The paper investigates the long-term fatigue and creep deterioration processes in historical brick masonry. Based on two independent laboratory test series, the relationship between stress level and life expectancy was considered for fatigue and creep loading in the form of SN type models. The process of deterioration was investigated with the help of acoustic emission technique to identify stages and characteristics of the damage accumulation process. Based on the test data and acoustic emission results, a joint SN type deterioration model was proposed to incorporate the static, fatigue and creep deterioration mechanisms. A mathematical relationship was proposed for the joint fatigue -creep model and good agreement was found between the test data and the proposed model.

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Acoustic emission monitoring is widely used for damage detection in materials research and for site monitoring. Its use for masonry structures is however challenging due to the highly heterogenic nature of masonry and rapid signal attenuation. However, the non-invasive nature and high sensitivity of the technique also provide interesting opportunities, especially for historical masonry structures, to locate damage, identify severity of damage and rate of deterioration. Aim of this paper is to provide an extensive literature review on the application of the acoustic emission technique for masonry structures, addressing specific challenges and recent findings. AE-based methods for damage assessment in masonry are discussed in view of monitoring approaches, wave propagation, source location and crack development under static, fatigue and creep loading. Site applications are discussed for identifying crack location and crack propagation in historical masonry towers, buildings and masonry arch bridges. The paper concludes with future challenges identified in this research field.

About 40% of the European railway bridge stock comprises masonry arch bridges and over 60% of these are over 100 years old. All are ageing and most are carrying loads well in excess of those envisaged by their builders. The maintenance and assessment of these bridges is a constant concern for the bridge owners. Although current masonry arch bridge assessment methods are able to predict the ultimate carrying capacity of the bridge with some confidence, serious concerns have been identified with respect to predicting long-term behaviour and residual life. A new assessment procedure (sustainable masonry arch resistance technique (SMART)) is presented which differs philosophically from all the current techniques in as much as it takes a holistic approach in considering all possible modes of failure that the structure may experience under any given loading regime. Limit states are discussed and a new permissible limit state that is specific for masonry is proposed. The method advocates consideration of the permissible working loads, long-term behaviour and residual life of the bridge. This enables the assessing engineer to prioritise conflicting maintenance demands on limited budgets. The method is based upon recent research related to the long-term fatigue performance of masonry arch bridges subjected to cyclic loading.

There are over 40 000 masonry arch bridges in the UK, 60% of which are over 100 years old. The ever increasing levels of loading and volumes of traffic make it imperative that the condition, life expectancy and load capacity of such bridges are accurately assessed. Assessment procedures, however, generally rely on visual methods without giving any information on the internal condition of the structure. The acoustic emission (AE) technique has the ability to record certain types of damages anywhere within the structure before their effect becomes visible on the surface. Although AE is increasingly widely used for monitoring concrete and metallic bridges, its application for masonry bridges is currently very limited. A series of multi-ring brickwork arches have been tested as part of an extended study on fatigue performance of masonry arch bridges at the University of Salford. The present study attempts to assess the applicability of the AE technique for masonry arch bridges under static and long-term cyclic loading, to study crack propagation and failure mechanisms.