Volume 18, Issue 5 (2019)                   MCEJ 2019, 18(5): 79-90 | Back to browse issues page

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Zamani A, Mousavi S R, Beheshti Nezhad H. Influence of stirrups spacing on the flexural strength of lap spliced beams in corrosion condition. MCEJ. 2019; 18 (5) :79-90
URL: http://mcej.modares.ac.ir/article-16-12797-en.html
1- Dept. of Civil Engineering, Univ. of Hataf
2- Assistant Professor, Sistan and Bloochestan University
3- Dept. of Civil Engineering, Birjand Branch, Islamic Azad Univ, Birjand, Iran
Abstract:   (6026 Views)
The lap-splice length of reinforcing bars is one of the practical aspects of the bond between concrete and reinforcing bars. Providing the adequate bond between the reinforcing steel and concrete in splice length is essential in structural concrete design. The bond strength of spliced bars in concrete depends on several factors such as surface deformation of reinforcing bars, embedment length, concrete cover, bar diameter, confinement, concrete strength and environment conditions. One of the major degradation processes of bond strength in reinforced concrete is the corrosion of reinforcement. In addition, to reducing the bond strength, corrosion of reinforcement leads to reduced flexural capacity and serviceability of reinforced concrete structures and ultimately affecting the structural safety. There has been little discussion about the simultaneous effect of stirrup spacing and corrosion of reinforcements on bond strength and flexural strength of lap-spliced reinforced concrete beams. Therefore, in this research, the simultaneous effect of stirrups distance and corrosion level on the flexural strength and behavior of lap-spliced reinforced concrete beams with different stirrups spacing was experimentally investigated. A total of 12 reinforced concrete beams were constructed and tested. The test beams were 150 mm deep, 100 mm wide, and 1500 mm long. The beams were divided into three main groups according to the type of reinforcement corrosion, S: stirrup corrosion, T: tensile rebar corrosion, and W: stirrup and tensile rebar corrosion. Three different stirrup spacing (53mm, 80mm, and 160mm in splice length) were considered in each group. After constructing and curing the specimens for 28 days, we fully immersed them in ponds containing chloride sodium 5%, and accelerated corrosion procedure was simulated for them by applying an electrochemical method. The accelerated corrosion process was induced by impressing a constant direct current 150 µA/cm2, on average, on the tensile steel bars. The degree of corrosion in all of the beams was 10%. After the accelerated corrosion process was completed, the beams were subjected to four-point loading by a 100-ton universal testing machine with a speed of 2 mm/min. The results are discussed in terms of normalized bond strength and residual ultimate strength of corroded beams with different stirrups spacing in each group. The rust products of bar corrosion had greater volume than the steel which increases stress in the concrete and results in cracks in splice length in all beams. Due to these cracks, the bonding of bar and the concrete decreased. The use of stirrups with low spacing in splice length can increase the bond strength by controlling the crack widths and maintaining the bonding of concrete surrounding reinforcement. Of course it should be noted that in specimens in group S, the decrease of stirrup spacing led to decline the ultimate strength capacity. Corrosion cracks interaction was the cause of reducing the confinement of longitudinal reinforcements in Group S. At the same degree of corrosion, the average reduction of flexural strength in Groups S, T and W were 15.3%, 7.5% and 14.3%, respectively. The experimental results obtained in this study are close to the results of Esfahani and Orangan equations, and the amount of existing error can be corrected using the correction factor.
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Article Type: Original Manuscript | Subject: Earthquake
Received: 2017/11/25 | Published: 2019/02/15

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