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To comprehend the empirical seismic vulnerability capability of various typical structures in towns and suburbs, this study considers, as the research background, the structural damage data observation from the Mw 7.1 Yushu earthquake that occurred on 2010 April 14th in China. The proposed research activity sorts out the actual investigation data (7156 buildings) of five types of typical structures in towns and villages and establishes the vulnerability and seismic fragility evaluation model of a group of buildings considering multidimensional parameters by using the Chinese macroseismic intensity standard. Using spatial modal, numerical calculation, and regression analysis methods, an updated lognormal distribution vulnerability and resilience assessment model based on multidimensional quantitative parameters is performed. Based on the principle of the conditional probability and damage quantification model, an innovative model (domain, point cloud, curve, surface, matrix, and function) is established for regional vulnerability and seismic resilience assessment of typical group buildings. A logarithmic relationship model considering both the updated Chinese macroseismic intensity and three-dimensional composite peak ground acceleration as intensity measures is proposed, and an empirical vulnerability assessment model for typical rural buildings is established. The traditional average earthquake loss index calculation model is updated, and an innovative regional domain vulnerability assessment model is conducted. Taking the samples of various typical structures surveyed in the Yushu earthquake, regional group structure vulnerability domain comparison models of various structures are performed. Ultimately, depending on the typical damage characteristics of structures, the actual damage features and mechanisms of various structures are analysed. [ABSTRACT FROM AUTHOR]

The robustness of a structural systems is understood as their ability to prevent or reduce the consequences of a local (exceptional and/or extreme) event. The current work aims to address the issues related to the evaluation of robustness of structures with incorporated damage. The case study of an existing reinforced concrete arch bridge is investigated in terms of robustness considering the variation of both the cracking state from concrete spalling and the corrosion of reinforcement bars. The damage variation related to these different matters is assessed both in terms of intensity and occurrence in the various structural elements of the bridge. Finally, the structural robustness index is estimated through push‐down analysis to make an overall assessment of the bridge behavior. [ABSTRACT FROM AUTHOR]

To study the seismic vulnerabilities and performances of typical bridges, data from a field investigation of 2134 bridges on 22 highway sections hit by the Wenchuan earthquake that occurred in China on May 12, 2008, were collected and processed. From the sample data of the empirical seismic-damage observations, 1409 simply supported girder bridges, 107 continuous girder bridges, and 612 arch bridges were selected. The latest version of the Chinese seismic intensity standard was utilized to evaluate the fragility of bridge samples in different macroseismic intensity zones, and the empirical vulnerability matrix and multidimensional regression comparison model of typical bridge clusters were developed. Taking the bridge length, the coordinate azimuth of the bridge location, the number of spans, the geometric form of the pier columns, and the type of bearings and foundations as the single factors influencing vulnerability and assuming (i) the line type and bridge length, (ii) the types of pier column and foundation, and (iii) the number of spans, the type of bearings, foundations, and linearity as the coupled factors influencing vulnerability, the aforementioned typical bridges were subjected to comparative vulnerability analysis. Innovative fragility regression and probability comparison models of typical bridges were developed considering the influence of multiple factor coupling. A novel vulnerability evaluation model was proposed based on the characteristic parameters and damage grade of bridge clusters in the umbrella earthquake area, and the model was optimized and verified by using the typical bridge database of the Wenchuan earthquake. [ABSTRACT FROM AUTHOR]

In the last decades, metal foams have been bringing increasing attention because they represent a new category of materials with very intriguing physical and mechanical properties like, for example, high stiffness and low density. These materials have not been studied completely, and many research efforts have been carrying out to investigate new foaming techniques. The present work aimed at evaluating the efficiency of electromagnetic induction as a heating technique of foam precursors for the manufacture of closed-cell aluminum foam specimens by the indirect foaming process known as the powder compact melting technique; a conventional and a flexible mold strategy, the latter using a stainless-steel wire mesh, were employed for the manufacture of parallelepiped specimens. The results outlined the interesting perspectives of this manufacturing method. In detail, they highlighted a significant process repeatability and the beneficial effects of the induction heating method, allowing heating the precursor in very little time and in a safe way compared to conventional heating through a muffle furnace; moreover, they showed the influence of the mould choice both on the processing time, with the synergistic interaction between the flexible mold and the induction system in terms of heat generation, and on the surface geometry of the foamed components, which reflected in their different compression behavior. [ABSTRACT FROM AUTHOR]

Conversely, the numerical modeling of the seismic behavior of masonry structures represents a very complex problem due to the constitutive law of this structural material and its highly nonlinear behavior. Historical structures represent a significant percentage of existing constructions in numerous seismic-prone regions, and some of these are iconic monuments of their countries. Damage fragility curves were identified for typological building classes, defined by considering parameters present in both post-earthquake observations and census data with the aim of extending the results to the whole national territory. [Extracted from the article]

Incremental sheet forming represents a relatively new process appointed to form sheets of pure metals, alloys, polymers, and composites for the manufacture of components in fields where customized production in a short time and at a low cost is required. Its most common variant, named single-point incremental forming, is a flexible process using very simple tooling; the sheet is clamped along the edges and a hemispherical-headed tool follows a required path, to deform the sheet locally. In so doing, better formability is reached without any dedicated dies and for low-forming forces, which represent some of the attractive features of this process. Nevertheless, and with special reference to thermoplastic sheets, incremental formed parts suffer from peculiar defects like twisting and wrinkling. In this numerical work, analyses were conducted through a commercial finite element code by varying the toolpath strategy of the incremental forming of polycarbonate sheets. The investigation of some features like the forming forces, the deformation states, the energy levels, and the forming time was carried out, to determine the toolpath strategy able to optimize the incremental forming process of polymer sheets. The results of the numerical analyses highlight a reduction of the forming forces when using toolpaths alternating diagonal up and vertical down steps and, presumably, a reduced risk of failures and defects. Furthermore, these toolpath strategies solutions also have a positive impact on the environment in terms of energy and do not significantly increase the manufacturing time. [ABSTRACT FROM AUTHOR]

Rainwater may penetrate through the cladding, enter the wall assembly, and cause damage to the façade components and interior finishes, which are moisture sensitive, most of the time. In the current paper, the performance assessment of a skylight with a full-scale mock-up has been evaluated. The mock-up was erected for an actual project to verify the acceptance criteria for the skylight's technical, functional, and architectural details. The test was conducted at the Aluminum Technology Auxiliary Ind. (ALUTEC) facility in the Industrial Zone, Doha, Qatar. The fabricated full-scale mock-up has a rectangular plane configuration of 6.625 m (length) by 3.315 m (width) that belongs to a skylight measuring 36 m by 18 m. The ASTM E283, ASTM E331, and ASTM E330 standards were followed during the experiment. Air infiltration/exfiltration, static water penetration, structural performance, post-structural static water penetration, and structural proof loading tests were performed in an airtight chamber. After recording the residual displacements, the test findings for all the make-up components, namely steel tubes, glass, and aluminum sandwich panels, were determined and found within acceptable limits. [ABSTRACT FROM AUTHOR]

This study provides the seismic scenario-based risk map of the small mountain city of Kerend-e-gharb. It evaluates the existing methods and formulations for the effects of a devastating earthquake using empirical fragility curves. A seismic vulnerability map is developed at the urban block-scale using a Geographic Information System for a variety of steel, reinforced concrete, confined masonry, unreinforced masonry, and adobe residential buildings. The estimated seismic damages are validated by comparing them with the building damages surveyed after the Sarpol-e-zahab earthquake. Moreover, the damages to the population, including the probability of homelessness, death, severe injuries that need immediate hospital treatment, moderate injuries that require hospital treatment, and light injuries, without hospitalization, are assessed. The estimation of debris, and the economic losses deriving from this natural hazard, are also investigated. Finally, the map of the mean damage index is presented. The mean damage index is reduced by the renovation and retrofitting interventions in high damaged buildings, while this index is increased in moderately damaged buildings that are not structurally upgraded. The results of this study are consistent with the earthquake damage distribution. In addition, and even with the reduction in vulnerability of buildings after seismic interventions, some blocks of the northeastern part of the city are still at high seismic risk. The results of this study can be used in seismic crisis management planning to achieve a sustainable city. [ABSTRACT FROM AUTHOR]

Incremental sheet forming has been largely investigated in the last two decades because of its versatility and cost-effectiveness, which make it viable for manufacturing highly customized parts as well as small- and medium-sized batches. This process allows for reaching greater formability compared to conventional sheet-forming processes. In contrast, it is affected by defects like twisting, which strongly influence the geometric accuracy of the formed parts. These aspects are dramatically accentuated when forming soft materials like thermoplastics. With these premises, the following research aims to investigate the effects of the toolpath strategy on the occurrence of failures and defects in the incremental sheet forming under very severe process conditions. Cone frusta with a fixed wall angle were obtained by thin polycarbonate sheets, imposing four unidirectional helical trajectory-based toolpaths, one traditional, and three stair strategies. The analysis of the forming forces, the evaluation of the worked surfaces, and the monitoring of the defectiveness highlight the advantages of a stair toolpath strategy in terms of reduced twisting and loading and high surface quality, regardless of the lubrication conditions. [ABSTRACT FROM AUTHOR]

The safety of the built heritage of our cities towards environmental factors and seismic actions is a pressing need for designers and researchers. The actual trend is to setup effective solutions to reduce thermal dispersions through the building envelope. Contrarily, combined systems able to enhance the resistance of constructions to earthquakes, on the one hand, and, on the other hand, to increase the energetic efficiency of existing buildings are scarcely diffused on the market and are rarely investigated in the scientific literature. In this framework, the seismic design of the new envelope DUO system for seismic-environmental requalification of existing masonry constructions is illustrated in the present paper with reference to a case study in the Neapolitan area. After the geometrical and mechanical characterization of the investigated building is performed, an FEM model of the masonry construction is setup by the SAP2000 analysis program, which has allowed performing pushover analyses. Based on the non-linear seismic response of the construction, an appropriate upgrading design mainly based on the innovative seismic envelope DUO system has been made. The static non-linear analyses applied to the upgraded FEM model of the building have shown a clear increase in performance in terms of strength, stiffness and ductility, thus confirming the effectiveness of the proposed envelope system. [ABSTRACT FROM AUTHOR]

In this framework, the current research work aims to analyse a sub-urban sector of the historic centre of Sant'Antimo, located in the province of Naples (Italy), in order to assess the seismic vulnerability of old masonry buildings in this sector and the expected damage scenarios resulting from seismic events with different characteristics. Moreover, in order to mitigate the identified risk, a set of retrofitting techniques are considered and analysed taking into account their contribution for the reduction of the seismic vulnerability of buildings. The vulnerability analysis is performed through the application of an index-based seismic vulnerability assessment approach integrated into a GIS tool in order to identify the structural units (S.U.) most susceptible at damage. Subsequently, typological vulnerability curves, according to the EMS-98 scale, are obtained for the building stock analysed. Finally, a parametric analysis, varying magnitude and seismogenic site-source distance, is performed to obtain and discuss urban damage and loss estimation scenarios in terms of number of collapsed and unusable buildings, as well as number of human casualties, severe injuries and homelessness. [ABSTRACT FROM AUTHOR]

The paper deals with the mechanical degradation of composite material components in seawater at room temperature. In particular, this study compares quasi-static and dynamic behaviour of carbon fiber/vinyl ester components, dry and water saturated in a saline environment at 3% to simulate the seawater exposition. At this regard, short-beam shear, flexural and low-velocity impact tests were systematically performed before and after the conditioning of the material under examination. Finally, the damage of the impacted specimens was carefully analyzed by visual inspections and ultrasound investigations. Despite a very low water absorption, the analyses allow to highlight different phenomena, reflecting on variations in the mechanical properties and in the extent of the damage of the investigated samples. [ABSTRACT FROM AUTHOR]

This study investigates the damage data after November 12, 2017, Iran earthquake (Mw 7.3), collected on 440 steel and reinforced concrete residential buildings. Structures have low-to-medium height and are located in Sarpol-e-zahab city, as well as in the west and northwest parts of Kermanshah province, Iran. The peak ground acceleration demands are determined according to data of the micro-shakemap of Sarpol-e-zahab city and the shakemap of Kermanshah province, while the mean values of intensities are determined from the existing empirical relationship between PGA and intensity. The investigated buildings are engineered steel and RC structures nominally erected according to the second and third editions of the Iranian code for earthquake-resistant buildings, but mostly under careless supervision and with low-quality materials. Damage probability matrix, vulnerability index and empirical fragility curves are presented for three subgroups of steel and RC structures on the basis of (i) structural materials and seismic resistant systems (i.e. braced, moment and combination of braced and moment steel frames, as well as moment and combination of moment and shear wall RC frames), without considering the height of structures; (ii) structural materials and height of structures, without considering the seismic resistant systems (i.e. low and medium-height steel and RC structures); (iii) structural materials, without considering the seismic resistant systems and height of structures (i.e. total data for steel and RC frames). The proposed fragility curves are compared with other fragility curves for steel and RC buildings from previous studies. Finally, since this earthquake was the first seismic event in Iran affecting a considerable number of steel and RC engineered buildings, the proposed empirical fragility curves are definitely unique and crucial for realistic damage and vulnerability assessment of similar buildings in future earthquake scenarios, as well as for developing rapid seismic loss assessment after damaging earthquakes. [ABSTRACT FROM AUTHOR]

Recent studies on innovative solutions in structural engineering fields highlight the effectiveness of closed-cell aluminum foams as traditional material/architecture core replacement in sandwich structures. This study aims to investigate the mechanical behavior and the collapse modes of innovative sandwich panels with aluminum foam as the core and stainless steel wire mesh-grid as the skins; the manufacturing process was based on the powder compact melting technique. The results of quasi-static three-point bending tests point out the beneficial effects, in terms of mechanical performance, of the reinforcement skin on the sandwiches, compared to the plain foams; this joins by their effectiveness in withstanding thermal and mechanical loads. Moreover, the investigation of the collapse mechanisms of the sandwiches with different thicknesses allows for testing the goodness-of-fit of the experimentally observed collapses with the ones predicted by the failure map from analytical models available in the literature. [ABSTRACT FROM AUTHOR]

Recent studies on innovative solutions in structural engineering fields highlight the effectiveness of closed-cell aluminum foams as traditional material/architecture core replacement in sandwich structures. This study aims to investigate the mechanical behavior and the collapse modes of innovative sandwich panels with aluminum foam as the core and stainless steel wire mesh-grid as the skins; the manufacturing process was based on the powder compact melting technique. The results of quasi-static three-point bending tests point out the beneficial effects, in terms of mechanical performance, of the reinforcement skin on the sandwiches, compared to the plain foams; this joins by their effectiveness in withstanding thermal and mechanical loads. Moreover, the investigation of the collapse mechanisms of the sandwiches with different thicknesses allows for testing the goodness-of-fit of the experimentally observed collapses with the ones predicted by the failure map from analytical models available in the literature. [ABSTRACT FROM AUTHOR]

The increasing interest towards environmentally friendly materials for economic reasons and to comply with ever more stringent environmental requirements has allowed the flax fibres to gain an extraordinary interest in the development of new polymer composites. In fact, among plant fibres, the flax ones, given their low density, are characterised by specific mechanical parameters even higher than those of E-glass fibres. However, the application of composites reinforced with natural fibres remains confined to non-structural components. This matter is due to the requirement of important challenges resolution such as their intrinsic hydrophilicity and poor interfacial adhesion with hydrophobic polymer matrices, widely used for their easy processability, economy and lightness. In this context, this research has been focused on the flexural and low-velocity impact properties of polypropylene-based laminates, containing woven flax fibres and subjected to a pre-selected hygroscopic ageing protocol. The presence of a coupling agent, polypropylene-grafted-maleic anhydride, was considered too. Mechanical results, integrated with micrographic observations and visual inspections, provide useful details about the potential use of the studied materials already screened in the nautical field. [ABSTRACT FROM AUTHOR]

The paper investigates the influence of tool diameter, sheet thickness, and geometry of the workpiece during single-point incremental forming (SPIF) of polycarbonate sheets. An experimental campaign was conducted and involved varying and fixed slope angle tests. The process was performed at room temperature. Cone and pyramid frusta geometries were analyzed. A FE model was developed to determine stress, strain, and thickness distributions during the process. Different defects affected the formability of the polymer, namely thinning, twisting, and wrinkling. Significant differences were found with respect to SPIF of metals due to mechanical behavior of the polycarbonate, in terms of amount of thinning, twisting, and wrinkling. The mechanism of development of the abovementioned defects was identified as well as how they are influenced by the process parameters. The comparison of fixed and varying slope angle tests indicated that these latter were not fully representative of the formability of the sheets. The presence of geometrical singularities in pyramid frusta affected the formability of the materials. This was due to great localization of thinning at the edges and the increase of the forming loads as approaching these regions. [ABSTRACT FROM AUTHOR]

Abstract Low velocity impact behaviour of laminates made of different reinforcements and matrices was studied in this paper. Impact tests were carried out up to penetration and at increasing energy values on glass fibre reinforced phenolic resin laminates, with different configurations (quasi-isotropic and orthotropic) and thicknesses, in order to correlate the indentation depth with the impact energy. Impact results obtained on basalt fibre reinforced epoxy resin laminates with different thicknesses were compared too. The stacking sequence of the glass fibre specimens was found to have no influence on the penetration energy but revealed lower indentation for the quasi-isotropic ones, under the same impact energy, for all the thicknesses tested. Moreover, basalt laminates showed lower indentation depths, compared to the data from this research and present in literature on other material systems. Finally, the results from the impact tests were used to validate existing semi empirical laws for the evaluation of the indentation and the penetration energy, in which the fibre content assumes the most relevant role. [ABSTRACT FROM AUTHOR]

Recent earthquakes have highlighted the high vulnerability of the industrial structures that are not specifically designed for accounting seismic forces. Among them, a widespread typology is characterised by steel structures without bracing or other anti-seismic details and with masonry infills. With the aim of increasing the knowledge on the seismic behaviour of these structures, this work focuses on a mechanical-based approach for the evaluation of fragility curves for industrial areas. The exposure data are obtained by in-situ survey and acquiring information available in existing databases, like the Italian Cartis-GL one that is specifically devised for industrial structures. The variability of geometrical and mechanical data and the presence of epistemic uncertainties are considered by constructing a population of structures using the Monte Carlo method. Each structure is analysed through static-nonlinear simulations adopting mixed finite elements accounting for geometrical and constitutive nonlinearities. The approach is tested for infilled steel structures in the industrial area of the municipality of Spezzano Albanese (Italy). Results show that the presence of masonry infill drastically modifies the seismic behaviour of this structural typology. In particular, it turns out that if the mechanical contribution of the infill is neglected, the structures exhibit high damages even for low intensities of the seismic action. [ABSTRACT FROM AUTHOR]

The influence of the contact conditions at the tool-workpiece interface and the toolpath strategy on the quality of incremental formed parts made by polycarbonate sheets is investigated. To this end, different experimental tests were conducted involving different tool types (with fixed and rotating end) and toolpaths (unidirectional and alternate), to determine their influence on the material formability, twisting, elastic springback, forming forces, sheet thinning and surface roughness. The alternate toolpath enabled achieving the highest formability and minimum twisting, as compared to that observed when the unidirectional toolpath was used. On the other hand, the adoption of the tool with fixed end enabled reducing the springback, while the tool type showed negligible influence on the other quality parameters. [ABSTRACT FROM AUTHOR]

In the paper, the seismic retrofitting of an existing reinforced concrete school building located in the district of Naples has been examined. The school, which was designed to sustain gravity load only, is composed of seven constructions separated with seismic joints. One of these constructions has been retrofitted with different intervention techniques, namely reinforced concrete walls, steel concentric, eccentric and buckling restrained braces and steel shear panels, whose non-linear behaviour under seismic actions in terms of performance point detection have been evaluated and compared using Capacity Spectrum Method. Finally, the choice of the best intervention technique from economic, structural and environmental point of view has been done utilising an efficient multi-criteria decision-making (MCDM) method, the so-called TOPSIS method. From the performed analyses it was found that buckling restrained braces provide optimal solution for the seismic upgrading of the examined reinforced concrete school building. [ABSTRACT FROM PUBLISHER]

Woven hemp fabric reinforced polylactic acid composites with different fibre volume fraction (20, 30 and 40%) were manufactured by compression moulding process. To better understand the industrial application limits of the investigated bio-composite, flexural and impact properties were determined and compared to those of the unreinforced bio-polymer and the creep behaviour at different values of temperature was widely investigated adopting the Arrhenius theory. In addition, to predict the long-term mechanical performance of the investigated bio-composite, the possibility to use the Time-Temperature Superposition model was investigated. For this purpose, Dynamic-Mechanical tests were conducted to evaluate the activation energy and then to apply the Time-Temperature Superposition model to the compliance curves, obtained by short-time creep tests under different load conditions. Therefore, to examine the validity of the theoretical model, experimental long-time tests were also carried out. The results show interesting mechanical properties and a good fit between the theoretical and the experimental creep curves, particularly when the fibre volume fraction was equal to 20 and 30%. [ABSTRACT FROM AUTHOR]

In this experimental work, the behaviour of unidirectional glass fibre-epoxy composites under a cutting force was studied, in order to better understand the cutting mechanisms of processes involving but not limited to composite materials. Starting from composite panels manufactured by resin infusion process, dedicated specimens were obtained and subjected to a quasi-static punch-shear test. Eight different fibre orientation angles with respect to the direction of the cutting force were considered. For each case, different stress-strain behaviours were observed and discussed. The differences were also investigated, in terms of damage propagation, by means of microscopic observations of the cutting zone. [ABSTRACT FROM AUTHOR]

Masonry building aggregates are large parts of the Italian building heritage often designed without respecting seismic criteria. The current seismic Italian code does not foresee a clear calculation method to predict their static nonlinear behavior. For this reason, in this article a simple methodology to forecast the masonry aggregate seismic response has been set up. The implemented procedure has been calibrated on the results of two FEM structural analysis programs used to investigate three masonry building compounds. As a result, a design chart used to correctly predict the base shear of aggregate masonry units starting from code provisions has been set up. [ABSTRACT FROM PUBLISHER]

• Seismic performance of an ancient Neapolitan Masseria has been evaluated. • Three analysis types based on the three evaluation levels foreseen by the Italian Guidelines on Cultural Heritage have been applied to the case study building. • The analysis results, compared to each other, have shown the problems and the high vulnerability degree of the building. • The simplest evaluation level (EL1), compared to the most detailed one (EL3), has provided unconservative results in predicting the building seismic vulnerability. • Consolidation interventions have been designed and applied to the structural parts of the Masseria to improve its seismic behaviour. In this paper, the seismic vulnerability appraisement, together with repairing and consolidation operations, of a masonry building with cultural and artistic value located in a small city near Naples are reported and discussed. After a brief digression about the condition of historical and cultural Italian heritage damaged by seismic events and usually in poor condition due to a lack of maintenance, the case study is presented and described, providing not only historical news but also information about as-built status, spaces, functions and structural issues. Once the principal failure modes affecting the building are identified, the estimation of seismic vulnerability is performed through three different evaluation levels given by the Italian Guidelines on Cultural Heritage. The analysis results, compared to each other, have shown the problems and the high vulnerability degree of the building. Finally, according to the Italian Guidelines, the consolidation and upgrading interventions are proposed and described to ensure a safety use of the Masseria under seismic actions. [ABSTRACT FROM AUTHOR]