STRUCTURAL STRENGTHENING

Strengthening Existing Concrete Structures

Buildings and infrastructure do not always continue to be used in the way they were originally designed. Loads increase, equipment is added, layouts change and older structures are sometimes required to meet different performance standards.

In other cases, deterioration, cracking or changes to the concrete can reduce the capacity of an existing structural element.

Entekra carries out structural strengthening work on concrete buildings and infrastructure. This includes carbon fibre strengthening, Carbon Fibre Reinforced Polymer (CFRP) systems and Fibre Reinforced Polymer (FRP) strengthening for beams, columns, slabs, walls and bridge components.

These systems can add strength to selected areas without the weight, disruption and space requirements that may come with more traditional strengthening methods.

When Is Structural Strengthening Required?

There are several reasons why an existing structure may need to be strengthened. Sometimes a problem is discovered during an inspection. In other cases, strengthening forms part of a planned refurbishment or change in the way a building will be used.

Structural strengthening may be considered when:

• The use of a building is changing

• Higher loads will be placed on an existing slab

• New equipment or machinery is being installed

• Beams or columns require additional capacity

• Openings are being introduced into slabs or walls

• The original structure no longer meets current project requirements

• Concrete has deteriorated or suffered damage

• Cracking or excessive deflection has occurred

• A bridge or infrastructure asset is being upgraded

• An existing structure needs to remain in use rather than being replaced

The system used will depend on the structure, the required increase in capacity and the type of forces acting on the affected element.

Carbon Fibre Strengthening

Carbon fibre strengthening is used where additional strength is required without adding significant weight or bulk to a structure.

CFRP plates or fabrics are bonded to the prepared concrete surface using structural adhesives. Once installed, the carbon fibre works with the existing concrete element to increase its capacity in the required area.

Because carbon fibre is thin and lightweight, it can be useful in locations where access is restricted or where headroom and appearance need to be considered. It also avoids introducing heavy steel sections into areas that may already be difficult to work in.

Carbon fibre strengthening may be used on:

• Concrete beams

• Suspended slabs

• Columns

• Concrete walls

• Bridge components

• Car park structures

• Commercial and industrial buildings

The layout and direction of the carbon fibre are determined by the strengthening requirements of the structure.

CFRP Plates and FRP Fabrics

Although the terms are sometimes used interchangeably, plates and fabrics are installed differently and may be selected for different strengthening requirements.

Prefabricated CFRP plates are generally bonded along the surface of beams or slabs. They are commonly used where additional flexural capacity is required.

FRP fabrics are more flexible and can be wrapped around columns, beams or other shaped elements. This makes them suitable for strengthening areas where the material needs to follow the profile of the structure.

Depending on the design, FRP systems can be used to improve flexural capacity, shear capacity or confinement.

Flexural Strengthening

Flexural strengthening is used when a beam or slab requires greater resistance to bending. This may be necessary after loads increase, the use of a building changes or an opening alters the way forces are transferred through the structure.

CFRP plates or fabrics can be bonded to the tension face of the concrete element to provide additional capacity. As the system adds very little thickness, it can often be installed without substantially changing the dimensions of the beam or reducing the available headroom.

Applications may include suspended slabs, bridge decks, concrete beams and car park structures.

Shear Strengthening

Shear forces can cause diagonal cracking and failure within concrete beams and other structural elements. Where additional shear capacity is required, CFRP or FRP fabric can be applied around the sides of the element in a designed configuration.

Unlike rigid plates, fabric systems can be wrapped around corners and changes in profile. This allows the strengthening material to reinforce the required areas while remaining closely bonded to the concrete surface.

Column Strengthening and Confinement

FRP fabric can also be wrapped around concrete columns to provide confinement. The wrap restrains the concrete and can improve the performance of the column under load.

Because the system adds little weight or thickness, it may be suitable for columns in car parks, commercial buildings and other areas where space is limited.

Before the strengthening material is installed, cracks, spalling or surface defects need to be repaired so the system is applied to a sound and properly prepared substrate.

Preparing Concrete for Structural Strengthening

The performance of a bonded strengthening system depends heavily on the condition of the concrete beneath it. Carbon fibre should not be installed over loose, contaminated or deteriorated concrete.

The preparation work may include:

• Inspecting the proposed strengthening area

• Removing coatings, contaminants and unsound concrete

• Repairing cracks or damaged sections

• Treating exposed or corroded reinforcement

• Reinstating the concrete profile

• Grinding or preparing the surface

• Rounding corners where fabric wrapping is required

• Cleaning the area before the adhesive system is applied

Once the substrate is ready, the specified plates or fabrics are installed in the required position. The completed work is then checked to confirm adhesion, coverage and finish.

Structural Strengthening and Concrete Repairs

Strengthening and concrete repair are related,  but they are not the same thing. Concrete repairs deal with deterioration such as cracking, spalling and corrosion damage. Structural strengthening is used to increase or restore the capacity of an element.On some projects, both are needed. Damaged concrete may first need to be removed and reinstated before the strengthening system can be installed. Carrying out the strengthening without addressing the condition of the underlying concrete could affect the performance of the finished system. Entekra’s experience in concrete remediation, crack injection, corrosion treatment and protective coatings allows the preparation and strengthening work to be considered as part of the same project.

Buildings, Bridges and Infrastructure

Structural strengthening systems can be used across a range of commercial and civil structures, including:

• Commercial buildings

• Industrial facilities

• Multilevel car parks

• Concrete bridges

• Suspended slabs

• Beams and columns

• Concrete walls

• Water infrastructure

• Existing structures undergoing refurbishment

Entekra has completed bridge maintenance and strengthening work involving crack injection, concrete repairs, CFRP reinforcement, FRP strengthening and expansion-joint replacement.

Where a building or asset needs to remain operational, the work can be planned in stages to reduce disruption and manage access around the repair area.

Why Use CFRP and FRP Strengthening?

Carbon fibre and FRP systems offer several practical advantages when strengthening an existing structure:

• Very little additional weight is added

• The systems have a low installed profile

• Plates and fabrics can be installed in restricted areas

• Fabric can follow columns, beams and irregular shapes

• Large structural elements do not always need to be removed or replaced

• Installation may cause less disruption than conventional strengthening work

• The systems do not reduce headroom as much as bulky steel supports may

• Carbon fibre is resistant to corrosion

The suitability of any strengthening system must be assessed for the individual structure and its intended use.

Talk to Entekra About Structural Strengthening

If a building, bridge or concrete structure requires additional capacity, Entekra can carry out the preparation, concrete remediation and installation work required for a specified structural strengthening system.



Contact Entekra to discuss carbon fibre, CFRP or FRP strengthening for your commercial or infrastructure project.

BENEFITS OF STRUCTURAL STRENGTHENING