TThe present work addresses the rigorous derivation of the Flügge treatment of the buckling of a thin cylinder. The incremental equilibrium equations in terms of generalized stresses are rigorously derived in terms of mean quantities (holding true regardless of the thickness of the cylinder), through a generalization of the approach introduced by Biot (1965) for rectangular plates. The incremental kinematics is postulated through a novel deduction from the deformation of a two-dimensional surface, thus generalizing an approach introduced to derive the incremental kinematics of a plate. The nonlinear elastic constitutive equations proposed by Pence and Gou (2015), describing a nearly incompressible neo-Hookean material, are used in a rigorous way. While the employed kinematics coincides with that used by Flügge, the incremental equilibrium and constitutive equations derived in this work are different from those given by Flügge, but are shown to reduce to the latter by invoking the smallness of the cylinder wall. The equations derived for the incremental deformation of prestressed thin cylindrical shells are general and can be used for different purposes. The study of the bifurcation problem of a thin-walled circular cylinder subject to compressive load is offered. When compared, the bifurcation landscape obtained from the formulation developed in this work and that given by Flügge are numerically shown to coincide and be consistent with results obtained by a fully three-dimensional theory of nonlinear elasticity. Furthermore the formula for the axial buckling stress of a ‘mid-long’ cylindrical shell made of a nearly incompressible neo-Hookean material and of a Mooney-Rivlin material are rigorously obtained from the presented formulation.

This thesis regards the study of the seismic behaviour of timber-frame buildings. Three are the main sections. Firstly, the study of the linear and non-linear behaviour of a timber-frame wall subjected to a horizontal force is presented, suggesting some analytical expression to correlate the mechanical behaviour of the entire wall to the mechanical properties of connection devices (i.e. fasteners, angle brackets and hold-down). Particular attention was paid to the ductility of each component. Secondly, a numerical modelling for the seismic linear analysis of multi-storey walls is proposed. In this section the horizontal force distribution between the walls is investigated too. Thirdly, a full-scale shake table test on a prefabricated 3-storey timber-frame building is described.

Permafrost degradation in high mountain environments is one of the effects of climate change in the Alpine region (IPCC, 2007). The consequences may be manyfold, ranging from rock falls and debris flows, to structural damages in infrastructures located on high mountains. The exceptional rock-fall activity during the summer 2003 is likely an indication of this rapid destabilization that takes place as an almost immediate reaction to extreme warming (Gruber et al., 2004a). The understanding and prediction of such phenomena requires ï¬ rst the localization of permafrost affected areas, and then the monitoring of permafrost sites through proper measurement and modeling techniques. However, the modeling of alpine permafrost is not an easy task because of a variety of causes that contribute to increase the complexity. In particular, the crucial factors dominating alpine permafrost are (1) topography and soil type heterogeneity, (2) snow insulating effect, (3) presence of ice in the ground and (4) high thermal inertia for temperature change at depth. These disturbances could be dealt with through a physically based approach that accounts for the topographical characteristics of the basin, allows heterogeneous parameterization of thermal and hydraulic properties of the ground, solves snow accumulation and melting, and calculates temperature, water and ice content in the ground. GEOtop (Rigon et al., 2006) is a distributed physically-based hydrological model that appears suitable to deal with the above outlined requirements, as it solves coupled water and energy budgets, allows heterogeneous input parameters in the form of maps and includes a snow module that calculates accumulation-melting of snow through a multilayer discretization of the snowpack (Endrizzi, 2007). The model, at the beginning of this work, was lacking of a freezing-soil module capable to account for phase change and heat advection in the soils, extremely important in permafrost affected areas (Roth and Boike, 2001). The inclusion of this part, however, needs a deep thermodynamical analysis of the system, in order to derive the relations between pressure and temperature in a ground subject to freezing conditions. Furthermore, the solution of the energy equation requires a robust numerical scheme, which has to cope with the high non-linearities present in the apparent heat capacity formulation for phase change (Hansson et al., 2004). Finally, the snow-soil thermal interactions require a special attention, as they command the energy flux in input to the ground when the snow is present. The objectives of this thesis are to develop a new freezing soil module inside GEOtop, to test the model against analytical solutions, experimental data and ï¬ eld observations, and to apply the model to investigate the influence of coupled heat and water flow in arctic and alpine permafrost areas.

Although industrial piping systems and their components have been found highly vulnerable under earthquake events, there exists an inadequacy of proper seismic analysis and design rules for these structures. Current seismic design Standards and Codes are found to be over-conservative and some components, e.g., elbows, bolted flange joints and Tee joints, do not have detailed design guidelines that take into account earthquake loading. Thus, a clear need for the development of improved seismic design rules for such systems is evident. In this respect, numerical and experimental studies on piping systems and their components subjected to earthquake loading could be useful. As a result, valuable information, such as seismic capacities and demands under different limit states, could be utilized for the amendment of relevant design Codes and Standards. This thesis undertook a numerical and experimental investigation on a typical industrial piping system and some of its components in order to assess their seismic performance. In particular, the following issues have been pursued: (i) design of two non-standard Bolted Flange Joints (BFJs) suitable for seismic applications; (ii) experimental testing of the designed BFJs under monotonic and cyclic loading in order to check their leakage, bending and axial capacities; (iii) finite element analysis of a piping system containing several critical components under seismic loading; (iv) implementation of a pseudo-dynamic and real time testing schemes to test the piping system under seismic loading; and (v) pseudo-dynamic and real time tests on the piping system under several levels of earthquake loading corresponding to both serviceability and ultimate limit states. The above-mentioned activities were attained in this thesis. In particular, two different non-standard BFJs, comparatively thinner than the Standard ones, were designed, and their performance was examined through a number of monotonic and cyclic tests. Experimental results exhibited a favourable performance of the BFJs under bending and axial loading and moderate internal pressure; a good capacity in terms of strength, ductility, energy dissipation and leakage was observed. Performance of a typical full-scale industrial piping system containing several critical components, such as elbows, a bolted flange joint and a Tee joint, under realistic seismic loading was investigated through extensive numerical and experimental activities. The techniques of pseudo-dynamic and real time testing with dynamic substructuring –hybrid testing- were adopted to carry out experimental activities on the piping system under several limit state earthquake loading suggested by performance-based earthquake Standards. Implementations of hybrid tests were challenging mainly because the piping system was endowed with distributed masses and subjected to distributed earthquake forces, for which these experimental techniques have been considered inadequate so far. A number of mode synthesis techniques, namely the Craig-Bampton and SEREP methods, were discussed and their effectiveness was analysed for the realization of these tests. A characterization of the actuators to be used in the experimental tests was performed based on a transfer function. Relevant hybrid tests were successfully executed and they displayed a favourable performance of the piping system and its components; they remained below yield limits without any leakage even for the collapse limit state.

Human wellbeing in cities, often associated to availability of engineered structures, is increasingly linked to the conservation of ecosystems. This is the case of the urban water sector where the focus is shifting from adequate infrastructural arrangements to the key role of ecosystem services, thus offering a unique opportunity to achieve sustainability transitions. The urban water sector entails significant complexities and uncertainties, which no longer can be addressed effectively with traditional approaches. A new paradigm of “adaptation and integration”, emerging as a collective effort of stakeholders that engage themselves in a process of social learning, is needed. However, real-life implementation is arduous: it requires linking diverse stakeholders and knowledge systems, across management levels and institutional boundaries. Three innovative concepts can help face this challenge, namely, ecosystem services, boundary work and learning organizations. Ecosystem services provide a holistic approach for framing socio-ecological issues and for integrating different biophysical and socio-economic data. Boundary work, i.e. the effort put in place to facilitate transfer of knowledge into action, informs active management of the tension at the interface between stakeholders that have differing views on what constitutes relevant knowledge. A learning organization is one that is skilled at creating and acquiring knowledge and modifying its behavior to reflect new insights. In this study, these three concepts are jointly explored to build operative approaches to support the implementation of adaptive management. To this end, the work is driven by four specific objectives presented hereafter. The first objective is to frame the urban water sector from an ecosystem services perspective, synthesizing the most relevant aspects related to the exchange of water between watershed and city, and within the city. The proposed framework highlights the role of the urban water sector in (i) linking ecosystem service production and benefit areas, (ii) bridging spatial scales ranging from the watershed to the household level and (iii) adopting ecosystem service-based responses to drivers of water vulnerability. The second objective is to explore practices of boundary work in adaptive watershed management. Thus, an empirical investigation of how boundary work can facilitate knowledge co-generation and cooperative application in a case study of adaptive management in the Fuhrberg watershed (Germany) is conducted. The results suggest that scientific insights have been crucial for "enlightenment", "decision-support", and in "negotiations" between a water utility and stakeholders in Fuhrberg watershed management. The successful implementation of adaptive watershed management is attributed to boundary work deployed by the water utility and ultimately to its high institutional capacity. This study, which is one of the first empirical assessments of boundary work in practice, presents many promising approaches for initiating boundary work in the case of water utilities. Yet, more comparative research is required to understand the influence of contextual differences on appropriate methods and potential outcomes of boundary work. The third objective is to build and test an approach for designing and assessing impact of watershed investments, aiming to implement adaptive management. The proposed approach is structured to facilitate negotiations among stakeholders. Its strategic component includes setting the agenda, defining investment scenarios, and assessing the performance of watershed investments. Its technical component consists of tailoring spatially explicit ecosystem service models, generating future land use scenarios, and modeling impacts on ecosystem services. The approach is applied to a case study in a data-scarce context: Toker Watershed (Eritrea), considering soil erosion -related challenges. It produced spatially explicit data, which has been aggregated to assess quantitatively the performance of watershed investments, in terms of changes in selected ecosystem services, thus answering key management and planning questions. By addressing stakeholders’ concerns of credibility, saliency, and legitimacy, the approach is expected to facilitate the negotiation of objectives, definition of scenarios, and assessment of watershed investments. The fourth objective is to explore water utilities as learning organization implementing adaptive watershed management. A conceptual framework for evaluating the institutional capacity of water utilities is used to characterize the water utilities in Hanover and Asmara. In particular, the institutional capacity of the “Hannover Water Utility” and “Asmara Water Supply Department” is investigated based on the available information from documents, literature and the previous results, and an interview with a key informant. The results show that the institutional capacity of Hanover Water Utility can be classified as Level 5 – “Progressive water utility” and Asmara Water Supply Department can be classified as Level 2 – “Basic water utility”. An empirical pathway to test the results, by involving senior managers and informed scientists from both case studies, is proposed. In any case, the preliminary results highlight the attributes that determine the capacity of water utilities to become a central actor in the in the implementation of an adaptive watershed management. This research, by jointly exploring the innovative concepts of ecosystem services, boundary work and learning organizations, builds operative approaches that can support the implementation of adaptive watershed management. Further work is needed to address some of the complexities and uncertainties underlying the proposed approaches, including data resolution, model calibration, and above all participation of real-life stakeholders

Water resources availability and its variability is one of the most pressing global problems. Hydrological models are useful to understand the water balance of a basin, providing information for water resource forecast, assessment, and management. The effectiveness of the models in estimating the freshwater space-time availability and variability, however, depends on concurrent and explicitly modelling of all water budget components instead of a single component estimation and optimization. The whole water budget modelling at basin scale requires a combined solution from hydrological and spatial information tools, in-situ and remote sensing data. The present dissertation describes an effort to improve estimation of each water budget component, and water budget closure at various spatial and temporal scales, by combining JGrass-NewAge model system, GIS spatial toolbox, in-situ and remote sensing data. JGrass-NewAge is a system which deploys modern informatics to facilitate models maintainability and reproducible research. It integrates advanced GIS features and the Object Modelling System version 3 infrastructures, which allow for a component-based modelling experience. This means that JGrass-NewAGE is not actually a model, but a set of elements (the components) that can be combined just before runtime to produce various modelling solutions. Topics like calibration of processes, the interpolation forcing and the assessment of forecasting errors can therefore be faced with consistent and solid approaches. In this context also the use of some remote sensing resources can be inserted appropriately and with new techniques. For all the analysis, two significantly different basins, in terms of size and hydrological processes, are considered as case studies. These are Posina river basin in northeast Italy (small size basin) and Upper Blue Nile basin(large size basin) are used as case study. The uDig Spatial Toolbox (uST) GIS infrastructure that is used for generating the hydromorphological parameters is described in the second chapter. A large number of tools are included in uST for terrain analysis, river network delineation, and basin topology characterisation. In addition, the geomorphological settings necessary to run JGrass-NewAGE are shown. The third chapter studies the effect of spatial discretisation and the hillslope size on basin responses. The possible epistemic uncertainty exerted by the use of sub basin spatial discretisation of topographic information in the semi-distributed hydrological modelling has been studied. The use of different spatial representation in hydrological modelling context has been also studied by comparing JGrass-NewAGE with a model configuration called PeakFlow. The latter is an implementation of the geomorphological unit hydrograph based on the width function. The experiment indicates that the Peak-Flow model, with a more accurate spatial representation, reproduce the storm events slightly better than the JGrass-NewAGE model. In the fourth chapter, the thesis set-up JGrass-Newage modelling solution for the estimation of hydrological modelling inputs (rainfall, snow, temperature data) and estimates them, as well as with their errors. Regards to the meteorological forcings (mainly temperature and precipitation), in Posina river basin where there are relatively dense meteorological stations, the effects of different interpolation schemes were evaluated. Since the hydrological processes from rainfall is different from snowfall, a new method of separating rainfall and snowfall was introduced using MODIS imagery data. In the fifth chapter, JGrass-NewAGE was used to estimate the whole set of water balance components. For evapotranspiration (ET) estimation, the Priestley-Taylor component of JGrass-NewAGE is used. In order to calibrate its parameter a new method based on the water budget was implemented. This method uses two different hypothesis on available data (budget stationarity "Budyko hypothesis", and local proportionality of actual evapotranspiration to soil moisture availability). Finally the spatial and temporal dynamics of water budget closure of Posina river basin is presented. The sixth chapter concerns about the inputs data, particularly precipitation, for water balance modelling in a region where ground-based gauge data are scarce. Five high-resolution satellite rainfall estimation (SRE) products were compared and analysed using the available rain gauge. The basin rainfall is investigated systematically, and it was found that, at some locations, the difference in mean annual rainfall estimates between these SREs very high. In addition to the identification of the best performing products, the chapter shows that a simple empirical cumulative distribution (ecdf) mapping bias correction method can provide a means to improve the rainfall estimation of all SREs, and the highest improvement is obtained for CMORPH. In the seventh chapter, using the capability of JGrass-NewAGE components and different remote sensing data, the spatio-temporal water budget of Upper Blue Nile basin is simulated. The water budget components (rainfall, discharge evapotranspiration, and storage) were analysed for about 16 years at daily time step using the modelling solution and remote sensing data set. For the verification of the approaches followed, wide ranges of remote sensing data (MODIS ET product MOD16, GRACE, and EUMETSAT CM SAF cloud fractional cover) are used.

The present Ph.D. dissertation is divided into two Parts: Green's function and problems of the inclusions and dislocations are addressed in the first Part, while implementation of elastoplastic constitutive laws are treated in the second. These subjects can be seen as different approaches to the investigation of the plastic behaviour of materials. In the first Part, infinite-body two-dimensional Green's functions are derived for the incremental deformation of an incompressible, anisotropic, prestressed body. These functions, given by Bigoni and Capuani, show the response of an infinite body to a concentrated force. The effect of prestress on dislocation (and inclusion) fields in non-linear elastic solids is analyzed by extending previous solutions by Eshelby and Willis. Employing a plane strain constitutive model (for incompressible incremental non-linear elasticity) to describe the behaviour a broad class of (anisotropic) materials, but with a special emphasis on ductile metals (J2-deformation theory of plasticity), it is shown that strongly localized strain patterns emerge, when a dislocation dipole is emitted by a source and the prestress level is high enough. These strain patterns may explain cascade activation of dislocation clustering along slip band directions. Several of the presented results remain valid within a three-dimensional context. Novel infinite-body three-dimensional Green's functions are derived for the incremental deformation of an incompressible, anisotropic, prestressed body. The case of a force dipole is developed within this framework. Results are used to investigate the behaviour of a material deformed near the limit of ellipticity loss and to reveal features related to shear failure cones development in a three-dimensional solid medium. Non-standard elastoplastic constitutive laws are treated in the second Part of the present Ph.D. dissertation, based on pressure-sensitive yield functions, such that proposed by Bigoni and Piccolroaz, which describes the inelastic deformation of ceramic powders and of a broad class of rock-like and granular materials. This yield function is not defined outside the yield locus, so that 'gradient-based' integration algorithms of elastoplasticity cannot be directly employed. Therefore, two ad hoc integration algorithms are proposed: an explicit scheme based on a forward Euler technique with a 'centre-of-mass' return correction and an implicit scheme based on a 'cutoff-substepping' return algorithm.

Dielectric elastomer (DE) actuators are electromechanical transducers that essentially consist of one layer of an insulating soft elastomer coated on both sides with com- pliant electrodes. When a voltage is applied between the electrodes, an electrostatic pressure deforms the elastomer triggering the motion of the actuator. In this the- sis, this principle is exploited for the development of three different actuators: an electroactive compression bandage, a hydrostatically coupled actuator for use in the field of soft manipulators and a dielectric elastomer based inchworm-like robot able to perform locomotion. By doing so, several challenges related to the design, to the modeling and to the manufacturing of this kind of devices are raised and tackled. During the development of the electroactive compression bandage, the issue of electrical insulation and prevention of electrical discharge in wearable devices was addressed by using coating layers as an interface between the DE actuator and the human body. Both experimental investigations and a finite electro-elasticity analyti- cal model showed that the passive layers play a key role for an effective transmission of the actuation from the active layers to the load. Indeed, the model showed that by increasing the number of electroactive layers, the pressure variation can be increased, although with a saturation trend, providing a useful indication for future designs of such bandages. The second piece of work here reported consists in a design upgrade of the Hy- drostatically Coupled Dielectric Elastomer Actuator (HC-DEA), already known in the literature, that enable its use in the field of soft manipulators. The new design fea- tures segmented electrodes, which stand as four independent elements on the active membrane of the actuator, enabling it for generating both out of plane and in plane motions. This novel design makes the actuator suitable for delicate transportation of a flat object. This capability was proven via an experimental investigation in which a flat Petri dish was roto-translated on a platform composed of two actuators. The electromechanical transduction performance of the actuator was characterized and its contact mechanics was modeled. Finally, a smart robot structure that exploits anisotropic friction to achieve stick- slip locomotion is presented. The robot, which is made out just of a plastic beam, a planar dielectric elastomer actuator and four bristle pads with asymmetric rigid metallic bristles, exploits the resonance condition to reach the maximum locomotion speed. The fundamental frequency of the structure, which was estimated both ana- lytically and numerically, was identified within the range of frequencies in which the top locomotion speed was observed during the experiments to be identified.

The developments in conceptual design, material technology and efficient construction techniques enabled the creation of longer, lighter, slender and stylish Cable-Stayed Foot Bridges (CSFB). Hence, modern CSFB can be characterized by interacting phenomena like cable nonlinearities, deck dynamic instability and deck lateral oscillations due to pedestrian walking. These phenomena, if intertwined, may bring these structures out of service or to failure. In view of a better performance, additional damping can be provided by passive dampers. However, amplitude dependent behaviour of dampers and slip in connections can make them effective only above a threshold amplitude. Hence, due to high uncertainties in the complex CSFB-damper system, usually, dynamic tests are performed to investigate the performance of the overall system. In this thesis, the effectiveness of the passive vibration reduction system in a complex cablestayed footbridge characterised by two curved decks was investigated. The amplitude dependent behaviour was found both with the output-only ambient vibration and free decay tests. In order to clarify these outcomes, modal quantities were calculated instantaneously,based on time-frequency identification techniques. A thorough analysis of dynamic response signals revealed that the structure with dampers actually behaved like a threshold system: i) for low vibration levels the dampers were still, so that they performed as constraints that stiffened the structure; ii) for high vibration levels, the dampers became fully working. Moreover, a deckcable interaction between one of the longest cables and the first global mode was detected. Initially, the modal properties estimated from the dynamic tests did not match those of the numerical model. In order to have a robust FE model capable to simulate the actual behaviour of the footbridge, model updating was performed. The sensitivity-based model updating techniques and Powell's Dog-Leg method of optimisation based on the Trust-Region approach were used. The final updated model showed a considerable reduction in the percentage error of frequencies. The updated model was able to reproduce the response of the footbridge under actual wind conditions. The revealed cable-deck interaction phenomenon was a motivation to investigate in depth the dynamics of long stay cables. Therefore, efforts were made towards the identification of the nonlinear behaviour of stay cables from measured response data. In view of the fact that actual measured data contained the response of a MDoF system, the first step in this direction was to investigate the feasibility of the nonlinear identification method, i.e. a nonparametric approach applied to a SDoF cable system. The results revealed a good fitting between identified and numerical data, where only a cubic type of nonlinearity was identified. Moreover, an increase of the parameter related to damping and a decrease of the parameter relevant to linear-frequency were observed versus the loading amplitude. However, the values of the parameters stabilised at higher load amplitudes and superharmonics were present in the response. The proposed non-parametric method exhibited a good capability in the nonlinear parameter identification of cables. Approaching towards a more complete understanding of the performance of cable-stayed footbridges, it was realized that the modern footbridges are more prone to pedestrian-induced vibrations that, eventually, degrades their serviceability performance. Moreover, several researchers tried to investigate the problem of synchronous lateral excitation of footbridges, but there is no general consensus on pedestrian models. Therefore, a model of pedestrian-footbridge interaction was proposed. In detail, pedestrian was represented by a modified hybrid Van der Pol/Rayleigh (MHVR) self-sustained oscillator. Amplitude, stability and phase of the MHVR oscillator solution under a harmonic external force associated with the floor motion were analytically evaluated by the harmonic balance method and was compared with numerical results. It was shown that the phase difference tended to become constant at high excitation amplitudes. Moreover, the stability domain was found useful in predicting the percentage of pedestrians synchronized to a given oscillating floor. The numerical results of MHVR oscillator was, then, compared with the experimental result of a shake table with harmonic floor motion. A good agreement in amplitude ratio was found, however, the phase difference resulted to be underestimated by the MHVR model.

A Dielectric Elastomer Generator (DEG) is an electromechanical transducer, basically a highly deformable parallel-plate capacitor, made up of a soft DE membrane coated with two compliant electrodes on its opposite surfaces. This device is able to convert mechanical work, emanating from its interaction with the environment, into electrical energy. The capacitance depends on the deformation undergone by the membrane, and its variability can be exploited to extract electric energy by (i) initially stretching, (ii) then charging the capacitor, (iii) subsequently releasing the stretch and finally (iv) harvesting the charge at a higher electric potential. The optimisation procedure for a load-driven soft planar DEG is presented, assuming hyperelastic and ideal dielectric behaviour. The DEG undergoes the ideal four-stroke electromechanical cycle previously described and its performance is evaluated on the basis of the energy extracted during a cycle and of the efficiency, defined as the ratio of the harvested energy on the total invested energy. The amount of extracted energy is limited due to possible failures of the device, which are, in the most general case, electric breakdown, material rupture, buckling-like instabilities due to loss of the tensile stress state and electromechanical instability. These failure mechanisms determine the allowable state region for the generator. Hence, in order to identify the best cycle that complies with these limits, a constrained optimisation problem is formulated and the generator performance is estimated. For the different loading cases examined, namely equibiaxial stress state and plane strain, numerical results show, as expected, a critical dependence of the harvested energy on the ultimate stretch ratio and, against expectations, a universal limit on the dielectric strength of the DE membrane beyond which the optimal cycle is independent of this parameter. Thus, there is an upper bound on the harvested energy, which depends only on the ultimate stretch ratio. In addition to the simple parallel-plate configuration, an annular DEG deforming out-of-plane has been analysed. In this configuration the generator is made up of an annular membrane constrained at the boundary by a rigid ring and at the centre by a rigid plate, on which an external force is applied. Due to the loading, the membrane deforms non-homogeneously out-of-plane. In order to avoid loss of the tensile stress state, electric breakdown and electromechanical instability, the applied voltage is controlled, thereby limiting the maximum voltage and keeping the maximum stretch in an admissible range. Numerical results show that the prestretch of the membrane is crucial for an effective behaviour of the device. In fact, the unprestretched generator performs poorly with regard to both energy and efficiency. A small prestretch, of approximately 5%, ensure a sixfold improvement in the gained energy and a fivefold increment in efficiency. The performance of the generator is evaluated for different values of the applied load and of the prestretch. This analysis shows that increasing the applied force the harvested energy increases monotonically, while the efficiency increases until a peak value and then decreases. Hence, for an out-of-plane DEG, the choice of the applied force is decisive to ensure a good trade-off among energy and efficiency. Moreover, a comparison of different DEG layouts demonstrates that the annular DEG can compete with the equibiaxial planar generator, in terms not only of efficiency, but also of harvested energy. What has been so far pointed out is valid under the hypothesis of ideal, lossless material. Since polymers are affected by time-dependent effects, this hypothesis appears to be not completely realistic. Indeed, a predicting model for soft dielectric elastomer generators must include a realistic model of the electro-mechanical behaviour of the elastomer filling, the variable capacitor and of the electrical circuit connecting all the device components. To this end, the ideality assumption of the material and of the cycle has to be removed. Hence, a complete framework for a reliable simulation of soft energy harvesters is proposed for a soft viscous dielectric elastomer generator, operating in an electrical circuit for energy harvesting and subjected to a periodic mechanical stretch. The electrical model of the generator takes into account the effects of the electrodes and of the conductivity current through the dielectric material. A phenomenological electro-viscoelastic model at large strain is proposed and calibrated on the basis of experimental data available in literature for a polyacrylate elastomer (VHB-4910). The effects of viscoelasticity and of possible changes of the permittivity with strains on the generator performance are hence investigated. Numerical results underline the importance of time-dependent effects on the evaluation of the generator performance. The main outcome of this analysis is that, compared with a hyperelastic model, the efficiency is reduced by viscoelasticity for high values of the mean stretch and of the amplitude of stretch oscillation. The reduction is almost insensitive of the mechanical frequency while the efficiency is further reduced by the variation of the permittivity with strain. Moreover, viscoelastic effects modify the allowable state region of the generator. At regime condition, the failure curves relative to electromechanical instability and to loss of the tensile stress state are strongly modified by the viscous effects. This fact results in the alteration of the allowable state region of the generator. Furthermore, due to the change in shape and size of the admissible region under this condition, a more surprising result is the fact that the natural configuration is a not-allowed state. As a consequence, there is an upper bound on the maximal stretch oscillation amplitude. Focusing on the main features of the electrical circuit, an important outcome of the analysis is the identification of a value range of the external electric load for which the efficiency is maximal. Furthermore, the viscous dissipation of the material dominates the energy loss arising from the leakage current across the dielectric membrane.