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Reinforced concrete strengthening with composite materials;

Structural reinforced concrete elements often need strengthening when there are faults in design or construction, or when there are changes in usage of structures. Over the last few years, the use of compound materials made of a resin matrix with high-strength fibers, usually glass or carbon, is becoming commonplace.

Strengthening of reinforced concrete structures by adding carbon fibre reinforced polymers (CFRP) or other high-strength materials is an excellent alternative to traditional strengthening systems. This technique allows the use of composite materials in different forms: sheet or fabric, simple or pre-stressed laminate, and pultruded rods.

This technology has great potential, but its success depends on its careful application. This is why personnel qualification and a Quality Policy are so important.

The advantages of this method are the speed of application, the ability to cover surfaces of any geometric shape (which allows, for example, the confinement of pillars from top to bottom), and the millimetric thickness of the materials to be added, which allows strengthening without significantly changing the original geometry and weight.

Structural strengthening system with pre-stressed carbon fibers

Recently, Stap signed a collaboration protocol with Scherer & Partner to be the exclusive provider, in Portugal, of the new structural strengthening system with pre-stressed carbon fibers. Until now, FRP (fiber reinforced plastics) laminates were used merely as passive strengthenings. In this new system, laminates are tensioned using specific equipment. This improves the efficacy of the strengthening, making full use of its strength and preventing the mobilisation of its contribution from being at the cost of further deformation of the element to be reinforced.

The system recently underwent its first experimental use in Portugal, in collaboration with the Civil Engineering Department of the Instituto Superior Técnico (IST).

Structure Strengthening with Pre-stressed CFRP Laminates

Strengthening with carbon fibre composites.
Application of composite materials to strengthen a reinforced concrete beam.
Surface grading check before applying carbon fibre reinforced plastic laminates (CFRP).
Checking substrate temperature and humidity before applying CFRP laminates.
CFRP laminate placing.
Verification of sound CFRP bond using percussion.
Pull-out test to control preparation of a surface in strengthening with composite materials.
Surface preparation for CFRP laminate application.
Preparation of a pillar to be reinforced with carbon fibres.
Application of epoxy resin adhesive to the laminate.
Strengthening with carbon fibre sheets.
Application of carbon fibre sheets.
Strengthening of a reinforced concrete pillar using carbon fibre sheets.
Pillar after the application of carbon fabric.
Test performed at the IST Civil Engineering Department.
Drilling to INSERT fixing rods of the metal anchorage plates for pre-stressed carbon fibre reinforced plastic (CFRP) laminates.
Cleaning holes to INSERT fixing rods of the metal anchorage plates for pre-stressed CFRP laminates.
Application of adhesive resin to pre-stressed CFRP laminates.
Applying and securing the metal plate at the end of the fixed anchorage of pre-stressed CFRP laminates.
Applying and securing the "Pre-Stress Kit" at the end of the movable anchorage end of pre-stressed CFRP laminates.
Fitting the pre-stressing jack.
Tightening of pre-stressed CFRP laminates' traction devices.
Overview of the electric-hydraulic power unit and control unit for pre-stressed CFRP laminate tensioning.
Pre-stressed CFRP laminate tensioning equipment

Reinforced concrete strengthening with composite materials;

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