Journal of Advanced Concrete Technology Vol. 20, 732-746, December 2022 / Copyright © 2022 Japan Concrete Institute 732 Scientific paper Influence of Transverse Sectional Pre-crack on Shear Failure Behavior of RC Slender Beams Based on Experimental Loading Test Li Fu 1 , Lijia Zhang 2 , Qiangsheng Yin 2 , Hikaru Nakamura 3 and Dengfeng Wang 4 Received 2 September 2022, accepted 22 November 2022 doi:10.3151/jact.20.732 Abstract For the RC members under cyclic loading, flexural cracks commonly propagate in two opposite transverse directions at the zone under high bending moment and possibly form the cracks penetrating through the entire cross sections (pre- crack), which is considered as a crucial factor for flexure-shear failure of member. This paper clarified the influence of imitation pre-crack on the shear failure behavior of RC slender beams by three point bending test. Shear span depth ratio (a/d=3.14, 4.69) and location and thickness of pre-crack were set as main variables. As the important findings, it was revealed that the influence of pre-crack on the shear strength of RC slender beams is relatively small because it does not affect the formation of the critical diagonal crack and the mode of diagonal tension failure. It was also noted that the pre- crack at 2d (the section of pre-crack is 512 mm, which is twice of the effective depth d, far away from the loading plate center) leads to a reduction of shear strength with increasing pre-crack width, and the maximum reduction is 21.4%. Based on the detailed analysis of crack propagation, it was clarified that pre-crack may result in two patterns of critical diagonal crack, and in the condition that the pre-crack plane vertically intersects with the lateral splitting part of diagonal crack, the lateral splitting part becomes more severe and thereby reduces the shear strength and deformation ability. 1. Introduction Sectional crack is a typical crack pattern in reinforced concrete (RC) member and it can be caused by a variety of reasons. At the early age of service life, the effect of drying shrinkage or thermal stress may induce random distribution of sectional cracks, and a part of them possi- bly penetrate through the whole transverse section (pre- crack) in RC member under constraints. Corrosion of re- inforcing steel bars and drying shrinkage are common causes of deterioration of RC structures. Extensive cor- rosion of stirrups and high-shrinkage concrete (Nakarai et al. 2016) may cause sectional cracks distributed along the axis of RC member. Moreover, concrete is a highly path-dependent material memorizing the loading history through which it has experienced and cracking is one of the most dominant factors representing. That is, previous loading may lead to cracking and residual deformation and these may significantly affect the next loading event (Pimanmas et al. 2001a, 2001b; Toongoenthong and Maekawa 2005). A typical case is the shear failure after flexural yielding of RC member under cyclic load. For cyclic-loaded member, previous loading in positive di- rection may cause sectional flexure-cracks at one side un- der high bending moment, while the next loading in the negative direction may cause flexure-cracks at the other side. It was proposed that the propagation of the sectional flexure-cracks in opposite directions possibly connect to the former transverse sectional cracks, which is the typi- cal cracking history due to reversed cyclic loading (Fu et al. 2017a). Shear and flexure are the major structural concerns to RC member. Transverse sectional cracks do not seem to affect the flexural strength because concrete can still ac- quire compression after closure of transverse sectional cracks. On the other hand, the shear behavior, which is characterized by diagonal cracking, is a different story, because the path of diagonal crack may be blocked by transverse sectional crack plane. However, it is hardly possible to comprehensively analyze the influence of transverse sectional crack on RC behavior in shear due to lack of experimental methods artificially introducing de- sired transverse sectional crack into RC member. The controlling of crack parameter such as thickness and lo- cation along member axis is also difficult. Introducing desired damage such as initial crack and hollow holes into concrete member by artificial methods has been attempted by some researchers. Yamada (2019) introduced multiple small transverse holes into concrete beams by embedding hollow pipes, and clarified their 1 Associate Professor, Zhejiang Engineering Research Center of Intelligent Urban Infrastructure, Zhejiang University City College, Hangzhou, 310015, China; School of Environment and Civil Engineering, Jiangnan University, No. 1800 Lihu Avenue, Wuxi, Jiangsu Province, 214122, China. *Corresponding author, E-mail: [email protected] 2 Master’s course student, School of Environment and Civil Engineering, Jiangnan University, No. 1800 Lihu Avenue, Wuxi, Jiangsu Province, 214122, China. 3 Professor, Graduate School of Civil and Environmental Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan. 4 Associate Professor, School of Environment and Civil Engineering, Jiangnan University, No. 1800 Lihu Avenue Wuxi, Jiangsu Province, 214122, China.
Influence of Transverse Sectional Pre-crack on Shear Failure Behavior of RC Slender Beams Based on Experimental Loading Test
May 30, 2023
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