An approach based on genetic algorithm and parallel computing has been presented and discussed for structural optimizations. Some details on its software implementation are given and explained. Numerical simulations demonstrate the applicability of the proposed approach for the optimization of large-scale real structures.

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.

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

Air-source heat pumps coupled with photovoltaic systems are going to be a more and more promising technology, as its widespread application in residential houses will help achieving the decarbonisation of the building sector, which is strongly promoted by the European Union. The aspects that inspire confidence for this solution are that: i) the average quality of heat pumps has recently improved; ii) new and renovated buildings, with well insulated envelopes, are more suitable for low-temperature heating systems; iii) photovoltaic modules price is significantly decreased and still shows a diminishing trend; iv) the share of the electricity production from renewable sources is progressively increasing, making the use of electricity more ecologically favourable and v) heat pump and photovoltaic systems can make the residential sector flexible and ready to face the changes in the electricity system. The aim of this thesis is to analyse the manifold relationships between the building, the HVAC system and the boundary conditions, as well as the interaction of this system with the electricity grid. The work is almost entirely based on the dynamic simulation, which is performed by using more or less detailed models, depending on the objective of the single study. The heat pump is a crucial element, since its behaviour is influenced by many factors. Therefore, particular attention is pointed toward the modelling of this component and its control. The general approach mainly adopted is the comparison between a reference system, defined case by case, and other similar scenarios in which one or more variations are introduced. Since different aspects are investigated, the variations can concern either the system component (building and HVAC system), the boundary conditions or the control strategy. In particular, one of the studies provide an extensive analysis on how the climate impacts the behaviour of the system, involving nine European cities in a wide range of latitude. The role of the thermal storage (water tank and building thermal mass) is also studied, showing that its potential is exploited only when it is properly controlled. The last part of the thesis focuses on the system control, which influences the system performance more than expected. Despite this, the benefits of applying the proposed smart control strategies are not as great as those deriving from the addition of the electrical storage, in a system in which only the thermal storage is present. Even better results can be obtained by applying control strategies that also manage the battery charging/discharging. A general conclusion is that rule-based control strategies would be cheap and e↵ective; however, they require a tailored implementation and their development for the mass-market is not easy.

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.

The concept of "integral abutment bridge" has recently become a topic of remarka-ble interest among bridge engineers, not only for newly built bridges but also during refurbishment processes. The system constituted by the substructure and the superstructure can achieve a composite action responding as a single structural unit; the elimination of expansion joint and bearings on the abutments, greatly reduce the construction and maintenance costs. To maximize the benefits from integral abutment bridges, the direct way is to achieve the super-long integral abutment bridge. However, as the environment temperature changes, the lengths of superstructure increase and decrease, pushing the abutment against the approach fill and pulling it away. The responses of bridge superstructure, the abutment, the approach system, the foundation/piles and the foundation soil are all different. And it's important to understand their interactions effective design and satisfactory performance of integral abutment bridges. In order to build longer integral abutment bridges, therefore in this research, the lit-erature survey on the applications of integral abutment bridges in worldwide, espe-cially the current development of super-long integral abutment bridges was carried out firstly. Another literature review on soil-structure interaction was conducted to find out the most suitable methods in considering this kernel issue in design of integral abutment bridge. Through proposing finite element models for integral abutment bridges that could involve the soil-structure interaction, thermal actions, non-linearity in materials and so on, structural study was performed on an existing super-long integral abutment bridge, including parametric analysis, pushover analysis, and dynamic tests. Then, the performance of integral abutment bridge was better understood, and no critical structural problem was found for integral abutment bridge. Based on that, length limit for this kind of bridge was evaluated and investigated in an analytical way. Considering capacities of abutments and piers, and under the conditions of an existing integral abutment bridge, the length limit was found to be around 540m. With this super length, the piles need to be designed with capacity of large lateral displacement. Therefore, an effective optimization approach, associating the finite element method with global optimization algorithm was presented for pile shape design. At the end, considerations accounted in the design of super-long integral abutment bridges were discussed, making construction of super-long integral abutment bridge of great possibility.

This study concerns a new probabilistic framework to evaluate road/railway bridges after an earthquake by means of analytical fragility curves and inspections on the structure. In particular, the assessment is performed on existing reinforced concrete (RC) bridges with a common structural scheme in Italy (multi-span simply supported girder bridges). The framework is set up of 6 steps and each step is investigated. Steps 1 and 2 are a sort of preliminary work before the seismic event occurs: the creation of a database to collect all information about bridges in specific road/railway networks (step 1) and the generation of fragility curves for each bridge (step 2): fragility curves are instruments describing the probability of a structure being damaged beyond a specific damage state for various levels of ground shaking. Since step 2 is a crucial step for the outcomes of the framework, a wide investigation on the generation of fragility curves is presented, considering bridges located in strategic road network points in Veneto region (North-Eastern Italy) and different numerical modellings, in order to evaluate the best seismic vulnerability assessment. Moreover, particular attention is given to retrofit interventions by means of Fiber Reinforced Polymer (FRP) and their effect on bridge seismic vulnerability reduction. The other steps concern activities to carry out after a seismic event, useful for emergency and post-emergency phases. Step 3 regards a method to decide if inspections on bridge are needed in relation to the occurred earthquake seismic intensity; if the seismic intensity measure reaches a specific threshold, step 4 suggests how to perform visual inspections on bridges, under a probabilistic point of view, and to generate the damaged bridge fragility curves. After that, the last two steps try to give useful information to Institution and owners of bridges in order to reach an optimal road/railway network management in post-earthquake phases. Step 5 concerns a quick procedure to decide whether or not allowing traffic over damaged bridges, whereas step 6 gives information about economical benefits coming from a comparison between replace costs and retrofitting costs (considering FRP retrofitting interventions) of damaged bridges. In order to clarify the framework procedure, an example for each step is developed.

Ecosystem Services (ESs) are the goods and services supplied by ecosystems. In order to fully understand their contribution to human wellbeing, there is a need to identify them, assess their supply, recognise areas where they appear together repeatedly and analyse the interactions that may exist among them. Most of these tasks are also specifically required by the European Biodiversity Strategy for 2020, which asks Member States, by 2014, to identify key ESs and to spatially assess their supply and demand (European Commission, 2011). Nevertheless, these are difficult tasks and to date they have been only partly performed: existing studies in fact have typically focused on a small sub-set of ESs and made use of information that poorly reflects the actual variability of the ESs distribution across a region. The present research aims to fill these gaps, by developing methods involving a wide set of ESs and providing a detailed ESs assessment, based on spatial and statistical analyses. The methods have been tested on an Alpine region of Italy, Trentino. The Alps present a heterogeneous landscape, resulting from the combination of natural and urbanized environments, that allows the supply of a wide range of ESs. The research has four specific objectives. The first objective focuses on the selection and the representation over specific spatial units of the real supply of multiple ESs. Operatively, 51 experts from the local administrative offices and research institutes have been involved in the selection of the most important ESs and spatial indicators for the case study. The experts identified 25 ESs and 57 representative spatial indicators (1 to 5 indicators for each service), and provided data for indicators mapping. To consider the heterogeneity of the ESs supply across the region, indicators were mapped over 20 different spatial units, including: land cover classes, cadastral parcels, fishing zones and catchments.The second objective is to develop and test a statistical method for identifying key indicators that are spatially-explicit and able to measure the biophysical, socio-cultural and economic values of ESs (both in terms of stock and flow). Spearman pairwise correlation analysis was performed among the indicators of the same service in order to identify the highly correlated ones, hence deemed to provide redundant information. Key indicators were selected among the lowly correlated ones. 35 indicators were selected for the case study (out of the 57 initial indicators). The analysis showed that there is a minimum number of key indicators for each ES. Accordingly, three general rules were identified for the selection: (i) if the supply of an ES is regulated, both its biophysical-stock and biophysical-flow indicators must be selected, (ii) if multiple stock (flow) biophysical indicators for a single ES are mapped over different spatial units, all stock (flow) indicators must be maintained, (iii) socio-cultural or economic indicators are always selected as key indicators. The third objective is to develop and test a statistical method for defining bundles of ESs, as sets of spatially correlated services. Principal Component Analysis was used to summarize the information of the 35 indicators, while hierarchical clustering was applied to identify 11 ESs clusters. Clusters were turned into bundles by analyzing the spatial variability of the services due to biophysical (e.g. morphological conditions) and human (e.g. land use) factors. The results of the analysis show that in Trentino multiple ESs can be grouped in a few number of bundles with a complex shape. In particular, areas with poor ESs supply are grouped in one single bundle and the largest bundle follows the spatial distribution of a single land cover class: i.e. forest.The fourth objective is to develop a method to study interactions among ESs, by combining statistical and spatial analyses. In fact, the supply of a given ES is correlated with the supply of other ESs and it is affected by multiple external factors. Correlations may be positive when an increase in the supply of one service corresponds to higher supplies of other services (i.e. synergies), or negative when an increase in the supply of one service corresponds to lower supplies of other services (i.e. tradeoffs). The degree of interactions among 35 key indicators is determined by performing a Spearman pairwise correlation analysis. The latter enabled to identify six patterns of ESs interactions, one pattern of tradeoffs and five of synergies. The analysis showed that the local land use management has not compromised the capacity of ecosystems to provide regulating services while supplying the provisioning ones. The external factors causing the variability of the services across the region were identified and explained by means of spatial and Spearman correlation analyses among the ESs principal components. Principal components were turned into drivers of change by analyzing the spatial variability of the ESs due to biophysical (e.g. forest density) and human (e.g. land use) factors. Land use management was found as the external factor that causes the greatest variability of the ESs distribution across the region. Within forest areas, forest management activities that involve loss of vegetation were found as the main drivers of ESs change. This research aimed to consider a wide set of ESs and information able to reflect the actual variability of the services distribution across a region. It proposed a scientifically sound methodology to deal with the main issues of the ESs spatial assessment, that may reveal efficiently applicable in other geographical areas where ESs are heterogeneously supplied.

The technologies for the use of biomass as an energy source are not always environmental friendly process: wood combustion, for example, can be a rather a dirty process that causes the release in air of several dangerous compounds. For those reasons it is important to develop approaches aimed at the use of biomass in a cleanest way, avoiding, whenever possible, direct combustion of solid biomass and, rather, pursuing fuel upgrade processes allowing a better combustion or direct conversion to electricity through fuel cells. The products originating from the gasification process mainly comprise a mixture of the permanent gases CO, CO2, H2 and CH4, steam, char, tars and ash. The raw synthesis gas needs to be cleaned from tars before it may be upgraded to other commodities. In most cases if tars deposit on the catalyst surface it will block the active sites i.e., carbon acts as catalyst poison. Furthermore, tars in the raw gas can also cause corrosion and blockage of pipes in downstream process equipment. One of the main challenges in biomass gasification is the minimization of tar content in the product gas in combination with optimization of the gas composition. That is, to reduce the tar content as much as possible and to increase the permanent gases. In this context, it is especially interesting the development of technologies for syngas production (i.e. synthesis gas) through biomass gasification and for syngas utilization in fuel cells system, in order to produce energy from renewable resources. In detail the SOFCs (Solid Oxide Fuel Cell) work at high temperatures, and can be fed with different type of fuels, such as methane, carbon monoxide and hydrogen. Thus, the syngas produced by means of biomass gasification, seems to be a suitable fuel for this kind of cells. This chance is particularly interesting, considering that small and medium size conversion plant technologies could be integrated in a distributed energy generation model that is expected to increase its diffusion. The aim of the present project is to verify the possibility of coupling a biomass gasifier with a SOFC for energy production. The use of steam as gasifying agent increases the syngas heating value in comparison with the use of air, since its nitrogen content cause a dilution of the obtained gaseous fuel. Moreover, another beneficial effect in using water steam, is the increase of the H2 percentage up to 50 % in volume. A high hydrogen concentration is kindly recommended if the final aim is to feed a fuel cell. However, the disadvantages of the steam gasification are the lower steam reactivity, comparing with the oxygen one, and the decreasing of the temperature inside the reactor due to the endothermicity of the main reactions. Thus, it is necessary to supply indirectly the heat of reaction. In fluidized bed gasifiers, the bed material acts as solid heat carriers and often provides the heat from char combustion; however fixed bed gasifier are more suitable for small scale application, especially when biomass is used as feedstock . In the first part of this project a small scale (semi continuous, fixed-bed) gasifier has been designed and built. The syngas composition produced has been analyzed and the hydrogen concentration was approximately 60%. In a second stage the plant has been modified in a continuous fixed-bed gasifier, to perform long test duration. The gas composition slightly changes, even if anyway exploitable in fuel cell. Between the gasifier and the fuel cell, a gas cleaning stage has been foreseen. A catalyst is needed for tar cracking. A series of air-gasification tests have been run in a fluidized bed gasifier to test two different catalysts: dolomite and iron. The results on tar concentrations have confirmed the higher efficiency of dolomite in tar cracking. Then, a catalytic filter filled with dolomite has been placed after the fixed bed gasifier for tar abatement. Finally, some tests coupling the gasifier with a solid oxide fuel cells stack have been run. The temperature field measured during the experimental activity by some K-thermocouples has been elaborated to estimate an apparent thermal conductivity coefficient to be used in a 2D model for heat transfer simulation; moreover the data on the syngas composition have been used to test the reliability of a thermo chemical equilibrium model previously developed. The agreement between the output of the equilibrium model and the experimental data is not satisfying. The main problems are the prediction of the residual solid carbon phase and the methane estimation. It is known that the methane prediction it is a difficult task, because it is mainly formed by tars cracking, and thus it is not an equilibrium compound. Several authors have already faced the problem of methane estimation modifying the model with different approaches. In this work, the experimental data have been used to tune up the model, considering the residual solid carbon formed by means of the definition of a parameter called “carbon conversion efficiency†. The accuracy between the thermodynamic equilibrium model and the experimental values significantly improves if the percentage of solid phase is considered. A second modification has been introduced to take into account the moles of carbon and hydrogen which contribute to the methane formation. A better agreement between the experimental results and the output of the modified model has been observed. The experimental campaign shows that steam gasification represents an interesting pathway for the biomass utilization, because it leads to a high quality effluent gas, suitable for feeding solid oxide fuel cells. The proposed modified equilibrium model seems to be a useful engineering tool, as the syngas composition measured is not so far from the thermodynamic predictions.