Week 1 Challenge

Aim:

1. To Calculate the Dead loads on a bridge located in a Seismic Zone IV,

2. To apply it in Staad pro and perform structural analysis for the following data.

Given data:

Location of the Bridge = Since the site is located in Seismic Zone 4, According to the given data the site is located within a 60 km radius which is in the southern part of West Bengal.

Type of Bridge = Reinforced Concrete Bridge

Diameter of Pier = 2.5 m

Deck Slab Width = 10.2 m

Span of Bridge = 12 m

Let's assume the following.,

Thickness of Deck Slab = 250 mm

Height of Pier cap = 1.5 m

Height of Pier = 6 m

The Pier is supported by a Well cap of 500 mm thickness and 12 m diameter

The Well cap is supported by a Well foundation with an internal diameter of 9 m and an external diameter of 10.5 m

Solution:

The calculation of dead loads of the box girder bridge is as follows.,

Dead load = Area x Unit weight of the material (kN/m)

or

Dead load = Volume x Unit weight of material (kN)

The area of the box girder is calculated by using the AREA command in AutoCAD.,

The area of the outer region of the box girder is calculated as 16347 in^2 (Refer above diagram)

The area of the inner region of the box girder is calculated as 9698 in^2 (Refer above diagram)

The difference in these areas gives the area of the bounded region which is the box girder = 6649 in^2

(Area is in inch^2 which needs to be converted to millimeter^2 for further calculations)

The area of the box girder = 6649 x 645.16 (1 in^2 = 645.16 mm^2)

= 4289669 mm^2

Self weight of deck slab = 10.2 x 0.25 x 25 = 63.75 kN/m

Self weight of box girder = 4.3 x 25 = 107.5 kN/m

Self-weight of Pier cap = ( Pi x 0.33 x 1.5 x ((3.5 x 3.5) + (3.5x4.5) + (4.5x4.5)) ) = 1895 kN

Self-weight of Pier = (Pi x 2.5 x 2.5 x 0.25) x 6 x 25 = 737 kN

Self-weight of Well cap = ( Pi x 0.25 x 12 x 12 ) x 0.5 x 25 = 1414 kN

Self-weight of Well foundation = ( Pi x 0.25 x ( 10.5^2 - 9^2 ) x 12 ) x 25 = 6892 kN

STADD Pro Analysis:

1. The Bridge box girder is plotted into STADD Pro with the help of AutoCAD drawing.

Geometry to Nodes / Beams / Plates / Solids.

2. The Nodes are drawn according to the distance of certain vital parts of the bridge box girder such as bends,  edges etc.

By Translational repeat or Ctrl C + Ctrl V.

3. After, The nodes of the super-structure are connected with plates forming the shape of the actual bridge.

Geometry to Add beam / Add plate / Add solid

4. The loading is given as dead loads to the bridge including self-weight of elements, and other imposed loads.

Loading to Loading classification to Dead loads to add self-weight / member load (UDL)/ plate load.

5. Once Loading is done, the analysis is run and results are generated without error and warnings.

Analysis and design to Run analysis.

Result generation:

The above image shows the bending moment of piers across Z direction.

The above image shows the shear of piers across Y direction.

The above image shows the bending moment of piers across Y direction.

The above image shows the stress in the plates of the box girder.

 The above image shows the von mises stress of the pier cap (designed as solid) of the box girder.