Mobile loads

The load system gr1a (according to table 4.4 EN1991-2) is the most efficient load system for design and check of bridges. This system consists from

Load model – LM1

Pedestrian or cyclist load

The combinations coefficients (ψ0, ψ1 a ψ2) are different for the separate loads in this load system according to table A2.1 from the EN 1990/A1. The procedure of modelling and check using characteristic, frequent and quasi-permanent combination including load system gr1a is different from the using of standard procedure with loadcases which belongs to appropriate loadgroup with defined combination coefficient in menu Project.

 

The rules for SLS combination according to tab. A2.6 from EN1990/A1

 

Permanent

Prestress

The dominant variable (traffic)

The subordinate variable (temperature)

Characteristic

Gi

P

1,0*Qk1

ψ0* Qki

Frequent

Gi

P

ψ1*Qk1

ψ2* Qki

Quasi-permanent

Gi

P

ψ2* Qki

ψ2* Qki

Preparation of mobile load in SEN

The load group

The new Load group (LG) with name Traffic is created, type is Variable exclusive. This LG will be registered to category of load G – traffic >30kN

The temperature load is possible to insert to different LG (temperature) with predefined combination coefficient (the coefficient cannot be set to 1,0)

The default combination factors should be set to 1,0 for  selected LG.

Mobile load track

New mobile load track (TR1) has to be defined by user Mobile loads > New mobile load track. The first and last node will be selected and track will be automatically defined on whole structure

Unit load

New Unit load (UL) will be defined by user Mobile loads > Unit loads.

Load system database

The new Load system databases will be defined for each type of combination including combination coefficients for characteristic and frequent combination. Mobile loads > Load system database

Traf_char – Load system for characteristic combination 1,0*TS+1,0*UDL

Traf_fre – Load system for frequent combination0,75*TS+0,4*UDL

Setup of generated loadcase

Two groups of generated loadcase should be set in Setup of generated loadcase. The same LG - Traffic should be assign to each group of generated LC. The components Vz and My will be evaluated.

T_char – Unit loads (UL) + load system database (Traf_char)

T_fre – Unit loads (UL) + load system database (Traf_fre)

The envelopes of LC will be automatically generated after linear calculation finish. These generated LC will be added into appropriate stages.

Definition of construction stages

The separated construction stages were created in construction stages library (see). The appropriate envelopes of variable LC will be add to each construction stage according to type of generated combination

Char_1 – characteristic combination

Fre_1– frequent combination

QP_1– quasi-permanent combination

ULS_1 – ULS(STR) combination

Evaluation of mobile loads - envelopes

The evaluation of maximum and minimum envelopes in one presentation in results is possible using Loadcases, Combination>Results classes.

Char_extrem_My – extreme of envelopes of mobile loads for characteristic combination
Fre_extrem_My – extreme of envelopes of mobile loads for frequent combination

The internal force are possible to see in Results> Internal forces. The user can select in Type of loads – Class and form the list of classes selects Char_extrem_My. The extreme moment is drawn from minimum and maximum envelopes of mobile load for characteristic combination.

And for frequent combination.