# Experimental Study and Modelling on the Structural Response of Fiber Reinforced Concrete Beams
## 1 Introduction  
Nowadays, development and introduction of more efficient mass-produced materials are among the main engineering challenges which can be encountered in all industrial areas. Today, concrete is the second most consumed material after water, with three tonnes of concrete being produced for every person living on the globe per year. Twice as much concrete is used in construction as the total of all other building materials [1, 2]. Reinforcement of various scale is increasingly used in modern materials and concretes, ranging from reinforcement at the nanoscale [3, 4, 5, 6, 7] to the macro-scale reinforcement that has already become classic [8, 9, 10]. Bars and fibres made of steel and other materials are used as the main or the secondary reinforcement bearing the tensile and shear stresses [11, 12, 13, 14, 15, 16]. If fibres are randomly uniformly dispersed in the concrete volume, the resulting material is supposed to be homogeneous Fibre Reinforced Concrete (FRC). One important property of FRC is its superior resistance to cracking and crack propagation [17, 18, 19, 20, 21]. Concrete matrix can be successfully reinforced with the fibres of various geometry [22, 23, 24, 25, 26] and made from various materials [27, 28, 29, 30, 31, 32, 33]. The properties of the concretes with non-metallic fibers are slightly less recognized, especially concretes with new types of the polymer fibers. Additionally, the lack of standardized methods of testing concrete with polymer fibersmake their application much more difficult. Designing elements or structures made of fiber-reinforced concrete requires knowledge of its basic mechanical parameters. Unfortunately, the currently available data describing this type structures are insufficient and research in this area is fragmentary. FRC and its modelling are interesting for future practical application. Every investigation in this field is important. Industrial use of the fibers, comparing with steel rebars is only in the starting point. Polypropylene fibre is used in concrete mix design mainly for shrinkage crack arrest, or, in combination with additional reinforcement [34; 35; 36], also for improvement of the non-linear deformation of FRC ensuring resistance to cracking of the concrete structures [37; 38; 39]. The bridging effect of the fibres across the cracks inside concrete volume improves the toughness of the concrete after cracking [40; 41; 42; 43]. It is also important to take into consideration that even when the concrete is called \"homogeneous\", it does not means it is really homogeneous, because during filling the construction formwork (mix flowing process), fibres added to the concrete mix obtain their slightly non-homogeneous distribution and non-random orientation in the fresh concrete volume mix, which inevitably affects the mechanical properties of FRC [44; 45; 46; 47; 48].  
The current research presents several concrete mixes were developed and prismatic FRC specimens were fabricated, reinforced with three different fibre types: hooked steel 35 mm, polypropylene PP 40 mm, and PP 45 mm. Their structural behaviours were studied using bending tests until prisms were fractured. Every group of FRC had the same concrete matrix, but different internal fiber architecture. All specimens were tested by 4 PBT. The analysis was carried out with a goal to determine the workability and flexural tensile strength of all FRC groups, comparing these parameters with fracture modelling results. Load bearing curves in the model were compared with experimentally obtained.