Small scale experiments are invented to analyze several aspects of instability and bifurcation occurring in structures and within materials. Photoelasticity is employed to analyze the localization of stress in ordered granular materials and near stiff and thin inclusions embedded in an elastic matrix. Prototypes have been designed and realized of elastic structures evidencing buckling under tensile dead loading and flutter and divergence instabilities as related to dry friction. All the experiments have been performed at the Laboratory for Physical Modeling of Structures and Photoelasticity of the Department of Mechanical and Structural Engineering of the University of Trento.

Nowadays, infrastructures are of strategical importance for allowing communication between countries. Owing to its usefulness, the design and the maintenance of bridges, streets and tunnels, which represent the network, become a fundamental issue. In order to investigate the behaviour of infrastructures under different loads, such as gravity, seismic phenomena, thermal differences, and so on, appears essential a comprehensive experimental campaign on scaled and full-scale specimens. In particular, in order to guarantee the safety of citizens, the seismic response of infrastructures under an earthquake requires a careful evaluation of the level of damage of structural elements. In this thesis, typical case studies are considered, such as a concrete tunnel lining and a composite steel-concrete bridge. In the first part of the thesis, a typical concrete tunnel lining is analysed. In order to investigate the inelastic behaviour of a concrete circular tunnel, several tests were performed. In greater detail, the best Fiber Bragg Grating (FBG) package configuration was obtained by means of monotonic and cyclic tests on substructures. Based on these results, the resulting suitable configuration in a full-scale tunnel test was used to measure deformations with high accuracy. Cyclic test on the full-scale tunnel provided data on the damage of reinforcing concrete and the developing of plastic hinges. With the aim of providing information on the structural safety of a tunnel after an earthquake, a damage index was calculated. In this respect, a nonlinear fiber F.E. model in the OpenSEES environmental was developed. This model calculated the stress in terms of bending moment in concrete sections with the use of experimental curvatures measured by FBGs system. Finally, the damage evolution in the concrete tunnel was reported and commented. In the second part of this thesis, a composite steel-concrete short-medium span bridge is treated. The innovation was the application of the PEER Performance-Based Earthquake Engineering (PBEE) to this type of bridge. Moreover, the use of the Hot-rolled (HRS) steel to manufacture I-girder beams has become an innovation in civil infrastructures in Europe, as much as the use of transversal concrete cross-beams (CCBs) to connect spans. With reference to the hazard selected, a suitable case study was chosen. With the aim of understanding the most critical and stressed parts of the case study, preliminary elastic shell and stick models were developed. After the identification of interesting parts, half-scale subassembly specimens were designed and built. Several quasi-static tests, both monotonic and cyclic, were carried out with the objective of exploring global and local mechanisms in the section owing to low-cycle fatigue phenomena. To detect damage in the connection detail, a refined F.E. model in ABAQUS was developed. Fragility curve parameters of the damage's interest quantities were obtained by fitting experimental and numerical data by means of the Maximum Likelihood Estimation method. The results and the numerical model could be ready for the application of the Performance-Based Earthquake Engineering tool, in which decision variables, such as repair costs, downtime, human life loss and lane closures, were taken into consideration in order to increase the confidence in the design for both engineer and owner's viewpoint.

The land-use and cover changes are the major causes of the biodiversity loss. This is particularly true in the contexts of Alpine valley floor, where increasing human-driven pressures affect remnant habitats and fragile ecosystems. To pursue biodiversity conservation, aiming environmentally sustainable development, spatial planning should maintain landscape ecological functions in order to guarantee the habitats and supporting processes for as many species as possible. Besides, planners as well as other stakeholders involved in land-use changes need value-based information or at least information easily obtainable that provides clear insights on the ecological consequences of these land-use changes. Currently, the assessments of the ecological impact of project or plan proposals have several shortcomings. Spatial planning often disregards the different biodiversity components, just focused on species richness of protected areas. Most of landscapeoriented indices fails especially in providing an understanding of disruptive changes of ecological processes. A former project, to which I contributed, was meant to provide an assessment of biodiversity assets for the Trento Province (northern Italy) in order to support environmental decision by a decision support system: the Information System of Ecological Value, or Sistema Informativo della Sensibilità Ambientale (SISA). This has been furnishing to planners value-based information, through a reliable and transparent evaluation, based on expert judgments, but this has some limitations for contexts of the valley floor and concerning ecological processes. The attempt to solve the above mentioned shortcomings and the SISA limitations fostered the motivation behind this study. To this end, a methodology for ecological assessment was proposed. The overall objective is to support land-use planning towards development of ecologically sustainable landscapes. In particular, the ecological assessment concerns the main processes supporting local biodiversity in human dominated and fragmented landscapes: habitat functioning and functional connectivity. The study has focused on one specific environmental context, i.e. the landscapes of the Alpine valley floor. A secondary objective of the study was to develop a decision support system easily applicable by environmental agency officers or planners. This means requiring as few data as possible in order to permit reliable evaluation of planning ecological consequences even in the cases where poor data sets are available. These objectives were pursued through the following steps and intermediate objectives: a) Review the current studies on ecological/biodiversity impact assessment applications, in order to identify the shortcomings and key-issues that need to be addressed (chapter 2). b) Description of the relevant characteristics of targeted environment. In this study the chosen environment was Alpine valley floor, showing it requires urgent attention regarding biodiversity conservation (chapter 3). c) Development of a methodology for the assessment of landscape ecological functioning, attempting to overcome the literature limitations reported from literature review (chapter 4) d) Application of the proposed methodology on a case study within Alpine valler floor, to test the applicability and usefulness of the proposal (chapter 5 and 6). The study derived the main theoretical foundation from landscape ecology; in particular, the main theoretical references were meta-population and spatial graph theory. The proposed approach starts by acknowledging that patches of habitats are open or constrained by landscape barriers and interact with others throughout habitat networks. The evaluation approach relies on a dynamic, rather than a static, interpretation of ecosystems and living communities, by considering spatial attributes of habitat functioning. This is meant to include more components of biodiversity, rather than simple species number. Thus, different ecosystems could have been valued not only by the presence of species, but also by the virtue of the processes acting in the landscape and sustaining them. The assessment framework involves three nested levels, each characterized by its own objects and properties, according to the complexity of hierarchical systems. The quality of each object depends on the quality of nearby objects at the same level and on the quality of upper-level (or lower-level) objects. This enables to evaluate “emergent properties†of a landscape; consequently allows assessing cumulative impacts on habitat functioning due to land-use changes, as shown in the case of master plans’ mosaic for study area. The overall habitat loss resulted larger than that resulted by summation of single habitat losses. The connectivity analyses include both structural and functional characteristics, using barrier effect and spatial graph concepts. Besides the distances, the species response to landscape features and finer-scale movement decisions are considered. The spatial graph of connectivity allows evaluating importance of patches by their contribution to overall connectivity. Thus, it permits to visualize remnant possible paths for species dispersal in highly fragmented areas. Moreover, the spatial-graph based approach allows assessing indirect impacts due to fragmentation. Since the loss of a habitatnode may affect not only nearby habitats but even the functioning of the whole habitat network, it is possible to scan the impacts “spreading†along the habitat networks. The methodology output consists in a GIS-layer and rule sets hierarchically structured in a geodatabase. Once a land use changes, by performing the rule sets is possible update all related information providing assessment for land-use change scenarios (i.e. planning or project proposal). The qualitative multi-attribute evaluation, proposed at the end of methodology procedure, performs a clear separation between prediction and assessment of impacts, according to guidelines for environmental impact assessment. This evaluation is meant to translate species-specific assessments into ecological relevance values. This makes the proposed methodology suitable for EIA applications and consequently may support the same environmental decision targeted by the SISA project.

Remotely-sensed precipitation and soil moisture products are becoming increasingly important sources of information in earth science system. However, there are still high degree of uncertainties inherited in remotely-sensed precipitation and soil moisture products, and limited studies have focused on evaluation of these products. In this study, GEOtop model (Rigon et al. 2006), which is physically-based distributed hydrological model, is used to assess the use of remotely-sensed precipitation and soil moisture products for hydrological applications. The study area is Little Washita watershed (583 km2), Oklahoma, USA. To assess these products, the model has to be first calibrated and validated at different locations in the watershed using extensive ground-based measurements. The Southern Great Plains 1997 (SGP97) and SGP99 Hydrology Experiment are used for model calibration and validation, respectively. The model is reasonably calibrated and validated at watershed scale at different locations in the watershed for: heat fluxes, soil temperature profiles, soil moisture profiles, and streamflows. Regarding soil moisture evolution, we studied the spatial variability of the near-surface soil moisture from GEOtop simulations and estimates from Electronically Scanned Thinned Array Radiometer (ESTAR). Results show that GEOtop simulations and ESTAR estimates show very different magnitude and spatial patterns of near-surface soil moisture. Spatial patterns derived from GEOtop simulations are in agreement with the previous findings obtained from the same study area using ground-based measurements of soil moisture and theoretical model simulations. We conclude that GEOtop simulation results are more accurate and that ESTAR estimates are not a reliable source of data for characterizing the spatial variability of near-surface soil moisture. GEOtop simulations show that the spatial distribution of near-surface soil moisture is highly controlled by soil texture and river network. Furthermore, we investigated the effect of vegetation, surface roughness, and topography on ESTAR. Results show that there are insignificant effects of vegetation except for interception, surface roughness, and topography on ESTAR. In addition, we investigated the scaling properties of near-surface soil moisture. Results show that near-surface soil moisture has multiscaling behaviour. On the other hand, spatial soil moisture patterns are studied using geostatistical techniques: Ordinary kriging, external drift kriging and conditional Gaussian simulations (CGSs). Krigings show that soil moisture patterns in the watershed are highly controlled by gradient and cosine aspect. All CGSs clearly show soil moisture patterns. Spatial soil moisture patterns produced by CGSs are much better than the patterns reproduced by kriging algorithms. Regarding remotely-sensed precipitation products, we have investigated the utility of these products for hydrological simulations during non-winter seasons. Results show that all remotely-sensed precipitation products (Climate Prediction Center’s morphing technique (CMORPH), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks - Cloud Classification System (PERSIANN-CCS)- and Next Generation Weather Radar (NEXRAD Stage III)) are fairly reproducing the streamflows, but CMORPH often overestimates streamflows. Thus it concluded that all the above mentioned remotely-sensed precipitation products have value for streamflow simulations.

The Seismic Performance Analysis of Bridges (SPAB) constitutes one of the biggest challenges for structural and civil engineers. In fact, the handling of these design problems requires a deep knowledge of structural behavior and a huge expertise with numerical and analytical tools necessary to perform advanced Finite Element (FE) simulations including dynamic and probabilistic aspects. Within the scope of SPAB, this thesis proposes the analysis of complex bridges assisted by the profitable well-known method of Dynamic ubstructuring (DS), advanced model updating strategies, fully probabilistic approaches and innovative time integration algorithms. SPAB includes the evaluation of several nonlinear behaviors inside the structural components and the quantification of benefits generated by safety systems such as isolation devices. As a result, in order to highlight the main advantages of a well designed isolation system, most of the cases analyzed include the comparison between non isolated and isolated configurations. In greater detail, four different bridges have been analyzed and will be presented in this thesis. First, the Rio Torto highway viaduct, an existing Reinforced Concrete (RC) viaduct on the A1 Italian highway between Florence and Bologna. The structure has been investigated at the laboratory of the Joint Research Center in Ispra (VA) by means of Hybrid Simulations (HSs). The set of 1 : 2.5 scaled substructures included two RC frame piers and the isolation system. The critical issues of the structure due to the complexity of the geometry and the awfulness was the presence of poor seismic details characterized by plain steel rebars. Owing to lack in knowledge for this type of rebars, tests were needed to analyze the seismic response in the as built configuration and to evaluate the effectiveness of a seismic retrofitting designed with a traditional Concave Sliding Bearings (CSBs) system. Then, a typical RC bridge with an innovative prototype of Concave Sliding Bearing (CSB) has been tested at the EUCENTRE Tress Laboratory in Pavia (PV) through HSs. The set of Physical Substructures (PSs) included a 1 : 2 scaled RC box section pier and a full-scale CSB. The prototype was characterized by an asymptotic relation between friction coefficient and load rate. All the benefits of the DS were exhibited during the test; in fact, to exploit the actual potentiality of the isolation system, even with the low speed of the test, the restoring force coming from the CSB was numerically corrected at each time step. Furthermore, a short-medium span Steel Concrete Composite Bridge made with Hot rolled I-girders (SCCBH) has been investigated. The SCCBH is an example of structural optimization; in fact, it combines both economic and functional benefits deriving from the reduction of in site works, e.g. welding, and short construction time. In particular, The novelties were threefold: i) the testing of a novel connection between a steel I-girder and a Concrete Cross Beam (CCB); ii) the development of a novel mechanical model for this connections; iii) the application of the Performance Based Earthquake Engineering (PBEE) to SCCBH. The experimental campaign has been performed on six 1 : 2 scaled substructures, representing a deck subassembly, tested in both longitudinal and transverse loading directions. Finally, a simulation-based reliability assessment of a complex cable-stayed foot/cyclic bridge located close to the sea and equipped with dynamic viscous dampers was performed. The scope was to investigate the benefits of Circular Hollow Section (CHS) structural members for this type of structure when erected in an aggressive environment. A FE model of the structure has been validated, and then used to perform a probabilistic time dependent analysis. Therefore, two corrosion models, i.e. general and localized, capable of evaluating the reduced load bearing section were implemented; and appropriate probability distribution functions were assigned to input model parameters to evaluate the response of the facility during its service life. As a result, the time dependent probabilities of failure have been evaluated and compared with the codes prescriptions.

The main aim of this research work was to deepen the understanding of the mechanical behaviour of timber-to-timber composite (TTC) floors with incomplete interaction in order to develop, design and test high performance solutions. Several types and arrangements of connections and different timber products, made from both softwood and hardwood species, were considered for the realisation of diaphragms suitable for a wide range of structural applications. An original assembly procedure, developed at the University of Trento, was adopted in the optimization process of these technical solutions. Such innovative procedure allows the designers to pre-stress and camber composite timber elements by simply relying on screw type connectors. The experimental tests presented in this thesis positively contributed to the calibration and validation of this assembly technique, confirming the method applicability. The test results were consistent with the numerical and analytical models, in terms of uplifts, stress levels and overall mechanical performance. The benefits from adopting the above-mentioned procedure appeared to be persistent over time, as the result of an experimental test where four composite specimens, 5.4 m long, were loaded out-of-plane and subjected to continuous monitoring under controlled environmental conditions for a period of two years. The research program was organized into two phases. The first phase was dedicated to the study of alternative strategies for retrofit interventions on timber diaphragms in historical heritage buildings. An extensive experimental campaign on the out-of-plane behaviour of the retrofitted diaphragms was performed in order to evaluate the effectiveness of the different techniques analysed. Specifically, hybrid solutions that coupled the reduced weight of softwood elements with the strength of hardwood components by means of different types of fasteners, were compared with “more common†timber-to-timber strengthening techniques. A large number of tests, covering fourteen configurations obtained by changing fasteners type, fastener arrangement and timber products, were performed to maximize the performance (cost/effectiveness) of the retrofit techniques. Test outcomes included characterization of stiffness, strength, static ductility and residual strength of the connection systems as well. The second phase of the program was devoted to the development of solutions for newly constructed diaphragms, either for new building applications or replacement of damaged/inadequate existing floors. The second phase research work included the design and testing of prefabricated timber-to-timber composite floor modules to be assembled by using laminated veneer lumber (LVL) made of beech wood. Full scale tests were performed on 6 m long and 10 m long modules, respectively designed for residential areas and offices. In addition to the full-scale testing of the modules, the connection system optimization was performed by referring to different types of test protocols, including both push-out and pull-out testing.

The thesis investigates the seismic behaviour of moment resisting joint in timber structures. The problem is analyzed starting from the single connector to get the understanding of seismic response of a complete frame structure. The design of earthquake resistant timber structures requires a deep knowledge of the mechanical behaviour of the structure as a whole and of its single component elements, especially for what concerns ductility and energy dissipation capability. In many timber structures, the ability to absorb kinetic energy and to attenuate effects of large amplitude ground motions is strongly dependent on energy dissipation associated with plastic deformation of metal parts in mechanical connections. The first part of the thesis illustrates some recent researches on timber joints assembled with traditional and innovative dowel type connectors. Experimental results are presented in terms of force-displacement relationship for specimens tested under monotonic procedure, or in terms of hysteretic diagrams for specimens tested under cyclic procedure. The goal is to find out some quantitative values from the experimental data, in order to characterize the ductility and dissipation capability of timber joints, taking into account the definition proposed by Standards for the design of earthquake resistant structures. The last chapters of the thesis present an analytical - numerical - experimental study aimed at the characterization of beam – to – column moment resisting joint behaviour. Through theoretical analysis it is possible to define a model able to describe the mechanical behaviour of tested moment resisting joint in terms of moment – rotation curve. The primary experiments are static and cyclic deformation tests on large timber moment connections. According to the standards, and applying the analytical model it is possible to obtain a reliable prediction of the resistance mechanism of each tested joint, but also to correct values of initial stiffness, maximum slip capability, reduction of resistance under fully reversed loading cycles and energy dissipation capacity. The mechanical characterization of the joint enables the implementation of a finite element model, aimed at predicting the seismical behaviour of wood multi-storey frames. The pushover analysis, performed through the FEM model, enables to assess the behaviour factors for frames built using the different typology of joint studied within the thesis.

This doctoral thesis deals with evaluation of the mechanical performance of brick-mortar masonry after high temperature exposition, by means of a theoretical and experimental research as well as finite elements analyses. The general aims are to assess the residual mechanical properties of masonry and its components and to define a constitutive law accounting for high temperature damage. To these purposes, high temperature exposition was reproduced by means of a brick furnace; then, mechanical testing was performed on the damaged and undamaged material samples; finally, the experimental results were employed to define theoretical-experimental constitutive laws as well as to set up finite elements analyses. The reliability and applicability of the proposed model is finally discussed, with reference both to the state-of-the-art and to possible further research. / La presente tesi affronta il problema della valutazione delle prestazioni meccaniche della muratura di malta e mattoni successivamente all’esposizione ad alte temperature, attraverso uno studio sperimentale e teorico ed analisi meccaniche agli elementi finiti. Gli obiettivi posti si sostanziano nella valutazione delle proprietà meccaniche residue del materiale muratura e dei suoi componenti e nella definizione di una legge di deterioramento meccanico per la muratura danneggiata dall’esposizione alle alte temperature. Al fine di tali obiettivi, per mezzo di un forno di cottura per laterizi è stata prodotta la simulazione fisica dell’esposizione ad alte temperature; quindi, prove di caratterizzazione meccanica sono state compiute sui materiali esposti e non esposti, ed infine i dati sperimentali sono stati utilizzati sia per la costruzione di modelli teorico-sperimentali di comportamento dei materiali sia per il confronto dei modelli stessi con le risultanze di analisi agli elementi finiti che rappresentano le condizioni della muratura integra e danneggiata. Infine, è discussa la validità ed applicabilità del modello proposto in relazione sia allo stato dell’arte sia ad eventuali sviluppi futuri.

Over the last two decades, the production of excess sludge has increased rapidly due to a more stringent legislation on effluent quality and a growing number of new plants, becoming an economic and an environmental critical issue. Processing excess sludge could account for half up to 65% of the total operation costs of a wastewater treatment plant. Technologies to reduce the excess sludge had been widely studied. Several studies reported that the technologies integrated in the wastewater handling units should be cost effective and preferable rather than the techniques integrated in the sludge handling units, as they allow to reduce the sludge production rather than treat it. Thus, the development and the optimization of a technology able to reduce the sludge production in the water line is now challenging. A lot of technique have been developed such as biological, thermal, high temperature oxidation, mechanical treatments, ultrasonication, ozonation or by using chemical compounds. Some of these have been proven not energy saving, while others can negatively affect the effluent quality of the process due to the formation of by-products. Among others, biological treatments are a challenging strategy for sludge reduction. In recent years, several studies showed that including an anaerobic bioreactor in the returned activated sludge line of a conventional activated process could significantly enhance the sludge reduction without causing negative effects on operational performances. Today, this configuration is known as anaerobic side-stream reactor (ASSR) process. Several laboratory applications highlighted that the sludge yield of the ASSR process could be reduced up to 60% compared to a conventional activated process. Despite the highest percentage of sludge reduction achieved, the process is still little applied to real scale because its main operating parameters and sludge reduction mechanisms are still unclear. This study focused on the verification of ASSR process, the mechanisms of sludge reduction and the microbial structure of the process. During the first part of the research, a laboratory experimental system was designed and implemented. A sequencing batch reactor (SBR), to simulate the water line of a real wastewater treatment plant, and an ASSR as a sludge treatment unit composed the system. Unlike most of the previous studies, the system was fed with real urban wastewater in order to obtain results that reflect as much as possible what can really happen to a municipal WWTP. Through a critical analysis of the literature, the influence of two important operating parameters, such as the solid retention time (SRT) of the ASSR and the interchange rate (IR), which means the percentage of biomass cycled into the ASSR, had been uncovered Given this, the experimental system was started up and reached a stable condition after 60 days. The research was developed in three different phases that lasted for about 90 days each. The experimental lab system was tested under three configurations: i) 10% sludge interchange rate and SRT in the ASSR of 10 days; ii) 20% sludge interchange rate and SRT in the ASSR of 5 days and iii) 40% sludge interchange rate and SRT in the ASSR of 2.5 days. The observed sludge yield (Yobs) of each phase was evaluated and was equal 0.21 g TSS/g COD, 0.14 g TSS/g COD and 0.12 g TSS/g COD in Phase I, II and III, respectively. These results confirmed that the process could significantly decrease the sludge production and a reduction up to 62% could be achieved. To explain the results obtained in terms of sludge reduction, different tests and analysis were performed. The release of soluble COD and ammonia in the ASSR have highlighted that the endogenous decay and cell lysis mechanism occur in the ASSR. Extraction of EPS, with CER and BASE methods, showed a release of protein and polysaccharides in the bulk solution that increased passing between Phase I and III. At the end of each experimental phase, batch tests were carried out to evaluate the activity of phosphorus accumulating organisms (PAO) and denitrifying phosphorus accumulating organisms (DPAO). Recirculation in SBR-ASSR selects DPAO microorganisms. This was a result of great interest because DPAO could enhance the biological nutrient removal since nitrogen and phosphorus can be simultaneously removed. Furthermore, DPAO has lower cell yield than PAO resulting in lower sludge production. Results showed an activity of PAO, DPAO and other slow growers such as sulfate reducing bacteria. All these results suggested that the high percentage of sludge reduction could be explained as a combination of aspects, such as the cell lysis, the cryptic growth, the selection of slowing microorganisms and EPS destructuration. The SRT and the IR could be considered as main parameters and their variation could significantly affect the performance of the process. Microbial analyses were carried out to investigate the bacterial and archaeal structure of the ASSR sludge during each phase.The results confirmed the presence of several bacteria that are typically heterotrophic responsible of hydrolysis and fermentative process of organic matter. Several slow growers bacteria were also detected. Moreover, according to the batch tests on PAO and DPAO activity, a relevant increase in Phase III of some genera able to enhance the biological phosphorous removal has been observed. In summary, the research found that the ASSR process is a sustainable solution for the sewage sludge reduction due to an efficient and a low sludge production, able to ensure both carbon, nutrients and phosphorous removal applying an extremely simple technology, easy to realize both in new and in existing wastewater treatment plants.

This work analyses the behaviour of in-plane timber floors which are differently refurbished. The task is to ascertain the stiffness of the different solutions and to study the influence on the global behaviour of the building. The first type analysed is a floor with simple boards to which different reinforcing techniques have been applied. These are double boards, steel plates, diagonally set FRP strips, glued plywood panels and concrete slabs. For each of these types of reinforcement experimental displacement control tests were carried out. They were monotonic and cyclic tests of specimens with dimensions 2x1 m and 5x4 m, with and without perimeter tie-beams. The same tests were numerically reproduced and a numeric model of simple implementation was created able to simulate non-linear behaviour of floor and tie-beam. On the end, the floor model was used in order to analyse a traditional building. Experimental analysis and numeric modelling confirmed the need to guarantee efficient floor-masonry connections and showed the notable contribution offered by perimeter tie-beam in terms of in-plane floor stiffness. The comparison between different techniques of reinforcement showed the inadequacy of simple boards to stand up to seismic action.