Lecturer:Prof. Dr. Mohammad Ismail

Faculty of Civil Engineering, UTM-Skudai, Johor Darul Ta’zim,

MALAYSIA

March 25, 2015

Strengthening And Stabilization

3

EVALUATE

Shear CapacityFlexural Capacity

Tensile

Capacity

Compressive

Capacity

Member

Stability

REPAIR

ANALYSIS

Repair Strategy

Strengthen

Passive Load

Carrying

Active Load Carrying

Stabilize

Composite

Construction

Post-TensioningEnlargement &

OverlaysStress

Reduction

External

Grouting

Internal

Grouting

Methods for stabilization and strengtheningof concrete structures and members can becategorized by the repair and techniquesemployed:

◦ Enlargement◦ Composite Construction◦ Post-Tensioning◦ Stress Reduction◦ Internal Grouting◦ External Grouting

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Enlargement is the placement of additional concrete and reinforcing steel on an existing structural member

Beams, slabs, columns, walls can be enlarged to add stiffness or load carrying capacity

The enlargement is bonded to the existing concrete to create a monolithic member

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Composite construction is a method wherein materials other than concrete are placed in concert with an existing concrete member to add stiffness or load carrying capacity

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Steel is the most common material used in this technique

Steel plates and structural shapes can be fabricated to meet almost any configuration requirement

Load transfer in the composite member is accomplished by the use of adhesives, grouts and mechanical systems

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Post-tensioning is a technique used to prestress reinforced concrete.

The tensioning provides the member with an immediate and active load-carrying capacity

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Placement of the tension components can be achieved either internally within the member or externally to the member.

Tension components are generally steel plates, rods, tendons or strands

Tension is imparted to the components by jacking or preheating.

Post-tensioning enhances a member ability to relieve overstressed conditions in tension, shear, bending and torsion.

This technique can also be used to eliminate unwanted displacements and to turn discontinuous members to continuous members

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External Tendons consist of:

o A strand bundle

o duct of plastic or steel

o End and intermediate

anchorages as well as tendon

couplers

o A grouting compound

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Stress reduction is a technique that reducesstress in a member or structure.

Common methods are cutting new expansionjoints, jacking displaced structures andinstalling isolation bearings.

Other radical technique involve the removalof portions of structures

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Internal grouting is the placement of a flow able material into an unwanted discontinuity such as cracks within the concrete member.

The flow able material, upon reaching the discontinuity, will solidify and assume necessary structural properties.

Internal grouting is used to repair fractured, honeycombed, or voided concrete placements.

The most common materials used for internal grouting are polymers and hydraulics cement-based materials

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External grouting is the placement of a pump able material outside the structure, generally within the surrounding foundation soils or at the interface between the structure and the soil.

The grouting materials can be used either to provide necessary load transfer between the structure and soil, or to displace unwanted settlement.

Most materials used include cement-based mixtures.

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REPAIR

ANALYSIS

EVALUATE

Altering

Service and

Exposure

Conditions

Methods of Protection

Enhancing the

Physical

Properties of

Repair Materials

Surface-

Applied

Barriers

Protection

Strategies

Methods of Insuring

the Long Term

Performance of

Repairs

PROTECTION STRATEGIES

Methods of achieving

User Performance

Requirements

Methods of Insuring

the Long term Life of

the Original Structure

Controlling

the Cause of

Deterioratio

n & User

Dysfunction

Altering the

Electro-

Chemical

Behaviour

USER Needs

Cause

Effect

Wear

Embedded

metal corrosion

spalling

Disintegration

Leakage

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