高強度鋼筋混凝土梁剪力強度與裂縫行為

Shear Strength and Crack Behavior of Concrete Beams Reinforced by High-Strength Longitudinal and Shear Reinforcement

黃婕渝(Chieh-Yu Huang)

指導教授 ： 歐昱辰

國立臺灣大學/工學院/土木工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202202814

摘要

ACI 318-19規範中，進行一般剪力設計時，剪力鋼筋降伏強度上限為420 MPa，用以控制斜向裂縫寬度。當使用之剪力鋼筋降伏強度高於規範限制，會導致斜向裂縫寬度增加且產生大量斜向開裂，違反規範在使用載重下的裂縫寬度限制，因此當使用高強度剪力鋼筋時，需特別關注斜向裂縫寬度發展情形。
本研究共規劃六座矩形梁試體進行簡支梁剪力試驗，試體採用高強度混凝土及高強度剪力鋼筋，由試驗結果探討高強度鋼筋混凝土梁構件之剪力強度及裂縫行為。結果顯示，斷面極限剪力強度與剪力跨深比 及剪力鋼筋間距成反比，與縱向鋼筋比成正比，且當採用較高強度之混凝土，高強度剪力鋼筋應變發展較為顯著，剪力強度有較好的發揮。僅試體B2-H350_B之剪力鋼筋未降伏，其餘試體剪力鋼筋皆於試體破壞前或試體達極限強度時降伏。降伏強度上限為600 MPa之計算結果，針對普通強度剪力鋼筋及高強度剪力鋼筋兩者之安全係數相近，本研究建議ACI 318-19[2]規範之剪力鋼筋降伏強度上限可由420 MPa提升至600 MPa。本研究以0.41～0.53 mm為使用載重下之容許剪力裂縫寬度，並將其定義為使用性需求，建議使用載重下之容許剪力強度。

關鍵字

高強度混凝土 ； 高強度鋼筋 ； 剪力強度 ； 剪力鋼筋降伏強度 ； 剪力裂縫控制

並列摘要

The yield strength of shear reinforcement has been limited to 420 MPa in ACI 318-19 to control the diagonal crack width, while ACI 318-19 permits this limit to be 550 MPa for seismic shear design. Nevertheless, the utilization of high-strength shear reinforcement with higher yield strain can lead to a larger diagonal crack width that probably violates the requirement of the codes at the service load. Thus, once high-strength shear reinforcement is used, the concern of diagonal crack width is raised when designing reinforced concrete beams.
In this research, a total of 6 simply supported beam specimens with high-strength concrete and high-strength reinforcement were tested. Test results showed that ultimate shear capacity is inversely proportional to shear span-to-depth ratio and spacing of the shear reinforcement, is proportional to ratio of longitudinal reinforcement. As observed, yielding of shear reinforcement occurred either before reaching, or at, the maximum loads in the most specimens, except for the specimen B2-H350_B. The ratio of shear capacity of normal-strength shear reinforcement and high-strength reinforcement were similar when limit of yield strength of shear reinforcement was 600 MPa. Analysis of the test data suggests that current ACI 318-19 limit on the yield strength of shear reinforcement can be extended from 420 MPa to 600 MPa. In this research, the equations of the allowable shear capacity at service stage were proposed. They were according to the allowable limit of crack width under service load, which were 0.41-0.53 mm.

並列關鍵字

High-Strength Concrete ； High-Strength Reinforcement ； Shear Strength ； Yield Strength of Shear Reinforcement ； Control of Shear Crack

參考文獻

[1] ACI Committee 224, “Control of Cracking in Concrete Structures (ACI 224R-01),” American Concrete Institute, Farmington Hills, Mich, 2001.

[2] ACI Committee 318, “Building Code Requirement for Structural Concrete (ACI 318-19) and Commentary,” American Concrete Institute, Farmington Hills, Mich, 2019.

[3] E. C. Bentz and M. P. Collins, "Updating the ACI shear design provisions," Concrete International, vol. 39, no. 9, pp. 33-38, 2017

[4] J.-Y. Lee, D. H. Lee, J.-E. Lee, and S.-H. Choi, "Shear behavior and diagonal crack width for reinforced concrete beams with high-strength shear reinforcement," ACI Structural Journal, vol. 112, no. 3, 2015.

[5] J.-Y. Lee, I.-J. Choi, and S.-W. Kim, "Shear behavior of reinforced concrete beams with high-strength stirrups," ACI Structural Journal, vol. 108, no. 5, 2011.