HPFRC Jacketing of Perimetral and Highly Stressed RC Columns

The improvement of bearing capacity of structural members has become an urgent issue in retrofitting existing R.C. structures, especially for those built according to the construction practice of the 60's-70's, which are often unable to meet the performance requirements of current codes, due to poor materials mechanical properties and reinforcement detailing. In recent years, the strengthening of existing R.C. structures, with the application of High Performance Fiber Reinforced jackets, has been demonstrated effective for the improvement of load carrying capacity of columns. The paper deals with the description of cyclic tests on full-scale retrofitted R.C. columns, with the aim to study the effectiveness of HPFRC jacketing technique for the seismic upgrade of perimetral columns, for which the jacket is applied on three sides. The results of an experimental test on a column subjected first to a high axial load and then to monotonic horizontal load are also reported. In this case, the jacket has been cast after the application to the un-retrofitted specimen of the serviceability axial load present before the execution of the retrofitting intervention. Then the axial load has been increased up to 1.3 times the load at ultimate limit state and finally the specimen has been subjected to a horizontal load. The results show a significant increment in the load carrying capacity of the retrofitted specimens, which reached an adequate level of ductility, proving the effectiveness of the HPFRC jacketing technique a with respect to both horizontal and vertical loads.