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Several strong earthquakes hit Croatia in 2020. Such earthquakes, after a long absence of strong seismic activities in the country, in combination with material degradation, lack of maintenance and structures that were built before modern seismic regulations, culminated with extensive damage to the existing building stock. Existing unreinforced masonry (URM) structures are quite vulnerable to earthquakes, largely due to a lack of connectivity between structural parts. The numerous damaged buildings emphasize the need to preserve, restore and strengthen URM structures, especially the ones under heritage protection. The main focus of this paper is on the first step of the assessment process, which is to determine the mechanical properties of masonry. For that purpose, the flat-jack method is used. Through stress transfer from a flat-jack to the masonry useful information can be obtained. The results of the extensive post-earthquake flat-jack tests (single, double and shear) on 17 case studies in Croatia are presented. The results are critically discussed and the mechanical properties of brick masonry in Mediterranean Europe are presented. The goal of the present work is to increase the confidence level in the definition of mechanical properties and, thus, to favorably influence the necessary reconstruction. [ABSTRACT FROM AUTHOR]

Historic urban cores in southern Europe are characterized by a significant number of existing unreinforced masonry structures that are known for their seismic vulnerability. The first step in the preservation of such damaged buildings is condition assessment and characterization of the mechanical properties of the masonry, which can be achieved using non-destructive, semi-destructive and destructive methods. In this paper, the emphasis is on determining the modulus of elasticity of unreinforced masonry through flat-jack and sonic pulse velocity tests. Both methods are explained in detail and results from eight different case studies are presented. The results are compared and correlations among the techniques are observed, showing that both methods can be suitable for estimating the elastic properties of existing masonry. The paper provides a wide set of experimental data that has been made available. Finally, a sensitivity analysis was performed. Differences between static and dynamic modulus of elasticity and operational and practicability issues regarding on-site testing are discussed.

Shital Niwas, presently serving as the “Office of the President of Nepal”, is a 96-year-old palace located at Maharajgunj, Kathmandu. It is a Rana-era building mixing Malla architecture with European Palladian (also called neoclassical) style building with a central courtyard system. It suffered damage during 2015 Gorkha earthquake. The block surrounding the northern courtyard was severely damaged, so after the earthquake it was demolished. Significant part of the building that stands is still operational and accommodates critical functions, thus its seismic safety is important. Initially, damage assessment was conducted and damage grade was assigned as per EMS-98 classification. Low strength of mud mortar masonry, heavy weight of the walls and floors, presence of long unsupported walls under flexible diaphragms, high ratio of openings, and absence of earthquake-resistant features are some of the seismic deficiencies of present building. To reduce seismic risk, existing materials were characterized, the present performance of the building was evaluated and deficiencies were identified. Based on the deficiencies, different intervention options were investigated, and finally retrofitting with steel plates and carbon fiber reinforced polymer (CFRP) bands were selected after detailed analysis and design.

Recently, Zagreb was struck by a strong earthquake. Damage throughout the city was tremendous due to numerous aged and vulnerable masonry buildings. Many damaged buildings are under a certain level of cultural heritage protection. Hence, reliable assessment and effective rehabilitation are important to preserve cultural significance and mitigate risk for human life. With that in mind, the procedure of a detailed condition assessment of the building under heritage protection is presented. A detailed historical background of the case study building is shown, and observed damage and conducted in situ tests are discussed. The nonlinear static seismic analysis performed in the 3Muri software is extensively elaborated. Four different levels of reconstruction according to new Croatian law are briefly presented. Additionally, several strengthening scenarios are proposed with various strengthening techniques.

This article focuses on the experimental characterization of constituent materials of stone masonry railway bridges. The study refers to two railway bridges, an overpass in Durrães (near Barcelos, Portugal) and a culvert in São Pedro da Torre (next to the north border Portugal-Spain), both included in the Portuguese railway network. The experimental campaign comprised core sampling and in situ tests using several techniques, namely Dynamic Probing Super Heavy (DPSH), georadar, Ménard pressuremeter (PMT) and flat-jacks, as well as lab tests on constituent materials’ samples taken from the studied bridges. The main objective of this work is therefore to use these experimental results for calibrating numerical models for structural behaviour simulation of the two bridge cases. [ABSTRACT FROM AUTHOR]

• Detailed overview of the flat-jack method, including execution costs. • Use of a laser scanner with the flat-jack method. • Difficulties and proposed solutions when using the flat-jack method. Masonry structures are usually much vulnerable to seismic excitations and their behavior depends on numerous factors. The focus of this research is the determination of masonry mechanical properties by an on-site testing campaign. Commonly used methods and procedure proposals are briefly explained and then the flat-jack method is described in detail. The flat-jack method is based on stress transfer from a flat-jack to the masonry and it provides valuable information regarding vertical stresses, modulus of elasticity and shear strength of masonry walls. The main goal of this paper is to introduce the theoretical background and practical issues of the flat-jack method. The potential shortcomings, practical advice and several improvements of the method are presented. Conclusions are based on the extensive experimental campaign in post-earthquake assessments in Croatia. The flat-jack tests were performed on seventeen case study buildings and over thirty-five test locations. [ABSTRACT FROM AUTHOR]

After an earthquake, which struck the Eastern part of Sicily in 1990, some structural elements of the Church of S. Nicolo` l'Arena in Catania, as the dome and the vaults, were damaged; vertical cracks on the two pillars were detected. It is not clear whether those cracks were already visible and were simply propagating during the earthquake. It is known that the two pillars probably belong to the original construction of the church.An investigation programme (including historical research and experimental investigation with sonic, radar, flat-jack, coring, boroscopy, etc.) has been recently planned to design the preservation and restoration actions.The results obtained from sonic tests were compared to the results of the other type of tests in order to set up an investigation procedure useful for these cases. The paper presents and discusses the preliminary results of the research carried out by the authors. [Copyright &y& Elsevier]

Recently, Zagreb was struck by a strong earthquake. Damage throughout the city was tremendous due to numerous aged and vulnerable masonry buildings. Many damaged buildings are under a certain level of cultural heritage protection. Hence, reliable assessment and effective rehabilitation are important to preserve cultural significance and mitigate risk for human life. With that in mind, the procedure of a detailed condition assessment of the building under heritage protection is presented. A detailed historical background of the case study building is shown, and observed damage and conducted in situ tests are discussed. The nonlinear static seismic analysis performed in the 3Muri software is extensively elaborated. Four different levels of reconstruction according to new Croatian law are briefly presented. Additionally, several strengthening scenarios are proposed with various strengthening techniques. [ABSTRACT FROM AUTHOR]

• The use of a flat-jack that can be inserted into hollow block masonry. • Flat-jacks that support high pressures of more than 20 MPa. • Obtaining mechanical properties without permanent damage to the walls' structure. • Numerical model determines cracks and stress-strain distribution in masonry wall. Flat-jack testing is considered efficient in the analysis of historical masonry built with stones or solid bricks. The advantage of this technique is obtaining important properties to a structural analysis, such as the stress-strain curve of the wall, masonry modulus of elasticity and an estimate compressive strength, without any permanent damage to the structure. Due to its advantages, the technique could also be applied in modern masonry, but the current available equipment has limitations in its geometry and maximum applied pressure. This paper presents the development and application of a new flat-jack equipment, that can fit hollow blocks and allow applying high pressures of more than 20 MPa, way more than the usual flat-jack limit of 5 to 7 MPa. The developed flat-jack was used to test hollow concrete-block masonry to evaluate masonry strength and elastic modulus values, that were compared to values obtained from destructive testing also performed. A good correlation on both results was observed. Based on the experimental results and using the Abaqus FEM package, a detailed micro modelling is presented considering the masonry units, mortar and their interfaces. The numerical model was able to successfully capture crack pattern and strain and stress distribution of the walls in good agreement with the experimental results. Both on the experimental and numerical analyses the testing procedure on where to clean the mortar joints, on the top-bottom of the tested area or also at the lateral vertical joint of the region, was assessed. Result indicate the success and validation of using flat-jack application in modern high-strength hollow block masonry, as far as we know for the first time, and point suggestions on were the cut the mortar joint before testing. [ABSTRACT FROM AUTHOR]