Fatigue performance of RC beams strengthened with non-prestressed and prestressed BFRP grids

The objective of the presented study was to evaluate the fatigue performance of reinforced concrete (RC) beams strengthened with basalt fiber -reinforced polymer (BFRP) grids. A total of eight RC beams (dimensions of 300 x 150 x 2240 mm) were constructed and tested. Out of these, three beams served as the control specimens, and the remaining five beams were strengthened. The variable parameters included the load ranges, presence of prestress, and number of prestress release. The experimental results indicated that the BFRP grids can be used to significantly extend the fatigue life of the beams. Moreover, when employing prestressed BFRP grids for strengthening, the fatigue life of the beams can be further prolonged. Nevertheless, the strengthening effectiveness of prestressed BFRP grids exhibited notable sensitivity to the number of prestress release. For all the strengthened beams, exceptional bonding performance between the BFRP grids and the concrete interface was evident under cyclic loading, and no interface debonding was observed prior to the fatigue failure of the strengthened beams. Based on the relevant experimental data, this study established a fatigue life prediction model for BFRP grid strengthened beams.