26.08.2015   Rudiger Meiswinkel, Julian Meyer, Jurgen Schnell

Partial safety factors for structural resistance

For verifications of the serviceability limit states, the partial safety factors for the resistance are generally to be taken as 1.00.

Table 6.1 Reference values for partial safety factors and combined coefficients

Effects

Partial Safety Factor

Combined Factor

gQ

C0

C1

C2

G

Dead load

1.35a)

—

—

—

Variable actions Q

Quasi-permanent service loads

1.50b)

1.0

1.0

1.0

Variable service loads

1.50b)

0.9

0.8

0.8

Crane loads

1.35

1.0

as

d

0

Indirect actions due to settlements

1.50c)

1.0

1.0

1.0

a) 1.00 at favourable effects

b) 1.35 if effect variable can be determined very precisely

c) 1.00 if a linear calculation is used and the rigidity in the structure can be reduced (by cracks forming or relaxation, for example) (see Section 7.2)

d) With category A3 requirements (cf. Section 6.3) the crane load can be ignored as a variable action, i. e. C = 0

The partial safety factors to determine the structural resistance of the ultimate limit states depend on the design situation (permanent and temporary, extraordinary) of the building materials used (concrete, concrete steel, pre-stressed steel, construction steel) and the demands on the structure or structural member in question.

Safety-related structural members are subject to different requirements under these effects. Factors to be taken into account here include:

— Chances of their occurring during working life

— Repair options available

— Limiting the extent of the damage, such that the structural members remain fit for use and system components remain intact and operational.

With these aspects in mind, requirements when designing structural components of nuclear installations are divided into three requirement categories, A1, A2 and A3. These are defined irrespective of the building materials involved as shown in Table 6.1.

Requirement category A1

Those combinations of physical effects corresponding to the permanent and temporary design situations in accordance with DIN 1055-100 will be assigned to requirement category A1. The partial safety factors specified in DIN 1045-1 for the load-bearing capacity regarding permanent and temporary design situations will be assigned to these combinations.

Requirement category A2

Following the method described in DIN 1055-100, those combinations of physical effects that comprise extreme design situations, which must be assumed to occur several times during service life, are assigned to requirement category A2. It must be ensured that the building elements designed accordingly are continuously useable after occurrence of these combinations. In regard to the stability or functional safety of plant components, additional requirements may have to be specified for individual locations (e. g. limit values for deformations and crack widths).

Requirement category A3

Combinations of physical effects comprising extreme design situations with a low probability of occurrence (internal or external events, < 10~4 per year) which must be assumed to occur once during service life will be assigned to requirement category A3. The forming of large cracks and permanent deformations is permitted, provided, these are not prohibited for safety-related reasons. In regard to the stability or functional safety of plant components, additional requirements may have to be specified for individual locations (e. g. limit values for deformations and crack widths) that go beyond the minimum requirements with regard to the load-bearing capacity.

Partial safety factors of structural strength for structural components of concrete, reinforced concrete and pre-stressed concrete in requirement categories A1, A2 and A3 to KTA-GS-78 [51] and DIN 25449 [15] are shown in Table 6.2. Table 6.3

Table 6.2 Partial safety factors for structural members of concrete, reinforced and pre-stressed concrete (ULS)

Reinforced and Pre-Stressed Concrete Structures

Requirement Category

A1

A2

A3

Partial

Concrete gc

1.50

1.30

1.00

safety

factors

Concrete steel/ pre-stressing steel gs

1.15

1.00

1.00

Non-linear

System resistance gR

1.30

1.10

1.00

procedures

Concrete compression strength fcRa)

0.85 • a • fck

0.85 • a • fck

1.00 • a • fck

Yield strength concrete steel fyRb)

1.1 • fyk

1.1 • fy, k

1.0 • fy, k

0.1% proof stress pre-stressing steel fp01,Rb)

1.1 • fpk

1.1 • fpk

1.0 • fpk

a) Reduction value a in DIN 1045-1:2001-07, 8.1

b) Tensile strength concrete steel: fte = 1.08 • fpk

Table 6.3 Partial safety factors for steel members (ULS)

Steelwork: Req. Category

A1/A2/A3

Notes

DIN 18800-1 gM

1.0/1.1a)

Cf. DIN 18800-1 Section 7.3.1

DINEN 1993-1-1

gM0

gM1

gM2

1.0

1.0/1.1a)

1.25

Major deformations due to yielding are acceptable for capacities of action effects that depend on the yield stress (for stability failures etc.)

For capacities of action effects which depend on tensile strength (net cross-section failures under tension or bolt or weld failures etc.)

a) Needs to be established on a case by case basis

contains the partial safety factors for structural members of steel as recommended in KTA-GS-78.