Week 1 Challenge

Q1. What are different types of foundations in bridges and how the selection of type and material is made?

Ans:- The different types of foundation in bridges are as follow:-

• Spread foundation
• grillage foundation
• pile foundation
• Inverted arch foundation
• raft foundation
• well foundation
• caisson foundation

Selection of type and material:-

• Spread foundation: This type of foundation is well suited for dry hard soil, rock, and also where the low height of the bridge is needed.
• Grillage foundation: This type of foundation is well suited for the individual heavy isolated footing where deep foundation can't have opted and also SBC of soil is not good.
• Pile foundation: This is the type of foundation have opted for when the depth of footing is very high because of the low SBC of soil.
• Inverted arch foundation: This type of foundation has opted when the depth of the excavation is less and also the bearing capacity of the soil is less.
• Raft Foundation:- This type of foundation is preferable when the bed of soil consists of silt and clay with water in it and there are no hard strata available to lay a foundation on.
• Well Foundation: It is best suited for the river or sea strata where good sandy soil is available at 3-4 m of depth and heavy scouring is liable because of the high velocity of the water.
• Cassion foundation:- This type of foundation is well suited where hard strata are available near river bed level but the depth of the water is so high that it would not be economical to drain water and sink foundation in it.

2. Name all the components of an RCC girder bridge resting on the open foundation in seismic zone 5.

Ans:

Fig.1 Components of bridges (https://www.midasbridge.com/en/solutions/substructures)

Broadly the components of the bridges are classified into three types:-

• Foundation
• substructures
• superstructures

Subdivisions are as follow:-

• Footing
• Piles
• Pile cap
• Piers
• Pericarp
• Bearings
• Girders
• Deck slab
• Handrails

3. 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.

Show the distribution of forces in the footing afterward due to the loadings.

Ans: The different kind of load acting on the bridges as according to IRC-6 2019 are as follow

• Dead load
• Superimposed dead load
• Earth pressure
• Surcharge
• Live load
• Braking load
• Water Pressure
• Seismic load
• Temperature Load

As the discussion is needed to be done regarding the difference in the type of forces acting on the fixed and free pier and abutments. Actually, as we have learned in structural analysis that if the joint is free it will be unable to resist the forces and moment coming on it contradictory on another hand if the pier is fixed that all the lateral load will be coming on the pier will be resisted and transfer to the ground by the means of foundation.