Damage analysis of brick-to-mortar interfaces

A novel laboratory procedure, developed at the Non Destructive Testing Laboratory of the Politecnico di Torino as a preliminary design stage for the pre-qualification of repair mortars applied to historical masonry buildings is described. The repair mortars tested here are suitable for production of dehumidifying plasters, to be used to stop the rising damp effects due to capillary action in historical masonry walls. Assessing the durability of repair products is a major concern, because of the potential de-bonding phenomena that could occur in time due to insufficient compatibility between original and repair materials, in terms of their mechanical characteristics. Therefore, the study of the long-term mechanical interaction between repair mortars and historical masonry substrate under fatigue loading turns out to be crucial for the design of durable repair works. The testing procedure here presented consists of a series of static and fatigue tests on brick-mortar specimens produced ad hoc, so as to investigate their long-term behaviour and express a judgement about the compatibility of different repair mortars in comparison with the mechanical characteristics of the historical masonry substrate. Special care is devoted to the study of fatigue phenomena at the interface between the materials, that could negatively affect the brick-mortar system. Experimental results are compared with the theoretical values obtained through the cohesive-crack model

Role of natural stone wastes and minerals in the Alkali activation process: A review

This review aims to provide a comprehensive assessment concerning alkali activation of natural stone wastes and minerals. In particular, the structure of the review is divided into two main sections in which the works dealing with alumino-silicate and carbonatic stones are discussed, respectively. Alumino-silicate stones are generally composed of quartz and feldspars, while carbonatic stones are mainly made of calcite and dolomite. The role of these minerals in the alkali activation process is discussed, attesting their influence in the development of the final product properties. In most of the works, authors use mineral additions only as fillers or aggregates and, in some cases, as a partial substitution of more traditional raw powders, such as metakaolin, fly ash, and granulated blast furnace slag. However, a few works in which alumino-silicate and carbonatic stone wastes are used as the main active components are discussed as well. Not only the raw materials, but also the entire alkali activation process and the curing conditions adopted in the literature studies here reviewed are systematically analyzed to improve the understanding of their effect on the physical, mechanical, and durability properties of the final products and to eventually foster the reuse of natural stone wastes for the purposes of sustainability in different applications

Nonlinear elastic response of thermally damaged consolidated granular media

The mechanical properties of consolidated granular media are strongly affected by large temperature changes which induce the development and localization of stresses, leading in turn to damage, e.g., cracking. In this work, we study the evolution of linear and nonlinear elasticity parameters when increasing the temperature of the thermal loading process. We prove the existence of a link between linear and nonlinear elasticity properties. We show that the change of the nonlinear elasticity parameters with the increase in the thermal loading is larger at the lower temperatures than the corresponding change for the linear parameters, suggesting that nonlinear elasticity can be exploited for early thermal damage detection and characterization in consolidated granular media. We finally show the influence of grain size upon the thermal damage evolution with the loading temperature and how this evolution is mirrored by the nonlinear elasticity parameter

An Experimental Validation of Phase-Based Motion Magnification for Structures with Developing Cracks and Time-Varying Configurations

In this study, Computer Vision and Phase-Based Motion Magnification (PBMM) are validated for continuous Structural Health Monitoring (SHM) purposes. The aim is to identify the exact instant of occurrence for damage or abrupt structural changes from video-extracted, very low amplitude (barely visible) vibrations. The study presents three experimental datasets: a box beam with multiple saw cuts of different lengths and angles, a beam with a full rectangular cross section and a mass added at the tip, and the spar of a prototype High-Aspect-Ratio wing. Both mode-shape- and frequency-based approaches are considered, showing the potential to identify the severity and position of the damage as well A high-definition, high-speed camera and a low-cost commercial alternative have been successfully utilised for these video acquisitions. Finally, the technique is also preliminarily tested for outdoor applications with smartphone cameras

Migraine and psychiatric comorbidity: a review of clinical findings.

Migraine is an extremely common disorder. The underlying mechanisms of this chronic illness interspersed with acute symptoms appear to be increasingly complex. An important aspect of migraine heterogeneity is comorbidity with other neurological diseases, cardiovascular disorders, and psychiatric illnesses. Depressive disorders are among the leading causes of disability worldwide according to WHO estimation. In this review, we have mainly considered the findings from general population studies and studies on clinical samples, in adults and children, focusing on the association between migraine and psychiatric disorders (axis I of the DSM), carried over after the first classification of IHS (1988). Though not easily comparable due to differences in methodology to reach diagnosis, general population studies generally indicate an increased risk of affective and anxiety disorders in patients with migraine, compared to non-migrainous subjects. There would also be a trend towards an association of migraine with bipolar disorder, but not with substance abuse/dependence. With respect to migraine subtypes, comorbidity mainly involves migraine with aura. Patients suffering from migraine, however, show a decreased risk of developing affective and anxiety disorders compared to patients with daily chronic headache. It would also appear that psychiatric disorders prevail in patients with chronic headache and substance use than in patients with simple migraine. The mechanisms underlying migraine psychiatric comorbidity are presently poorly understood, but this topic remains a priority for future research. Psychiatric comorbidity indeed affects migraine evolution, may lead to chronic substance use, and may change treatment strategies, eventually modifying the outcome of this important disorder

Experimental evaluation of tensile performance of aluminate cement composite reinforced with weft knitted fabrics as a function of curing temperature

Cement composites (CC) are among the composites most widely used in the construction industry, such as a durable waterproof and fire-resistant concrete layer, slope protection, and application in retaining wall structures. The use of 3D fabric embedded in the cement media can improve the mechanical properties of the composites. The use of calcium aluminate cement (CAC) can accelerate the production process of the CC and further contribute to improving the mechanical properties of the cement media. The purpose of this study is to promote the use of these cementitious composites by deepening the knowledge of their tensile properties and investigating the factors that may affect them. Therefore, 270 specimens (three types of stitch structure, two directions of the fabric, three water temperature values, five curing ages, with three repetitions) were made, and the tensile properties, absorbed energy, and the inversion effects were evaluated. The results showed that the curing conditions of the reinforced cementitious composite in water with temperature values of 7, 23, and 50 °C affect the tensile behavior. The tensile strength of the CCs cured in water with a temperature of 23 °C had the highest tensile strength, while 7 and 50 °C produced a lower tensile strength. The inversion effect has been observed in CC at 23 °C between 7 and 28 days, while this effect has not occurred in other curing temperature values. By examining three commercial types of stitches in fabrics and the performance of the reinforced cementitious composites in the warp direction, it was found that the structure of the “Tuck Stitch” has higher tensile strength and absorbed energy compared to “Knit stitch” and “Miss Stitch”. The tensile strength and fracture energy of the CC reinforced with “Tuck Stitch” fabric in the warp direction, by curing in 23 °C water for 7 days, were found to be 2.81 MPa and 1.65 × 103 KJ/m3, respectively. These results may be helpful in selecting the design and curing parameters for the purposes of maximizing the tensile properties of textile CAC composites

Analysis of a Motocross Knee Brace: From the Real Model to the Numerical Finite Element Model via 3D Scanning and Reverse Engineering

Featured Application: This study outlines a novel procedure for the Finite Element Modelling and Analysis of motocross knee braces under race conditions. The aim is to quantitatively evaluate the effectiveness of such stabilisers in reducing the risk and consequences of musculoskeletal injuries, considering the current lack of industrial standards and dedicated scientific research works. Musculoskeletal injuries often occur when performing motocross; almost half of the overall ligamentous injuries (42%) are knee ligaments injuries. Lesions can be greatly reduced with knee braces. Commercial knee braces are expected to oppose and limit unwanted and potentially harmful movements such as hyperextension and excessive rotation of the knee joint. However, this aspect has not been fully investigated from a biomechanical point of view. This would require proper Finite Element Modelling (FEM) and Analysis (FEA). However, to perform FEA and evaluate the efficacy of the brace simulating sportive conditions, numerical models need to be built. It requires a dedicated setup and several preprocessing steps, for which no industrial standard or widely accepted better practise is available as of today. Firstly, the brace and the lower limb are scanned using a 3D scanner. The geometry is reconstructed using reverse engineering techniques. These allow us to obtain a smooth, reliable 3D model starting from the points cloud acquired during scanning. A lower limb model was created using a mixed approach, combining MRI data and 3D scanning. Finally, a simulation of the impact condition after a jump using the developed model was carried out

Update on Hemicrania Continua

Hemicrania continua (HC) is a rare primary headache syndrome, characterized by unilateral pain and an absolute response to indometacin. Since the term was first coined in 1984, more than 100 cases have been described worldwide. Most recently, detailed case series that provide more detailed information concerning the sometimes complex clinical presentation of HC have been reported. Functional imaging studies suggest a unique pattern of subcortical involvement in HC: contralateral to the pain posterior hypothalamic region, ipsilateral dorsal pons and ipsilateral ventral midbrain, which, along with the particular effect of indometacin, probably justifies its classification as a unique entity. Increasing the awareness of this primary headache form among clinicians will aid in its diagnosis while further work is being undertaken to characterize the syndrome