Week 1 Challenge

1.What are different type of foundation in bridges and how selection of type is made.

Ans. Different types of foundation in bridges are as follows

1. Shallow foundation - Depth of foundation is less than or equal to breadth of foundation
2. Deep foundation - Depth of foundation is greater than breadth of foundation

Shallow foundation are of following types depending on site and design requirements:

• Combined
• Mat/Raft
• Spread or isolated
• Strip
• Strap or Cantilever

Types of deep foundation are:

• Pile foundation
• Well foundation

Decision to go for deep foundations over shallow foundation is based on following factors:

• Poor bearing capacity of the soil at upper strata on the site.
• Liquefaction of soil strata.
• Large fluctuations in subsoil water level.
• Presence of canal or deep drainage lines near the foundation due to which width of foundation is restricted.
• Structure near seashore or riverbed.

If the above factors are not present on the site shallow foundation can be adopted.

2.Name all the components of a RCC girder bridge resting on open foundation. what additional effects it will create if we have

a) seismic case 5,

b)3 span continuous bridge Position all the loads on the bridge having 12 m and 7.5 m carriageway transverse width with to the scale drawings. Also mention all the clauses of IRC 6

Ans.

1. Components of a RCC girder bridge resting on open foundation are as follows:

1. Parapet wall
2. Deck slab
3. RCC girder
4. Bearing
5. Pier cap
6. Pier
7. Foundation

B. Additional effects if we have seismic case are:

• Decreases the bearing capacity and increases the settlement.

3 span continuous bridge Position all the loads on the bridge having 12 m and 7.5 m carriageway transverse width with to the scale drawings.

C.Clause of IRC 6

203 Dead Load
204 Live Loads
206 Foot Over Bridges, Footway, Kerb, Railings, Parapet and Crash Barriers
209 Wind Load
210 Horizontal Forces due to Water Currents
211 Longitudinal Forces
213 Buoyancy
214 Earth Pressure
215 Temperature

What are the various forces acting on the shallow foundations. how they will be different in the case free pier, fix pier and abutment. Show a diagram and loads acting on it.

Various Forces acting on the shallow foundation are:

Dead Load
Live Loads
Super imposed dead load
Wind Load
Horizontal Forces due to Water Currents
Longitudinal Forces (Braking)
Buoyancy
Earth Pressure
Temperature Load

All the longitudinal force of Wind,Seismic, braking will act on fix pier/ fix abutment and not on free pier.