Experimental investigation of CFRP-strengthened steel beams with web openings

The introduction of web openings in existing steel floor beams is a common occurrence in practice. Such modifications are often necessary to accommodate additional services driven by a change of building use, thus extending the service life of the structure. Depending on their size and location, openings in the web can present a major challenge to the strength and stiffness of the beam. Strengthening around an opening is often necessary to maintain the required performance of the floor beam, traditionally this is affected via application of additional steel plate, either bolted or welded. This paper focusses on the novel application of carbon fibre reinforced polymer (CFRP) to the problem of strengthening web openings, taking advantage of the material's ease of handling, superior strength-to-weight ratio and corrosion resistance. An experimental study involving 4 full scale universal beams was conducted in order to investigate the ability of CFRP to recover the strength and stiffness of beams following the introduction of web openings. All the specimens were tested under 6-point bending in the experiments. For further comparison, the equivalent test series without the addition of strengthening was modelled numerically via finite element analysis. The effectiveness of the strengthening technique was demonstrated with increases in the load carrying capacity over the un-altered beam of between 5 and 20% being achieved.