Innovative mechanical device for the post-tensioning of glass fiber reinforced polymer bars for masonry type retrofit applications

A mechanical device specially designed for the application of low-level post-tensioning forces to glass fiber reinforced polymer (GFRP) bars has been developed at the University of Missouri-Rolla. Some of the advantageous features of this device are that it is simple to assemble and the low-level post-tensioning forces can be applied manually and safely without the need for hydraulic jacks or heavy equipment. This device has been conceived with the main objective of retrofitting masonry buildings, some of which remain in service despite large, open cracks leading to considerable instability and serviceability concerns. According to the method derived in this paper, GFRP bars are installed in artificially imposed grooves and then post-tensioned with low-level stresses with the main objective to partially close these cracks, such that the serviceability and in-plane capacity of un-reinforced masonry (URM) buildings may be regained. In this paper we describe the mechanical components of this device, along with its advantageous features and potential application for the retrofit of URM walls.