ISO 14484:2020 pdf download – Performance guidelines for design of concrete structures using fibre- reinforced polymer (FRP) materials
4.1 General
Concrete structures with FRP materials include concrete structures with the sole use of FRP materials and those with the combined use of FRP materials and steel reinforcement. Design of concrete structures with FRP materials should consider safety, serviceability, and restorability during service life. Where applicable, limit states caused by fire, seismic actions, or other extreme loading or actions (e.g. impact and fatigue) should also be appropriately considered, according to the intended applications of FRP materials (i.e. as the strengthening layer or the internal reinforcement). In addition to the above, costs should also be taken into consideration. Suitable analysis should be performed to verify that the performance requirements for concrete structures with FRP materials in terms of limit states such as serviceability limit states (SLS) and ultimate limit states (ULS) in accordance with ISO 2394 are satisfied.
4.2 Design methodology
A design methodology for concrete structures with FRP materials should be based on quantitative performance evaluation at the limit states. A rational method should be adopted for analysing each limit state. Design of concrete structures with FRP materials should consider the linear elastic material properties of FRP and the properties of bond, if available, between the FRP and concrete, based on quantitative performance evaluation at the ultimate limit states.
5.2.1 General
The FRP materials used for concrete structures should be those whose quality and performance characteristics have been confirmed to be compatible with environmental conditions under which the structure will be exposed. The characteristics of FRP materials should be defined in general conformance with reliability-based design requirements. The elastic moduli of FRP materials deviate significantly from that of steel reinforcement depending on the types of fibre used, such as carbon, aramid, glass or basalt, and the fibre volumetric ratio. The compressive strength of FRP materials should be generally ignored in design unless specified otherwise. If necessary, the temperature-sensitive characteristics of FRP materials should be appropriately considered in design, with attention to its possible strength and stiffness loss at elevated temperatures. An environmental reduction factor should be introduced to account for the environmental effect on the strength of FRP materials during the expected service life of the structure. FRP materials shall be designed against creep-rupture under sustained loads unless otherwise noted. FRP materials shall be designed against fatigue under cyclic loading unless otherwise noted.
7.3.2 Tension and flexural cracks
The calculated crack width should be limited as appropriate through detailing the size, spacing and location of FRP reinforcement appropriately. Conventional formulae may be used to calculate the tension and flexural crack width, provided that they are modified to take into account the stiffness of the FRP and the bond characteristics between the FRP and concrete. It may not be necessary to consider the limit for tension and flexural crack width from the viewpoint of durability for those concrete structures in which FRP is used as the only reinforcing material. In the case of FRP-upgraded concrete structures, crack widths should be checked to ensure that the internal steel reinforcement is protected against corrosion at service conditions. The upgrading effects of FRP materials should be taken into account in the calculation.