Dr. P Pravin Kumar Venkat Rao’s research proposal on the topic Seismic Retrofitting for Historic and Contemporary Masonry Buildings using Textile Reinforced Mortar Composites: An Alternate to FRP was awarded a Startup Research Grant (SRG) by the Science and Engineering Research Board (SERB), Government of India. Project summary as explained by Dr. P Pravin Kumar Venkat Rao:
Seismic vulnerability of unreinforced masonry (URM) walls of contemporary & existing buildings with heritage value or historical importance under out-of-plane action is the most significant cause of earthquake-induced damage. This is due to the low tensile strength of masonry, poor interconnections with cross-walls and floor diaphragms. While the vulnerability due to poor interconnections can be overcome by positive connections through tie or bond beams, whereas walls in existing URM buildings often require retrofitting. Several retrofitting systems have been used in the past including the fibre reinforced polymer (FRP) composites targeted at improving the flexural strength and deformation of URM walls in the out-of-plane direction. FRP solutions have shown significant drawbacks when applied to masonry because of the use of organic matrix (epoxy and hardeners). Hence, a more innovative composite system known as ‘Textile Reinforced Mortar (TRM)’ consisting of bi-directional fibre mesh, externally applied to masonry substrate using an inorganic matrix (lime- and/or cement-based mortar), has emerged combining the benefits of both ‘traditional’ and ‘modern’ systems. This retrofitting technique eliminates the need for an organic matrix, no requirement of protective coatings, improves the ease of installation at wet surfaces, high performance at elevated temperatures, no higher level of care and supervision is required in the application, and has better compatibility (bonding) with the masonry substrate.
So far, several researchers have used man-made fibre composites, viz. carbon, glass, and aramid for the out-of-plane retrofitting of masonry walls, whereas only a few focused their attention on the use of natural or vegetable fibres (e.g., basalt, aramid, flax, hemp, sisal, jute, and cotton fibres). The results of the past tests conducted on retrofitted masonry specimens using different types of TRM composites have shown a promising solution for the structural upgrade. As a result, designers have difficulty in selecting the most appropriate TRM composite. The main aim of the proposed study is to investigate the non-linear behaviour of different TRM composites in direct tension and one-way bending. The study will also identify the relative effectiveness of the system. This will help the designer to choose the most efficient, cost-effective, high strength and large deformation capacity TRM system for retrofitting of URM buildings. The proposed study will utilize different bi-directional mesh of man-made and natural fibres for structural retrofitting using cement- and/or lime-sand mortar matrix. The test results will be used to quantify the efficacy of each system and to determine the damage indices that will provide a useful decision-support model for selecting the retrofitting system for the URM wall. Further, the research will lead to the development of an analytical model and design guidelines for the application of the TRM system to masonry.