Seminar presentation

Assessment of Structure & Maintenance of Bridges

Seminar GuideMr. Mukesh

SawAsstt. Professor

Presented byNeha Singh

1212200073CE-73

SHRI RAMSWAROOP MEMORIAL GROUP OF PROFESSIONAL COLLEGES,

LUCKNOWAffiliated to

G.B. TECHNICAL UNIVERSITY, LUCKNOW

INTRODUCTION• Bridges represent a considerable capital asset not only

because of the heavy investment required in constructing or replacing them but also because of them form part of the historic and cultural heritage of a Country.

• The fundamental justification for assessment of bridge structure lies in assurance of safety .

• The adage “prevention is better than cure" and " a stitch at time saves nine" are eminently true for bridges, where defects can rapidly lead to serious consequences if action is not taken in time.

• It is essential to prolong the life of structures and rehabilitate them wherever necessary and possible.

PURPOSE OF INSPECTION• To provide assurance that the bridge is structurally safe and fit for its designed

use.

• To identify actual and potential sources of trouble at the earliest possible stage.

• To record systematically and periodically the state of the structure.

• To provide feed-back of information to designers and custodians of bridges on those features which are likely to give maintenance problems and to which necessary attention is best given during design and construction stages

• To provide necessary information on which decision will be made for carrying out maintenance repairs, strengthening or replacement of the structure.

PLANNING THE INSPECTIONRead completion plans, when available

See pile and well foundation details

Go through earlier Inspection reports

Go through reports regarding repairs/ strengthening carried out in past.

Go through stress sheets for major girder Bridges.

INSPECTION EQUIPMENTSPocket Tape

Feeler Gauges

Magnifying

Glass

Torch Light

Steel Scale

Chipping

Hammer

Log Line

With 20 Kg Lead

Ball

Crack Meter

Screw Driver

Inspection

Hammer

Plumb Bob

Elcometer

Waterproof

Pencil

Paint Brush

Rivet Testing Hamme

rStraight

EdgeWire Brush

Centre Punch

Gauge –Cum-level

Schmidt Hamme

r 30 M Steel Tape

Mirror Callipers

Piano Wire

Scaffolding

SAFETY PRECAUTIONWear suitable dress so that

loose end doesn’t get caught; too-

tight a dress may hamper your free

movements.If you normally

wear glasses for improving your eye sight, wear

them when climbing up or

down sub-structures & super

structures.Keep clothing & shoe free from grease

and steel stars or nail etc which

causes slipping.Scaffolding or

platforms should be free from grease

or other slippery

substances.

Scaffolding and working

platforms should be adequate

strength and be secured

against

Slipping or overturning.

No shortcut at any cost. Vigil over passing

trains

FOUNDATION

Disintegration of

foundation

material

Heavy localized scour in

the vicinity of piers /

abutments

Uneven settleme

nt

ASSESSMENT OF BRIGDE : INSPECTION

ABUTMENT AND PIER

Crushing

And Cracking Of Masonry

Weathering

Failure Of

Mortar

Bulging

Transverse Cracks In

Piers

BED BLOCKSShaken bed blockGaps between bed block and base plate of bearing due to uneven contact area.Cracks in bed due to improper seating of bearings.Cracks in bed block due to cracking and crushing of masonry under the bed block.

BEARINGSA bridge bearing is a component of a bridge which typically provides a resting surface between bridge piers and the bridge deck.The purpose of a bearing is to allow controlled movement and thereby reduce the stresses involved. Movement could be thermal expansion or contraction, or movement from other sources such as seismic activity.

Types of

bearing

Sliding Bearing

Expansion

bearing

Elastomeric

Laminated

bearing

Roller and

rocker bearing

PTFEbearing

The rockers, debris ,pins, rollers should be free from corrosionProper function of plain bearingsPeriodical cleaning of phosphor bronze sliding bearingsTilt of segmental rollersExcessive longitudinal movements of the superstructures.

ASSESSMENT OF STEEL BRIDGELoss of camber• Heavy overstressing of girder members• Play between rivet holes and rivet shanks• Overstressing of joint rivetsDistortion• Members affected are top chord , tension members,

diagonal web, top flanges of plate girders.• Possible due to longitudinal movement of girders

because of temperature variation.Loose rivets• Subjected to heavy vibration prone to get loose• Critical areas are: Top flange of plate girder ,Gusset

at panel

Corrosion• Reduces structural capacity• Sleeper seats, top lateral of through girders, are in

vicinity of bearings

ASSESSMENT OF CONCRETE BRIDGE

Cracking• Location of cracks, their nature and width can

bed used to diagnose the cause . Minor hair cracks showing map pattern generally occur because of shrinkage of concrete and hence not of much significance.Scaling

• It is the gradual and continuing loss of mortar and aggregate over an area

• Scaling is observed when repetitive freeze and thaw action on concrete takes place.Spalling

• Tendency to spall can be identified by tapping the area with a small chipping hammer when hollow sound is heard.

Reinforcement corrosion• Improper drainage of deck slab• Leads to cracking and spalling

TRACK ON GIRDER BRIDGESDeparture from line is caused by Incorrect seating of girder , Shifting of girders laterally or longitudinally, Incorrect seating of bridge timber on girderDeparture from level is caused by errors in level of

bed

Condition of timber and fastenings should be checked

At fishplated joints the clear spacing should not exceed 200mm.

Creep should be checked and rails pulled back wherever necessary.

UNDER WATER INSPECTION OF BRIDGES

• To ensure safe condition of sub-structure during the course of its life.•To detect any distressed condition of sub-structure out lived or pre-mature•To prevent any possible mishap due to structure failure by timely action

Anaerobic

bacterial

growth

Scaling of

concrete

Spalling of

concrete

Disintegration

of concret

e

Deep Cavitati

on

Initial inspection requires careful planningPrior site survey for selection of inspection methods, type and intensity level, equipment required

Review of available records and past history

Availability of tools and plants

Ability/qualification of diving team

Scour investigation

Inspection of sub structure

UNDERWATER INSPECTION PROCEDURE

METHODS OF UNDERWATER INSPECTION

SCU

BA D

IVIN

G

• Advantages• Most suitable for

short duration dives

• Lower operating cost,

• Low effort dive, • Allows increased

diver mobility, • Best in low

velocity currents.

• Disadvantages • Limited air supply

SURF

ACE

SUPP

LIED

AIR

DI

VIN

G

• Advantages • Long duration

dives/deep water diving (more than 36 m),

• Unlimited air supply,

• Backup system available,

• Better for low water temperature and high-effort dives,

• Safe line attachment to surface,

• Better for high velocity currents

• Disadvantages• Large size of

operation

DIVING INSPECTION INTENSITY LEVELSVisual

inspection, a feel inspection using large sweeping motions of the hands where visibility is limited. If needed, a clear box can be used. This inspection is supplemented by water depth soundings. This inspection is often characterized as a “swim by” inspection

Level 1

Detail visual inspection that includes cleaning of areas for closer inspection and obtaining limited measurements of damaged or deteriorated areas that may be hidden by marine growth.

Level 2

Investigation of specific components using Non Destructive Testing (NDT). The purpose of special instruction is to assess the material state/strength.

Level 3

NON DESTRUCTIVE TESTING• Non-destructive testing (NDT) is a wide group of analysis

techniques used in science and industry to evaluate the properties of a material, component or system without causing damage.

• Estimating the in-situ compressive strength.• Estimating the uniformity and homogeneity.• Estimating the quality in relation to standard requirement.• Identifying areas of lower integrity in comparison to other

parts.• Detection of presence of cracks, voids and other

imperfections.• Monitoring changes in the structure of the concrete

identification of reinforcement profile and measurement of cover, bar diameter, etc.

NDT FOR CONCRETERebound Hammer

UPVT

Pull Off test

Pull Out Test

Windsor probe

Rebar Locators

Covermeter

Half –cell potentiometer

Resistivity test

Acoustic emission Technique

NDT FOR MASONARY BRIDGES

Flat Jack testing

Impact echo testing

Impulse Radar

Infrared thermography

Liquid Penetrant Inspection

Magnetic Particle Inspection

Eddy Current Testing

Radiographic testing

Ultrasonic testing

NDT FOR STEELBRIDGES

NUMERICAL RATING SYSTEM• The numerical rating system is an aid in

objectively reporting of the results of the inspections and in giving an idea to the scrutinizing officers as to the type of input required to be given to the bridge.

• The present system of recording condition of bridges in bridge inspection register being qualitative in nature, it is not possible to readily identify the relative seriousness of the detects/ distress conditions in the bridge, required for rebuilding rehabilitation/ major repairs etc.

RELEVANCE TO INDIAN RAILWAYS The numerical Rating System for

Bridge inspection envisages assigning numerical rating to the physical condition of bridge as whole, as also to its components.

The following table gives the Condition Rating number (CRN) and brief description of the corresponding condition. --------------------------------------------------------

At present this system has been widely used all over Indian railways.

Bridges are inspected assistant engineer once a year after the monsoon season as per the provision in the Indian railways way and works manual.

It is, therefore, difficult to have an overall picture of the condition of bridges, as the registers are returned to the AEN’s after they are scrutinized by territorial HOD.

The number of bridges on the railways is very large.

CRN DESCRIPTION

1 A condition which warrants rebuilding/ rehabilitation immediately.

2 A condition which requires rebuilding/rehabilitation on programmed basis.

3 A condition which requires major/special repairs.

4 A condition which requires routine maintenance.

5 Sound condition.

6 Not applicable

0 Not inspected

ORN - URN

OVERALL RATING NUMBERIn addition to CRN for different bridge components, an overall rating number (ORN) for the bridge as a whole is also to be given which in general, will be the lowest rating number, except 0 , given to any of the bridge components. UNIQUE RATING NUMBER (URN)The physical condition of each major bridge is to be represented by a Unique Rating Number (URN)consisting of 8 digits. The first digit will represent the ORN and each of the subsequent digits will represent the CRN of the different bridge components in the following sequence.

URN 20362544DIGIT NO. VALUE INDICATION

1(ORN)

2 Whole bridge or one or more of its components require rebuilding /rehabilitation on programmed basis.

2 0 Foundation and flooring were not inspected.

3 3 Substructure requires major/ special repairs.

4 6 Not applicable i.e. the bridge doesn’t have any training or protection works.

5 2 Bed blocks are cracked and shaking

6 5 Bearings and expansions arrangements are in sound condition.

7 4 Superstructure require routine maintenance.

8 4 Track requires routine maintenance.

MAINTENANCE AND REPAIRS

Source: Handbook For Bridge MaintenanceRDSO

CEMENT PRESSURE GROUTING OF MASONARY STRUCTURES

• Unmodified Portland cement Mortar or Grout

• Latex Modified Portland cement Mortar or Concrete

• Quick Setting Non-shrink mortar.• Polymer Concrete• Epoxy Mortar or Concrete• Methyl Methacrylate Concrete

REPAIRS OF CRACKS IN REINFORCED CONCRETE AND

PRESTRESSED CONCRETE GIRDERS AND SLABS

• Cracks wider than .3 to .4 mm should be filled and sealed with injection.

• Materials used:– Epoxy resin– Polyurethane resin– Acrylic resin– Unsaturated polyester resin

• Guniting– Process of depositing a dense layer of

sand cement mixture can be used profitably for repairing spalled concrete structures or weathered stone or brick masonry.

• Jacketing– To strengthen the substructure , the

cross sectional area may require to be increased. For this purpose jacketing of existing structures is resorted to.

• Painting– Girder painting is essentially an

application of surface coating to the steel work so as to inhibit corrosion.

REPLACING LOOSE RIVETS

• During technical inspection it is essential to check critical location and record the status of the rivets properly.

• This is particularly true for open web girder for which a special proforma is used.

• Rivets which are driven at site and rivets which are subjected to heavy vibrations are prone to get loose corrosion around rivets also cause loosening.

• To test whether a rivet is loose, left hand index finger is placed on one side of the rivet head in such a manner so that your finger touches both the plate and the rivet head.

ThankS