BRIDGE WORK

 

    Bridge is purposely design to convey traffic flow smoothly over river,railway tracks,over deep valleys and now for elevated transport like MRT,LRT and so on.Many type of bridge since 100 years ago.From bamboo,banana trunks,timber,metal,cast in situ until the high technology like modular or pre cast unit.

Here I am bring my experience to supervise one bridge over 20 m river using a cast in situ concrete for all element from beam to parapet wall.

• 5T BRIDGE
• For limiting 5 T of vehicle
• No pile cap
• Piles sizing 300 mm x 300 mm driven until set and this piling also act as column
• Using a modified crane to drive the pile
• No rake pile was design
• Abutment seat on pile at every site
• Abutment were cast first
• Long beam,cross beam and slab cast together
• Parapet wall is the last cast element

MRT PILERS

• Not involved 
• Just from visual only
• Foundation :Bored Piles more than 600 mm
• Metal formwork
• Sizes from 3000mm x 3000mm
• Modular segment install from launcer
• Technology from outside
• Only 8 or 9 tendon wire connect each of the concrete segment
• Segment are pre-stress
• Only when last segment,the segment will leave hanging ,dangerous for vehicle

MULTI-STOREY HIGHWAY

• For SG Besi uraian trafik project
• More than 3 storey bulding
• Using a bored piles as foundation
• Conventional piers
• Using T,U ,T inverted pre cast beam
• Insitu slab concrete
• Safety issue on the vehicle below the structure
• No enough safety netting below

2.BRIDGE ABUTMENT

Last few days,one of the bridge at one district at Sabah collapsed and wash away by the water.The bridge collapsed due to a right abutment collapsed and wash away by the river current.The strong river flow due to heavy rain at the upstream push the abutment to the down stream.

The upstream river flow have a strong lateral load to push the abutment structure.What is the lateral load mean?.The lateral load are define as the total force act from the horizontal direction.Example of the lateral are wind load act to the wall of the buildings.The lateral load will transfer to the base or foundation as a moment act at the base structure.The another example for lateral load is wind load.The wind load act to the perpendicular to the structure like a building,a pole,high mast and etc.For the building,a bracing element were designed to resist this load.

What is a bridge abutment?.All the bridge a 2 abutment ,left and right.The abutment are design to receive a load from a beam and distribute all the load evenly to the foundation.The foundation are design to receive all the vertical load and lateral load perpendicular to the road direction.The lateral load are from the traffic when try to stop the vehicle so the raked pile are design to resist these type of load.So many type of abutment will use for the bridge depending on the site condition,loading characteristic and etc,There all also depend on the bridge designer.

For foundation of the bridge especially at the abutment,there are two type of pile driven into the ground.One type of pile to resist the vertical load and the another type to resist the lateral load from the vehicle.The raked pile is designed to resist the lateral load.What are the raked pile means?

The raked pile is define a pile driven at inclined to the vertical to provide resistance to the horizontal force.The axial force can be calculate by the formula and by  draw a graph.So to resist the horizontal force from the upstream water force, the abutment foundation must be pile with a raked pile also.These design only for river bridge only.

The usage of raked pile will increased the construction cost at the beginning but for a long time they can avoid from collapse that will bring the difficult to all the people and also to replace a new bridge which the  latter 2 factor will bring more cost.

May be for the old bridge structure need to replace with a new technology bridge.Dont wait for the collapse tragedy or someone fall down to the river and die.The assessment for the old bridge structure need to be done and from that assessment the decision can be made to classified the old bridge.

Which bridge have to repaired,to demolished and when and also the budget.The unsafety and unstable old bridge must be totally replaced to avoid any accident in future.Thank you