鋼筋混凝土梁之最大剪力鋼筋量研究

A Study on Maximum Amount of Shear Reinforcement of Reinforced Concrete Beams

孫宗梅(Tsung-Mei Sun)

指導教授 ： 黃世建

國立臺灣大學/工學院/土木工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201801501

摘要

鋼筋混凝土梁的剪力強度，來自混凝土與剪力鋼筋的剪力強度貢獻。若希望提升鋼筋混凝土梁的剪力強度，可增加斷面的剪力鋼筋量。剪力破壞可分為斜拉破壞及剪壓破壞，當鋼筋混凝土梁配置之剪力鋼筋量提升至一定上限時，梁會由剪拉破壞轉變成剪壓破壞，造成剪力強度無法隨著剪力鋼筋量上升而持續上升。上述兩者均屬於脆性剪力破壞；但剪拉破壞之破壞程序較剪壓破壞和緩。為了排除剪壓破壞發生的可能，需要規定最大剪力鋼筋量上限，以控制斷面剪力鋼筋之配置數量。目前 ACI 318-14 規範規定了最大剪力強度設計上限，即 V_s≤4V_c。但規範對於梁在何種情形下會轉換破壞模式，以及對於此設計上限之物理意義，尚未提出剪力傳遞模型來解釋此一現象發生之原因。
本論文將提出一般梁之剪力傳遞模型，並建立鋼筋混凝土梁資料庫，以驗證剪力傳遞模型於強度預測及破壞模式預測之準確性，並且利用解析模型，解釋剪拉破壞轉變成剪壓破壞之破壞模式的轉換，以了解剪力如何傳遞，也希望藉由剪力強度影響參數之比對，提出最大剪力鋼筋量的建議計算公式，能夠提供工程設計上最大剪力鋼筋量之設計依循。

關鍵字

鋼筋土混凝土梁 ； 剪力強度 ； 最大剪力鋼筋量

並列摘要

Shear strength of reinforced concrete beams is derived from shear strength contribution of concrete and shear reinforcement. If we want to increase the shear strength of reinforced concrete beams, we can increase the amount of shear reinforcement in the section. The proposed model recognizes two failure modes, which are shear tension and shear compression. When the amount of shear reinforcement is raised to upper limit, the beam will be transformed failure modes from shear tension into shear compression. Therefore, the shear strength cannot continue to rise as the amount of shear reinforcement increases. Both of failure modes belong to brittle shear failure; however, the destruction process of shear compression is more dramatic than shear tension. In order to eliminate the possibility of shear compression, it is necessary to specify the maximum amount of shear reinforcement to limit the number of shear reinforcements. The current ACI 318-14 specification specifies the maximum amount of shear reinforcement. That is V_s≤4V_c. However, the specification does not propose a shear transfer model to explain the reason why this phenomenon occurs and does not provide the physical meaning of the upper limit.
This paper will propose a shear transfer model and build a reinforced concrete beam database to verify the accuracy of the shear transfer model in prediction of strength and failure mode. Then, use the proposed model to explain the transformation of the shear failure modes and comprehend how the shear force is transmitted. In addition, it is hoped to propose calculation formula for the maximum amount of shear reinforcements by using the comparison of influence parameter to provide the design of the maximum shear strength of the engineering design.

並列關鍵字

Reinforced Concrete Beams ； Shear Strength ； Maximum Amount of Shear Reinforcement

參考文獻

1.ACI 318-14 (2014), “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (318R-14),” American Concrete Institute, Farmington Hills, Mich., 520 pp.

2.Clark, A. P. (1951), “Diagonal Tension in Reinforced Concrete Beams,” ACI Journal, Proceedings V. 48, No. 2, Feb., pp. 145-156.

3.Collins MP, Vecchio FJ. (1986),“ The modified compression-field theory for reinforced concrete elements subjected to shear.” ACI Journal Proceedings, V .83., No. 2, Jan, pp. 219-231.

4.Enomoto, H.; Iwai, I.; Kakita, Y.; Watanabe, F. (1990); and Muguruma, H., “Shear Strength of High Strength Concrete Beams, Part 1,” Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, pp. 287-288.

5.Fukuhara, M., and Kokusho, S. (1982), “Effectiveness of High Tension Shear Reinforcement in RC Members,” Journal of Structural Construction Engineering, Architectural Institute of Japan, No. 320, pp. 12-20.