新型預力混凝土梁扭力實驗

New Torsion Experiment of Prestressed Concrete Beams

林廷衞(Ting-Wei Lin)

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(2016年)

摘要

本研究延續前期研究中空鋼筋混凝土(RC)梁扭力實驗，將實驗推展至預力混凝土(Prestressed Concrete, 簡稱PC)梁實驗，設計製作五組PC梁試體，其中，四組為實心斷面一組為中空斷面試體，改變斷面尺寸、混凝土強度、預力比及鋼筋量進行純扭力試驗，並將實驗結果與一初步理論分析做比較。
本試驗製作之PC梁試體可分為三個部分：固定端之RC block、測試區主梁、及轉動端十字型RC橫梁。試驗前在預埋的預力套管安裝鋼絞線、端錨等裝置，再使用後拉法施加預力。實驗量測包括扭矩、扭轉角、剪力流有效厚度 、鋼筋和混凝土表面應變、試體縱向伸長、及預力鋼腱拉力等。
實驗結果顯示，5組PC梁試體混凝土強度與預力比愈高韌性愈低，且預力比愈大混凝土表面裂縫水平斜角愈小。試體B17、B19、C11在開裂點前的扭矩-扭轉角曲線與理論分析曲線大致符合；試體A09的扭矩-扭轉角曲線在達到極限點前都與理論分析曲線高度吻合；試體B-090-06(中空斷面)的全程扭矩-扭轉角曲線皆與分析曲線相當一致。試體B-090-06預力鋼腱張力實驗值與分析值相當接近。

關鍵字

預力混凝土 ； 扭力 ； 實驗 ； 梁 ； 扭矩 ； 扭轉角

並列摘要

As a succeeding part of the previous research on reinforced concrete (RC) beams, this study extended the torsional experiment to prestressed concrete (PC) beams by conducting test on five PC beam specimens subjected to pure torsion. This thesis describes the experimental project and presents the experimental results. The experimental results are also compared with the analytical results using a rudimentary theoretical model.
Each of the PC beam specimens consists of three parts: the RC block at the fixed end, the middle longitudinal test beam, and the cruciform transverse beams at the twist end. Before the test, the prestressing strands and end anchorages were installed into the embedded ducts and the prstressing forces were applied in a post-tensioned manner. Eight quantities were experimentally determined for each specimen, including (1) torque, (2) twist angle, (3) thickness of the shear flow, (4) longitudinal elongation of test beam, (5) strain of nonprestressing reinforcing steel bar, (6) diagonal compressive strain at concrete surface, (7) diagonal tensile strain at concrete surface, and (8) prestressed forces.
The test results of the five specimens showed that higher concrete strengths and higher prestressing levels tended to reduce the torsional ductility, and that higher prestress ratios decreased the inclination angles of the concrete cracks. The experimental torque-twist curves of specimens B17, B19, and C11 agree reasonably well with the analytical curves before cracking point. The experimental torque-twist curve of specimens A09 coincides with the analytical curve almost perfectly before ultimate-torque point. The entire experimental torque-twist curve of specimens B-090-06 (hollow) closely agree with the analytical curve, and its experimental values of tendon stress also match the analytical values closely.

並列關鍵字

prestressed concrete ； torsion ； experiment ； beam ； torque ； twist

參考文獻

Chander, H., (1967), Behavior of Prestressed Concrete Rectangular Members Subjected to Pure Torsion, PhD dissertation, West Virginia University, Morgantown, West Virginia, USA, 148 pp.

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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.

Jeng, C.-H. (2010), “Simple Rational Formulas for Cracking Torque and Twist of RC Members,” ACI Structural Journal, Vol. 107, No. 2, Mar.-Apr.

Jeng, C.-H., Peng, X. and Wong, Y. L. (2011), “Strain Gradient Effect in RC Elements Subjected to Torsion,” Magazine of Concrete Research, Vol. 63, No. 5, pp.343-356, May.