Kariou, Florentia
(2020)
Textile reinforced mortars for masonry structures.
PhD thesis, University of Nottingham.
Abstract
Unreinforced masonry (URM) is a common engineering practice in different types of construction, e.g., structural bearing walls and infill panels, bridge arches and cultural heritage buildings. Recent catastrophic events such as the earthquakes in L’Aquila (2009), Tohoku, Japan (2011), Christchurch (2011), Northern Italy (2012), and Central Italy (2016–2017) have tragically pointed out the need for restoration and strengthening of existing masonry structures. Masonry structures are also prone to ageing related structural deterioration, accelerated by the effect of adverse environmental actions, e.g., high speed winds and heavy rainfalls.
Structural strengthening has emerged as a cost efficient solution for extending the life-span of critical infrastructure, as opposed to decommissioning and rebuilding. Furthermore, provided that the solution has a low footprint, structural strengthening has been proven vital for the preservation of cultural heritage.
Within this context, the Textile Reinforced Mortar (TRM) strengthening has been established over the last 15 years as a prominent, low footprint structural strengthening technique. Despite the significant research endeavours involved, questions remain on the effect of various design parameters on the performance of TRM strengthened URM structures. These pertain to the uncertainties of the underlying materials, i..e, masonry, mortar and textile fibre composites that are overall non-standardized, depend on the variability of the pertinent manufacturing methods.
The overarching aim of this project was to experimentally and numerically investigate the performance of the TRM technique when used for the strengthening of URM structures and hence provide valuable data that can be used for towards the robust and reliable standardization of the method. To achieve this, an extensive experimental campaign was undertaken and corresponding numerical simulation tools were established.
In this project, uniaxial tensile tests on the fibre textiles used in this study (carbon, glass, basalt) were conducted to determine their mechanical properties. Following that, bond tests were performed to investigate the response between the TRM and masonry substrate. The investigated parameters were the bond length, the textile fibre material and the epoxy-resin coating. Next, the out-of-plane performance of the TRM strengthened masonry walls was examined. The investigated parameters involved were the textile reinforcement ratio, the textile material, the coating of the textile reinforcement with epoxy resin, and the wall thickness. Following that, the TRM strengthened clay brick masonry arches response under monotonic loading at the quarter length of the span was studied. The experimental parameters comprised the number of TRM layers, the textile fibre material, and the strengthening layout.
The experimental results establish TRM as an effective strengthening solution which provides increased load and deformation capacity. Furthermore, this work manifests the beneficial effect of epoxy-resin coating compared to the uncoated counterpart specimens; increase the tensile properties of the fibre textiles, improve the bonding conditions, and alter the failure mode of carbon and glass fibre-textile material. The amount of reinforcement utilised affects both the strength and deformation characteristics of the corresponding specimens, while it may alter the failure mode. The Finite Element (FE) investigation comprised a micro-modelling approach with the cohesive method to account for the non-linear response of the masonry components. Through an extensive numerical investigation, the employed models are proven to provide a satisfactory agreement to the experimental results and hence pave the way for further research to be conducted on the mechanics of TRM strengthened masonry, considering also the interface properties of the two materials.
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