DEFECTS IN BRIDGES AND REMEDIAL MEASURES

•Prepared by:

Matariya Rahul D

CONTENT

INTRODUCTION TYPES OF DEFECT IN BRIDGE REMEDIAL MEASURE FOR DEFECT IN BRIDGE REFERENCES

INTRODUCTION In the past, bridges were expected to last

about 60 years; however, current technology and design allow the bridges that are built today to last longer. High traffic volume, heavy trucks, and freeze/thaw cycles along with exposure to salt used for winter maintenance all reduce a bridge’s lifespan. Regular maintenance, repair, and rehabilitation can largely offset the impact of these factors on a bridge’s lifespan.

Various defects arising in bridges and their remedial measures are discussed below:

Weakening of foundation Erosion of foundation Damaged flooring and approaches Improper drainage of storm water Cracks in the abutment and wing wall Cracks in the super structure Damage to the pointing Defects in bearing Damage in parapet wall and railing Scouring Corrosion of the structural steel

WEAKENING OF FOUNDATION

Causes of weakening of foundation -Weak Bearing Soils -Poor Compaction

If foundation soil below abutment and piers is washed out, there may be possibility of unequal settlement resulting in heavy damage.

So use underpinning technique the foundation should be strengthened by providing grillage foundation or pile foundation

EROSION OF FOUNDATION In such case the bridge should be closed for

traffic. By under pinning technique the entire pier is supported in I girders.

The soil surrounding the old foundation is excavated and new concrete bed is provided.

If depth of scour is more sheet piles are driven around the old foundation.

The soil is excavated and new concrete layer is provided on a thick bed of boulders, moorum or sand.

DAMAGED FLOORING AND APPROACHES

In case of cement concrete road, if the wearing surface of road is worn out due to heavy traffic and reinforcement are visible , it is advisable to provide a new layer of cement concrete or bituminous concrete.

If concrete work of girders, slab is damaged, it may be repaired by guniting technique.

IMPROPER DRAINAGE OF STORM WATER

The following measure should be taken for effective drainage of storm water.

The size of storm water drain should be sufficient

The surface course should be given proper camber or cross slope.

The drain should be cleaned at regular time. The drain pipe should be placed below

wearing course at sufficient depth. The upper end of pipe should be so arranged

that water does not penetrated into the formation.

CRACKS IN WING WALL AND ABUTMENT

Initially , it is necessary to examine the causes of cracks , like….

Improper drainage system Earth pressure behind the abutment Insufficient thickness of the mortar joints in

the masonry.

In such case the cracks are stretched to a depth of 2 to 3 cm and covered with cement mortar of proportion 1:2 , if width of cracks is large, wire mesh of iron can be used, then it is covered with cement mortar.

CRACKS IN THE SUPER STRUCTURE

Such cracks may develop due to,,,,

Unequal settlement Temperature changes Moisture effect

Normally in quality construction such cracks hardly appear such cracks can be filled up by using rich quality of cement mortar, if cracks are wider, guniting can be done.

DAMAGE TO THE POINTING

If pointing work of the rubble masonry piers, abutment, and wing is damaged , old surface is cleaned by using wire brushes, old joints are racked out to a depth of 1.5 to 2 cm, after sprinkling the water , new pointing work can be carried out.

DEFECT IN BEARING

For effective functioning of bearing following care is to be taken.

Cleaning of bearing regularly. Regularly lubrication. There should not be cracks in the bearing It should be free from corrosion.

DAMAGE TO PARAPET WALL AND RAILING

Masonry parapet wall may get damaged due to collision of vehicles. Such damaged parapet should be dismantled and new parapet wall should be constructed .

It should be painted whenever necessary.

SCOURING

Due to scouring , the foundation may get open out. The depressions formed due to scouring should be filled up with empty cement bags filled with sand.

CORROSION OF THE STRUCTURAL STEEL

Following care must be taken

Clean the corroded part by rubbing glass paper,

Apply three coat of painting Inspect the steel work regularly for corrosion.

REFERENCES Emmons P.H.(1994): “ concrete Repair and Maintenance

Illustrated : Problem Analysis , Repair , Strategy, Techniques” Means USA.

“Design Manual for Road and Bridges” Vol, 3; Highway Structures : Inspection and Maintenance

Department of Transport(UK) Kadiyali, L. R., (2008) ‘Traffic Engineering and Transport

Planning’, Seventh Edition, Khanna Publishers. Transit New Zealand “ Bridge Inspection and Maintenance

Manual (2001)

Thank you…..