20.1 Characteristic Strength of Materials
The term ‘characteristic strength’ means that value of the strength of the material below which not more than 5 percent of the test results are expected to fall. The
characteristic strength for concrete shall be in accordance with Table 1. The characteristic strength shall be assumed for prestressing steel and the characteristic strength for reinforcing steel shall be assumed as minimum yield/0.2 percent proof stress.
20.2 Characteristic Loads
The term ‘characteristic load’ means that value of load which has a 95 percent probability of not being exceeded during the life of the structure. Since data are not available to express loads in statistical terms, for the purpose of this Section, the dead load, imposed load, wind load, seismic forces and snow load as given in 2, 3, 4, 5 and 6 of Part 6 ‘Structural Design, Section 1 Loads, Forces and Effects’ of the Code shall be assumed as the characteristic loads.
20.3 Design Values
20.3.1 Materials
The design strength of the materials, is given by:
20.4 Partial Safety Factors
20.4.1 Partial Safety Factor for Material Strength
20.4.1.1 When assessing the strength of a structure or structural member for the limit state of collapse, the values of partial safety factor should be taken as 1.5 for concrete and 1.15 for steel.
PART 6 STRUCTURAL DESIGN — SECTION 5 CONCRETE: 5B PRESTRESSED CONCRETE
NOTE — values are already incorporated in the equations and tables given in this Section.