0011_bridge_refurbishment_javad_akhtar

abcBridge Refurbishment Javad Akhtar

Bridge Refurbishment

Bridges Forum November 2000

J Akhtar Bridges Division, Croydon


Aims

To illustrate general approach to investigating a refurbishment problem “From Scratch”

Client may not be aware he has a potential problem

Usually reluctant to undertake investigation

Bridge may be a component of a larger scheme: Conflict of interests

Difficult to actually agree solution with all parties

Implementation of solution may not be straightforward

Many defects due to construction original faults


Aims

To highlight differences from UK practice

The Nature of Defects Encountered

Construction Practices and Standards

Organisational and “Cultural” Difficulties


Investigation and Solution Approach

Correct identification of Cause

Devise Solution

Convince Client and Approving authorities

Obtain Financial Approval

Implement Solution

Monitor Structure following implementation

Install maintenance Regime


Motivators For “Fettling”

Defects

During Construction

Arising In Service

Change of Use

Alignment/Layout Change

Increase in Loading

Nature of Loading change

Hazards [Potential Causes of Defects]

Erosion

Settlement

Rockfall

Earthquake

Explosion


Sample Schemes

Mozambique

Pakistan Motorway - Salt Range Bridges C5 and C6

Karakoram Highway

Chota Ravi Bridges, Lahore

Brest-Minsk Highway Belarus

Heuston Bridge Dublin


Construction Defects

Belarus: Bridge Immediately After Construction

Hollow Columns: Verticality Parapet Welding

Tack welds

to ribbed bar


Construction Defects

Pakistan Motorway

65m High Columns out of plumb


Defects arising In Service

Brest-Minsk: Deck Damage

Design Deficiency: Absence of deck diaphragm beams


Defects arising In Service Mozambique: Settlement caused by

erosion of pier foundations

Mozambique: Road erosion


Change of Use


Cast Iron Arch, built 1827

Introduction of Tramway



Erosion

Impact

Rockfall

Earthquake

Explosion

Corrosion

Vibration

Overloading


Hazards

Erosion

Due to Unusual discharge from Dam



Belarus: Impact Damage To Hollow Columns


Hazards

Mozambique: Bomb Damage

Solution:Replace Structure


HazardsKarakoram Highway

Impact Damage by

BouncingRocks, Rock/mudflows


Hazards - Karakoram HighwayBailey Bridge replaces RC

arch swept away by rock/mudflow.

Bridges across

terminal moraine of Glacier


Investigate Cause

Information Gathering

Records

Loading

Ground Conditions

Environment

Construction Method

Materials

History and Local Knowledge


Investigate Cause

Risk Assessment


Investigate Cause

Field Investigation Buried Valley

Folded Sandstones /

Mudstone

Buried Valley

Shattered Sandstone

Micaecous Bedding


Investigate Cause

Field Investigation

Get Expert Advice!

Gypsum Marl,

surface solution features

develop after exposure to rain

Gypsum Marl,

As excavated

(Grey is anhydrous)


Investigate Cause

Drilling


Investigate Cause

Initial presumptions may be confirmed


Investigate Cause

Interpretation

What does it mean?

Could there be other factors?

Do you need further investigation?

If you must proceed on incomplete information, ensure that the client is aware of the risks


Investigate Cause

Things are not always as they seem


Investigate Cause

Reality may be worse than expected!


Investigate Cause

Analysis

Desk Studies

Specialist Advice

Modelling

Reporting

64

.2

Gantry No. 4 - Euston Station

DEAD, SUPERIMPOSED DEAD LOADINGSTAGE 2 DEFLECTION PLOT


Demonstrate Cause


Discuss Solutions and Alternatives

Evaluate Consequences

Financial Aspects

Construction Methods

Value Engineering

Risks

Explain what you intend to achieve, may not always be able to restore structure to design condition!


Gather Design Team

How will you Communicate?

Where will it be Located?

Mix of Skills


Approach to Solution

Remove Cause of Problem

Correct design Deficiency

Strengthen/Restore Structural Elements

Protect Structural Elements against deterioration

Monitor Structure


Remove Cause of Problem

Lowering and widening of v-shaped drainage channel tobelow bridge foundation level.

Original intention was todemolish bridge and rebuild.

Hazards included old brickarch culverts at aboutfoundation level.

Solution was to divert drainagechannels around piers in linedchannel, and closed culverts

Chota Ravi Bridges, Lahore:


Correct design Deficiency

Brest-Minsk: Absence of deck diaphragm beams

Recommended

Diaphragm Beam

Abutment

Local Wheel loads causing damage

Reinforced Concrete Deck Slab

Maintain access to deck joint


Strengthen/Restore Structural Elements and Protect against deterioration

For a “new” structure a “Repair” solution to correct construction defects may not be acceptable to the client.

Should the client accept the “Repair” approach, then the design of the repair will be on a FITNESS FOR PURPOSE basis.

This requires consideration of the Consequences of a Departure from Standards



Bridge 7, Euston

Arch Rib Strengthening

Working Entirely From Below


Agree Solution

Get all Parties “On-Board”


Monitor Implementation


Monitor Structure

Is the structure behaving as expected?

Aspects monitored may include:

Geometry: Levels, Tilts

Corrosion rates

Strain Guage

Cracks: Pattern, gap opening

Visual Inspection

Environment: Ground water levels, rainfall, river flows


Open to Traffic

0011_bridge_refurbishment_javad_akhtar

Documents

refurbishment problem

j akhtar bridges division

nature of defects

fettling defects

construction practices

investigation bridge

construction hollow

bomb damage solution