119 © 2012 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin · Structural Concrete 13 (2012), No. 2 The predominant failure mode of concrete members reinforced with fibre-reinforced polymer (FRP) bars is flexural, due to either concrete crushing or FRP rupture. Many design tools have been developed for the flexural design of FRP-reinforced concrete. These tools are sufficiently accurate, but an iterative procedure is required when dealing with flexural failure due to FRP rupture. In addition, despite the fact that the design concepts involved are similar to those used for conventional steel-reinforced concrete, the changes in the design philosophy and the linear behaviour up to rupture of the FRP bars lead to the sectional properties having a different influence on the design, which not everyone may be familiar with. Therefore, this study proposes a general methodol- ogy for evaluating the design flexural capacity of FRP-reinforced concrete sections. This methodology is based on the design pro- visions of Eurocode 2 and comprises non-dimensional, closed- form equations, derived independently of the concrete and FRP characteristics. The proposed methodology can be used to derive universal dimensionless design charts as well as tables. The ac- curacy of the proposed design tools has been verified by compar- ing the predictions with the experimental results of 98 beams, which are available in the published literature. Keywords: design, reinforced concrete, FRP bars, flexural capacity, FRP rupture, concrete crushing 1 Introduction Since the early 1980s, fibre-reinforced polymer (FRP) bars have emerged as an alternative type of internal reinforce- ment for concrete structures exposed to aggressive envi- ronments and normally reinforced with conventional steel bars [1, 2]. In addition to improving the durability of rein- forced concrete, FRP bars have been used in structural concrete applications where magnetic neutrality or good cutting characteristics are required [3, 4]. The major differences between steel-reinforced con- crete (SRC) and FRP-reinforced concrete (FRP RC) arise from the mechanical properties of FRP bars, which behave linearly up to failure. As a result, FRP RC members fail in a brittle manner and this leads to a change in the predom- inant mode of failure, i. e. flexure, assumed by limit state design [3–6]. FRP RC members fail in flexure either due to con- crete crushing (compressive failure type) or rupture of the FRP bars (tensile failure type). Although existing design guidelines for FRP RC (e. g. [3, 7–8]) accept both types of flexural failure, concrete crushing failure is marginally more desirable since it is more progressive and has a high- er degree of deformability [9]. Nevertheless, design prac- tice indicates that for some members, e. g. bridge deck FRP RC slabs, the amount of reinforcement provided is usually lower than the theoretical limit required to achieve a balanced flexural failure; the design can therefore be governed by tensile failure of the reinforcement [10]. Various studies of the flexural behaviour of FRP RC members have been carried out over the years, e. g. [11–27], and it may be generally stated that the design methodologies adopted by existing guidelines for FRP RC (e. g. [3, 7–8, 28]) predict the moment capacity of FRP RC sections with sufficient accuracy. These methodologies utilize the assumptions made for SRC which are modified to account for the specific mechanical properties of FRP bars, and the proposed design equations are based on equivalent rectangular compressive stress block proce- dures. A similar approach is proposed by fib task group 9.3 [4, 29], which adopted the equivalent rectangular stress block procedure of Eurocode 2 [30]. When FRP rupture governs the design, a rigorous calculation of the moment capacity leads to an iterative process, which is required to determine the depth of the compressive stress block. To avoid this iteration, simpli- fied procedures can be adopted, such as the proposal of ACI440.1R [3]. In this case, the nominal moment capacity of the FRP RC section is approximated by using the equiv- alent rectangular stress block of a balanced FRP RC sec- tion. This simplification is regarded as conservative and assumes a constant maximum value for the depth of the compressive stress block [10] without taking into account the possible variation in the lever arm which may result when there is a change in the geometrical and mechanical properties of the FRP RC section. Furthermore, despite the fact that the concepts in- volved in the design of FRP RC sections are similar to those for SRC sections, the changes in the design philoso- phy and the linear behaviour up to rupture of the FRP bars lead to the sectional properties having a different influ- ence on the design, which not everyone may be familiar with. Articles Design procedure and simplified equations for the flexural capacity of concrete members reinforced with fibre-reinforced polymer bars Lluis Torres* Kyriacos Neocleous Kypros Pilakoutas DOI: 10.1002/suco.201100045 * Corresponding author: lluis.torres@udg.edu Submitted for review: 26 September 2011 Revised: 16 December 2011 Accepted for publication: 28 January 2012