## 1 Introduction  
Fiber-reinforced concrete is a widely used material nowadays. The most common fiber type is steel fiber [1], but in recent years, polymer fibers have gained popularity [2] due to their insensitivity to corrosive environments. Adding polymer fibers to concrete does not significantly increase the concrete tensile strength (stress that results in crack formation). However, the fiber dosage heavily influences the residual tensile strength of concrete in terms of the load-bearing capacity after crack formation. Subjecting structural components made of polymer fiber-reinforced concrete to uniform tensile loading leads to nonlinear load-displacement behavior, with flexural loading accentuating this effect even further. Different computational procedures were developed to capture fiber-reinforced concrete's highly nonlinear load-displacement behavior. The most common is the plastic hinge approach, as mentioned in [3], where three different kinematic assumptions are also mentioned, which are usually considered for the plastic hinge. The first assumption considers that the crack surface remains plane and the crack opening angle equates to the overall angular deformation of the nonlinear plastic hinge [4]. The second assumption is similar to the first one as it (in addition to the first assumption) considers that the curvature varies parabolically across the plastic hinge length between the uncracked cross-section and the cracked cross-section [5]. The third assumption considers that the crack surface does not remain plane [6]. With the resulting relation (based on one of the three assumptions) between the plastic hinge rotation and the bending moment, the load-displacement relation, according to [3], can be calculated as the sum of the classical beam theory displacement and the displacement due to the plastic hinge rotation according to rigid body rotation. In [7], a semi-analytical model for the flexural behavior of fiber-reinforced concrete was presented, where the midspan displacement was calculated as the sum of the classical beam theory displacement and displacement due to a rotation at the crack. The rotation at the crack was calculated as the ratio of the crack width to the crack depth. The crack width was calculated by expressions from [8], which directly relate the crack width to the acting bending moment. In [9], closed-form solutions for the flexural response of fiber-reinforced concrete members were presented based on a simplified constitutive model where linear elastic behavior up to the tensile strength, a constant residual tensile strength, and the elastoplastic behavior under compression were considered. A simplified bilinear moment-curvature relation was calculated and used to calculate the displacements with [PERSON]'s moment-area method. In [10], similar closed-form solutions for the flexural response of fiber-reinforced concrete members were presented, with the main difference being in considering a four-linear constitutive model for tension and a parabola-rectangle constitutive model for the fiber-reinforced concrete. The study [11] compared the load-displacement responses of a concrete beam reinforced with classical steel and fiber reinforcement, calculated based on different constitutive models for fiber-reinforced concrete. A numerical model based on the moment-curvature relation and [PERSON]'s moment-area method was used for calculating the load-displacement behavior. While most studies on fiber-reinforced concrete consider rectangular cross-sections, in [12], a study on the load-bearing behavior of polymer fiber-reinforced concrete tetrapods with circular cross-sections is presented. The finite element method is also an essential computational procedure for evaluating fiber-reinforced elements' flexural behavior. Different approaches are used for the consideration of fibers and concrete.