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Opportunistic computing is a paradigm for completely self-organised pervasive networks. Instead of relying only on fixed infrastructures as the cloud, users' devices act as service providers for each other. They use pairwise contacts to collect information about services provided and amount of time to provide them by the encountered nodes. At each node, upon generation of a service request, this information is used to choose the most efficient service, or composition of services, that satisfy that request, based on local knowledge. Opportunistic computing can be exploited in several scenarios, including mobile social networks, IoT and Internet 4.0. In this paper we propose an opportunistic computing algorithm based on an analytical model, which ranks the available (composition of) services, based on their expected completion time. Through the model, a service requesters picks the one that is expected to be the best. Experiments show that the algorithm is accurate in ranking services, thus providing an effective service-selection policy. Such a policy achieves significantly lower service provisioning times compared to other reference policies. Its performance is tested in a wide range of scenarios varying the nodes mobility, the size of input/output parameters, the level of resource congestion, the computational complexity of service executions.

In this work, an ‘on-the-fly’ measurement technique for the monitoring of CMOS inverters performance degradation is presented. This technique allows the characterization of the circuit degradation simultaneously with the applications of the stress. In our experiments, the inversion voltage (VINV) shifts measured during the application of pulsed voltage stresses at the input. It is demonstrated that the shifts can be described by a power law that accounts for the stress time and voltage dependences. Moreover, the circuit degradation has been correlated to the NMOS and PMOS degradations. The results show that the degradation of the CMOS inverter can be evaluated from an analytical equation that considers only the shifts of two parameters (threshold voltage VTH, and mobility µ) of the two transistors in the inverter.

A new formulation of a Logistic deterministic S-N curve is applied to fatigue data of metallic materials from ancient Portuguese riveted steel bridges. This formulation is based on a modified logistic relation that uses three parameters to fit the low-cycle- (LCF), finite-life- and high-cycle-fatigue (HCF) regions. This model is compared to the Kohout-Vechet fatigue model, which has a refined adjustment from very low-cycle fatigue (VLCF) to very high-cycle fatigue (VHCF). These models are also compared with other models, such as, power law and fatigue-life curve from the ASTM E739 standard. The modelling performance of the S-N curves was made using the fatigue data considering the stress fatigue damage parameter for the materials from the Eiffel, Luiz I, F�o and Trez�i riveted steel bridges. Using a qualitative methodology of graphical adjustment analysis and another quantitative using the mean square error, it was possible to evaluate the performance of the mean S-N curve formulation. The results showed that the formulation of the S-N curve using the Logistic equation applied to the metallic materials from the old bridges resulted in a superior performance when compared with others models under consideration, both in the estimation of fatigue behaviour in the low-cycle fatigue (LCF) region and in the lowest mean square error.

In recent years, the ever-increasing interest in intelligent tyre technology has led to the formulation of different empirical models correlating deformation measurements provided by the sensors with tyre dynamics. In this paper, a real-time physical model, suitable for describing the dynamics of intelligent tyres based on measurements of strains and/or displacements of the tyre carcass, is presented. The proposed flexible ring model can reproduce the tyre dynamics for both concentrated and distributed forces by introducing a discrete approach that also allows to analyse the longitudinal dynamics of the tyre in real-time. The analytical description of the problem allows to obtain solutions in closed form and to quickly identify model parameters from experimental data. The comparison between the simulated results and the ones provided by indoor tests of two intelligent tyre concepts highlighted that the proposed tyre model can estimate with an acceptable precision both the carcass deformations and the forces acting on the tyre.

Sandwich panels are commonly used in facades and the roofs of industrial buildings due to their well-known advantages. However, there is limited data about the in-plane behavior of the panels. Hence, this paper aimed to propose a pseudoelastic truss model to represent the effective in-plane stiffness and strength properties of the corrugated sandwich panels with a polyurethane foam core. Two separate sets of experiments (mock-up and system test) were conducted in the laboratory. The variables were the number of fasteners, sheet thickness, loading direction, and number of ribs. The number of fasteners, sheet thickness, and loading direction are the most effective parameters for the in-plane behavior. A formula was proposed to compute axial stiffness of the truss members by considering the effective parameters. Experimental results showed that the proposed robust truss model could give a good estimate of the pseudoelastic stiffness and maximum load bearing capacity of the sandwich panels. Turkish Precast Concrete Association This study was conducted in the framework of ITuNOVA Technology Transfer Office Research Project titled Determination of In-plane Behavior of Corrugated Sandwich Panel Type Roof Shelters. The finan-cial support provided by Turkish Precast Concrete Association through this project is greatly appreciated. The study was conducted at the Structural and Earthquake Engineering Laboratory (STEELab) of Istanbul Technical University. Support of the laboratory staff and the contributions of Gunkut Barka and Hakan Atakody are gratefully acknowledged.

Million cubic meters from abandoned mines worldwide could be used as subsurface reservoirs for large scale energy storage systems, such as adiabatic compressed air energy storage (A-CAES). In this paper, analytical and three-dimensional CFD numerical models have been conducted to analyze the thermodynamic performance of the A-CAES reservoirs in abandoned mines during air charging and discharging processes. Unlike other research works, in which the heat transfer coefficient is considered constant during the operation time, in the present investigation a correlation based on both unsteady Reynolds and Rayleigh numbers is employed for the heat transfer coefficient in this type of application. A tunnel with a 35 cm thick concrete lining, 200 m3 of useful volume and typical operating pressures from 5 to 8 MPa were considered. Fiber-reinforced plastic (FRP) and steel were employed as sealing layers in the simulations around the fluid. Finally, the model also considers a 2.5 m thick sandstone rock mass around the concrete lining. The results obtained show significant heat flux between the pressurized air and the sealing layer and between the sealing layer and concrete lining. However, no temperature fluctuation was observed in the rock mass. The air temperature fluctuations are reduced when steel sealing layer is employed. The thermal energy balance through the sealing layer for 30 cycles, considering air mass flow rates of 0.22 kg s−1 (charge) and −0.45 kg s−1 (discharge), reached 1056 and 907 kWh for FRP and steel, respectively. In general, good agreements between analytical and numerical simulations were obtained.

Large office buildings are responsible for a substantial portion of energy consumption in urban districts. However, thorough assessments regarding the Nordic countries are still lacking. In this paper we analyse the largest dataset to date for a Nordic office building, by considering a case study located in Stockholm, Sweden, that is occupied by nearly a thousand employees. Distinguishing the lighting and occupants’ appliances energy use from heating and cooling, we can estimate the impact of occupancy without any schedule data. A standard frequentist analysis is compared with Bayesian inference, and the according regression formulas are listed in tables that are easy to implement into building performance simulations (BPS). Monthly as well as seasonal correlations are addressed, showing the critical importance of occupancy. A simple method, grounded on the power drain measurements aimed at generating boundary conditions for the BPS, is also introduced; it shows how, for this type of data and number of occupants, no more complexities are needed in order to obtain reliable predictions. For an average year, we overestimate the measured cumulative consumption by only 4.7%. The model can be easily generalised to a variety of datasets.

Textile Reinforced Concrete (TRC) is a prefabricated novel lightweight high-performance composite material that can be used as a load-bearing or non-load-bearing component of prefabricated buildings. Making TRC with Ultra-High-Strength Concrete (UHSC) (&ge, 100 MPa) can be considered as a potential improvement method to further enhance its properties. This paper investigated the performance of Ultra-High-Strength Textile Reinforced Concrete (UHSTRC) under flexural loading. A detailed experimental program was conducted to investigate the behavior of UHSC on TRC. In the experimental program, a sudden drop in load was observed when the first crack appeared in the UHSTRC. A detailed analytical program was developed to describe and understand such behavior of UHSTRC found in experiments. The analytical program was found to be in good agreement with the experimental results and it was used to carry out an extensive parametric study covering the effects of the number of textile layers, textile material, textile mesh density, and UHSTRC thickness on the performance of UHSTRC. Using a high number of textile layers in thin UHSTRC was found to be more effective than using high-thickness UHSTRC. The high modulus textile layers effectively increase the performance of UHSTRC.

For the design of composite structures with circular cut-outs analytical, experimental and numerical methods are available. This paper investigates numerous exact analytical methods introduced in literature as an example of the Airbus Industries Test Method for determination of open hole tensile strength, conforming to AITM 1-0007. Experimental testing accompanied by digital image correlation of unidirectional 0° and 90° laminates as well as quasi-isotropic CFRP laminates with width-to-diameter (w/d) ratios of 3 and 5 is conducted. In addition, 3D finite element models of the test specimens are created for detailed analysis on lamina level. A preliminary study on numerous analytical methods introduced in literature shows that application of any of those methods results in one of two possible stress distributions. A qualitative comparison of 2D strain fields on laminate level reveals the high prediction quality of the analytical solutions. Furthermore, a detailed stress analysis on lamina level by comparison to a validated FE model is conducted. The results show that exact analytical solutions exhibit a satisfactory stress prediction quality for w/d ratios as low as 3 and thus can be recommended for preliminary design purposes.

The main aim of this work is to propose and validate an analytical strategy to correlate the electric and mechanical response of bi-directional laminates in the presence of both off-axis cracks and delamination. To this end, the attention is initially focused on the electrical problem, developing and validating against numerical results a new, fully analytical, model to properly assess the electrical resistance increase in the laminate as a function of the damage state. Subsequently, an analytical model to predict the laminate stiffness as a function of the damage scenario is derived and later combined with the electric one, thus establishing a direct correlation between the resistance change and the stiffness degradation.

Ultra-High Performance Fiber-Reinforced Concretes (UHP-FRC) subjected to uniaxial tensile loads are investigated in the present paper. The study comprises a new procedure to assess the effectiveness of the hybridization, herein obtained by reinforcing UHP-FRC with micro and macro steel fibers. A comprehensive experimental campaign is also performed on monofiber and hybrid UHP-FRC. In all the concretes, the distance between the cracks and the minimum fiber volume fraction, which produces strain hardening response and multiple cracking, are theoretically and experimentally evaluated. If the bond parameter of the macro-fibers is properly calculated, the results of the analytical model, in terms of crack-spacing vs. fiber volume fraction, are in good agreement with the test data. Moreover, to increase the number of the cracks, and to reduce crack spacing, the hybridization is suitable only when the amount of macro-fibers is within a well-defined range.

This paper presents an analysis of the performance of different existing formulations to quantify the FRP contribution to the shear strength of RC elements strengthened in shear by externally bonded FRP sheets. A large database of 555 tests has been assembled distinguishing between the shape of the section, the existence of internal transverse reinforcement and the FRP configurations. In general, predictions are more conservative for beams without transverse reinforcement. In addition, in some cases predictions are unsafe for beams with transverse reinforcement, showing a possible interaction with the internal transverse reinforcement which is not considered in the experimental FRP contribution to the shear strength. For wrapped FRP configurations, models generally assumed failure at the bottom corner of the section and results are very conservative in some cases where failure was experimentally observed along the web. For U-shaped and side-bonded configuration, results depend mainly on the assumed bond model and are more accurate than in the previous case, showing for some models unsafe predictions for the continuous FRP system applied in beams with transverse reinforcement. This paper has been developed under the framework of the Research Projects “BIA2015-64672-575 C4-1-R” and “RTI2018-097314-B-C21” funded by the Spanish Ministry of Economy and Competitiveness (MINECO) and co-funded by the European Regional Development Funds (ERDF). The authors would also like to thank the Cost Action TU1207 which funded a short term scientific mission of the first author in Lodz University of Technology.

International audience; A simplified model based on the shakedown theory (Zarka method) has been developed in this study for unsaturated expansive soils subjected to wetting and drying cycles. This method determines directly the stabilised limit state. The parameters of the proposed shakedown-based model are calibrated by the suction-controlled odometer tests obtained for an expansive soil compacted at loose and dense initial states, and then validated for the same soil compacted at intermediate initial state by comparing the model predictions with the experimental results. Finally, the finite element equations for the proposed shakedown model are developed and these equations are implemented in the finite element code CAST3M to carry out the full-scale calculations. The performed simulation is on a 2D geometry, made up of the expansive soil at the intermediate state subjected to successive extremely dry and wet seasons for the different applied vertical loads. The results show the swelling plastic deformations for the lower vertical stresses and the shrinkage deformations for the higher vertical stresses. Only inelastic heaving displacement can be observed in the geometry after considering the residual field.

Since precise linear actuators of a compliant parallel manipulator suffer from their inability to tolerate the transverse motion/load in the multi-axis motion, actuation isolation should be considered in the compliant manipulator design to eliminate the transverse motion at the point of actuation. This paper presents an effective design method for constructing compliant parallel manipulators with actuation isolation, by adding the same number of actuation legs as the number of the DOF (degree of freedom) of the original mechanism. The method is demonstrated by two design case studies, one of which is quantitatively studied by analytical modelling. The modelling results confirm possible inherent issues of the proposed structure design method such as increased primary stiffness, introduced extra parasitic motions and cross-axis coupling motions.

This paper presents design optimization of axialflux induction motors (AFIMs) for electric vehicles. The approach is based on an analytical resolution of the Maxwell's equations inside a set of subdomains. The analytical method is verified against 2D finite-element analysis. It allows detailed modelling and accurate steady-state performance prediction of AFIMs in a very short time (under 1sec), making possible evaluation of numerous design for the optimization. The optimization effortlessly simulates and predict the performance of various AFIM designs based on driving cycles and vehicle limitations. An optimization based on driving cycle of electric vehicles is studied through considering a driving cycle and designing minimum-mass AFIMs capable of fulfilling it. It is observed that driving-cycle based motor designs benefit from mass reduction and ensures the feasibility of all operating conditions Refereed/Peer-reviewed

[Abstract] This paper presents a study of a novel shear connector in a timber-concrete composite solution, focussing on the determination of an analytical expression that makes it possible to predict its behaviour and a numerical analysis that describes it accurately. The shear connector is composed of a perforated steel plate inserted into a slot within the timber rib and glued, in combination with reinforcing corrugated steel bars affixed to the top of the plate. Previous tests made it possible to establish failure mode in different T composite section plate-rebar configurations. These results determine the effectiveness of the system in terms of force-slip behaviour, with systematic failure in the timber section. A simple predictive model is proposed to determine the ultimate capacity of the joint, taking into account the mechanical properties of timber in relation with the fracture plane and the timber-adhesive interface. This model makes it possible to apply a design process that is able to predict the stiffness of the connection. FEM models were analysed for each configuration in a variable load process equal to that used in the test, according to the standard procedure. A variable friction coefficient in contact definition made it possible to achieve an accurate descriptive model in association with the test procedure. MINECO; BIA2016-77184-P

Steel-concrete composite beams are widely used in practice because of their economic cross-section design. As sustainability becomes more and more important in the construction industry, the design of composite beams must be adapted to meet the requirements of the circular economy. This calls for demountability and reusability of the structural components, as well as optimized use of materials, for example by using non-prismatic beams. Linear-elastic design and the (optimized) use of demountable shear connectors are key in the design of reusable composite structures. In this paper, analytical prediction models for the elastic behaviour and the first eigenfrequency of non-prismatic composite beams with non-uniform shear connector arrangements are derived. The approach is based on 6th and 2nd order differential equations used to define matrix equations for a finite number of linearized composite beam segments. The analytical models are validated using experimental and numerical results obtained with a simply supported tapered composite beam. The analytical models are suitable for comprehensive structural analysis of non-prismatic composite beams with non-uniform shear connection.

The seismic behaviour of arches is investigated to provide a contribution to the stability of arches with a pointed shape supported by buttresses. The limit analysis (LA) for masonry structures has been herein implemented in analytical modelling based on the use of nonlinear programming techniques for investigating the potential failure mechanisms associated with pointed arches under horizontal forces. A critical assessment of the positioning of hinges over the arch embrace is conducted here. This will allow for a better prediction of the capacity of these structures under seismic actions. The lateral action, which activates the investigated failure mechanisms, is also computed by implementing this new analytical model. This is assessed both in terms of horizontal loading multiplier and associated ground accelerations. Furthermore, by comparing numerical results derived from scientific literature, it was possible to validate the reliability of the here presented analytical model.

Auxetic materials are gaining special interest in technical sectors due to their attractive mechanical behaviour. This paper reports a systematic investigation on missing rib design based auxetic structures produced from braided composites for civil engineering applications. The influence of various structural and material parameters on auxetic and mechanical properties was thoroughly investigated. The basic structures were also modified with straight longitudinal rods to enhance their strengthening potential in structural elements. Additionally, a new analytical model was proposed to predict Poisson’s ratio through a semi empirical approach. Auxetic and tensile behaviours were also predicted using finite element analysis. The auxetic and tensile behaviours were observed to be more strongly dependent on their structural parameters than the material parameters. The developed analytical models could well predict the auxetic behaviour of these structures except at very low or high strains. Good agreement was also observed between the experimental results and numerical analysis., University of Minho – UMINHO/BI/146/2012, under the scheme of ‘‘Strategic plan of school of engineering – Agenda 2020: Multidisciplinary projects.”

This paper presents a static analysis of laminated cross-ply beams by using an unavailable unified higher order shear deformation theory (HSDT) for composite beams which includes the thickness stretching effect. The generalized governing equations are derived by employing the principle of virtual work. Navier-type closed-form solution is obtained for several beams subjected to several kinds of loads (sinusoidal, uniform, linear and point load). Infinite HSDTs for beams can be further developed just by modifying the shear strain shape functions. Several hybrid type shear strain shape functions were introduced to evaluate the generality of the proposed theory. The stretching effects for the accurate prediction of the transverse stresses are analyzed. Numerical results of some HSDTs for beams are compared with the elasticity solutions and other HSDTs. Convergence studies were carried out to determine the necessary half-wave number for the different models.

This paper presents a tension stiffening model for Fiber Reinforced Concrete (FRC) tensile member reinforced by hybrid glass fiber reinforced polymer (GFRP) and steel bars. The model is developed through an explicit analytical bond formulation by considering a four-linear bond shear stress-slip relationship to simulate the bond behavior between reinforcing bars and surrounding FRC. The model is also capable of simulating both the fiber reinforcement contribution and the yielding stage of steel bar at cracked section. Additionally, a FE Model is carried out using a multi-directional smeared crack approach for modeling cracking process in FRC, and adopting interface finite elements to simulate the bond behavior between reinforcements and FRC, whose constitutive model was defined from the aforementioned bond law. Both the analytical and numerical approaches showed a good agreement with some recent experimental results on tension-stiffening in the literature. Finally, an extensive parametric study is performed by using the analytical model, and the influence of the involved parameters on the tension-stiffening and cracking behavior of hybrid GFRP/steel FRC tensile member is investigated., QREN project n. 30367 – UrbanCrete, Portuguese Foundation for Science and Technology (FCT) - SFRH/BD/77409/2011

The Embedded Through-Section (ETS) is a recent strengthening technique that has been developed to retrofit existing reinforced concrete (RC) elements with shear reinforcement deficiencies. This technique is based on the execution of holes drilled through the element cross section, in which steel or fiber reinforced polymer (FRP) bars are inserted and bonded to the surrounding concrete with an epoxy adhesive. An experimental program was carried out with RC T-cross section beams strengthened in shear using steel ETS bars. The influence of the inclination and shear strengthening ratio of ETS on the shear strengthening efficiency was evaluated, as well as the interaction of ETS bars with existing steel stirrups. Two different analytical models are presented in this paper in order to calculate the contribution of ETS to shear resistance. The first model follows an empirical approach (experimental-based approach), while the second model takes into account the physical and mechanical principles of the technique (mechanical-based approach). The predictive performance of both models is assessed by using the experimental results., The authors wish to acknowledge the support provided by the CutInov project QREN n. 38780 supported by ADI, and by the Engineering Department of the University of Ferrara.

International audience; The evaluation of the predictive capabilities of models proposed in the literature for laminated composites calls for experimental testing providing detailed results of both the global and local response in terms of degradation mechanisms, such as delamination, transverse cracking and fibre breaking. Scaled tests, in which one or more characteristic dimensions are modified, allow variation of the different mechanisms. In this paper, a unique series of scaled indentation tests are performed on quasi-isotropic composite plates, and a detailed assessment of the damage evolution is carried out through non-destructive techniques, including ultrasonic C-scan and X-ray Computed Tomography (CT). Four different configurations are tested, presenting changes in both in-plane dimensions and fully three dimensional scaled cases. The latter are performed with sublaminate and ply scaling to show the effect of ply thickness on response. A detailed set of results for both global behaviour and the damage evolution is provided to demonstrate the mechanisms controlling behaviour and to create a reference set of data for model validation. The scaling effects observed are also discussed making use of simplified analytical models.

Three different models with increased complexity to study the effects of hybridization on the tensile failure of hybrid composites are proposed. The first model is a model for dry bundles of fibres based on the statistics of fibre strength. The second is a model for composite materials based on the multiple fragmentation phenomenon. Lastly, a micromechanical numerical model is developed that considers a random distribution of fibres and takes into account the stochastic nature of fibre strength. This study aims to understand the controlling factors that lead to pseudo-ductility, as well as establish the sequence of failure mechanisms in hybrid composites under tensile loadings.

In this paper, a novel analytical model for predicting the post-crushing compressive response of progressively crushable sandwich foam cores is presented. The calibration of the model is performed using experimental measurements obtained exclusively from standard monotonic compressive tests. Therefore, the need for performing time-consuming compressive tests including multiple unloading–reloading cycles is avoided. Model predictions have been validated against experimental measurements available for three different foam materials. The model is shown to accurately predict the thickness of the crushed material layer during progressive crushing and the residual after-crushing strain (with a maximum error of 12.1 % ). The proposed model is capable of predicting the residual after-crushing strain with a significantly smaller error (error-reduction over 56 % ) than existing models, whose calibrations require the same experimental measurements as the present model. The results presented in this work demonstrate the relevance of the proposed model for a damage-tolerant design of foam-cored composite sandwich structures.

In this paper a piecewise exponential model is proposed for analysis of three-dimensional elastic deformation of rectangular sandwich panels with graded core subjected to transverse loading. The model can be applied to any functionally graded plate or sandwich panel with graded core as long as the through thickness stiffness variation can be described by a smooth function. The new piecewise exponential model is fully validated through both comparison with results from the literature and a three-dimensional finite element method which employs user-implemented graded finite elements. As an example the new model is applied to three dimensional elasticity analysis of sandwich panels with power law variation in stiffness properties of the core and a comparative study is carried out to examine the effect of panel thickness and varying the power law index on panel’s response.

The paper analyses the application of high-frequency periodic timetables on single track railways. A mesoscopic approach is first of all presented, in order to provide a simple but rather complete model. On this basis, a mathematical and deterministic evaluation formula is presented, as well as a simulation tool able to evaluate the effects of traffic perturbations. All the main parameters which characterise railway operations (with a special focus on single track infrastructure) are taken into consideration and their influence is pointed out, as regards the possibility to realise high frequency periodic timetables. The analysis is subsequently extended for assessing how these timetables can behave in case of traffic perturbations, in order to provide also in these circumstances a sufficient service quality. The influence of the abovementioned parameters on buffer times and hence on timetable stability and robustness is therefore outlined, highlighting the benefits that an effective rescheduling algorithm could play. The presented calculation method is then applied to a real case, i.e. to a part of the railway network of Piedmont, Italy. This case study provides some considerations about the elements that can actually play a determinant role and what measures can be planned for achieving certain service targets. Finally, conclusions are drawn together with some considerations for future work about the possible implementation of effective rescheduling logics within advanced driver advisory systems as well as modern signalling and control systems.

© 2015 Elsevier B.V..A variational model describing the behaviour of a thin-walled I-section strut suffering from local-global buckling mode interaction is presented where global (Euler) buckling about the strong axis is the critical mode. A system of differential and integral equations is derived that describe the equilibrium states from variational principles and are solved numerically using the continuation and bifurcation software A. uto-07. p for the perfect case. Initially stress relieved out-of-straightness imperfections are subsequently introduced and the nonlinear response is modelled. The modelled interaction is between the critical global buckling mode about the strong axis and local buckling in the flange and web simultaneously, where the flange-web joint is assumed to be free to rotate as a rigid body. The initial eigenmode is shown to be destabilized at a secondary bifurcation where interactive buckling is triggered. A progressive change in the buckling mode is then observed, initially with local buckling localizing at the mid-span of the compression flange, which also triggers sympathetic local buckling in the web. The results from the analytical model have been validated using the commercial finite element (FE) software A. baqus with good comparisons presented for the initial post-buckling behaviour. The strut also exhibits sensitivity to initial out-of-straightness imperfections, with a notable decrease in the ultimate load as the imperfection size increases. The ultimate loads for a range of imperfection amplitudes are found using both analytical models and FE analysis, with very good correlation observed.

Symmetry is very necessary in flexure mechanisms, which can eliminate parasitic motions, avoid buckling, and minimize thermal and manufacturing sensitivity. This paper proposes two symmetric and compact flexure designs, in-plane 3-DOC (degree of constraint) mechanisms, which are composed of 4 and 6 identical wire beams, respectively. Compared to traditional leaf-beam-based designs, the two present designs have lower stiffness in the primary motion directions, and have smaller stiffness reduction in the parasitic directions. Analytical modelling is conducted to derive the symbolic compliance equations, enabling quick analysis and comparisons of compliances of the two mechanisms. A prototype has been tested statically to compare with analytical models.

Steel Reinforced Grout (SRG) composites are becoming a common technique for strengthening masonry arches and vaults. These composites are made of Ultra High Tensile Strength Steel unidirectional textiles applied to the substrate by means of inorganic mortar. The structural performance is generally controlled by the bond properties of the interface between the matrix and the textile, which in the case of arches or vaults is also affected by the curved geometry of the substrate. In this work, a closed-form analytical solution of the debonding process of a thin plate bonded to a rigid substrate with constant curvature is proposed. The work provides an upgrade of the model previously proposed by the author [1]. In the present work the substrate curvature is such that the normal stresses arising at the interface are tensile, as in the case of the reinforcement applied to the intrados of the vault [1] or compressive, as for the reinforcement applied to the extrados of the vault. The proposed model describes the interfacial stresses transfer mechanism in the framework of fracture mechanics, adopting two cohesive material laws to model the interfacial behaviour in normal (pure opening mode: Mode I) and in tangential (in plane shear mode: Mode II) direction. The coupling deriving from curvature is introduced directly in the cohesive laws that describe the bond properties. The outcomes of the proposed predictive model are validated by comparing them with the results derived from an experimental campaign of bond tests on straight and curved substrates made of brickwork strengthened with SRG. Finally, a simple design formula for the evaluation of the debonding load of a SRG-masonry joint in the case of curved substrate, is proposed.

Proceedings of the 23rd International Conference on Advances in Liquid Scintillation Spectrometry (LSC), Copenhagen, DENMARK, APR 30-MAY 05, 2017. Organizer: Tech Univ Denmark; International audience; Designed for triple to double coincidence ratio measurements based on liquid scintillation, the three-photomultipliers detection system can also be applied for Cherenkov counting using aqueous solutions. For activity determination, a specific modelling of Cherenkov light emission has to be constructed. For that purpose, the analytical modelling first developed at PTB was adapted to account for the physical features of the detection system used at LNHB. The first results are presented in the case of activity measurements of two high-energy β−-emitters (90Y and 89Sr). The analytical modelling was also tested for the standardization of 68Ge in a solution of 68Ge/68Ga in equilibrium in the framework of a BIPM international comparison in 2014.

This paper presents a novel composite production cost estimation model. The strength of the model is its modular construction, allowing for easy implementation of different production methods and case studies. The cost model is exemplified by evaluating the costs of a generic aeronautical wing, consisting of skin, stiffeners and rib feet. Several common aeronautical manufacturing methods are studied. For studied structure, hand layup is the most cost-effective method for annual volumes of less than 150 structures per year. For higher production volumes automatic tape layup (All) followed by hot drape forming (HDF) is the most cost-effective choice. QC 20150918

This article introduces new methods for static and free vibration analyses of functionally graded annular and circular micro-plates, which can take into account spatial variation of the length scale parameter. The underlying higher order continuum theory behind the proposed approaches is the modified couple stress theory. A unified way of expressing the displacement field is adopted so as to produce numerical results for three different plate theories, which are Kirchhoff plate theory (KPT), Mindlin plate theory (MPT), and third-order shear deformation theory (TSDT). Governing partial differential equations and corresponding boundary conditions are obtained following the variational approach and the Hamilton's principle. Derived systems of differential equations are solved numerically by utilizing the differential quadrature method (DQM). Comparisons to the results available in the literature demonstrate the high level of accuracy of the numerical results generated through the developed methods. Extensive analyses are presented in order to illustrate the influences of various geometric and material parameters upon static deformation profiles, stresses, and natural vibration frequencies. In particular, the length scale parameter ratio -which defines the length scale parameter variation profile-is shown to possess a profound impact on both static and dynamic behaviors of functionally graded annular and circular micro-plates. (C) 2015 Elsevier Ltd. All rights reserved.

© 2015 Elsevier B.V..An analytical model for axially loaded thin-walled stringer stiffened plates based on variational principles is exploited to study the sensitivity to initial geometric imperfections and the effects of altering geometric properties. Studies on different forms of global and local imperfections indicate that the post-buckling response governs the worst case imperfections. The investigation also focuses on the effect of changing the global and the local slendernesses on the post-buckling behaviour. The parametric space in which the stiffened plates are imperfection sensitive and susceptible to highly unstable cellular buckling is identified.

The purpose of this paper is to study the vibrational behavior of advanced composite plates by using a novel first shear deformation theory (FSDT). This theory contains only four unknowns, with is even less than the classical FSDT. The governing equations are derived by employing the Hamilton's principles and solved via Navier's solution. The present results were validiated by comparing it with the 3D, classical FSDT and other solutions available in the literature. Shear correction factor apper to be unfovarable in some cases (case dependent). Finally, authors recommend further study of this new manner to model the displacement field.

Milling forces play an importantrole in the milling process and are generally calculatedbythe mechanistic or numerical methods which are considered time-consuming and impractical forvarious cutting conditions and workpiece-toolpair. Therefore, this paper proposes an analytical method for modelling themilling forcesin helical end milling process based on a predictive machining theory, which regards the workpiece material properties, tool geometry, cutting conditions and types of milling as the input data. In this method,each cutting edge is discretized into a series of infinitesimal elements along the cutter axis and the cutting action of each elementis equivalent to the classical oblique cutting process. The three dimensional cutting force components applied on eachelement are predicted analytically using this predictive oblique cutting modelwith the effect of cutting edge radius. Finally, the proposed analytical model of milling forcesis verified by the publishedresultsandthe simulation values using the software AdvantEdgeFEM.

This paper considers a low-level unit-load warehouse employing single-deep storage lanes and a single-command manual storage and retrieval policy. Analytical travel distance models are developed for class-based and full turnover storage policies under across-aisle, within-aisle and a newly proposed hybrid product placement schemes. Our computational studies show that the analytical models developed in this paper are very accurate as compared to simulation results and a comparative study with a real-world warehouse case. Hybrid storage policies proposed in this paper outperform all other traditional storage policies. The paper also presents insights and simple design rules to warehouse practitioners.

Man-made composites, like reinforced and fiber-reinforced concrete elements, behave similarly to natural composite structures (e.g., brittle rocks lying on a ductile substratum). In both cases, the cracking phenomenon of brittle layers depends on the scale of observation and is ruled by the Golden Ratio. Thus, a unique size-effect relationship, herein called Golden Scaling Law (GSL), is introduced and used to predict the crack pattern of concrete and rock structures. In accordance with several experimental data, GSL permits to calculate the values of crack width and crack spacing when the geometry of crack patter is known at a lower scale. Moreover, GSL can be applied to large composite structures without knowing the material performances, but by testing prototypes of lower dimensions.

This work describes the manufacture and characterisation of a PEEK-based zero Poisson’s ratio honeycomb (SILICOMB) produced using Kirigami-inspired cutting and folding techniques. The flatwise compression and transverse shear properties of the structure are determined through ASTM mechanical testing, and the results compared against commercially available honeycombs, including several other zero Poisson’s ratio cellular structures. An analytical model to predict the shear strength is compared to the results. SILICOMB specimens are found to have lower stiffness compared to other honeycomb configurations, but comparable strength. Factors influencing the results and variations to the manufacturing process are discussed.

Mechanical properties and failure modes of carbon fiber composite egg and pyramidal honeycombs cores under in plane compression were studied in the present paper. An interlocking method was developed for both kinds of three-dimensional honeycombs. Euler or core shear macro-buckling, face wrinkling, face inter-cell buckling, core member crushing and face sheet crushing were considered and theoretical relationships for predicting the failure load associated with each mode were presented. Failure mechanism maps were constructed to predict the failure of these composite sandwich panels subjected to in-plane compression. The response of the sandwich panels under axial compression was measured up to failure. The measured peak loads obtained in the experiments showed a good agreement with the analytical predictions. The finite element method was used to investigate the Euler buckling of sandwich beams made with two different honeycomb cores and the comparisons between two kinds of honeycomb cores were conducted. Fil: Xiong, Jian. Harbin Institute of Technology. Center for Composite Materials and Structures; China Fil: Zhang, Meng. Harbin Institute of Technology. Center for Composite Materials and Structures; China Fil: Stocchi, Ariel Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina Fil: Hong, Hu. The Hong Kong Polytechnic University; China Fil: Ma, Li. Harbin Institute of Technology. Center for Composite Materials and Structures; China Fil: Wu, Linzhi. Harbin Institute of Technology. Center for Composite Materials and Structures; China Fil: Zhang, Zhong. Beijing Institute of Structure and Environment Engineering; China

Mobile clouds are a new paradigm enabling mobile users to access the heterogeneous services present in a pervasive mobile environment together with the rich service offers of the cloud infrastructures. In mobile computing environments mobile devices can also act as service providers, using approaches conceptually similar to service-oriented models. Many approaches implement service provisioning between mobile devices with the intervention of cloud-based handlers, with mobility playing a disruptive role to the functionality offered by of the system. In our approach, we exploit the opportunistic computing model, whereby mobile devices exploit direct contacts to provide services to each other, without necessarily go through conventional cloud services residing in the Internet. Conventional cloud services are therefore complemented by a mobile cloud formed directly by the mobile devices. This paper exploits an algorithm for service selection and composition in this type of mobile cloud environments able to estimate the execution time of a service composition. The model enables the system to produce an estimate of the execution time of the alternative compositions that can be exploited to solve a user's request and then choose the best one among them. We compare the performance of our algorithm with alternative strategies, showing its superior performance from a number of standpoints. In particular, we show how our algorithm can manage a higher load of requests without causing instability in the system conversely to the other strategies. When the load of requests is manageable for all strategies, our algorithm can achieve up to 75% less time spent in average to solve requests.

The paper is aimed at investigating the effects of stitching or tufting on displacement and stress fields of sandwiches, whose homogenised mechanical properties are computed through virtual material tests with 3D finite element analysis. After that, structural analysis is carried out using the adaptive model by the authors, which has variable representation of displacements across the thickness and fixed degrees of freedom. This choice is done considering its accuracy and computational efficiency. Numerical applications show that using these technical skills it is possible to considerably reduce stresses and displacements in sandwiches.

International audience; The aim of this study is to propose a calculation method for predicting the geometrical characteristics of the end-closures of composite pressure vessels used in gaseous hydrogen storage applications. We present here a method for predicting the characteristics of domes made by multi-sequence lay-up and subject to changes in winding angle and thickness. In the proposed model, winding angle and thickness calculations are based on two existing methods that have been investigated in a single dome lay-up context. Using them for multi-sequence dome lay-up calculation is the originality of this work. The first predictive results are compared with experimental pressure vessel data and discussed. A good correlation between the theoretical approach and the experiments was found, indicating that the predictions could be helpful in a procedure of overall optimisation.

The aim of the paper is to provide practical guidelines for the design of welded joints of steel truss for encased composite steel–concrete beams. The results of experimental tests are presented and interpreted. The steel truss is made of a steel plate acting as the bottom chord, made of S355 structural steel, coupled with steel rebars which form the upper chord, and steel inclined web rebars (V-reverse) welded to the two chord elements, both of them made of steel B450C. Butt welded joints of web bar to bottom steel plate and fillet welding joints of inclined web bars to top chord bars were tested, as they are different from the ones which are normally used due to the coupling of different steel types and complex geometry. For the prediction of strength of fillet welding joints, two analytical expressions are derived: the first is based on a local failure criterion and the second on a limit domain of the welding section. Comparison with experimental data proves the equivalence and reliability of the proposed indications. Guidelines for choosing the effective dimensions of the fillet weld able to ensure a required strength are provided. For validation of the suggested guidelines, a high precision digital scanner is used to determine the geometrical characteristics of the fillet weld.

The present paper analyzes a stress–strain state of a composite timber–concrete T cross section under a short-term pure bending. The behaviour of a bending moment in respect of a curvature of the cross section was investigated as well. It is assumed that the plane section hypothesis is valid and layers do not slip with respect to each other. The parabolic stress–strain diagram with a descending branch, according to MC90, was applied to the compression concrete while a linear elastic relationship was applied to the timber. The stress–strain state of the cross section was investigated from the beginning of the loading up to the stage exceeding ultimate limit state. The analysis was conducted by applying control of the curvature of the considered cross section. The influence of the tension fibre-reinforced polymer (FRP) and compression steel reinforcements on the stress–strain state of the cross section was also considered. The obtained analytical equations of the layered members were solved numerically. It was found out that the bearing capacity of the cross section is restricted mainly due to low strength of the timber and the tension reinforcement is more effective than the compression reinforcement.

Wakeboarding is a water sport born in the mid 1980s that derives from surfing and water skiing. The objective of this work is to understand the failure mechanism and evaluate the maximum hydroelastic loads during the slamming phenomena of the board used in this sport, in order to provide reliable design rules to follow during the design process. Wakeboards are usually built as a composite sandwich structure, with plastic foam core and CFRP (carbon fibre reinforced plastics) or GFRP (glass fibre reinforced plastics) faces. Several specimens were extracted from a real board and tested in three point bending to investigate the major failure mechanisms. These data are later used in a parametric full-scale SPH numerical model investigation of the water-entry event. The numerical results show that, due to the fluid–structure interaction, there is a maximum deformation that the board cannot overreach even for very high impact energies. This limits the maximum impact stresses reached during the water entry of wakeboards. From these numerical results, mathematical relations between design variables are drawn by using analytical formulas based on classical sandwich theory. As result of this research, practical guidelines (formulas, tables and graphs) on the effects of total mass, initial impact velocity, board curvature and core and face strength and thickness are outlined to give reliable design rules.

Different mathematical models are proposed and their analytical solutions derived for the analysis of linear elastic Reissner’s multilayer beams. The models take into account different combinations of contact plane conditions, different material properties of individual layers, different transverse shear deformations of each layer, and different boundary conditions of the layers. The analytical studies are carried out to evaluate the influence of different contact conditions on the static and kinematic quantities. A considerable difference of the results between the models is obtained.

This paper presents exploratory research related to novel full-scale multi-layered timber beams with composite action achieved with welded-through wood dowels. Different multi-layer beam designs, where the timber layers were interconnected with welded wood dowels providing interlayer shear resistance, were tested in bending with different dowel densities. The main originality of this study is the achievement of dowel welds through greater depths of sections than has previously proved possible. The practical difficulties encountered in constructing deeper multi-layer beams, and the successful solutions arrived at, are discussed. The significance of the research reported is the demonstrated ability to produce multilayered timber sections which are structurally efficient and do not require non timber based joining agents such as nails or adhesive. Deposited by bulk import

This paper presents a bending and free vibration analysis of functionally graded plates (FGPs) resting on elastic foundation by using an original first shear deformation theory (FSDT). This theory contains only four unknowns, which is even less than the classical FSDT. The elastic foundation follows the Pasternak (two-parameter) mathematical model. The governing equations for the bending and free vibration analysis are obtained through the principle of virtual work and Hamilton's principle, respectively. The original displacement field allows obtaining interesting governing equations. These equations are solved via Navier-type, closed form solutions. The accuracy of the current solution is verified by comparing it with 3D and other closed form solutions available in the literature.

An analytical investigation into the non-linear elastic response of helical lattice structures coupled with an elastic medium is presented. Novel composite templates are then obtained to produce bespoke material characteristics by exploiting tuned hierarchy. System behaviour is approximated as a combination of three non-linear “springs”, representing the helical lattice, and the axial and circumferential components of the elastic medium via an energy based approach. Non-dimensional parameters governing each component’s non-linear load–displacement behaviour are identified, demonstrating tailoring potential. Further tunable parameters that govern the combined system response, involving form factor, geometric and stiffness ratios are identified. In particular, pseudo-ductile responses are observed. The feasible region of pseudo-ductility, as determined by these non-dimensional parameters, is obtained, allowing discussion of viable materials and geometries. Finally, load–displacement behaviour is utilised to obtain indicative effective stress–strain curves, thus showing promise as a model for future material development.