Stress Loss of Pre-Tensed CFRP Strips Strengthening Square RС Column

Abstract:

Pre-tensing the CFRP strip strengthening RC column can improve the strain lag of the confined concrete and avoid unloading of column in advance. The pre-stress of strip has an important influence of strengthen. Stress loss of the strip pre-tensed by using the device proposed were investigated by using an experimental test. Firstly, the reasons for the stress loss of strip were analyzed according to the working principle of the device and the strengthening procedure. Then the primary causes of the stress loss, such as friction, relaxation and removing device, were experimentally tested. The influence of the pretension, detail and sectional geometric dimension on the stress loss of the strip were studied. The results show that all three types of pre-stress losses increase significantly with the initial stress. Increasing the cross-sectional size would reduce the relaxation and unwinding losses, but it has little effect on friction losses. The influence of fillet radius on the pre-stress loss was negligible, but in order to avoid premature tearing of local CFRP caused by stress concentration, the chamfer should be made as large as possible within the thickness of concrete protective cover. The test also found that friction was the main cause of stress loss, and friction loss accounts for more than 90% of the total loss.

• Periodical: Key Engineering Materials (Volume 871)
• Pages: 321-329
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.871.321
• Online since: January 2021
• Authors: Zhao Qi Wu*, Min Shi, Sheng Ping Wu, Hua Li, Han Liu
• Keywords: Belt Tensioning Device, Pre-Stress Loss, Pre-Stressed CFRP, Square RC Column

References

[1] Teng J G, Chen J F, Smith S T, et al. FRP: strengthened RC structures [J]. Frontiers in Physics, 2002: 266.

[2] Smith S T, Kim S J, Zhang H. Behavior and effectiveness of FRP wrap in the confinement of large concrete cylinders [J]. Journal of Composites for Construction, 2010, 14(5): 573-582.

DOI: 10.1061/(asce)cc.1943-5614.0000119

[3] Gu D S, Wu G and Wu Z S. Ultimate flexural strength of normal section of FRP-confined RC circular columns. Journal of Southeast University (English Edition), 2010, 26(01): 107-111.

[4] Feng P, Lu X Z and Ye L P. Infrastructure application of FRP composites.Beijing: China Architectur Publishing Press, 2011. (in Chinese).

[5] Zhou C, Qiu Y, Pan Q. Experimental investigation of axial compressive behavior of large-scale circular concrete columns confined by pre-stressed CFRP strips[J]. Journal of Structural Engineering, 2019, 145(8): 1-17.

DOI: 10.1061/(asce)st.1943-541x.0002351

[6] Yang Y, Li Hui, Chen Wei, et al. Experimental study on seismic behavior of reinforced concrete frame structure retrofitted by pre-stressed steel strips. Engineering Mechanics. 2017, 34(10): 53-60. (in Chinese).

[7] Zhou C D, Chen J and Zeng X L. Research on seismic behavior of circular RC hollow high-pier strengthened with pre-stressed CFRP. Journal of Basic Science and Engineering. 2016, 24(04): 804-812. (in Chinese).

[8] Cheng D H, Yu Y N and Ye X. Mechanical properties of low strength concrete square-columns strengthened with prestressed CFRP sheets. Journal of Architecture and Civil Engineering. 2013, 30(01): 25-31. (in Chinese).

[9] El-Sokkary H, Galal K. Performance of eccentrically loaded reinforced-concrete masonry columns strengthened using FRP wraps[J]. Journal of Composites for Construction, 2019, 23(5): 04019032.

DOI: 10.1061/(asce)cc.1943-5614.0000958

[10] Yan Z, Pantelides CP. Concrete column shape modification with FRP shells and expansive cement concrete[J]. Construction and Building Materials, 2011, 25(1): 396-405.

DOI: 10.1016/j.conbuildmat.2010.06.013

[11] Janke L, Czaderski C, Ruth J, et al. Experiments on the residual load-bearing capacity of pre-stressed confined concrete columns[J]. Engineering Structures, 2009, 31(10): 2247-2256.

DOI: 10.1016/j.engstruct.2009.04.006

[12] Lu C L, Wu Y S, Wang Q, et al. Experimental research on the prestressing loss of square concrete columns strengthended with prestressed CFRP sheets. Industrial Construction. 2017, 47(11): 41-46+22. (in Chinese).

[13] Wu Z Q, Zhang Z X, Li H. Novel tensioning device for reinforcing column with prestressed fiber strips, CN 206636248U (2017) (in Chinese).

[14] Zhou C D, Li J and Lv X L. Experimental research on pre-stress loss of concrete circular columns confined with post-tensioned FRP. Journal of Tongji University: Natural Science. 2012, 40(12):1760-1765. (in Chinese).

[15] Lu C L, Liu C C, Wu Y S, et al. Experimental study on prestress loss of concrete circular columns strengthened with prestress CFRP sheets. Journal of Highway and Transportation Research and Development. 2018, 35(09): 41-48+70. (in Chinese).