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Title: Experimental and analytical investigations of brick masonry under compressive fatigue loading
Author: Koltsida, Iris
ISNI:       0000 0004 6423 1975
Awarding Body: University of the West of England
Current Institution: University of the West of England, Bristol
Date of Award: 2017
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About 40% of bridges in European transport network are masonry arch bridges (most built over 100 years ago) and are being subjected to increasing loading regimes. Assessment of the long-term fatigue capacity of masonry bridges is necessary to ensure that increased traffic loading does not result in premature deterioration and/or reduce their life expectancy. The study investigates the influence of compressive fatigue loading on the behaviour and mechanical properties of soft brick masonry, relevant to the structural loadbearing elements, for example the arch ring in canal masonry bridges. Masonry prisms were tested (n=70) under quasi-static and long-term fatigue loading to collect information on the number of loading cycles under a range of stress levels, changes in the stress-strain curves, evolution of strain and Young’s modulus during fatigue deterioration. Laboratory tests were performed under maximum stress levels between 55–80% of the compressive strength, at 2Hz frequency for a maximum of 107 loading cycles. Test data were analysed to develop analytical expressions to predict the response of masonry under fatigue loading. Test results reveal that fatigue deterioration is characterised by three distinct stages in strain evolution and stress-strain curves. The Young’s modulus decreased by 25%, while the maximum recorded strain increased up to 5.25 times. An expression for the stress - number of cycles - probability (S-N-P) curves was proposed based on probabilistic analysis to predict the fatigue life of masonry at any desired probability. A set of three formulas were developed to predict strain evolution at different stages of fatigue life and a linear equation was derived for the evolution of the Young’s modulus. The proposed S-N-P model can provide numerical data for fatigue analysis of masonry arch bridges, e.g. for the SMART method to evaluate the remaining service under any traffic loading level. The rate of change in strain can provide useful reference data for long-term monitoring to identify the stage of the fatigue life the structure is experiencing. A reduction factor for the Young’s modulus between 0.9–0.75, depending on the stress level, can be used for assessing masonry arch bridges under fatigue loading. As consequence, it is recommended that the evolution laws of the mechanical properties of masonry can be used for finite element software packages to develop time-dependent models for the analysis of masonry under fatigue.
Supervisor: Not available Sponsor: International Union of Railways
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: brick-masonry ; long-term fatigue ; SN curves ; strain evolution ; experimental ; probability