Experimental tests on shallow foundations of onshore wind turbine towers

The current effort towards the progressive switch from carbon-based to renewable energy production is leading to a relevant spreading of both on- and off-shore wind turbine towers. Regarding reinforced concrete shallow foundations of onshore wind turbine steel towers, possible reductions of reinforcement may increase their sustainability, speed of erection, and competitiveness. The article presents the results of an experimental program carried out at Politecnico di Milano concerning both cyclic and monotonic loading, simulating extreme wind conditions on 1:15 scaled models of wind turbine steel towers connected by stud bolt adapters to reinforced concrete shallow foundations embedded in a sandy soil. Three couples of foundation specimens were tested with different reinforcement layouts: (a) similar to current praxis, (b) without shear reinforcement, and (c) without shear reinforcement and with 50% of ordinary steel rebars replaced by steel fibers. Additional vertical loads were added to the small-scale models in order to ensure similarity in terms of stresses. The test results allowed to (i) characterize the mechanical behavior of the foundation element considering soil-structure interaction under both service and ultimate load conditions, (ii) assess the foundation failure mode, (iii) highlight the role of each typology of reinforcing bars forming the cage, and (iv) provide hints for the optimization of these latter

Aerobic/anaerobic/aerobic sequenced biodegradation of a mixture of chlorinated ethenes, ethanes and methanes in batch bioreactors

A novel aerobic/anaerobic/aerobic treatment was implemented in batch reactors containing aquifer materials from a site contaminated by tetrachloroethylene (PCE), trichloroethylene (TCE), vinyl chloride (VC), 1,1,2-trichloroethane (1,1,2-TCA) and chloroform (CF). Consortia grown aerobically on methane, propane, n-pentane and n-hexane completely biodegraded the chlorinated solvent mixture, via aerobic cometabolism of VC, CF, TCE and 1,1,2 TCA, followed by PCE reductive dechlorination (RD) to 1,2-cis-dichlorothylene (cis-DCE) or TCE, and cis-DCE/TCE cometabolism in a further aerobic phase. n-hexane was the best substrate. No electron donor was supplied for RD, which likely utilized cellular material produced during the aerobic phase. Chloride release was stoichiometric with chlorinated solvent biodegradation. According to the Lepidium sativum ecotoxicity test, a decreased toxicity was observed with propane, n-pentane and n-hexane, but not methane. A kinetic study of PCE RD allowed to estimate the PCE maximum specific rate (0.57 \ub1 0.07 mg/ mg protein/day) and half-saturation constant (6.7 \ub1 1.5 mg/L)

Feed frequency in a Sequencing Batch Reactor strongly affects the production of polyhydroxyalkanoates (PHAs) from volatile fatty acids

The production of polyhydroxyalkanoates (PHAs) by activated sludge selected in a sequencing batch reactor (SBR) has been investigated. Several SBR runs were performed at the same applied organic load rate (OLR), hydraulic retention time (HRT) and feed concentration (8.5 g COD L-1 of volatile fatty acids, VFAs) under aerobic conditions. The effect of the feeding time was only evaluated with a cycle length of 8 h; for this particular cycle length, an increase in the storage response was observed by increasing the rate at which the substrate was fed into the reactor (at a fixed feeding frequency). Furthermore, a significantly stronger effect was observed by decreasing the cycle length from 8 h to 6 h and then to 2 h, changing the feed frequency or changing the organic load given per cycle (all of the other conditions remained the same): the length of the feast phase decreased from 26 to 20.0 and then to 19.7% of the overall cycle length, respectively, due to an increase in the substrate removal rate. This removal rate was high and similar for the runs with cycle lengths of 2 h and 6 h in the SBR. This result was due to an increase in the selective pressure and the specific storage properties of the selected biomass. The highest polymer productivity after long-term accumulation batch tests was 1.7 g PHA L-1 d(-1), with PHA content in the biomass of approximately 50% on a COD basis under nitrogen limitation. The DGGE profiles showed that the good storage performance correlated to the development of Lampropedia hyalina, which was only observed in the SBR runs characterized by a shorter cycle length

Prove dinamiche su strutture controllate con dispositivi magnetoreologici (MR)

In this paper a shaking table experimentation is presented, which refers to a coupled adjacent structures configuration, that may be used in civil and industrial applications. The physical model is a 1:5 scaled coupled structures. The first structure is a 4-story model, while the second structure is a 2-story model. The introduction of the magnetorheological (MR) device between the adjacent structures is shown to be able a viable method to protect the structures from seismic excitation. The MR damper is applied as passive and semiactive device. The results confirm good performance of the passive and semiactive control system in reducing the response of both structures. Finally a mathematical model of the structures and the device has also been identified and validate

Role of numerical modelling choices on the structural response of onshore wind turbine shallow foundations

Structural modelling of wind turbine shallow foundations on granular soil strata deals with combined complex phenomena, such as soil-structure interaction, material nonlinearities, local stress concentration in both reinforced concrete foundation and soil. Numerical finite element analyses are performed employing three-dimensional elements for both concrete foundation and soil and one-dimensional elements for reinforcement. The results of the nonlinear static simulations are validated with experimental results of recent tests carried out on 1:15 scaled models having reinforcement ratios and stress conditions similar to the prototype foundations designed according to current codes. The validated modelling strategies are also applied to investigate the role of nonlinearities in both soil and concrete foundation, emphasizing the parameters and the nonlinear constitutive laws that significantly affect the foundation response. Three different reinforcement layouts are considered in both testing and simulations of the prototype: (a) complete prototype reinforcement, (b) prototype without shear reinforcement and (c) prototype without shear reinforcement and with 50% of remaining reinforcement replaced by steel fibres. A critical comparison is also made with models employing elastic two-dimensional shell finite elements lying over elastic supports, typically adopted for design purposes

Fondazioni superficiali di torri eoliche su terraferma: studio sperimentale e interpretazione teorica

Per la produzione di energia elettrica è comune utilizzare torri eoliche di notevole altezza. Nel caso di opere realizzate su terraferma le fondazioni sono in generale superficiali e sono progettate principalmente in fun-zione delle sollecitazioni da vento. Gli autori hanno eseguito una serie di prove sperimentali su modello con rapporto di scala 1:15 al fine di comprendere il comportamento meccanico del sistema terreno-struttura. In particolare, si è considerato il ca-so di una fondazione superficiale posta su di uno strato omogeneo di materiale granulare secco. Il sistema è stato caricato ciclicamente mediante l’applicazione di una forza orizzontale in sommità. Al termine dei cicli di carico, si è monotonamente incrementato lo spostamento sommitale sino al raggiungimento della condi-zione di rottura del sistema. I risultati sperimentali mettono in evidenza che nella progettazione di queste opere sia necessario considerare il comportamento irreversibile sia per il terreno che per la fondazione

Numerical analyses of shallow foundations of wind towers / analisi numeriche di fondazioni superficiali di torri eoliche

La memoria mostra i principali risultati ottenuti da analisi numeriche agli elementi finiti condotte per simulare il comportamento monotono di fondazioni di torri eoliche. I carichi applicati simulano le condizioni estreme prodotte dal vento. Le analisi numeriche vengono confrontate con i risultati sperimentali ottenuti da prove condotte su prototipi in scala 1:15 che riproducono i rapporti d\u2019armatura e le condizioni di sforzo della prassi realizzativa corrente. Tre differenti tipologie di provini sono state realizzate in laboratorio; esse si differenziano per la quantit\ue0 d\u2019armatura utilizzata: (a) armatura completa, (b) armatura priva di armatura a taglio e (c) senza armatura a taglio e con il 50% di armatura rimanente sostituita da fibre in acciaio. I prototipi del tipo (a) e (b) sono stati simulati numericamente in questo studio. I provini sono stati simulati con un approccio tridimensionale. L\u2019interazione suolo-struttura \ue8 inclusa in tutte le analisi ed \ue8 discussa la scelta della modellazione del terreno. La scelta dei parametri necessari per definire i legami costitutivi non lineari \ue8 descritta enfatizzando i parametri che influenzano significativamente la risposta della fondazione.The paper shows the main results obtained from numerical FE analyses carried out to simulate the monotonic behaviour of wind tower foundations. The applied loads simulate the extreme conditions produced by the wind. The numerical analyses are compared with the experimental results obtained from tests carried out on 1:15 scale prototypes that reproduce the reinforcement ratios and the stress conditions of the solutions designed according to current codes. Three different types of specimens were made in the laboratory. They differ in the amount of reinforcement used: (a) complete reinforcement, (b) without shear reinforcement and (c) without shear reinforcement and with 50% of remaining reinforcement replaced by steel fibres. Prototype types (a) and (b) are numerically simulated in this study. The prototypes are simulated with a three-dimensional approach. Soil-structure interaction is included in all the analyses and the choice of soil modelling is discussed. The choice of the parameters necessary to define the non-linear constitutive laws is described by emphasizing which are the parameters that significantly influence the foundation response

Emotional processing in early and late stage non-demented Parkinson's disease patients

Background: The basal ganglia are thought to be critical for the expression and possibly the perception of emotions. Processing of emotional faces was found to be impaired in Parkinson's disease (PD) in some but not all studies. The aim of this study was to test whether performance in emotion discrimination would differ as a function of stage of the disease. Method: Early (N=21) and late stage (N=18) nondemented PD patients, and healthy controls (N=21), matched for age, sex and education level were studied. Early PD patients (mean±S.D. age: 61.7± 8.6; Hoehn and Yahr rating score: 2±0.5; PD duration (year): 3.9±1.9), had no signs of dementia as per the Mattis Dementia Rating Scale. Late stage PD patients (mean±S.D. age: 61.2± 9.5; H&Y: 3.9±0.5; disease duration (year): 11.9±5.4), were candidates for STNDBS neurosurgery, and not demented as per a comprehensive neuropsychological assessment (CAPSIT); a sub-sample was reassessed under STN-DBS. Emotion discrimination was assessed with a computeradministered task presenting facial exemplars of basic emotions paired to convey the same or different emotions. Results: Late but not early stage PD patients showed significantly lower performance than healthy controls in emotion discrimination (p<0.0001). Performance did not differ on a control task for face recognition (Benton); lower performance in advanced PD was not explained by other variables such as depression, or impairments in executive functions. Conclusion: Emotional processing is impaired in non-demented late stage PD patients and appears to be stage dependent