Evaluation of axial load-bearing capacity of concrete columns strengthened by a new section enlargement method
Abstract
The objective of this study is to evaluate the axial load-bearing capacity of section-enlargement concrete columns. To reach the objection, a new strengthened method in which columns are jacketed with a large welded octagonal stirrup at the center and four spiral stirrups at the corners of column is developed. The new section-enlargement method avoids interrupting existing columns and improves the reliability of strengthened part, besides, the confining stress generated by octagonal stirrup and spiral stirrups enhances the compressive strength and deformability of strengthened columns. In addition, sixteen large-scale concrete columns strengthened by the new strengthened method were tested under axial compressive loads. The experimental results show that the axial compression ratio of existing column generates stressstrain lag in strengthened part and decreases the load-bearing capacity of specimens; the stirrups in strengthened part significantly enhance the axial load-bearing capacity of specimens. According to confinement conditions, the cross-section of specimens is divided into five parts and the confinement factor for each part is calculated to establish the prediction models for the load-bearing capacity of specimens. Furthermore, by comparing the results between the developed model and existing models, the developed model has high accuracy in evaluating the load-bearing capacity of strengthened columns.
First published online 20 December 2021
Keyword : strengthened concrete columns, section-enlargement method, axial load-bearing capacity, confined concrete, prediction models
This work is licensed under a Creative Commons Attribution 4.0 International License.
References
American Concrete Institute. (2014). Building code requirements for structural concrete (ACI 318-14) and commentary.
Cao, Q., Tao, J., Ma, Z. J., & Wu, Z. (2017). Axial compressive behavior of CFRP-confined expansive concrete columns. ACI Structural Journal, 114(2), 475–485. https://doi.org/10.14359/51689450
Cheng, C. S. (2003). Theoretical analysis of load capacity of reinforced concrete columns strengthened with reinforced concrete cover. Hunan University, Hunan, China.
Ersoy, U., Suleiman, R., & Tankut, T. (1993). Behavior of jacketed columns. ACI Structural Journal, 90(3), 288–293. https://doi.org/10.14359/4236
European Committee for Standardization. (2005). Eurocode 2: Design of concrete structures: Part 1-1: general rules and rules for buildings (EN 1992-1-1). Brussels.
Hwang, Y. H., Yang, K. H., Mun, J. H., & Kwon, S. J. (2020). Axial performance of RC columns strengthened with different jacketing methods. Engineering Structures, 206, 110179. https://doi.org/10.1016/j.engstruct.2020.110179
Julio, E., & Branco, F. A. B. (2008). Reinforcing concrete jacketing-interface influence on monotonic loading response. ACI Structural Journal, 105(4), 471–477. https://doi.org/10.14359/19861
Liao, W. D. (2006). Theoretical research and application of enlarging section method in reinforcing axially loaded RC columns. Southwest Jiao-tong University, Chengdu, China.
Liu, W. (2005). Research on mechanism of concrete-filled steel tubes subjected to local compression. Fuzhou University, Fuzhou, China.
Luo, L. L. (1989). Calculation method of cross-section strength of concrete components strengthened by enlarged cross-section methods. Sichuan Building Science Research, 4, 17–20.
Mander, J. B., & Priestley, M. J. N. (1988). Theoretical stress-strain model for confined concrete. Journal of Structural Engineering, 114(8), 1804–1826. https://doi.org/10.1061/(ASCE)0733-9445(1988)114:8(1804)
Ministry of Housing and Urban-rural Development of the people’s Republic of China. (2010). Code for design of concrete structures (GB 50010-2010). China Building Industry Press.
Ministry of Housing and Urban-rural Development of the people’s Republic of China. (2012). Standard for test method of concrete structures (GB/T 50512-2012). China Architecture & Building Press.
Ministry of Housing and Urban-rural Development of the People’s Republic of China. (2014). Code for design of strengthening concrete struc-tures (GB/T 50367-2013). China Building Industry Press.
Su, S. Q., Feng, D. G., & Wang, Q. M. (1997). Calculation of load-capacity of axially compressive RC columns strengthened with enclosed rein-forced concrete. Journal of Xi’an University of Architecture and Technology, 29(4), 381–385.
Tang, Y. Q. (2000). Building reconstruction and severe defect treatment. China Building Industry Press.
Thermou, G. E., Papanikolaou, V. K., & Kappos, A. J. (2014). Flexural behavior of reinforced concrete jacketed columns under reversed cyclic loading. Engineering Structures, 76, 270–282. https://doi.org/10.1016/j.engstruct.2014.07.013
Vandoros, K. G., & Dritsos, S. E. (2008). Concrete jacket construction detail effectiveness when strengthening RC columns. Construction & Building Materials, 22(3), 264–276. https://doi.org/10.1016/j.conbuildmat.2006.08.019
Zhang, J. S. (2004). Development of seismic evaluation and strengthening techniques in China. Earthquake Resistant Engineering and Retrofitting, 5, 33–39.
Zhang, Z. M., Xue, D. T., & Su, S. Q. (2001). Non-linear finite element analysis of RC column strengthened with enclosed reinforced concrete. Chinese Quarterly of Mechanics, 22(2), 221–227.
Zhang, Z. M. (2016). The compressive bearing capacity of normal section of RC short column reinforced by section-increased method considering secondary loading. Fuzhou University, Fuzhou, China.