Week 8 Challenge

Aim: To calculate the centrifugal load and apply it to the bridge model in staad model.

Given data:

• The span of the bridge is 12 m.
• The width of the carriageway is 7 m.
• The bridge is subjected to a live load of Class 70R tracked vehicle.
• The design speed(V) of the vehicles is 75 km/hr.
• The radius of curvature(R) in the bridge is 3 m

Assumed data:

Bridge deck thickness-250 mm.

Support condition is pinned at end of the span.

There are 3 Main girders with section sizes of 0.8 m x 2 m.

And Cross girder at 3 m c/c along the longitudinal length of the bridge and having a section size of 0.8 m x 1.5 m.

Solution:

Weight of 70R tracked vehicle (W) = 700 kN.

Centrifugal load (C) = WV^2/127R = 700 x (75)^2/(127*3)= 10334 kN

The above-calculated load will be applied as a double axle moving load with each axle load as (10334/2=5167 kN) in staad pro.

Modeling & Analysis in Staad Pro:

The bridge model as prepared in staad pro is can be seen below.

The following properties are assigned to the members respectively.

The moving load definition created as shown below.

Then the above-defined load is considered as a moving load by applying 30 generated load cases.

Results:

(Moving Load Diagram)

Main Girder:

(Bending Moment Diagram)

(Shear Force Diagram)

Maximum Bending moment encountered: 15876 kN.m

Maximum Shear Force encountered: 5235 kN

Cross Girder:

(Bending Moment Diagram)

(Shear Force Diagram)

Maximum Bending moment encountered: 5037 kN.m

Maximum Shear Force encountered: 5071 kN

Bridge Deck:

Maximum Bending Moment encountered: 93.4 kN.m