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

Issues on the Vibration Analysis of In-Service Laminated Glass Structures: Analytical, Experimental and Numerical Investigations on Delaminated Beams

Load-bearing laminated glass (LG) elements take the form of simple members in buildings (i.e., columns, beams, and plates) or realize stand-alone assemblies, where glass and other traditional constructional materials can interact. Among several relevant aspects, the dynamic response of LG structures requires dedicated methods of analysis, towards the fulfilment of safe design purposes. A combination of multiple aspects must be taken into account for dynamic calculations of even simple LG elements when compared to static conditions, first of all the sensitivity of common interlayers to the imposed vibration frequency. The challenge is even more complex for the vibration serviceability assessment of in-service LG structures, where the degradation of materials and possible delamination effects could manifest, hence resulting in structural performances that can markedly differ from early-design conditions. Major uncertainties can be associated to the actual mechanical characterization of materials in use (especially the viscoelastic interlayers), as well as the contribution of restraints (as compared to ideal boundaries) and the possible degradation of the bonding layers (i.e., delaminations). All of these aspects are examined in the paper, with the support of extended analytical calculations, on-site experimental measurements, and parametric Finite Element (FE) numerical analyses. When compared to literature efforts accounting for ideal boundaries only, an analytical formulation is proposed to include the effects of flexible restraints in the dynamic performance of general (double) LG beams. Special care is also spent for the presence of possible delaminations, including size and position effects. In the latter case, existing formulations for composite laminates are preliminarily adapted to LG beams. Their reliability and accuracy is assessed with the support of test predictions and parametric FE simulations

Wearable and Smartphone-Based Sensors in Support of Human-Comfort-Driven Structural Analysis of Building Components

The continuous progress and advancement of innovation in technology and development of digital tools makes modern structural engineers and technicians of the building and construction sector increasingly able to solve a multitude of design issues. In most of cases, they can take advantage of, and support from, low-cost and even portable sensors characterized by generally medium-high accuracy and commercial availability. In this paper, the attention is focused on the analysis of recent investigations which have been carried out within the scope of human-comfort-driven structural analysis and design of building components. More precisely, the use of wearable and smartphone-based sensors for the experimental derivation of mechanical parameters of utmost importance and technical interest for the design of pedestrian systems is explored. On the one hand, as shown, the elaborated setup makes it fast and easy to acquire body motion parameters for pedestrians moving on different substructures. At the same time, relevant feedback could possibly be obtained from customers on their corresponding comfort

Pilot Experiments for Multi-Criteria Human Comfort-Driven Structural Glass Design Assessment

Civil engineering design and industry are continuously evolving with the support of advancements in technology. Digital tools are able to assist designers in solving several issues with more accuracy and minimized efforts. In parallel, maximization of human comfort is a target for various design procedures, where mathematical models and standardized protocols are conventionally used to optimize well-being of customers. Major challenges and troubles can indeed derive, structurally speaking, from human reactions, which are related to a multitude of aspects, and may further enforced by slender/transparent glass components. The so-called “emotional architecture” and its nervous feelings are intrinsic part of the issue, and hence the mutual interaction of objective and subjective parameters can make complex the building design optimization. This paper presents some recent studies in which human comfort for glass structures occupants is quantitatively measured, both with the support of remote digital technologies based on facial micro-expression analysis and in-field experiments able to capture kinematic and biometric parameters for customers moving in glass environments

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

Single body sensor for calibration of Spring-Mass-Damper parameters in biodynamic pedestrian modelling

For structural design and vibration monitoring purposes, several simplified equivalent-force models or more complex computational strategies are available to describe Human-Structure Interaction (HSI) phenomena on pedestrian systems, and in particular the vertical reaction forces induced by walking occupants. Among others, various Spring-Mass-Damper (SMD), Single Degree of Freedom (SDOF) biodynamic models of literature can be used to mechanically describe a single pedestrian in the form of equivalent body mass m, spring stiffness k and viscous damping coefficient c. Basically, existing SMD formulations are characterized by specific theoretical assumptions and (often complex) experimental methods for the calibration of m, k, c. Usually, SMD parameters can be optimally quantified when multiple sensors (on pedestrian’s body and on the structure) are used to capture motion features and the corresponding reaction force. In this paper, body accelerations of a pedestrian are tracked by means of a single Centre of Mass (CoM) sensor and are elaborated to derive basic input parameters for an alternative, newly optimized SMD model. Experimental registrations from a total of 30 random walks and more than 300 gaits (on rigid floor) are taken into account, and fitting expressions for m, k, c are proposed. The present SMD formulation (SMD-0) is validated towards a selection of literature proposals (SMD-1 to SMD-4), based on parametric numerical dynamic analyses (100 in total), which are carried out by taking into account various pacing frequencies (fp = 1.5–2 Hz the explored range) and four different pedestrian structures / floors (F#1 to F#4). The comparison of classical performance indicators for human-induced structural vibrations proves the efficiency and potential of current SMD-0 approach, and suggests further investigations in support of optimized protocols

Mechanical analysis and characterization of IGUs with different silicone sealed spacer connections - Part 2: modelling

Insulated Glass Units (IGUs) typically consist of two glass layers, either monolithic and/or laminated sections, that mechanically interact via an hermetically-sealed air (or gas) cavity, and a series of linear spacer connections along their edges. In this paper, based on the experimental tests for small-scale IGU joints under pure shear and IGU prototypes in bending discussed in \u201cPart I\u201d, a special care is spent for the Finite Element (FE) numerical characterization and analysis of these composite systems, with a focus on the actual mechanical properties and load-bearing mechanism for the involved components. Major advantage is taken from the full 3D solid geometrical description of the connection components and the gas cavity infill. The actual role of both primary and secondary sealant layers is first assessed. Further support is derived from analytical calculations for the connection efficiency assessment, based on the adaptation of simplified formulations of literature. Finally, a calculation example is proposed to assess the magnitude of load sharing phenomena, based on FE numerical and analytical calculations for selected configurations

Enhancement of the seismic performance of multi-storey buildings by means of dissipative glazing curtain walls

Glazing facades are widely used in building structures, due to a series of aesthetic, thermal, lightening aspects. From a structural point of view, under the action of exceptional loads as impacts, explosions or seismic events, the glazing envelopes often represent the critical component for multi-storey buildings, due to the typically brittle behavior and limited tensile resistance of the glass panes, hence requiring specific design concepts. In this paper, the feasibility and potential of special mechanical connectors interposed at the interface between a given multi-storey primary building structure and the glazing facade are extensively investigated via accurate Finite-Element models, under the action of a set of seven natural seismic records. As shown, the proposed vibration control devices can markedly improve the dynamic performance of the traditional structure, both in terms of global (i.e. building seismic response) and local performances (i.e. at the component level). The final result, once the input parameters of the vibration control devices are properly designed, is an assembled structural system in which the glazing fa\ue7ade works as passive control system for the primary structure

Rapid Safety Assessment and Experimental Derivation of Damage Indexes for In-Service Glass Slabs

The mechanical performance of pedestrian structures attracts the attention of several studies, especially with respect to unfavourable operational conditions or possible damage scenarios. In terms of vibrations, for example, specific customer comfort levels must be satisfied, depending on the class of use, the structural typology, the involved materials, in addition to basic safety requirements. A special consideration should be given to in-service systems that are possibly affected by degradation or even damage, and thus potentially unsafe for pedestrians. In this regard, the availability of standardized non-destructive protocols for a reliable and rapid structural safety assessment may result in efficient support for diagnostic analyses. In this paper, 3 different laminated glass (LG) modular units belonging to 2 different indoor in-service pedestrian systems located in Italy are investigated. Operational Modal Analysis (OMA) procedures and dynamic identification techniques are used to quantify the residual capacity of the examined systems, including damage and material degradation, based on a single triaxial Micro Electro-Mechanical System (MEMS) accelerometer. The experimentally derived performance indicators and calibrated mechanical parameters for the examined structural system are assessed towards traditional design procedures, and further quantified with the support of Finite Element (FE) numerical model updating. A comparative analysis is carried out to explore the structural performance and safety levels of in-service LG slabs in regards to vibration comfort, deflection control and stress analysis