Numerical Evaluations of Functionally Graded RC Slabs

Nowadays, using fibrous materials is used widely in strengthening applications such as cross-section enlargement and using functionally graded reinforced concrete. Functionally graded reinforced concrete is used as multireinforced concrete layers that can be reinforced by different fiber types. The objective of this research was to address the structural benefits of functionally graded concrete materials by performing analytical simulations. In order to achieve this purpose, in the first stage of this study, three functionally graded reinforced concretes by steel and polypropylene (PP) were experimentally tested under flexural loading. Inverse analysis was applied to obtain the used material properties of reinforced concrete by FEMIX software. After obtaining the material properties, to assess the performance of proposed slabs, some other cases were proposed and numerically evaluated under flexural and shear loading. The results showed that increasing steel fiber in reinforced entire cross section led to achieve better shear and flexural performance while the best performance of reinforced functionally graded slabs was achieved for slab at 1% fiber content. In the second stage, nineteen reinforced functionally graded RC slabs with steel bars were simulated and assessed and some other cases were considered which were not experimentally tested. 1. Introduction Using fibrous materials leads to improve mechanical properties of concrete. Fibers transfer stresses after cracking of concrete by bridging action and, subsequently, ductility and load transferring are increased. In this direction, wide studies have been conducted to manifest different effects of various fibers in concrete reinforcement. The effective parameters on mechanical performance of reinforced concrete are type, geometry, and orientation and volume contents of used fibers in the matrix [1]. Using fibers in order to reinforce cementitious composites leads to enhance both toughness and mechanical strength [2]. In the last four decades wide studies have been conducted on the flexural behavior of FRCCs [3]. According to Figure 1, fibers are categorized into three groups which include continuous fibers: long, straight, and generally layered-up parallel to each other; chopped fibers: short and generally randomly distributed (fiberglass); woven fibers: which come in cloth form and provide multidirectional strength. Figure 1: Various kinds of fibers which are used in FRC. According to material types, basic groups of fibers for using in the structural concrete are classified [4].(i)Steel fibers with