Loads acting on Bridges

 

In this article we discuss loads and types of loads acting on Bridges 

After reading you will answer

1) Types of load

2) Different types of live load

3)IRC classification,etc.

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Loads and Load Combinations

Loads on Bridges

 The various types of loads are as follows:-

1- Dead load

2- Live load

3-Impact load

4- Longitudinal force 

5-Themal force 

6-Wind load 

7- Seismic load 

8-racking force

9- Forces due to curvature.

10-Forces on parapets 

11-Frictional resistance of expansion 

12- Erection forces

 Dead Load

 The dead load is the weight of the structure and any permanent load fixed there on.

 The dead load is initially assumed and checked after design is completed and the design should be revised if the dead weight exceeds the assumed load by more than 2.5%

 Live Load

 On bridges main live load is due to the road traffic and railway trains for designing road bridges, standard live loads are taken as specified by Indian Road Congress Section ii for railway bridges as specified by

railway board

IRC has classified the live loads for road bridges as follows:

1. IRC class AA loading

2. IRC class A loading

3: IRC class B loading

4. IRC class 70R loading

1. IRC Class AA Loading:

 This class of loading is based on heavy military vehicles likely to run on national highways, state highways and other specified areas as industrial areas in class AA loading following two types of vehicles are specified 

Tracked vehicles such as tanks and chained tractors 

Wheeled vehicles such as trucks, busses etc

2 IRC class A loading: 

The IRC class A loading is based on the heavier type of commercial vehicles

likely to run on Indian roads

• it is adopted on all types of roads where permanent bridges are constructed

3. IRC class B loading: 

This class of loading generally is adopted for temporary bridges as timber bridges and in specified areas I

It is same as class A loading except that it is 40% less than class A loading.

 4.  IRC Class 70R loading: 

The  letter R Indicates revised classification. For specified highway bridges IRC class 70R loading is used in place of IRC class AA loading. It consist of tracked as well as wheeled vehicles