Week 7 Challenge

Aim and Introduction:-

• The aim of this challenge is to calculate the water current load of river on the structure and to evaluate types of load acting on the structure and to calculate the effect on the structure as various forces like shear force, bending moment etc using staad Pro.
• So first of all the details components for calculating the water current load and for scour calculation is need to be determined from the given data. For determining the same IS-78 is to be refered.
• Then the model will be created in Staad pro., water current load is applied in each side of the the structure separately and the reactions due to the loading is being analyzed for the structure as given.

Data Given:-

• HFL above foundation level - 2m
• Span of bridge - 45m
• Mean Velocity - 3 m/s
• Abutment Size - 3660-(1150+1445)=1065mm

Considering the same size for the pier.

Calculation of the Water current :-

Ht. of pier and abutment subjected to water current = 2m

Vmean= 3 m/s

Max. Velocity = V = √2 x Vmean

= √2 x 3 = 4.242 m/s

Water current pressure = P = 0.52x k x V ^2

as the abutment and piers are rectangular structure

So, the value of k = 1.5

⇒ P = 52 x 1.5 x 4.242^2

= 1403.57 KN/m2

Calculation of Scour Depth:-

Mean Discharge = 3 m/s

Design Discharge = Db=(30/100) x 3 + 3

= 3.9 m/s (Considering the catchment area below 3000 km2)

( From IRC-78, 703.1.1)

Considering the the bed of soil as medium sand

• Silt factor for coarse sand will be = 1.25 from 703.2.2.1, IRC-78

Mean Scour Depth = dsm = 1.34(Db/Ksf)^(1/3)

= 1.34(3.9/1.25)^(1/3)

= 1.95 m

Scour Depth = 2 x dsm

= 2 x 1.95 = 3.9 m (For Pier)

• = 1.27 x dsm

= 2.48 m (For Abutment)

STAAD Pro. Analysis:-

• The bridge has been created by considering 2 spans of 45 m length and the cross section of the bridge is taken as 15 m width.

• The Pier and abutment size has been taken as - 1.2m x 1.2m
• The Main girder size has been taken as - 0.75m x 1.2m
• The cross girder size has been taken as - 0.75m x 0.75m
• Deck slab (Plate) thickness is considered as - 0.30m

• The properties as described has been defined and asigned to the above structure.

Fixed Support has been created and has been assigned to the structure.

The 3D render view of the defined structure.

Loads and Definitions:-

Applying the water current load on the piers from both the side up to HFL.

Total water current load = 1403.57 x 1.2 = 1685 KN/m

• Defining the linearly varring load in the the direction

• The result after the analysis after the structure.

The deflection due to water current load 1.

The deflection due to water current load 2.

The deflection due to dead load.

• The end point reactions due to the loads.

Mz:- For load case 1

Mz:- For load case 2

My:- For load case 1

My:- For load case 2

Fy :-For load case 1

Fy :-For load case 2

Plate Stress for load case 1

Plate Stress for load case 2

Plate Stress for load case 3

Further the reports can be generated for design and detailing of the structure.