مقاله انگلیسی رایگان در مورد رفتار لرزه ای ساختمان قدرتمند URM – الزویر 2017

Various technologies of strengthening the unreinforced masonry (URM) buildings are available. Although effective, the traditional strengthening techniques are time consuming and require that the users temporarily move out of their buildings. Therefore, strengthening methods based on using fibre reinforced polymers (FRP), which provide a simpler, faster and cleaner application, are replacing the traditional ones and their use is on the rise [1,2,3]. Additionally, the cost of many FRP materials has been steadily dropping and has become affordable. An FRP coating consists of the fibres of the reinforcing FRP material which normally have high tensile strength. Different materials are used for the fibres (e.g. glass, carbon, aramid, basalt, etc.). The fibres themselves are inside a coating, which acts as the protecting cover for the FRPs and as the adhesive to the masonry. Despite its function as the adhesive, anchors for fixing the coating to the masonry are normally used. As in case of fibres, different materials are used for coating (e.g. epoxy resin, cement based mortar or even flexible polymers). The strengthening can be applied to different types of masonry (stone masonry, brick masonry, hollow clay masonry, etc.). Finally, the layout of the fibres on the surface of the wall can have many different configurations (vertical, horizontal, diagonal, it can be applied to one side or to both sides of the wall and there can be different densities anchors for anchoring the coating to the wall). The coating, the fibres and the masonry together constitute a complex composite system and the number of combinations of FRP materials, materials for coating and of layouts is virtually inexhaustible. The complexity of the composite system and high number of possibilities is perhaps one of the main reasons, why research in this field is so active and there is a lot of research in papers and conferences on this topic. Furthermore, some combinations appear to not work well together and are best avoided (e.g. coating without wrapping with glass or carbon fibres in epoxy on brick masonry [4]). There has been a substantial amount of experimental research performed on this subject over several years at Slovenian National Building and Civil Engineering Institute (ZAG). In this paper this research will be briefly presented along with the main lessons learned. The research can be chronologically divided into four phases, and the structure of the paper follows these phases. The first tests were performed in-situ in a building that was about to be demolished [5]. It was a brick masonry building from 1935. Two walls were strengthened by wrapping them in carbon fibre fabric and using epoxy resin as the adhesive. In the second phase, presented in third section, a large series of walls were tested in laboratory using the cyclic shear tests. Different materials and especially different layouts of the FRP materials were used [4,6]. In the third phase, an innovative solution for gluing the fibres to the wall was used. A deformable material (called polymer PM) with elastic modulus of about 4 MPa was used and results were surprising [7]. Finally, a three storey model of a building was built in full scale and tested next to a reaction wall. The model was first tested in unstrengthened state up to considerable, but still repairable damage and then strengthened using glass fibre grids and cement based mortar. The model was then tested again, this time up to collapse. Similar laboratory experiments on multistorey buildings were performed by e.g. [7,8]. In the conclusions, the summary of the four experimental campaigns is presented.