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سلوك الانحناء للاعتاب الخرسانية المسلحة الحاوية على الركام المعاد تدويره والمقواة بالياف الكربون == Flexural Behavior of Reinforced Recycled Aggregate Concrete Beams Strengthened by CFRP
Author name:
ملاك حيدر داود
Supervisor name:
علي كريم رزاق
General topic:
Civil Engineering
Specific topic:
Civil Engineering
Degree:
Master
University:
University of Thi-Qar - College Of Engineering - civil engineering Department
Language:
English
University location:
Dhi Qar
Key words:
- RCA
- CFRP
- Beams
- Flexural
Abstract:
Flexural behavior of reinforced concrete beam specimens containing recycled concrete aggregate (RCA) and strengthened externally by carbon fiber reinforced polymer (CFRP) sheets was discussed in this study. CFRP has been widely used to strengthen reinforced concrete members in recent years. In the experimental program, twelve reinforced concrete beams, 150×200 mm in cross-section over a total span of 1300 mm, with a tensile reinforcement ratio of 0.9%, with four-point load are tested. The beams were subdivided into two groups. The first group consists of four beams; one of them is a control beam with natural aggregate (NA), while the others contain different RCA ratios (30%, 50%, and 70%), whereas the second group consists of eight beams with a 50% RCA and uses CFRP sheets to strengthen them in various techniques. Two strengthening techniques were investigated:Externally bonded reinforcement (EBR) and externally bonded reinforcement on groove (EBROG). In general, the test results showed that the replacing of natural aggregate (NA) in the concrete mixes by recycled concrete aggregate (RCA) have a drop in the compressive strength, modulus of elasticity, flexural strength, and splitting tensile strength of plain concrete in varying proportions with increasing in the RCA ratio. As for reinforced concrete, the test results indicated that the flexural strength of RCA beams decreases significantly from 3% to 10.5% as RCA content increased. While the utilization of CFRP sheets to strengthen specimens caused an increase in the flexural strength of RCA beams, where the rate of increase ranged from 5% to 30.9% for the EBR method (one layer) and 30.5% to 40.4% for the EBROG method. Whereas, when two layers of CFRP sheets instead of one layer, the ultimate load capacity was about 19% greater than one layer of CFRP. Additionally, the investigated RCA concrete specimens showed four different II failure modes: flexural failure for unstrengthen beams, CFRP debonding, CFRP rupture, and concrete cover separation for strengthened beams. The failure modes of CFRP material in specimens enhanced by U-anchorages and EBROG have changed to rupture, whereas using two layers of CFRP changed the failure mode to concrete cover separation. The measured ultimate flexural loads of beam specimens without CFRP are compared with ACI 318-19, while the beam specimens with CFRP have been compared with ACI 440.2R, CNR-DT 200 R1, and the Teng et al. model. ACI 318- 19 gave a significant association with the experimental results of RCA beams. While the ACI 440.2R-17 and Teng et al. Model gave the best correlation with the experimental results of RCA beams with CFRP.
Full text:
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