Week 8 Challenge
Q 1 :
Calculate the loads as per IRC 6 assuming bridge in Bangalore on the pile group of the below given bridge for the abutment.(ignore temperature and wind)
Weight of Crash barrier and railing can be assumed as 10kn/running meter
Soln :
Q 2 :
List all the components of the well foundation and list the minimum kg/cumec(poundage) in them mentioning clauses from IRC codes.
Also list their functionality in respect to bridges loadings.
Soln :
Components of well foundation
- Well cap
- Top plug
- Steining
- Bottom plug
- Cutting edge
- Well Kerb
- Filling inside( sand /water)
Well Cap
It is constructed as slab resisting on the well to transfer load from pier to well.It forms an interim layer to accomodate the pier.It should be designed in such a way that the base of pier should have minimum offset allround.Centre of well cap should coincide with centre of pier to nullify the minor shifts due to shrinkage of well.
Top plug
It is provided after filling.It transfers load of substructure and superstructure to the steining walls.The thickness should be greater than 50% of smaller dimension of the dredge hole in foundation.If sand filling is used the top plug is constrcuted with PCC 1:2:4 or reinforced with steel.
Stening
The walls of well is called steining.Its is made of brick/Stone masonry/Plain or reinforced concrete.Skin friction & unit weight influences the design.FEM design is recommended for this.Thickness value should allow all the platform of well foundation to sink under its own weight.Mid steel
Bottom plug/cutting edge
Mild steel cutting edge is used.It should not be less than 40 kg/m to facilitate sinking.It should be anchored to the well kerb and designed to withstand hard strata.Bottom plugging of well is done after PCC works.Concrete used in bottom plug shall have cement content of 330 kg/cum and should be kept not lower than 300mm in the center above the top of the kerb.
Well Kerb
It transfers all the loads from top to the soil through the cutting edge while sinking.It can be made of timber or RCC.Internal angle should be kept at 30 to 37 degrees.Concrete grade M25 with minimum 72 kg/cum reinforcement should be used.
