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  • 學位論文

實心與中空預力混凝土梁之扭力實驗與開裂扭矩

Torsion Experiment and Cracking Torques of Solid and Hollow Prestressed Concrete Beams

指導教授 : 鄭全桓

摘要


摘要 本論文延續前期研究預力混凝土(Prestressed Concrete, 簡稱PC)梁扭力實驗,依不同斷面尺寸、混凝土強度、鋼筋量及壁厚比設計製作一組實心與四組中空PC梁試體,進行純扭力實驗。本論文並將本研究五組、以及本系列前期研究六組,共11組PC梁試體的實驗結果,與一套受扭RC桿件開裂點前(pre-cracking)統一解析公式的計算值進行比較與討論。 本研究實驗沿用前期研究實驗裝置與方法,所製作之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的十字型RC橫梁。於試驗前在試體預埋的預力套管內安裝鋼鉸線和端錨等裝置,再使用後拉法施加預力。實驗量測的數據包括扭矩、扭轉角、剪力流有效厚度 、鋼筋應變、混凝土表面應變、預力鋼腱拉力及試體縱向伸長等。 實驗結果顯示,五組PC梁試體的扭矩-扭轉角實驗曲線的初始線段近乎直線,無任何夾具滑移或摩擦跡象,所得成果將能提供探討PC梁開裂前後扭力行為所需的精確實驗資料。本系列11組PC梁試體實驗值與上述RC開裂前解析公式比較結果顯示,實驗開裂扭矩(PC)與計算開裂扭矩(RC)之比值大致隨著預力比增大而變大。其中,實心PC梁試體在預力比大約介於0.09至0.16之間時,開裂扭矩比大約自1.2隨著預力比增加而線性增大至1.8;當預力比超過約0.16以上時,此開裂扭矩比趨近於約1.8的上限值。

關鍵字

預力混凝土 實驗 扭矩 扭轉角 開裂扭矩

並列摘要


ABSTRACT As a succeeding part of the previous researches of prestressed concrete (PC) beams, this study extended the torsional experiment by conducting test on one solid and four hollow PC beam specimens subjected to pure torsion. The test results of eleven PC beam specimens, which consist of the five specimens in this study and six other specimens from the previous researches, are compared with predicted values calculated using a rational formula for pre-cracking torque-twist responses for reinforced concrete (RC) members. This study uses the test apparatus and method of the previous researches. Each of the PC beam specimens consists of three parts, namely, the RC block at the fixed end, the middle longitudinal test beam, and the cruciform transverse beams at the twist end. The anchorage bearing plates and longitudinal prestressing duct were embedded in the concrete of each specimen. After the specimen had been cast and reached its concrete strength, the longitudinal prestressing forces were applied by tensioning the individual strands one by one. Eight quantities were experimentally determined for each specimen using continuous measurement and automatic data reading and recording: (1) torque, (2) twist angle, (3) thickness of shear flow zone, (4) strain of nonprestressing reinforcing steel bar, (5) diagonal compressive strain at the concrete surface, (6) diagonal tensile strain at the concrete surface, (7) longitudinal prestressing force, and (8) longitudinal elongation of test beam. Test results of the five specimens exhibited a high degree of linearity in the initial branches of the five experimental torque-twist curves, showing a high level of accuracy in the small-twist measurement. The comparison between the test results of the eleven PC beam specimens and the values calculated using the rational formula for RC members showed that the cracking-torque ratio increases with the increase of the prestress ratio . For the solid PC specimens, the cracking-torque ratio increases from 1.2 to 1.8 almost linearly when the prestress ratio increases from 0.09 to 0.16, and approaches asymptotically to the upper limit 1.8 when exceeds 0.16.

並列關鍵字

prestressed concrete experiment beam torque twist cracking torque

參考文獻


參考文獻
1. Chao, M., and Jeng, C.-H. (2016). Nov. “Pre- and Post-cracking Torsion in PC Beams: Experimental Study”, accepted by Magazine of Concrete Research.
2. 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, pp.290-303, May-June.
3. Hsu, T. T. C. and Zhu, R. R. H. (2002). “Softened Membrane Model for Reinforced Concrete Elements in Shear.” ACI Structural Journal, Vol. 99, No. 4, pp. 460-4690, July-Aug.
4. 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, pp.1944-1954, Sept.

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