Combinations (Traffic Load Case)

 

Section 6 of EN 1990:2002 describes how the partial factor method is applied in limit state verifications. It provides the overall framework for the applications of the partial factor method, including the way in which actions are combined and partial factors are applied. It is best considered, however, in conjunction with EN 1990:2002, Annex A2 which gives supplementary bridge-specific requirements for establishing combinations of actions, provides ψ-factors and material-independent partial factors, and also gives methods and rules for some material-independent serviceability limit states (e.g. vibrations and deformations of rail bridges).

Ultimate Limit States
Serviceability Limit States (according to Table A2.6 - Design values of actions for use in the combination of actions from EN-1990 - Annex A2)

 Notes

- with the horizontal traffic loads (group 2 - braking, acceleration and centrifugal forces);

- nor with the loads on footways and cycle tracks (group 3);

- nor with Load Model 4 (group 4 - crowd).

National Annexes

Traffic Load Combinations Case Study

Load combinations to be considered for ULS and SLS verifications of the bridge are summarized in the following case study, where the following load cases are considered:

 

Combination of action for the ultimate limit state

 

EQU combinations: ∑ γG*G + γQ1*Qk1 + ∑ γQ0*Qk

Thermal action is the leading variable action

1.05*Gsup + 0.95*Ginf +1.5*Tk + 1.35* [0.75*TS + 0.4*UDL + 0.4*Footways & Cycle Tracks]

Note

Load groups are mutually exclusive (gr1a and gr1b cannot be involved in the same combination).

 

gr1a is the leading variable action

1.05*Gsup + 0.95*Ginf +1.35*gr1a

Note

We use ψ0 = 0 for thermal actions.

 

gr1b is the leading variable action

1.05*Gsup + 0.95*Ginf +1.35*gr1b

 

STR/GEO combinations: ∑ γG*G + γQ1*Qk1 + ∑ γQ0*Qk

Thermal action is the leading variable action

1.35*Gsup + 1.00*Ginf +1.5*Tk + 1.35* [0.75*TS + 0.4*UDL + 0.4*Footways & Cycle Tracks]

 

gr1a is the leading variable action

1.35*Gsup + 1.00*Ginf +1.35*gr1a

 

gr1b is the leading variable action

1.35*Gsup + 1.00*Ginf +1.35*gr1b

 

Combination of action for the serviceability limit state

 

Characteristic combinations: ∑ G + Qk1 + ∑ ψ0*Qk

Thermal action is the leading variable action

Gsup + Ginf + Tk + 0.75*TS + 0.4*UDL + 0.4*Footways & Cycle Tracks

 

gr1a is the leading variable action

Gsup + Ginf + gr1a

 

gr1b is the leading variable action

Gsup + Ginf + gr1b

Frequent combinations: ∑ G + ψ1*Qk1 + ∑ ψ2*Qk

Thermal action is the leading variable action

Gsup + Ginf +0.6*Tk

 

gr1a is the leading variable action

Gsup + Ginf +[0.75*TS + 0.4*UDL] + 0.5*Tk

 

gr1b is the leading variable action

Gsup + Ginf +0.5*Tk

Quasi-permanent combinations: ∑ G + ψ2*Qk1 + ∑ ψ2*Qk

Gsup + Ginf +0.5*Tk

 

gr1a is the leading variable action

Gsup + Ginf +0.5*Tk

 

gr1b is the leading variable action

Gsup + Ginf +0.5*Tk

For models involving several load families (Wind, Snow, Thermal actions, Traffic actions, etc.), combinations will be generated using the detailed combination generator:

Traffic loads concomitance

Concomitance between load cases

Related Topics