracking and the cracking torque and twist can provide linear torsional stiffness for the members, this study aimed at developing a new test setup and method that can achieve precise small-twist measurement. Most previous torsion tests of RC beams used steel members to clamp the RC specimen and exert the applied torque. Such setups, however, often had inevitable gaps and slips between the clamping steel members and the RC specimens, introducing significant errors for small twist measurement. To overcome this handicap, this experiment uses a monolithic transverse RC beam to convey the applied torque at the twisting end of the specimen, and designs a monolithic RC block at the fixed end. The RC block of a specimen is also fastened to the underneath steel seat and strong floor using prestressed steel rods. To effectively transmit the applied torque, a novel curved device is used between the upper and lower unit of the twisting end, and a new force transmission setting is added to the force delivering members linked to the actuator. The torque, twist angle, shear flow zone thickness, steel and concrete surface strains, and longitudinal elongation of the specimens are continuously measured and recorded in the tests. This thesis describes the test specimens construction, test equipments, measurement facilities, installation and test procedure, and presents the experimental results of four specimens.
Keywords: reinforced concrete, hollow section, torsion, experiment, beam, torque, twist angle

並列關鍵字

reinforced concrete ； hollow section ； torsion ； experiment ； beam ； torque ； twist angle

參考文獻

參考文獻

ACI Committee 318 (2008), “Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary,” American Concrete Institute, Farming Hills, Mich., pp.465.

Bernardo, L. F. A. and Lopes, S. M. R. (2009), “Torsion in High-Strength Concrete Hollow Beams: Strength and Ductility Analysis,” ACI Structural Journal, Vol. 106, No.1, Jan.-Feb., pp.39-48.

Hsu, T. T. C. and Mo, Y. L. (1985), “Softening of Concrete in Torsional Members—Theory and Tests,” ACI Journal, Proceedings, Vol. 82, No. 3, May-June., pp.290-303.

Jeng, C.-H. and Hsu, T. T. C. (2009), “A Softened Membrane Model for Torsion in Reinforced Concrete Members,” Engineering Structures, Vol. 31, No. 9, Sept., pp.1944-1954.