Bridge

Bridge is a structure that provides passage over obstacles such as valleys, rough terrain or bodies of water by spanning those obstacles with natural or manmade materials. In the beginning bridges were very simple structures that were built from easily accessible natural resources-wooden logs, stone and dirt.

 

Survey of Bridge

Bridge surveying necessary to locate a site, obtain information for design, and furnish lines and grades for construction. A preliminary survey is made at the best site to establish horizontal and vertical control and to obtain information for the bridge design and construction planning.

 

Foundation

A foundation is the lowest and supporting layer of a structure. Foundation are generally divided into two categories-

• Shallow Foundation
• Deep Foundation

 

Shallow Foundation

There are variety of shallow foundation types used in construction of foundation columns-

• Combines or Cantilevered
• Mat
• Wall (strip)
• Spread footing
• Strap footing

 

Shallow Foundation

There are variety of shallow foundation types used in construction of foundation columns-

• Combined or cantilevered
• Mat
• Wall (strip)
• Spread footing
• Strap footing

 

Deep Foundation

Deep foundation are those foundation in which the depth at the foundation is very large in comparison to its width.

• Deep strip, rectangular and square footing
• Pile foundation
• Pier foundation or drilled caisson foundation
• Well foundation or caisson

 

Types of well foundation or cassion

• Box caissons
• Excavated caissons
• Floating caissons
• Open caissons
• Pneumatic caissons
• Sheeted caissons

 

Method of Installation

• Dropping weight or drop hammers commonly used method of insertion of displacement piles.
• Diesel Hammers- Most suitable to drive pile in non cohesive granular soil.
• Vibratory hammers or vibratory method of pile driving very effective in driving piles through non cohesive granular soil.
• Jacking method of insertion.

 

Dropping Weight / Drop Hammers

• A weight approximately half that of the pile is raised a suitable distance in a guide and released to strike the pile head.
• When driving a hollow pile tube the weight usually acts on a plug at the bottom of the pile thus reducing any excess stresses along the length of the tube during insertion.

 

Diesel Hammer

• Rapid controlled explosion can be produced by the diesel hammer.
• The explosions raise a ram which is used to drive the pile into the ground, although the ram is smaller than the weight used in the drop hammer.
• Increased frequency of the blows can make up for this efficiency.
• This type of hammer is most suitable for driving piles through non-cohesive granular soil where the majority of the resistance is from end bearing.

 

Vibratory method of pile driving

• Vibratory methods can prove to be very effective in driving piles through non cohesive granular soils.
• The vibration of the pile excites the soil grains adjacent to the pile making the soil almost free flowing thus significantly roughing friction along the pile shaft.
• However the large energy resulting from the vibrations can damages equipment, noise and vibration propagation can also result in the settlement of near by building.

 

Jacking method of insertion

• Jacked piles are most commonly used in underplaying structure.
• By excavating underneath a structure short lengths of pile can be inserted and jacked into the ground using the underside of the existing structure as a reaction.

 

Precast segmental erection techniques

• Erection on false work
• Erection by Gantry
• Erection by crane
• Erection by Lifting frame
• Full span erection techniques