Dr. Eng. Ahmed Elyamani

This paper studies the response of unreinforced masonry (URM) members made of hydraulic lime mortar and fired clay bricks, commonly found in heritage structures, strengthened with textile reinforced mortar (TRM) overlays. The investigation includes URM and TRM-strengthened diagonal compression tests on square panels, and relatively large-scale wall specimens subjected to combined gravity and lateral cyclic loads. Complementary compression, tension, and interface material tests are also carried out. The diagonal panel tests show that the TRM effectiveness depends in a non-proportional manner on the overlays, render thickness, and substrate strength. The enhancement in stiffness, strength, and ultimate shear strain, using one to four mesh layers on each side, is shown to vary in the range of 49–132%, 102–536%, and 300–556% respectively. It is shown that strut crushing typically governs the response of such low-strength URM masonry elements confined by TRM overlays. The cyclic tests on the comparatively larger walls show that the TRM is effective, shifting the response from URM diagonal tension to rocking, and enhancing the stiffness, strength, and ultimate drift capacity by more than 160%, 30%, and 130%, respectively. It is shown that analytical assessment methods for predicting the response of TRM-strengthened and URM members in terms of stiffness, strength and load-deformation can be reliably adapted. The cumulative contribution of the URM and TRM components, in conjunction with a suitable fibre textile strain, is also found to offer an improved prediction of the shear strength compared to codified procedures. The findings enable the evaluation and improvement of analytical models for determining the main inelastic response parameters of TRM-strengthened masonry and provide information for validating future detailed nonlinear numerical simulations.

Historic Cairo has been a UNESCO World Heritage Site since 1979. It has more than 600 historic structures, which require extensive studies to sustain their cultural, religious, and economic values. The main aim of this paper is to undertake dynamic investigation tests for the dome of Fatima Khatun, a historic mausoleum in Historic Cairo dating back to the 13th century and consisting of mainly bricks and stones. The challenge was that the structure was difficult to access, and only a small portion of the top was accessible for the attachment of accelerometers. Current dynamic identification procedures typically adopt methods in which the sensors are arranged at optimal locations and permit direct assessment of the natural frequencies, mode shapes, and damping ratios of a structure. Approaches that allow for the evaluation of dynamic response for structures with limited accessibility are lacking. To this end, in addition to in situ dynamic investigation tests, a numerical model was created based on available architectural, structural, and material documentation to obtain detailed insight into the dominant modes of vibration. The free vibration analysis of the numerical model identified the dynamic properties of the structure using reasonable assumptions on boundary conditions. System identification, which was carried out using in situ dynamic investigation tests and input from modelling, captured three experimental natural frequencies of the structure with their mode shapes and damping ratios. The approach proposed in this study informs and directs structural restoration for the mausoleum and can be used for other heritage structures located in congested historic sites.

Cultural heritage buildings are prone to failures when subjected to seismic events, and recent earthquakes worldwide resulted in many losses of these buildings. Therefore, there is a need for methodologies for assessing their seismic safety that should be based on enough knowledge of the building. Here, dynamic investigation by dynamic identification testing and dynamic monitoring increase significantly the level of knowledge about the assessed building. The dynamic identification tests give global information about the dynamic properties like natural frequencies that are useful in calibrating and updating a numerical model of the building that could be used in the seismic safety evaluation. Dynamic monitoring gives the dynamic properties’ evolution in time and may be used as an early warning tool able to send alarms when meaningful changes in dynamic properties are observed. This chapter gives some considerations on the different investigation activities of dynamic identification, dynamic monitoring, numerical model updating, and seismic safety assessment of cultural heritage buildings. As an application, the case study of the historic Mallorca cathedral is discussed.

This paper summarizes recent investigations into the structural and material response of ambient-dry and wet clay-brick and lime-mortar masonry elements, with focus on those used in heritage structures in Historic Cairo. In addition to cyclic tests on large-scale masonry walls subjected to lateral displacement and compressive gravity loads, the studies included complementary tests on small scale masonry panels and material specimens. It is shown that moisture can have a notable effect on the main material properties, including the shear and compression strengths, brick-mortar interaction parameters, and the elastic and shear moduli. The extent of the moisture effects is a function of the governing behaviour and material characteristics as well as the interaction between shear and precompression stresses and can lead to a loss of more than a third of the stiffness and strength in addition to a reduction in ductility. Simple and cost-effective strengthening techniques, using textile-reinforced mortars, for enhancing the lateral performance of low-strength heritage masonry element, are also considered in this study. The effectiveness of the strengthening approach is illustrated and quantified through additional tests on the small-scale panels and large-scale wall specimens. It is shown that simple analytical assessment methods can be reliably adapted for predicting the response of the wall specimens, in terms of the lateral stiffness, strength and overall load-deformation behaviour.

This work intends to provide seismic vulnerability analysis for a building stock in Al Khalifa District, Fatimid Cairo while focusing on the historic buildings in the area. The work represents part of an interdisciplinary study targeting the management and conservation of a UNESCO World Heritage Site. The project inspects several aspects including behavior of masonry walls, structural health monitoring of selected structures, conservation studies, in addition to influence of rising ground water. In the current study, seismicity of Egypt generally and Cairo specifically is reviewed. Afterwards, large-scale seismic vulnerability is adopted to calculate the vulnerability index for buildings within the study area. Data are collected through extensive on-site surveys for more than one hundred buildings. Observed typologies are listed alongside possible mechanisms of failure. Egypt has moderate seismic hazard; however, many buildings are prone to damage due to inadequate seismic design. This leads to retrofitting requirements to reduce seismic vulnerability and adhere to imposed seismic requirements in design codes. The study is intended to understand seismic risk of buildings within study area as part of a comprehensive study. Developed vulnerability map show that many buildings are prone to damage during seismic events.

This paper examines the experimental structural response of clay brick lime mortar masonry walls in wet and ambient-dry conditions. The properties of fired-clay bricks and hydraulic lime-mortar materials are selected to resemble those of existing heritage masonry structures in Historic Cairo. The investigation includes tests on square panels under diagonal compression, and large-scale walls subjected to gravity loading and in-plane lateral cyclic displacements. In addition to the conditioning type, the effectiveness of strengthening with helical bars in horizontal bed joints is also investigated. Implications of embedding helical bars in lime mortar as well as the provision of end anchorages are assessed. The complete load-deformation response of the large-scale members is also evaluated, including the main behavioural characteristics and failure modes. The results show that moisture has a notable effect on the main mechanical properties and overall structural response of such masonry components. For the panels subjected to diagonal compression, the strength reduction under wet conditions is shown to be more than 40% compared to the dry counterparts. For the large-scale walls, subjected to combined lateral loading and precompression, this reduction is significantly lower but can exceed 10%. It is also shown that the provision of helical bars can, depending on their end anchorage and arrangement, double the diagonal tension strength of masonry and offset the adverse effects occurring due to moisture.

This paper presents an experimental investigation into the structural and material response of ambient-dry and wet clay-brick/lime-mortar masonry elements. In addition to cyclic tests on four large-scale masonry walls subjected to lateral in-plane displacement and co-existing compressive gravity load, the study also includes complementary tests on square masonry panels under diagonal compression and cylindrical masonry cores in compression. After describing the specimen details, wetting method and testing arrangements, the main results and observations are provided and discussed. The results obtained from full-field digital image correlation measurements enable a detailed assessment of the material shear-compression strength envelope, and permit a direct comparison with the strength characteristics of structural walls. The full load-deformation behaviour of the large-scale walls is also evaluated, including their ductility and failure modes, and compared with the predictions of available assessment models. It is shown that moisture has a notable effect on the main material properties, including the shear and compression strengths, brick–mortar interaction parameters, and the elastic and shear moduli. The extent of the moisture effects is a function of the governing behaviour and material characteristics as well as the interaction between shear and precompression stresses, and can lead to a loss of more than a third of the stiffness and strength. For the large scale wall specimens subjected to lateral loading and co-existing compression, the wet-to-dry reduction was found to be up to 20% and 11% in terms of stiffness and lateral strength, respectively, whilst the ductility ratio diminished by up to 12%. Overall, provided that the key moisture-dependent material properties are appropriately evaluated, it is shown that analytical assessment methods can be reliably adapted for predicting the response, in terms of the lateral stiffness, strength and overall load-deformation, for both dry and wet masonry walls.