Investigation of the effectiveness of strengthening with FRP applied in metal elements of suspension roof: an analytical approach

Abstract

The building patrimony of Ukraine includes various examples of metallic structures, especially applied for industrial purposes and in large-span structures. The use of metal structures in construction is due primarily to their mechanical properties. They are frost-resistant and able to withstand temperatures down to -65 degrees as well as they are hard, durable, strong and reliable. They can also be used in areas with high seismic activity. However, as in the case of other types of structures, there is a need to restore or strengthen metal structures due to structural defects, wear of load-bearing elements, as well as to increase the load-bearing capacity. In several situations, strengthening with Fiber Reinforced Polymer composites (FRP) gives better results. The current article deals specifically with this strengthening technique. The main cultural reason to restore the old metallic structures and provide a structural functionality, is based on the need to preserve not only their historical origins but also the scenery value of the places in which they are located. That is why the strengthening should be carried out with the aim of maintaining the original design idea.
 Due to the long-term operation without timely maintenance and major repair, unique and metal large-span structures require strengthening of the load-bearing structures. It is especially important to choose the most efficient method, both in terms of reliability and cost effectiveness. This can lead to the long term interruption of the structure operation and production process, or the inability to use the adjacent territory due to the reconstruction work. At the same time, it is necessary to preserve not only the structure as a whole, but also the external architectural appearance.
 Traditional methods of strengthening are effective, but in some cases not effective or not applicable for use. An example is the increase of the load-bearing structures of the buildings, preserving the external appearance of which is the determining factor. In this case, the use of the discussed methods can be justified alternative. Disadvantages of steel panels and rods for strengthening are possible corrosion, considerable weight, need for high labor content of the work, and consequently the high cost of labor required to perform the work that need large area.
 Nowadays, one of the most dynamic types of large-span structures in architectural and structural view are suspension roofs. The aim of the research is the evaluation of the bearing capacity of the suspended rigid threads strengthened with CFRP (carbon fiber reinforced polymer) laminates and provision the general recommendations to implement reconstruction and strengthening with this type of material. Therefore it was considered variant of strengthening suspended bending-rigid fibers by composite materials. Computations are performed in software ABAQUS, as a result of which the percentage reduction in vertical deformation was 26.6% for bending-rigid fibers strengthened with CFRP laminates. The value of tensile stresses reduced by about 14 %.
 The obtained results of the study confirm the need for further studies and research.