A computational assessment of the aerodynamic performance of a tilted Darrieus wind turbine

The aerodynamic performance of a Darrieus wind turbine operating with the rotation axis tilted with respect to the free-stream wind speed is investigated in this paper. An Unsteady Reynolds Averaged Navier Stokes (URANS) Computational Fluid Dynamics (CFD) model is proposed in order to provide wind turbine manufacturers with a reliable simulation tool to forecast the power conversion characteristics of vertical axis wind turbine prototypes that operate in tilted conditions. The outputs of the model are compared against experimental performance of a non-tilted rotor corrected to the standard sea level conditions. Two different tilted configurations are studied (i.e., a tilt angle of 10 and 20), and the aerodynamic performance are presented in terms of the mechanical power production and the power coecient. A sensible decrease in the power production is observed for increasing tilt angles. Comprehensive physical interpretations of the results are provided, considering also the predictions of a methodology based on semi-empirical methods

Review on the use of FRP composites for fa\ue7ades and building skins

Fiber Reinforced Polymer (FRP) composites represent a class of materials typically able to offer excellent mechanical, thermal and insulation properties, taking advantage of a combination of their constitutive fibers and polymers. Due to their intrinsic lightweight properties, FRP composites are in use for aerospace, automotive, marine industries and ballistic armor since several decades. Only in a subsequent phase, i.e. since the late 1990s, FRP composites found application in civil engineering constructions, including both building systems and infrastructures, for retrofitting purposes in existing structural systems, as well as for pure architectural or structural purposes in novel assemblies. This review paper aims to highlight the most recent applications of FRPs in fa\ue7ades and building skins, with careful attention for case studies and novel design concepts

Comparative assessment of analytical models for the ULS resistance verification of structural glass elements under variable loads

The design of glass structures, due to the intrinsic material properties, is mainly governed by the typical tensile brittle behavior of the material. In this regard, a currently open question related to the use of glass in buildings as a load-bearing constructional material, is represented by the correct estimation of static fatigue phenomena due to a generic combination of design actions. In this study, taking advantage of past literature contributions and existing design standards for glass, a novel analytical formulation is proposed for the resistance verification of a given structural glass elements under a Ultimate Limit State (ULS) combination of variable loads. The novel proposal is assessed towards three existing analytical formulations, based on two worked examples as well as an extended analytical analysis. In conclusion, the potential and criticisms of the examined approaches are discussed

Multi-Objective Optimization of FRP Jackets for Improving the Seismic Response of Reinforced Concrete Frames

In this study, a multi-objective Genetic Algorithm (GA) optimization procedure is proposed for the seismic retrofitting of Reinforced Concrete (RC) building frames via Fiber-Reinforced Polymer (FRP) jackets. The optimization problem is solved via numerically efficient but accurate Finite-Element (FE) models able to take into account the strengthening and ductility increase contribution for a given FRP jacketing configuration. Based on a reference RC frame case study, an optimization approach aimed to maximize the frame ductility and minimize the FRP volume/cost is proposed, by taking into account different FRP jackets thicknesses for the internal and external columns and well as for each separate frame floor. In doing so, careful consideration is paid also to the expected collapse mechanism for the frame and the approach to embed a further objective able to control the collapse mechanism into the procedure is described. The results show the potential of the approach, which not only provides the entire Pareto Front of the multi-objective optimization problem, but also allows for general considerations about the influence of the design variables on the response of a given RC building

Experimental and numerical study on the shear behavior of stone masonry walls strengthened with GFRP reinforced mortar coating and steel-cord reinforced repointing

The research work herein presented is aimed at investigating the structural behavior of stone masonry walls reinforced through different strengthening techniques. In particular, the difference between them is given by (i) application on both faces of a mortar coating reinforced with a GFRP (Glass Fiber Reinforced Polymers) mesh; (ii) application of the GFRP jacketing on one side only and (iii) application of a hybrid technique, obtained by the combination of a GFRP jacketing, on one side, and a reinforced repointing with steel-strands, on the other. Shear-compression (SC) and diagonal compression (DC) experiments were carried out on full-scale masonry walls both reinforced (RM) and unreinforced (URM), as reference. The structural effectiveness of the various reinforcing techniques is highlighted. Further assessment of test predictions was then performed by means of well-calibrated finite-element (FE) numerical models able to properly take into account the effective contribution of each specimen component. Interesting correlations were generally found between test predictions and corresponding numerical models. The experiments, as shown, generally evidenced a good effectiveness of the strengthening techniques proposed, with particular concern to that with the reinforced coating on both sides, and highlighted also the importance of the transversal connectors to prevent in plane cracks in the masonry and the detachment of the reinforced coating

Preliminary Experimental and Finite-Element Numerical Assessment of the Structural Performance of SMA-Reinforced GFRP Systems

In this study, the feasibility and potentiality of a novel design concept is explored by means of small scale experimental tests and Finite-Element numerical simulation. Taking advantage of the intrinsic potentiality of Shape-Memory Alloys wires able to work as adaptive actuators when subjected to joule heating, a \u2018smart-GFRP\u2019 concept consisting in Glass-Fiber-Reinforced-Polymer (GFRP) structural members with a SMA reinforcement is preliminary assessed. As shown, as far as the working temperature increases, important structural benefits can be achieved in terms of overall performance of the proposed composite systems. The potentiality of the same design concept is then further assessed by means of a practical calculation example

Derivation of buckling design curves via FE modelling for in-plane compressed timber log-walls in accordance with the Eurocode 5

In \u2018Blockhaus\u2019 systems the structural capacity derives from surface interactions and friction mechanisms between multiple timber logs stacked horizontally one upon each other. Unlike masonry or concrete walls, timber log-walls are characterized by the absence of a full structural interaction between the basic components, hence resulting in \u2018assembled\u2019 rather than \u2018fully monolithic\u2019 structural systems characterized by high flexibility of timber and usually high slenderness ratios. The current Eurocode 5 for timber structures, however, does not provide formulations for the prediction of the critical load of log-haus walls under in-plane compressive loads. In this work, based on past experimental tests and detailed Finite-Element (FE) models, extended numerical investigations are performed on timber log-walls. A wide number of configurations (more than 900) characterized by different geometrical properties, timber log cross-sections, number and position of door and window openings, presence of in-plane rigid (RF) or fully flexible (FF) inter-storey floors, as well as initial curvatures and/or load eccentricities, are analyzed under monotonic in-plane compressive load. Careful consideration is also given to the influence of additional out-of-plane pressures (e.g., wind pressures) combined with the in-plane compressive load. In accordance with the buckling design approach proposed by the Eurocode 5 for timber columns, non-dimensional buckling curves are then proposed for timber log-walls under in-plane compression. These curves are based on an accurate calibration of the k c buckling coefficient and the related imperfection factors on the results of the numerical parametric study. The developed simple and conservative approach for the design of log-walls can be proposed for implementation in the new generation of the Eurocode 5

Passive control systems for the blast enhancement of glazing curtain walls under explosive loads

Glass curtain walls are used in modern buildings as envelopes for wide surfaces due to a multitude of aspects. In glass curtain walls, tensile brittle panels are connected - through mechanical or adhesive joints - with steel frameworks or aluminum bracing systems, and due to the interaction of several structural components, the behaviour of the so assembled system is complex to predict, especially under exceptional loading conditions such as explosive events. In the paper, glazing curtain walls are investigated by means of Finite-Element (FE) numerical simulations, under the effect of air blast pressures of variable intensity. Their typical dynamic behaviour and criticalities under high-strain impact loads are first analyzed. By means of extended nonlinear dynamic FE parametric studies, innovative devices are applied to traditional curtain walls, at their support points, in order to improve their expected dynamic response. Two possible solutions, namely consisting of viscoelastic (VE) or elasto-plastic (PL) dampers, are proposed as passive control systems for the mitigation of maximum effects in the fa\ue7ade components deriving from the incoming blast pressures. As shown, although characterized by specific intrinsic mechanical behaviours, either VE or PL dampers can offer beneficial structural effects. In the first case, major advantages for the fa\ue7ade components derive from the additional flexibility and damping capacities of VE devices. In the latter case, PL dampers introduce additional plastic energy dissipation in the traditional curtain wall assembly, hence allowing preventing severe damage in the glazing components. It is thus expected that the current outcomes could represent a valid background for further experimental validation as well as detailed assessment and optimization of the proposed design concept

Finite-element analysis of post-tensioned SG-laminated glass beams with mechanically anchored tendons

Based on past experimental research results, this paper aims to investigate the structural performance of laminated glass beams with post-tensioned, mechanically anchored tendons, via extended finite-element (FE) simulations. The post-tensioned glass beam concept offers the advantage of providing a certain amount of initial compressive stresses in glass, hence resulting in a marked increase of the initial fracture load and in a rather appreciable redundancy, compared to typically brittle, unreinforced glass beams. Due to the presence of the post-tensioned tendons, a significant level of residual strength can also be guaranteed, thus resulting in a structurally efficient and safe design concept. In order to fully optimize the expected resistance and redundancy potentialities, however, careful consideration should be paid for a multitude of geometrical and mechanical aspects. In this research contribution, both full 3D and shell models are implemented for post-tensioned laminated glass beams. Based on validation of these FE models towards the past full-scale experimental results, the effects of several mechanical parameters are emphasized (e.g. steel tendon percentage, level of the applied pre-stressing force and the presence of possible geometrical imperfections) under room temperature and quasi-static loads. It is expected, based on the current study, that the examined design concept could be further developed and optimized

Adaptive Glass Panels using Shape-Memory Alloys

Due to the growing application of laminated glass panels in building facades and roofs, tending towards the minimization of frameworks, substructures and supports, technological solutions based on the use of glass panels with increasingly wide dimensions and modern design principles are becoming more frequent. The growing use of structural glass applications is leading to \u201clighter\u201d and \u201csmarter\u201d optimized design solutions. The design of such applications greatly depends on the material mechanical properties of their structural elements and on their sensitivity to ambient and loading conditions. This is the specific case of laminated glass, where a temperature and time loading sensitive interlayer is generally used to bond together two (or more) glass panes with brittle behavior and rather limited tensile resistance. In this research paper, a novel adaptive glass panel concept is developed by using shape-memory alloy (SMA) cables, and assessed by means of Finite-element numerical studies and experimental validation. Based on the case study of an existing laminated glass roof panel, several geometrical configurations of practical interest are investigated. A key role in the proposed approach is the application of external pre-stressing based on the Joule heating of the SMA bracing system. The structural efficiency of the cable system is emphasized by taking into account the effects of ordinary wind pressures and temperature variations. Due to the innovative adaptive control system, as shown, the structural performance of traditional laminated glass panels can be enhanced, e.g. optimized in terms of maximum displacements and stresses in the glass, as well as in the overall dimensions and thicknesses of the glass panes