Masonry Type Retrofit Applications

A mechanical device especially designed for the application of low-level posttensioning forces to glass fiber reinforced polymer (GFRP) bars was 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 was conceived with the main objective of retrofitting masonry buildings, some of which remain in service despite large, open cracks leading to considerable out-of-plane 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) building may be regained. The mechanical components of this device, along with its advantageous features and potential application for the retrofit of URM walls, are described in this paper.