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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]

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]

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]

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]

A new hybrid system consisting of wood shear walls, concrete columns, bracing system, and viscous damper devices is introduced in this paper. A benchmark wood building is adopted here as a case study, and different configurations of the new hybrid system are applied on it in order to investigate its seismic performance under some near-fault ground motion records. The performance base design method is used to design the considered models. In order to make the models comparable, their performance levels are considered to be identical. Detailed finite element models are built in OpenSees software to conduct nonlinear static and dynamic analyses. The parametric study is done to optimize the viscous damper system parameters. At the end, the damage potential of the models is investigated through their fragilities. The results demonstrate the high potential of the proposed system in improving the seismic performance of the mid-rise wood buildings. It is also observed that the good behavior of the system is achieved when the viscous damper coefficient and its supporting tendon cross-sectional area is dependently increased. [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]

In this work, incremental forming of pure niobium planar isotropic sheets was studied; in particular, two different types of test were conducted by varying the tool/sheet contact conditions, in order to understand the complex phenomena interesting this hard-to-form non-conventional material and to focus the attention on its formability and the finishing of the worked surfaces. From the tests, the formability limits were determined, the forming forces were acquired and analysed, the quality of the worked surfaces was evaluated with measures of roughness and high-magnification visual inspection, as well as the failures of the sheets were observed and interpreted. The results highlight that a proper choice of the contact conditions can avoid the occurrence of galling while preserving an optimal carrying out of the process. In any case, very good surface finishing and workability of niobium sheets, despite their brittle nature, is found when incrementally formed. As a consequence, incremental sheet forming of this non-conventional material can be considered a faisible way of manufacturing highly customized components. [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]

In this paper, some seismic factors, namely response modifiers, ductility, overstrength and deflection amplification, of steel moment resisting frames (MRFs) under near-field records are evaluated. To this purpose, two separate groups of near-field records (e.g., pulse-like and non-pulse-like) on the behaviour of MRFs are studied. In particular, four models with different storey heights (3-, 6-, 9-, and 12-storeys) are examined through IDA analyses under 20 pulse-like and 20 non-pulse-like ground motion records. Finally, the achieved results are compared with the recommendation values of the ASCE code to assess their reliability. According to the results, the MRF structures demonstrate better seismic behaviour under the non-pulse-like ground motions rather than pulse-like ones. The average response modification factor obtained from non-pulse-like ground motions is about 5.0, which is 1.19 times higher than the corresponding results achieved from pulse-like records. [ABSTRACT FROM AUTHOR]

The paper deals with the investigation of the seismic behaviour of a masonry church sited in Poggio Picenze (district of L'Aquila) and damaged by the L'Aquila seismic event occurred in Italy on 2009 April 6th. This earthquake, classified as an exceptional event, caused significant damages to about 15,000 buildings. Above all, many of the cultural sites of L'Aquila and the surrounding villages, including churches, palaces and other monuments dating from the Middle Ages and Renaissance, were harmed in a severe way or demolished. The current work is framed in the post-seismic scenario of Poggio Picenze, a small town located about 10 km to the South-East of L'Aquila, and it is aimed at the seismic response assessment of the St. Giuliano church by means of experimental dynamic testing and numerical analyses. Firstly, an experimental campaign based on Ambient Vibration Tests (AVTs), that are non-destructive tests especially applied to historical and monumental buildings for evaluating their modal response, has been performed on the selected construction in the framework of the COST C26 Action as a cooperation activity between the Ss. Cyril and Methodius University of Skopje and the University of Naples "Federico II". As a result, the method has allowed to obtain the dynamic properties of the examined structure, namely natural frequencies, vibration mode shapes and damping coefficients. The experimental results have been subsequently used to implement a numerical FEM model of the church in the ABAQUS non linear code environment. Linear FEM analysis has been carried out to calibrate the experimental results and a suitable investigation in the nonlinear field has been conducted to predict the post-seismic structural behaviour of the church. Finally, the performed analyses have been of a fundamental importance for both detecting damages into the construction and programming effective retrofitting interventions. [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]

A series of simplified approaches are evaluated for their effectiveness to estimate the seismic vulnerability of historical masonry towers. First, collapse loads are evaluated on sixteen “idealized” benchmark cases with different slenderness and shear area. Both analytical and computational approaches are used, namely the analytical procedure proposed by the Italian Guidelines on the Built Heritage and pushover analyses conducted using the commercial codes UDEC and 3Muri. The sixteen towers are representative cases which can be encountered in practice. Their geometry is idealized into parallelepiped blocks with hollow square cross-sections, thus favoring the utilization of 2D approaches, beneficial to drastically reduce the effort required for repeated computations. In addition, a Monte Carlo MC upper bound limit analysis strategy is proposed, in order to have an insight into the possible failure mechanisms for the different cases investigated. Deliberately is avoided the introduction of any form of irregularity and they are supposed isolated from the neighboring buildings, to obtain results exclusively dependent from geometric features. Among all the possible collapse mechanisms, five of them are selected according to the probability of occurrence based on past earthquake experiences. Five million cloud points of collapse accelerations are obtained by carrying the height, slenderness and shear area of the idealized towers. The approach is very fast and allows identifying different regions where single mechanisms are active. The results are confirmed repeating MC simulations with a triangular FE upper bound limit analysis discretization of the idealized towers. A series of equations are provided in order to assist engineers and practitioners to obtain a preliminary estimation of their expected collapse acceleration. For validation purposes, the results obtained previously with refined full 3D FE models of 25 towers located in the Northern Italy are reported. Satisfactory agreement between the predictions provided by simplified methods and sophisticated analyses are obtained. [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 behaviour. For this reason, in this paper firstly, a simple methodology to forecast the seismic response of masonry aggregates in San Pio delle Camere (L'Aquila, Italy) has been set up starting from the provisions of the Italian Guidelines on Cultural Heritage. 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. Later on, the large-scale seismic vulnerability and damage appraisal of the inspected historical centre has been done on the basis of a quick methodology, already implemented and experienced by the author in some historical centres of the Campania region. The analysis result was a numerical correlation between vulnerability index and mean damage grade of examined building compounds. In particular, a damage forecast under numerical way has been firstly estimated and then compared with the real one. The post-earthquake scenario has represented an ideal term of comparison for effectively testing the reliability of the employed technique, which should be further extended to other Italian historical centres. [ABSTRACT FROM AUTHOR]

This work approaches the seismic vulnerability assessment of an old stone masonry building aggregate, located in San Pio delle Camere ( Abruzzo, Italy), slightly affected by the 2009 April 6th earthquake occurred in L'Aquila and its districts. This building aggregate has been modelled by using the 3muri software for seismic analysis of masonry constructions. On one hand, static non-linear numerical analyses were performed to obtain capacity curves together with the prediction of damage distributions for the input seismic action (hybrid technique). On the other hand, indirect techniques, based on different vulnerability index formulations, were used for assessing the building aggregate's behaviour under earthquake action. The activities carried out have provided a clear framework on the seismic vulnerability of building aggregates, as well as aid future retrofitting interventions. [ABSTRACT FROM AUTHOR]