Examination of the use of BFRP in reinforced concrete tunnel formwork structures

The rapid increase in the population and the intense migrations to the cities have led to an increase in the housing need. This situation has led to mass housing production and the emergence of new techniques in housing production. Among these emerging new techniques, the tunnel formwork technique is widely preferred. This rapid increase in the need for housing has led to the necessity of continuing to use the existing structures by improving them with various repair and strengthening methods, as well as new housing production techniques. In reinforced concrete structures constructed with tunnel formwork technique, as in other structures, some repair and strengthening needs may arise before the structure has yet completed its service life. The most common of these strengthening methods are sheathing, reinforcement with steel flats or steel plates. In addition to these, reinforcements made with fiber reinforced polymers (FRP), have also gained great speed in the world recently. When FRP products, which provide application speed and ease, are considered, they come to the forefront in basalt fiber reinforced polymers in terms of superior properties such as high corrosion resistance and low cost. In this study, a 20 storey reinforced concrete tunnel formwork structure was modeled in the SAP2000 program and analyzed under the effect of vertical loads. Then, the analysis was carried out by applying a single-sided 5 mm thick BFRP on the bulkheads of the same building. Finally, the analysis was made by applying 5 mm thick BFRP on both sides to the bulkheads of the same building. As a result of the analyzes made, it was aimed to examine the changes caused by the BFRP applications in the earthquake behavior of the structure. As a result of the analyzes made, it was observed that the dominant period of the structure with one-sided 5 mm BFRP applied to its bulkheads decreased by 4.33%, compared to the structure without BFRP, and the dominant period of the structure to which 5 mm BFRP was applied bilaterally to its bulkheads was reduced by 4.93%. Likewise, when the results of Fmax, Mmax, Vmax, Smax and displacement were examined, it was concluded that although the unilateral application to the bulkheads showed a significant difference compared to the situation without BFRP, the bilateral application to the bulkheads did not make a significant difference.