Flexural behavior of functionally graded concrete beams with different patterns

• Published in: Archives of Civil and Mechanical Engineering 2021-10, Vol.21 (4), p.169, Article 169
• Main Authors: Othman, M. A., El-Emam, H. M., Seleem, M. H., Sallam, H. E. M., Moawad, M.
• Format: Article
• Language: English
• Subjects: Aggregates; Bending stresses; Cement; Civil Engineering; Compression zone; Compressive strength; Concrete; Engineering; Fiber reinforced concretes; Fiber volume fraction; Flexural strength; Lightweight concretes; Mechanical Engineering; Modulus of rupture in bending; Numerical models; Original Article; Reinforced concrete; Reinforcing steels; Steel fibers; Structural Materials
• ISSN: 2083-3318; 1644-9665; 2083-3318
• DOI: 10.1007/s43452-021-00317-0

Flexural behavior of functionally graded concrete (FGC) beams was experimentally investigated. Fourteen sets of beams, including full depth (FD) fiber-reinforced concrete (FRC) and FGC with different patterns and fiber volume fractions (V f %), were investigated under three-point bending. These patterns consisted of three layers with a constant middle part of lightweight concrete. The upper layer in the compression zone was either normal strength concrete or FRC having different V f %. The lower layer in the tension zone was made from either FD FRC has the same V f % or functionally graded FRC. The fibers used were hooked end steel fibers with V f % of 0.5, 1.0, and 1.5%. The experimental results were also analyzed numerically and analytically. The experimental results showed that the flexural strength of FGC patterns ranged between 94 and 100% from that of FD FRC beams. However, their toughness indices ranged between 49 and 93% of the corresponding value of FD FRC beams. These ratios depend on V f % and the presence of fibers in the compression zone. The effect of V f % is more obvious in the descending part of the load–deflection curve than the ascending part due to the presence of fibers bridging phenomenon following the maximum load. V f % is more pronounced in the descending portion in all FGC patterns than in the FD FRC beams. There is a good agreement between the experimental results and those predicted by analytical and numerical models.