Design of X-Concentric Braced Steel Frame Systems Using an Equivalent Stiffness in a Modal Elastic Analysis

In this work, a general method for the design of concentric braced steel frames (CBF) with active tension diagonal bracings, applicable to single- and multi-storey structures, is presented. The method is based on the use of an elastic modal analysis with a response spectrum, which is carried out using an appropriate modified elastic stiffness of diagonal bracings. The reliability of the proposed method is validated through the analysis of significant case studies, making a series of numerical comparisons carrying out time-history non-linear dynamic analysis

Identification of mesoscale model parameters for brick-masonry

Realistic assessment of existing masonry structures requires the use of detailed nonlinear numerical descriptions with accurate model material parameters. In this work, a novel numerical-experimental strategy for the identification of the main material parameters of a detailed nonlinear brick-masonry mesoscale model is presented. According to the proposed strategy, elastic material parameters are obtained from the results of diagonal compression tests, while a flat-jack test, purposely designed for in-situ investigations, is used to determine the material parameters governing the nonlinear behaviour. The identification procedure involves: a) the definition of a detailed finite element (FE) description for the tests; b) the development and validation of an efficient metamodel; c) the global sensitivity analysis for parameter reduction; and d) the minimisation of a functional representing the discrepancy between experimental and numerical data. The results obtained by applying the proposed strategy in laboratory tests are discussed in the paper. These results confirm the accuracy of the developed approach for material parameter identification, which can be used also in combination with in-situ tests for assessing existing structures. Practical and theoretical aspects related to the proposed flat-jack test, the experimental data to be considered in the process and the post-processing methodology are critically discussed

MECHANICAL ENERGY DIFFERENCES BETWEEN WALKING AND RUNNING AT DIFFERENT VELOCITIES ON TREADMILL

INTRODUCTION: Cavanagh (1990) described a variation from 170 to 1700 W in power output for the same movement (running at 3.6 m/s) calculated by six different authors. These differences occurred mainly due to different procedures for energy calculation and generated data that are not comparable. The purpose of this investigation was to describe, analyze, and compare the mechanical energy curves (total, internal and external energies) for six subjects while walking and running on treadmill, by using the same procedure for energy calculation. METHODS: Six male subjects were filmed with two video-cameras (Sony-50Hz) while walking at 1.5 m/s and running at 3.0 and 4.0 m/s on a treadmill. After a manual digitizing process, a 3D analysis was performed from the kinematics. The analysis was based on a 13 segment model. Positions of segmental centers of gravity, segmental weights, and moments of inertia were estimated on the basis of tables devised by Dempster (1955) as revised by Winter (1979). The components of mechanical energy were calculated at each instant of time, using the equations described by Zatsiorsky et al. (1987). RESULTS AND DISCUSSION: In relation to the differences between walking and running, the following observations were made: a) in walking the greatest contribution to the total change derived from the internal energy, while in running it derives from the external energy; b) the internal and external energy were in phase in walking, and in opposition in running. Comparing the variations in the two velocities of running, the following conclusions were drawn: a) the average value of the absolute total energy at 3.0 m/s was 1237.9 J and at 4.0 m/s 1544.2 J; b) there was a linear correlation (r = 0.84) between the change in velocity and the change in total energy; b) with the increase in velocity, the average increase in the total contribution of the change in internal energy was about 72% and of the external energy 36%; c) there was no change in the contribution of the potential energy to the change in external energy; d) the increase in the internal energy was chiefly dependent on the increase in the kinetic energy. CONCLUSION: Although the results related to the shape of the curves for mechanical energy for walking and running are already a matter of consensus in the field of biomechanics, it would appear that the numerical results are still open to broad discussion

A STUDY OF THE MECHANICAL ENERGY DIFFERENCES BETWEEN TREADMILL AND OVERGROUND WALKING

The aim of this paper was to analyze the components of the mechanical energy of the body considering the differences between treadmill and overground walking. One subject was filmed while walking at 1.5 m/s on treadmill and overground. The results show that the patterns of the curves are very similar, but the change in the total energy, both in the upper as in the lower extremity were greater on overground (23.20J and 17.47J respectively for overground and treadmill and for the upper extremity 4.91J and 2.56J). The potential energy change of the trunk was also greater on overground (overground 45.97J; treadmill 24.88J). These findings, showing a lower measured mechanical cost on treadmill address the problem whether the treadmill can be used as a valid simulator for overground walking

Introdução à biomecânica do esporte considerações sobre métodos de investigação

Através de análise da literatura específica, discute-se o domínio da área de atuação da Biomecânica do Esporte, a interdisciplinaridade de Ciências Esportivas para a investigação do movimento e padronização conceituai, quanto à composição, classificação e metas na investigação. Quanto aos métodos de medidas, discutem-se os principais processos e suas características, visando a complexa investigação para a análise do movimento esportiv

Advancements in Design, Analysis, and Retrofitting of Structures Exposed to Blast

The objective of this special issue is to provide an overview on the current trends and recent advancements in terms of design, analysis, experimental testing, and retrofitting of structural systems and assemblies exposed to exceptional loads such as explosions

Eye-Light on Age-Related Macular Degeneration: Targeting Nrf2-Pathway as a Novel Therapeutic Strategy for Retinal Pigment Epithelium

open6noThis work was supported by the University of Pavia [to MA, grant number BSR1744747; 2017] and the Italian Ministry of University and Research [to MA, FFABR2017]. The University of Bologna is acknowledged by MR [Grants from RFO].Age-related macular degeneration (AMD) is a common disease with a multifactorial aetiology, still lacking effective and curative therapies. Among the early events triggering AMD is the deterioration of the retinal pigment epithelium (RPE), whose fundamental functions assure good health of the retina. RPE is physiologically exposed to high levels of oxidative stress during its lifespan; thus, the integrity and well-functioning of its antioxidant systems are crucial to maintain RPE homeostasis. Among these defensive systems, the Nrf2-pathway plays a primary role. Literature evidence suggests that, in aged and especially in AMD RPE, there is an imbalance between the increased pro-oxidant stress, and the impaired endogenous detoxifying systems, finally reverberating on RPE functions and survival. In this in vitro study on wild type (WT) and Nrf2-silenced (siNrf2) ARPE-19 cells exposed to various AMD-related noxae (H2O2, 4-HNE, MG132 + Bafilomycin), we show that the Nrf2-pathway activation is a physiological protective stress response, leading downstream to an up-regulation of the Nrf2-targets HO1 and p62, and that a Nrf2 impairment predisposes the cells to a higher vulnerability to stress. In search of new pharmacologically active compounds potentially useful for AMD, four nature-inspired hybrids (NIH) were individually characterized as Nrf2 activators, and their pharmacological activity was investigated in ARPE-19 cells. The Nrf2 activator dimethyl-fumarate (DMF; 10 μM) was used as a positive control. Three out of the four tested NIH (5 μM) display both direct and indirect antioxidant properties, in addition to cytoprotective effects in ARPE-19 cells under pro-oxidant stimuli. The observed pro-survival effects require the presence of Nrf2, with the exception of the lead compound NIH1, able to exert a still significant, albeit lower, protection even in siNrf2 cells, supporting the concept of the existence of both Nrf2-dependent and independent pathways mediating pro-survival effects. In conclusion, by using some pharmacological tools as well as a reference compound, we dissected the role of the Nrf2-pathway in ARPE-19 stress response, suggesting that the Nrf2 induction represents an efficient defensive strategy to prevent the stress-induced damage.openCatanzaro M.; Lanni C.; Basagni F.; Rosini M.; Govoni S.; Amadio M.Catanzaro M.; Lanni C.; Basagni F.; Rosini M.; Govoni S.; Amadio M

Review of experimental cyclic tests on unreinforced and strengthened masonry spandrels and numerical modelling of their cyclic behaviour

A reliable numerical modelling for the cyclic behaviour of unreinforced and strengthened masonry spandrels is herein presented. The proposed numerical model is adapted from Tomazevic-Lutman\u2019s model for masonry piers in shear and it has been validated upon an experimental campaign conducted at Department of Engineering and Architecture of University of Trieste. The tests were conducted on Hshaped full-scale specimens imposing vertical displacements of increasing amplitude on one leg. Four unreinforced masonry specimens arranged with different masonry material (bricks and stones) and lintel supports (wooden lintel, masonry arch) were considered. Each specimen was then reinforced with a different strengthening technique (tensioned bars, steel profiles, CFRP laminates) and re-tested. Analytical relationships were proposed, based on those available in some Codes of Practice, to estimate the maximum shear resistance of URM and RM spandrels. These relationships provide resistance values in good agreement with the experimental results and can be correctly employed to define the cyclic model of the spandrel to be used in the numerical simulation. The cyclic shear-displacement curves obtained through the numerical model are in good agreement with those of the experimental tests and very good assessment of the dissipated energy was obtained

BIOMECHANICAL APPROACH TO BALLET MOVEMENTS: A STUDY OF THE EFFECTS OF BALLET SHOE AND MUSICAL BEAT ON THE VERTICAL REACTION FORCES

Ballet movements can be the focus of biomechanical studies in order to better understand the characteristic mechanical loads of the locomotor apparatus related to classic dance. "Pointe shoes" have been associated to high incidence of morphological and physiological alterations of ballet dancer's feet, however its contribution to injury mechanisms must still be precisely known. On the other hand, movements like jumps and leaps are frequently repeated in a standard ballet training, where the musical beat also plays a role on the motor behavior and its mechanical aspects. Therefore the purpose of the present study was to describe ground reaction forces during the "saute -1st position" under the influence of footwear (slippers and pointe shoes) and musical beat in order to identify the relative contribution of these factors on the external loads measured. It was observed that the musical beat played a greater role on the ground reaction force magnitudes than the footwear