Document Information

Document Type: FAQ

Product(s): LEAP CONSPAN/Precast/Prestressed Girder

Version(s): All

Original Author: Bentley Technical Support Group -VM

QUESTION: How the program is calculating Live Load Maximum Shear (LL+I : Vmax) for SERVICE III Limit State at Mid span ?

ANSWER:

A single Span bridge with 6 girders were considered for this design.

In the Design TAB only Design lane and Design Truck option was selected.

After Running the Analysis the program was showing a LL+I:Vmax value of 26.3 kips at the mid span for Service III load combination.

From Analysis TAB --> Load Case --> Beam 1 --> Design Lane - Max Shear , Fy = 4.68 kips at mid span.

From Analysis TAB --> Load Case --> Beam 1 --> Design Truck- Max Shear , Fy = 24.51 kips at mid span.

Just to add a note in Conspan Lane Loads are analyzed by loading only those parts of the bridge that would cause a maximum moment or shear at each section.

Calculation :

Span 1 Beam 1

Live Load Factor = 0.8

Distribution Factor = I loaded Lane = 0.882353

Impact factor for Design Truck = 1.33

Impact Factor for Design Lane = 0.00

Total Max Shear = Design truck + Design lane

LL+I : V max = (24.51 x 0.8 x 0.882353 x 1.33) + (8.68 x 0.8 x 0.882353) =  26.3 kips which matches Conspan results

Please see the attached screenshots for more information.