| a | = | depth of equivalent rectangular stress block, mm |
| Ac | = | area of the concrete for member, mm2 |
| Af | = | area of fiber-reinforced polymer (FRP) reinforcement, mm2 |
| Ap | = | area of the pre-stressed reinforcement, mm2 |
| As | = | area of tension steel reinforcement, mm2 |
| B | = | width of rectangular cross section, in |
| c | = | distance from extreme compression fiber to the neutral axis, mm |
| cb | = | distance from extreme compression fiber to the neutral axis at balanced strain condition, mm |
| CE | = | environmental reduction factor for various fiber type and exposure conditions |
| d | = | distance from extreme compression fiber to centroid of tension reinforcement, in |
| dp | = | distance from extreme compression fiber to centroid of prestressing reinforce-ment, mm |
| e | = | eccentricity, mm |
| E | = | modulus of elasticity, kPa |
| Ec | = | modulus of elasticity of concrete, kPa |
| Ef | = | design or guaranteed modulus of elasticity of FRP defined as mean modulus of sample of test specimens |
| Ep | = | Elastic modulus of pre-stressed steel, kPa |
| f′c | = | specified compressive strength of concrete, kPa |
| ff | = | stress in FRP reinforcement in tension, kPa |
| ffu | = | design tensile strength of FRP, defined as the guaranteed tensile strength multiplied by the environmental reduction factor (ffu= CE*ffu*), kPa |
| ffu* | = | guaranteed tensile strength of FRP bar, defined as mean tensile strength of sample of test specimens minus three times Standard deviation (ffu* = ffu, ave-3σ), kPa |
| fpe | = | stress in steel due to effective pre-stress force (Pe or F) after all losses, psi. (fse in the ACI code) |
| fpu | = | specified tensile strength of prestressing reinforcement, kPa |
| fps | = | stress in prestressing reinforcement at nominal flexural strength, kPa |
| fy | = | specified yield stress of non-pre-stressed steel reinforcement, kPa |
| F | = | Pre-stress force, kN |
| H | = | overall height of flexural member, mm |
| I | = | moment of inertia, mm4 |
| L | = | span length of the member, m |
| Mn | = | nominal moment capacity, kN?m |
| Pe | = | effective pre-stress (after all losses), kN |
| r | = | radius of gyration of cross section, mm |
| Greek letters |
| β1 | = | factor relating depth of equivalent rectangular compressive stress block to depth of neutral axis |
| ?p | = | factor used for type of prestressing reinforcement |
| D | = | the flexural displacement due to pre-stress F, in |
| δmax | = | maximum elastic deflection on a member supported by two simple supports, in |
| ε1 | = | first component in three to the sum of εps (total steel strain at failure) |
| ε2 | = | second component in three to the sum of εps (total steel strain at failure) |
| ε3 | = | third component in three to the sum of εps (total steel strain at failure) |
| εc | = | maximum usable strain at extreme concrete compression fiber |
| εfu | = | design rupture strain of FRP reinforcement, defined as the guaranteed tensile rupture strain multiplied by the environmental reduction factor. (εfu = CE?εfu*) |
| ρ = | = | ratio of As to bd |
| ρ' | = | ratio of A′s to bd |
| ρf | = | fiber-reinforced polymer reinforcement ratio |
| ρfb | = | fiber-reinforced polymer reinforcement ratio producing balanced strain conditions |
| ρp | = | ratio of Aps to bdp |
| ω | = | tension reinforcement index |
| ω′ | = | compression reinforcement index |
