It’s been recognized that unreinforced masonry show susceptibility to either in-plane or out-of-plane load actions or sometimes both which often leads to partial or complete collapse of a building. The fiber reinforced polymer techniques are often utilized when improving seismic performance of unreinforced masonry. However, there arises certain setbacks with the use of organic epoxies in fiber reinforced polymer application which limits its effectiveness.
In order to overcome this, textile reinforced mortar which makes use of an inorganic cementitious matrix was developed. It is better than epoxy impregnated fiber reinforced polymer overlay with attributes such as compatibility with unreinforced masonry materials, stiffness, and flexibility etc. Despite this, little or no understanding on experimental results have been provided on effectiveness of textile reinforced mortar for seismic strengthening and perforated unreinforced masonry wall repairs.
Dr. Najif Ismail from United Arab Emirates University and Professor Jason M. Ingham from University of Auckland in New Zealand took the task of investigating the structural performance of unreinforced masonry walls strengthened by making use of two different types of polymer textile reinforced mortar by using a full scale reversed cyclic in-plane and out-of-plane testing. The research is published in peer-reviewed journal, Engineering Structures.
Two series of test were used for implementation of this study. The first, series 1 involved a pseudo-static reversed cyclic in-plane testing of two textile reinforced mortar strengthened full scale pier-spandrel assemblages and series 2 which involve reversed cyclic out-of-plane testing of three full scale slender unreinforced masonry walls which was further performed in two stages.
They also used two different test walls of either as-built or textile reinforced mortar strengthened coupled with specific loading directions and different tests.
Researchers found that textile reinforced mortar strengthening of unreinforced masonry walls increased in-plane strength by 128% to 136% and increased from 575% to 786% in case of out-of-plane loading when compared to as-built strength with notable increment in deformation capacity and ductility. It was also noticed that introduction of galvanised steel mesh in addition to the textile reinforced mortar resulted in a small increase in the strength and ductility of the test walls.
Moreover the study described reasons in failure for in-plane loaded strengthened pier-spandrel assemblages which were either through rupture of textile rovings spanning masonry cracks or shear failure of unstrengthened piers without any spandrel cracking.
The findings of this study have proven that textile reinforced mortar increases the strength, ductility and energy dissipation properties of unreinforced masonry walls.
Najif Ismail, Jason M. Ingham. In plane and out of plane testing of unreinforced masonry walls strengthened using polymer textile reinforced mortar.