## 1 Introduction  
Continuous concrete beams are often used within RC structures that are exposed to aggressive environmental conditions, such as garages, bridges, overpasses, reservoirs, marine structures, and retaining walls. In these environments, a reduction of concrete alkalinity occurs, which often results in steel reinforcement corrosion, endangering the serviceability and functionality of the RC structures. In order to overcome this problem, fiber-reinforced polymer (FRP) bars and stirrups have lately been used as alternative solutions in RC structures, especially in aggressive conditions. The use of FRP reinforcement can provide significant savings related to the maintenance, strengthening and recovery of structures, in particular when they are exposed to various destructive influences during their service life, certainly leading to economic benefits. Additionally, FRP bars are successfully used to improve the mechanical performance of others structural elements, for example laminated glass beams [1] or structural timber elements [2]. Numerous studies have been conducted on simple beams reinforced with FRP bars to estimate the flexural behavior regarding deflection and cracks [3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. Several authors have proposed modification of [PERSON]'s equation for calculation of the effective moment of inertia ([PERSON] and [PERSON] [4], [PERSON] et al. [5], [PERSON] and [PERSON] [6], [PERSON] and [PERSON] [7], [PERSON] et al. [8], [PERSON] et al. [9]), while [PERSON] [10; 11] calculated the effective moment of inertia derived from curvatures in order to predict the load-deflectionresponse. For cracking behavior, prediction models are generally based on design equations for members with steel reinforcement. Extensive analysis was conducted to determine values of the bond coefficient \(k_{b}\), which depends on the characteristics of the FRP bars and the surrounding concrete [12; 13; 14; 15; 16], of which the crack width in the member is significantly dependent. A modest number of research works on the FRP-reinforced continuously supported beams [17; 18; 19; 20; 21; 22; 23; 24; 25; 26] show that moment redistribution between the cross-sections in the critical sections is possible. The possibility of this phenomenon occurring depends most on the arrangement of the reinforcement along a beam [17; 18; 19; 20; 21; 26]. Increasing the bottom FRP reinforcement at the midspan of a continuous beam with reduction of the top FRP reinforcement in the middle support leads to increase in the load capacity of the beam, reducing deformation and postponing crack propagation in the beam midspan [18; 20; 21; 23; 24]. On the other hand, the increase of the top reinforcement over the middle support with identical reinforcement in the midspan does not contribute to increasing the load capacity or to reduction of deformation [23]. There is an indication that continuous beams with FRP bars show some warnings before failure regarding large deformations and wide cracks [18; 19; 21; 26]. Additionally, due to the low modulus of elasticity of the FRP reinforcement, moment redistribution from the middle support, compared to the elastic analysis, starts at low load levels [18; 19]. All of the above stated points represent a good basis to introduce internal force redistribution to improve the behavior of continuous beams with FRP reinforcement, in turn improving the serviceability and ultimate limit state. Due to the low modulus of elasticity, FRP elements exhibit significant deformations and wide cracks, meaning their design is often governed by the serviceability limit state, especially when GFRP bars are used. This study is part of the conducted research on continuous beams with GFRP reinforcement, with aim of investigating a number of parameters to assess flexural behavior [27]. Some preliminary results from this experimental program have been published in a previous study [26], which are repeated in this paper because they are the basis for the analysis in this work.