Week 2 Challenge

Aim : To calculate the live load on a bridge of span 24 m.

Given data :

Width of bridge deck – 7 m

Thickness of bridge deck – 0.2 m

Main girder dimension 1.5 x 0.5 m

Cross girder dimension is 1.5 x 0.3 m

Span of the bridge - 24 m

Pier size – 2 m dia

The seismic zone – zone 3

Wind speed – 42 km/hr

Unit weight of soil is 18 KN/m^3

Theory : Live Load as per IRC – 6 for different criteria is listed below.

• IRC Class AA loading – IRC tracked loading and IRC wheeled loading
• IRC Class 70R loading _ tracked loading and wheeled loading
• IRC Class A loading , IRC Class B loading
• Footway loading

Here, for given problem am applying a IRC Class A wheeled loading. For the live load consideration the IRC gives a guide lines in a code book. So here am attaching a code book of page IRC – 6 page number 12. According to that we have to follow the rules and apply the load.

Explanation : In the IRC Class A loading totally 8 axle loads. Width of the spacing is 1.8m.

8 axle load consideration and spacing between the axle are given below.

Axle load (KN)	Spacing (m)
27	-
27	1.1
114	3.2
114	1.2
68	4.3
68	3
68	3
68	3

Aim : To prepare the model in a STAAD Pro and perform the analysis and justify with the results.

Theory : The general steps to be create a STAAD Pro model is given below,

Step 1 : Create the nodes by using the nodes cursor.

Step 2 : Joining the nodes by using the respective beam plate cursor.

Step 3 : Supports given to the nodes whether its pinned or fixed or any other custom supports

Step 4 : specifications given to the respective beams plates

Step 5 : Assign the live load as per calculation

Step 6 : Save the model and perform the analysis

Step 7 : The results are obtained and discuss with the results

Step 8: Take the print out of report of necessary results.

Creating the nodes by using node cursor.

Open the STAAD Pro window > Select > Node cursor > enter the value with respect to X Y Z axis > click enter.

Join the nodes by using beam cursor.

Select > beam cursor > join by dragging the mouse or enter the node numbers > click enter

Supports are given to the respective nodes.

Specifications > Supports > select the supports > click enter

Assigning the properties to the beam ( piers ) .

Specification > Prismatic > Rectangle > enter dimensions > select the beam > assign the properties to selected beams.

Assigning the properties to the beam ( cross girders ) .

Specification > Prismatic > Rectangle > enter dimensions > select the beam > assign the properties to selected beams.

By using translational repeat the model has been completely generated .

geometry > translational repeat > enter the axis , number of steps > ok

Deck slab has been created and assigned the properties.

Select > specifications > select plate > draw

assigned properties to the plate of thickness of 0.2m

Defining the load cases .

Loading > definition > vehicle definition > Add > define load

Load case > Add > load generation > add > give the range value to be load start and end of the bridge.

Run analysis > go to post processing mode > Results

The reactions are generated at the end of the nodes .

• The shear force is maximum at the end and minimum at the mid span.
• The shear force is 0 for all the piers.
• The bending moment is maximum at midspan and minimum at the end support.
• The maximum bending moment is 0 KNm
• The maximum displacement is 0 mm.
• Reports are taken printout which ever is necessary by using report option.
• In the report option we obtain the results of section forces, displacement, reactions, plate stresses.
• The exact report is to be taken further move to design process.