22 research outputs found
Mohr-Coulomb failure domain of rural masonry through slightly-destructive tests
No full textThe experimental campaign presented in this paper consisted in performing slightly-destructive
tests on rural masonry buildings damaged by the 2012 Emilia earthquake, in order to determine the mechanical
parameters of masonry and its shear behavior. A particular focus is here devoted to the construction of a Mohr-
Coulomb failure domain for the rural masonry investigated. To this purpose, the results obtained from shove
tests and splitting tests on masonry cores with inclined mortar joints have been considered. The output of these
tests, indeed, is the failure state of stress (σ;τ ) of the samples, to be reported in the Mohr-Coulomb diagram.
The linear interpolation of the points determined, represents the failure domain searched. The results on eight
buildings investigated are here analyzed, together with a discussion on the interpretation of the shove test, in
order to evaluate the applicability of the proposed methodology
Environmental durability of FRCM strengthening systems and comparison with dry fabrics
No full textFiber Reinforced Cementitious Matrix (FRCM) composites have been recently introduced for repairing and strengthening masonry structures. Even if they proved to be an effective solution for structural applications, their durability is still an open issue, which is fundamental to guarantee the long-term effectiveness of the strengthening intervention. In fact, FRCMs may be subjected to a combination of different environmental conditions that may affect their performances: humidity, rainfall, freeze/thaw cycles, exposure to saline and alkaline environments are some of the conditions that may promote deterioration over time. In order to investigate FRCMs durability, an extensive experimental campaign has been carried out on different FRCM systems (basalt, glass and steel fibers) through tensile tests on conditioned and unconditioned samples. Tests have been performed both on FRCM coupons and on dry fabrics, with the aim of analyzing the effect of the matrix in terms of mechanical behavior and external protection of the fabric under aggressive environments. The creation of an experimental database on the effects of environmental conditions is a first step to analyze long-term properties of these composite materials and to suggest appropriate strength reduction factors to be taken into account for the design of durable retrofitting interventions
In-plane behaviour of FRCM-strengthened masonry panels
No full textThe evolution of seismic design regulations together with the degradation of the monumental heritage made necessary to increase the structural safety of a large variety of masonry buildings. A recent strengthening technique consists in the application of a fiber grid/unidirectional sheet with lime or cementitious mortar (FRCM), thanks to several advantages of this retrofitting system in comparison to traditional epoxy-based materials (FRPs), such as better compatibility with the masonry substrate, resistance to high temperatures and reversibility. In this paper, the results of in-plane tests performed on panels strengthened with different types of FRCM systems (that differ in layout, matrix, grid materials and spacing) are presented, after a complete mechanical characterization of FRCM materials, carried out through direct tensile tests and single-lap shear tests. In diagonal compression tests (DCT), failure modes and global behavior of the panels were also analyzed using Digital Image Correlation (DIC) technique, for a better understanding of their in-plane behaviour
In-situ diagonal compression and shear-compression destructive tests on masonry panels from rural buildings in Emilia Romagna region
No full textThe great damages produced by the 2012 Emilia earthquake on masonry buildings made it necessary to study the mechanical properties of masonry structures in the zones most affected by the earthquake. The experimental campaign presented in this paper focuses in particular on rural masonry buildings of the Italian provinces of Ferrara, Modena and Reggio Emilia. Due to the high level of damages of the buildings under investigation, intended to be demolished, it was possible to perform destructive tests in order to characterize the masonry in terms of shear behavior. In-situ shear-compression tests and diagonal compression tests on full-scale masonry panels were performed, trying to select samples with similar characteristics, when possible. The results of the tests on three buildings investigated are presented and analyzed with the aim of comparing the shear strength parameters obtained from the two types of test performed
Grout injection effect on the shear behavior of FRCM strengthened stone masonry panels
No full textDuring the last decades, several seismic phenomena have shown the high vulnerability of existing stone masonry structures subject to horizontal actions. Innovative composite materials, such as Fiber Reinforced Cementitious Matrix (FRCM), can be adopted for the retrofitting of masonry structures. The use of these innovative FRCM systems is usually combined with a more traditional retrofitting technique: grout injection. It allows to restore or improve the transversal connection between wall leaves, ensuring a monolithic behavior of the structural element. The objective of this research was to analyze the effect of the quality of the grout injection on the shear response of FRCM strengthened stone masonry panels. Results from an experimental campaign, where stone masonry specimens were subject to diagonal compression tests, are therefore presented in this paper. Two samples were subject to grout injection and one of them was strengthened with Steel Reinforced Grout (SRG). Comparisons between the experimental results showed that grout injection alone, if correctly executed, could determine a significant improvement in the shear capacity of masonry panels. The application of the FRCM strengthening system could further enhance the behavior of the samples, especially influencing the failure mode. Comparisons with analytical formulations for the evaluation of the capacity of strengthened walls are also presented
Influence of matrix properties on FRCM-CRM strengthening systems
No full textDuring the last decades, widespread seismic events in the Southern European zone have significantly damaged the masonry built heritage. Designers and researchers studied different techniques to increase the performance of masonry panels subjected to horizontal actions due to seismic phenomena. In particular, two of the most common strengthening systems are Fiber Reinforced Cementitious Matrix (FRCM) and Composite Reinforced Mortar (CRM). These systems are usually applied on both surfaces of the load-bearing elements in order to increase their shear strength properties. This work aims at analyzing the effects of three different matrices, comparing FRCM and CRM systems applied on double-leaf masonry panels subjected to diagonal compression test in displacement control (ASTM E519). Compressive strength and thickness of the matrices applied on the masonry substrate were investigated in order to evaluate the relationship between the performance of matrices used within composite strengthening systems (FRCM or CRM) and the density of fiber grids adopted (basalt and glass). The mechanical characterization of the different strengthening systems was performed by means of tensile and bond tests on masonry prisms. Finally, the experimental results obtained were analyzed in terms of failure modes and maximum capacity attained by strengthened panels
Energy absorption tests on fibre-reinforced-shotcrete round and square panels
No full textThe present paper presents the results of an experimental campaign aimed at investigating the mechanical performances of different FRC shotcrete mixes by means of tests on square (EN 14488-5) and circular panels (ASTM C1550-12). In particular, two different concrete mixes were tested, they featured the same aggregates, but one of the two mixes contained silica fumes a replacement of a fraction of cement. Different dosages of macro synthetic fibres (3 to 8.5 kg/m3) were used in each of the two mixes as well as a single dosage of steel fibres (30 kg/m3). Both sprayed and cast panels were considered. In addition to these panels cast notched prisms were tested in three-point bending. The paper discusses the mechanical behaviour of the various specimens, analysing the influence of concrete mix and fibre dosage, and presents correlations among different tests
Pancreatic pseudocyst-inferior vena cava fistula causing caval stenosis, left renal vein thrombosis, subcutaneous fat necrosis, arthritis and dysfibrinogemia
No full textAIM: We describe the case of a 38 year old man, with a story of alcohol abuse, who developed a very painful nodular subcutaneous fat necrosis, fever and polyarthritis, denying any abdominal symptoms due to a pancreatic pseudocyst-inferior vena cava fistula. MATERIAL OF STUDY: The authors discuss the unusual and protracted course with intermittent hyperamylasemia and hyperlipasemia related to clinical manifestations such as subcutaneous fat necrosis, polyarthritis, pleural effusion and dysfibrinogenemia, and vascular complications as inferior vena cava stenosis and left renal vein thrombosis without abdominal symptomatology. RESULTS: After ultrasonograms and CT Scans showing a 3-4 cm cyst at the pancreatic head with a solid bud protruding into the pseudocystic cavity, and an ERCP showing a communication between the pancreatic duct and the pseudocyst but failing in demonstrating the vascular fistula, the patient underwent a Roux-en-y pseudocyst-jejunostomy and suture of the caval communication leading to complete recovery with normalization of laboratory findings. DISCUSSION: In our case, the locally sclerosing activity of the enzymes in the endothelium led to a communication between the inferior vena cava and the pseudocyst and to a complete thrombosis of the left renal vein and to a stenosis of the inferior vena cava itself. The fluctuance of the symptomatology severity was probably due to an intermittent opening of the passage between pseudocyst and vena cava. Such a clinical case, to the author knowledge, has never been reported. CONCLUSION:When in presence of very high levels of amylasemia and lipasemia in spite of the paucity of abdominal symptomatology, and the onset of unusual complications such as panniculitis, pleural effusion, arthritis and coagulative disorders, a pancreatic pseudocyst-inferior vena cava fistula should be kept in consideration during diagnosis
Pancreatic pseudocyst-inferior vena cava fistula causing caval stenosis, left renal vein thrombosis, subcutaneous fat necrosis, arthritis and dysfibrinogemia
No full textAIM: We describe the case of a 38 year old man, with a story of alcohol abuse, who developed a very painful nodular subcutaneous fat necrosis, fever and polyarthritis, denying any abdominal symptoms due to a pancreatic pseudocyst-inferior vena cava fistula. MATERIAL OF STUDY: The authors discuss the unusual and protracted course with intermittent hyperamylasemia and hyperlipasemia related to clinical manifestations such as subcutaneous fat necrosis, polyarthritis, pleural effusion and dysfibrinogenemia, and vascular complications as inferior vena cava stenosis and left renal vein thrombosis without abdominal symptomatology. RESULTS: After ultrasonograms and CT Scans showing a 3-4 cm cyst at the pancreatic head with a solid bud protruding into the pseudocystic cavity, and an ERCP showing a communication between the pancreatic duct and the pseudocyst but failing in demonstrating the vascular fistula, the patient underwent a Roux-en-y pseudocyst-jejunostomy and suture of the caval communication leading to complete recovery with normalization of laboratory findings. DISCUSSION: In our case, the locally sclerosing activity of the enzymes in the endothelium led to a communication between the inferior vena cava and the pseudocyst and to a complete thrombosis of the left renal vein and to a stenosis of the inferior vena cava itself. The fluctuance of the symptomatology severity was probably due to an intermittent opening of the passage between pseudocyst and vena cava. Such a clinical case, to the author knowledge, has never been reported. CONCLUSION:When in presence of very high levels of amylasemia and lipasemia in spite of the paucity of abdominal symptomatology, and the onset of unusual complications such as panniculitis, pleural effusion, arthritis and coagulative disorders, a pancreatic pseudocyst-inferior vena cava fistula should be kept in consideration during diagnosis
Pancreatic pseudocyst-inferior vena cava fistula causing caval stenosis, left renal vein thrombosis, subcutaneous fat necrosis, arthritis and dysfibrinogenemia.
No full textAIM:
We describe the case of a 38 year old man, with a story of alcohol abuse, who developed a very painful nodular subcutaneous fat necrosis, fever and polyarthritis, denying any abdominal symptoms due to a pancreatic pseudocyst-inferior vena cava fistula.
MATERIAL OF STUDY:
The authors discuss the unusual and protracted course with intermittent hyperamylasemia and hyperlipasemia related to clinical manifestations such as subcutaneous fat necrosis, polyarthritis, pleural effusion and dysfibrinogenemia, and vascular complications as inferior vena cava stenosis and left renal vein thrombosis without abdominal symptomatology.
RESULTS:
After ultrasonograms and CT Scans showing a 3-4 cm cyst at the pancreatic head with a solid bud protruding into the pseudocystic cavity, and an ERCP showing a communication between the pancreatic duct and the pseudocyst but failing in demonstrating the vascular fistula, the patient underwent a Roux-en-y pseudocyst-jejunostomy and suture of the caval communication leading to complete recovery with normalization of laboratory findings.
DISCUSSION:
In our case, the locally sclerosing activity of the enzymes in the endothelium led to a communication between the inferior vena cava and the pseudocyst and to a complete thrombosis of the left renal vein and to a stenosis of the inferior vena cava itself The fluctuance of the symptomatology severity was probably due to an intermittent opening of the passage between pseudocyst and vena cava. Such a clinical case, to the author knowledge, has never been reported.
CONCLUSION:
When in presence of very high levels of amylasemia and lipasemia in spite of the paucity of abdominal symptomatology, and the onset of unusual complications such as panniculitis, pleural effusion, arthritis and coagulative disorders, a pancreatic pseudocyst-inferior vena cava fistula should be kept in consideration during diagnosis
