Abstract
This paper analyses the results obtained from the testing of reinforced concrete beams additionally strengthened with composite materials pressed into the concrete cover using the near-surface-mounted reinforcement (NSMR) method. The testing program comprised two series of beams with cross-sectional dimensions of 0.12 x 0.30 x 3.30 m. The series differed in the amount of longitudinal steel reinforcement, 0.51% and 1.00%. Three beams were cast in each series. One beam was assigned as the control beam, while two other beams were strengthened with carbon fibre strips. A two-component thixotropic epoxy resin was used as a bonding agent. One of the two beams was cured for 7 days (to the product information document). The bonding process in the other beam was accelerated to last 1.5 hours by heating the strip up to 70°C. As the strengthening of "new" elements is not an accepted practice in engineering, the beams were pre-loaded. The load was maintained during the strengthening procedure and curing period (for 7 days and 1.5 hours) and then the beams were monotonically loaded to failure. The comparison of load capacity results for the CFRP strengthened and control beams revealed the effectiveness of the strengthening method. The paper also presents the strengthening technique in the NSMR application with the prototype heating device.
Highlights
In many countries worldwide, including Poland, new construction projects are becoming limited both in scale and scope
As the duration of the strengthening process is of key importance, this paper proposes an accelerated strengthening procedure in which carbon fibre reinforced polymer (CFRP) strips are heated using the prototype heating device [13, 14]
The amount of steel and composite reinforcement was determined from formulas 1 and 2: ρs where As is the surface area of the steel reinforcement; ds is the usable height from the beam compression face to the centroid of the steel reinforcement; Af is the surface area of the composite reinforcement; df is the usable height from the beam compression face to the centroid of the composite reinforcement; b is the width of the beam
Summary
In many countries worldwide, including Poland, new construction projects are becoming limited both in scale and scope. The need to strengthen may originate from poor workmanship, design errors, misuse of the building, wear-out of its structural components used beyond their design service life, or increased user requirements. The required increase in usable loads will create the need for adequate increase in the load capacity of structural elements of the building. Traditional strengthening techniques [1], such as increasing the cross-section of the member, adding internal or external reinforcement, gluing steel flat bars or reducing internal https://doi.org/10.10 51/matecconf /20192840600 5 forces by changing the static scheme of the member, usually generate high deconstruction costs. Load-bearing capacity improvement can be achieved through the use of innovative solutions employing externally-bonded composite materials in place of more conventional techniques. New techniques and methods of increasing load carrying capacity of members in bending, shear or compression are being developed
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