Piezoelectric vibration energy harvesting from airflow in HVAC (Heating Ventilation and Air Conditioning) systems

This study focuses on the design and wind tunnel testing of a high efficiency Energy Harvesting device, based on piezoelectric materials, with possible applications for the sustainability of smart buildings, structures and infrastructures. The development of the device was supported by ESA (the European Space Agency) under a program for the space technology transfer in the period 2014-2016. The EH device harvests the airflow inside Heating, Ventilation and Air Conditioning (HVAC) systems, using a piezoelectric component and an appropriate customizable aerodynamic appendix or fin that takes advantage of specific airflow phenomena (vortex shedding and galloping), and can be implemented for optimizing the energy consumption inside buildings. Focus is given on several relevant aspects of wind tunnel testing: different configurations for the piezoelectric bender (rectangular, cylindrical and T-shaped) are tested and compared, and the effective energy harvesting potential of a working prototype device is assessed

Development of a piezoelectric energy-harvesting sensor: from concept to reality

This study focuses on the development and integrated design over a 24-month period of a high efficiency energy-harvesting (EH) temperature sensor, based on piezoelectric materials, with applications for the sustainability of smart buildings, structures and infrastructures. The EH sensor, harvests the airflow inside Heating, Ventilation and Air Conditioning (HVAC) systems, using a piezoelectric component and an appropriate customizable aerodynamic fin that takes advantage of specific air flow effects, and is implemented for optimizing the energy consumption in buildings. The project was divided in several work-packages (some running in parallel) that cover different aspects of the device development. Some of them focus on engineering aspects (starting from the numerical modeling, then prototyping, and concluding with experimental testing). Other aspects focus on the sensor promotion (including the development of a business plan, the intellectual property rights, the final design and the go-to-market actions). Considering the multidisciplinary character of the project (involving knowledge from fields such as wind engineering, electrical engineering, industrial design, entrepreneurship), this study tries to provide an insight on the complex design issues that arise when such complex, sometimes conflicting and overlapping aspects have to be managed within strict deadlines. In doing so, the most important design and development aspects are critically presented

L'investigazione antincendio sugli aspetti strutturali: una proposta di codifica

Lo scopo di questo articolo è quello di esporre una metodologia codificata di Structural Fire Investigation (Investigazione sugli aspetti strutturali in caso di incendio) atta ad individuare le cause scatenanti, pregresse e latenti, che hanno determinato l’evento accidentale. L’iter investigativo, associato a determinate operazioni strutturali e forensi che partono dalla raccolta delle informazioni iniziali al repertamento e controllo documentale per poi completarsi con le verifiche computazionali, sicuramente aiuta a determinare, in maniera rigorosa, le cause e l’origine di un incendio. La modellazione degli incendi con il software del NIST, Fire Dynamics Simulator (FDS) e l’analisi strutturale con vari codici di calcolo, permettono di verificare determinate ipotesi maturate durante il repertamento e di avvalorare scientificamente l’analisi semiotica rilevata sulla scena, fornendo dati forensi utili in fase dibattimentale. Quindi un’attività investigativa pianificata, permette a qualsiasi utente, (VV.F., personale delle Forze dell’Ordine, Consulente, Perito, CTU o Libero Professionista), di svolgere indagini in maniera appropriata secondo una linea guida che permette di non tralasciare controlli a volte rilevanti per la stesura della documentazione complessiva in forma di report finale

Structural response of steel high rise buildings to fire:System characteristics and failure mechanisms

Due to the significant vertical elevation and complexity of the structural system, high rise buildings may suffer from the effects of fire more than other structures. For this reason, in addition to evacuation strategies and active fire protection, a careful consideration of structural response to fire is also very important. In this context, it is of interest to investigate the characteristics of the structural system that could possibly reduce local damages or mitigate the progression of failures in case of fire. In this paper, a steel high rise building is taken as case study and the response of the building is investigated up to the crisis of the structure with respect to a standard fire in a lower and in a higher storey: the comparison of the fire induced failures at the different height allows highlighting the role played in the resulting collapse mechanisms by the beam-column stiffness ratio and by the loading condition

Experimental and Numerical characterization of ultralow-Cycle Fatigue Behavior of Slit Dampers

Slit Damper devices (SDs) have been increasingly studied in last years for they implementation in building constructions to enhance the seismic resistance of structures. SDs are designed as yielding fuses that dissipate energy through large inelastic deformations, while the rest of the structure remains mainly elastic. They are mainly implemented in structural connections at pre-identified locations along the structure and should be able to sustain as much hysteretic cycles as possible before material collapse or fatigue failure in order to prevent local collapses and consequent loss of dissipative capacity. In this paper, finite element (FE) detailed models of single SD devices are presented and analysed under experimental testing-like pseudo-static load protocols by the commercial FE code ABAQUS®. The FE analyses of a variety of SDs in steel which varies each other in shape (hourglass-like shaped) and thickness in order to investigate hysteretic dissipation performances for the preliminary planning of a set of experimental tests. On the basis of the indications provided by the FE analyses, a subsequent experimental campaign is carried out to investigate the low-cycle fatigue damage for the proposed SDs. The SDs was designed for excellent fatigue performance, since the low-cycle fatigue characteristics of the steel SD can be efficiently defined by the Manson-Coffin relationship. These enhanced analyses provided good predictions of the onset of failure in full-scale steel castings across various specimen sizes and loading histories. Finally, it may be said that the newly proposed model can predict well the residual plastic displacements and the remaining life of the damper damaged after an earthquake

Experimental Study on Steel Slit and Shear Panel for Seismic Resistance

AbstractThis paper summarizes the experimental campaign carried out for the development of new steel energy dissipative devices named Slit Dampers (SDs) designed for earthquake protection of structures. A total of eighty‐two steel shear plates with different openings and thicknesses are tested to investigate their behaviour under cyclic pseudo‐static loading. Eight types of steel shear plates are studied, including the SD with narrow slits that divide the plate into rectangular links, and the butterfly fuse with a diamond‐shaped opening that creates butterfly shape links in the plate. Other varying test parameters are loading rate, material strength, and the number of in‐parallel damper elements. It is expected that the proposed model can be successfully used to predict the behaviour of dampers in real‐world applications

Ultimate capacity of diagrid systems for tall buildings in nominal configuration and damaged state

One of the evocative structural design solutions for tall buildings is recently embraced by the diagrid (diagonal grid) structural system. Diagrid, with a perimeter structural configuration characterized by a narrow grid of diagonal members involved both in gravity and in lateral load resistance, requires less structural steel than a conventional steel frame, provides for a more sustainable structure and has emerged as a new design trend for tall-shaped complex structures due to aesthetics and structural performance. The purpose of this study is twofold. First, to assess the optimal structural design of a diagrid tall-building, also compared to a typical outrigger building, focusing on the sustainability (the use of structural steel) and the structural safety and serviceability. To this aim, dierent diagrid geometries are tested and compared. Second, to provide some insight on the residual strength of diagrid structures, also in the damaged state (modelled by the elimination of diagonal grids). Both goals are accomplished using FEM nonlinear analyses

Cellular automata approach to durability analysis of concrete structures in aggressive environments

This paper presents a novel approach to the problem of durability analysis and lifetime assessment of concrete structures under the diffusive attack from external aggressive agents. The proposed formulation mainly refers to beams and frames, but it can be easily extended also to other types of structures. The diffusion process is modeled by using cellular automata. The mechanical damage coupled to diffusion is evaluated by introducing suitable material degradation laws. Since the rate of mass diffusion usually depends on the stress state, the interaction between the diffusion process and the mechanical behavior of the damaged structure is also taken into account by a proper modeling of the stochastic effects in the mass transfer. To this aim, the nonlinear structural analyses during time are performed within the framework of the finite element method by means of a deteriorating reinforced concrete beam element. The effectiveness of the proposed methodology in handling complex geometrical and mechanical boundary conditions is demonstrated through some applications. Firstly, a reinforced concrete box girder cross section is considered and the damaging process is described by the corresponding evolution of both bending moment-curvature diagrams and axial force-bending moment resistance domains. Secondly, the durability analysis of a reinforced concrete continuous T-beam is developed. Finally, the proposed approach is applied to the analysis of an existing arch bridge and to the identification of its critical members