Challenge

Week 7 Challenge

Aim: To calculate the water current forces and apply them to the staad model of the bridge and do the analysis.

Given data:

Assumption:

Bridge deck width = 10 m.

No of piers = 3

The support condition for the pier is fixed.

It can be seen that the Superstructure and sub-structure part of the bridge is isolated by bearings.

So here only Piers will be modeled (only a Single frame ) for analysis in Staad pro.

Pier will be circular in shape having a diameter of 1.2 m & Pier cap having a section size of 1.2 m(H) x 1.5 m (V).

From bed level of the river to bottom of footing =2 m

Clear distance to be maintained between bed level and bottom of the bridge = 5.36 m.

Total height of pier = 5.36+2 =7.36 m

Solution:

Calculation of Water current forces:

Maximum Velocity = SQRT(2) X Mean velocity of the river

=SQRT(2) X 3 =4.24 m/s

Water Current Force = 52 x K x V^2 (As per IRC 6,clause 210.2,P in kg/m2 and V in m/s)

K= 0.66 for Circular shape pier.

Water current force = 52 x 0.66 x4.24^2 =617 kg/m2 =6.17 kN/m2

As the diameter of the pier is 1.2 m, the Uniformly varying load to be applied = 6.17 x1.2 =7.4 kN/m

The HFL is 2 m from the bed level, So let's apply this load on the pier from the bottom of the footing up to the HFL level.

Analysis in Staad Pro:

Using the assumed data, Staad model was prepared as shown below

The following properties were assigned.

The 3D model can be seen below.

For loading, uniform varying load is considered to vary from 7.4 kN/m at HFL to 0 at Footing level.

The application of the load can be seen below.

Results:

Bending moment & shear force diagrams are plotted as shown below.

(Bending Moment Diagram)

(Shear Force Diagram)

Ship work like this
in your own course.