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.

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.

This thesis focuses on fatigue problem on riveted structures and the correlated experimental tests. The term “fatigue” denotes the cracking of metals under repeated loading. The technique of riveting structures is obsolete due to the low level of standardization in the construction process. Knowledge concerning riveted structure’s ability to withstand fatigue has not been investigated to the same extent as for modern structures assembled by welding. Nevertheless, many riveted structures are still in service after over 100 years. Clamping force originates when the hot rivet is placed into the hole of the plates and the rivet shorten in length due to cooling. In Europe, a large number of railway bridges are riveted. Moreover, all over the world, the rivet assembly technique has been largely used for different types of buildings. The riveted structures are subjected, evidently, to fatigue degradation as all the other steel structures. The riveted joint complexity and the non-uniform realization lead to a structure-specific consideration. In Europe, current regulations recognise only one fatigue class for riveted structures neglecting the clamping force effect. This approach is characterized by an elevated standard deviation for the assessed results. This research aims to improve the riveted structures fatigue comprehension and to propose appropriate tests. Some elements have been extracted from a dismantled railway bridge located near San Stino di Livenza (Venice). An innovative clamping test (TCT) has been conceived: applying a torsional moment to the rivets and evaluating the sliding friction, the clamping force has been estimated. Contrary to traditional clamping tests, this setup, at an affordable price, provides good precision. Moreover, the test is in-site and does not provoke damages to the examined structure. Fem models of rail bearer have been realized taking into account rivets, holes and multilayer plates section inertia. A specific laboratory set up has been designed with the intention to calibrate the fem models. Frictions and clamping force have been taken into account in the rail bearer models. There is a close correspondence between the non-linear models and the experimental tests. The clamping assumptions, derived from the TCT, have been verified. A full scale fatigue test has been prepared and the first cycles have been monitored. Full scale fatigue tests are sophisticated and involve many parameters. For this test, a specific metallic frame has been designed and realized using advanced fatigue models. An advanced analysis (hot spot method) has been carried out, for the frame, in order to evaluate the stress into the welds. This frame will be used by the DICEA laboratory to test, principally, specimens extracted from bridges.

The interaction between frames and infills in case of earthquake is a topic of great significance in structural engineering. Infills, often considered non-structural elements, in fact behave as they were. Sometimes they make low engineering buildings behave better than one would expect, other times they are responsible of rather bad seismic performances even in recently built constructions. Infills, often stiff and brittle if constructed with common fired bricks and strong mortar, are able to change to a great extent the seismic structural response, invalidating many of the basic design assumptions. Nevertheless, it is not possible to think of buildings without infills, due to the requirement of controlling energy consumption for residential climate control. To overcome this problem, the possibility of assembly ductile infills was investigated in the current thesis. The basic idea was to use weakness as the main tool, pursued both through the choice of materials and the proposal of a new, simple though effective building technique. Particular attention was devoted to adobe (earthen bricks) infills, specifically chosen in a structural perspective to take advantage of the intrinsic weakness, often unacceptable for other applications. Sustainability and thermo-hygrometric performances are considered important characteristics, even though background themes in comparison with weakness, according to the main perspective of this research work. The aim of the research was to evaluate the possibility of forcing a predefined damage pattern, consistent with reuse requirements, by means of ductile mechanisms. The modus operandi was to lay weak (horizontal) surfaces in the panels, breaking their continuity to allow a frictional, stable and ductile sliding to take place. The idea was investigated both numerically and experimentally. During a first phase, shear behavior of mud mortar joints was tested. Then, four full scale panels, confined by a steel frame, were subjected to lateral cyclic load. The four tests differed both in building technique, traditional or with internal partitions, and in material, hollow clay bricks or adobes. The experimental work was then extended numerically by means of FE analysis (through two modeling techniques) to different geometrical and mechanical situations. Attention was focused on the role of partitions in the structural response and on the possibility of capturing global behavior through a local calibration (on small assemblies) of model parameters. As a conclusion, the use of partitioned adobe infills was proposed in association with ductile timber frames because of the compatibility of materials. The solution may provide adequate stiffness and energy dissipation in case of earthquake. Moreover, this kind of buildings usually suffer for a lack of summer thermal insulation: the addition of mud infilling would improve such a performance.

When hybrid simulation (HS) with substructures is employed for assessing the seismic behavior of a large complex structure, it is unrealistic to test all the components that may exhibit strong nonlinearity. Hence, the accuracy of the numerical substructure (NS) faces an increased challenge. To this end, this paper will emphasize on improving the accuracy of the NS in hybrid simulation based on the model updating approach. Most hybrid simulations with model updating (UHS) focus on updating the parameters of the component constitutive model (story shear model) leading to large modeling errors and the unknown detail responses. Moreover, the most extensively used component constitutive models, such as the Bouc-Wen model, are the models in a narrow sense because they are different for various RC members when the size of the component, boundary conditions, axial compression ratio, and the volumetric stirrup ratio are different from one component to the other. Thus, numerous parameters are needed to describe the displacement-force relations of different components, which leads to the huge computational burden. With this respect, this paper proposes a novel hybrid simulation approach based on identifying and updating the parameters of the material constitutive model. The main work and results are concluded as follows, 1. The unified constitutive model of unconfined and confined concrete is derived from the existing uniaxial concrete constitutive models by introducing the volumetric stirrup ratio. 2. To solve the problem that the relation of the measurements (force of the specimen of a RC member) and the identified parameters (concrete constitutive parameters) are difficult to analytical expressed, an OpenSees embedded unscented Kalman filter is proposed for parameter identification. To this end, several parts of the OpenSees source codes are developed and modified. 3. The proposed identification method and hybrid simulation based on updating the concrete constitutive parameters are respectively validated through a monotonic loading test on a RC column and a UHS on a RC frame. The results show that the convergence values of each parameter under various experimental cases are close to each other with a small variance, which indicates that the proposed identification method is robust and reliable. Comparing to the standard HS, the accuracy of the NS, hence the UHS, is significantly improved. 4. Apply the proposed UHS to a RC continuous rigid bridge with tall thin-walled piers. It concludes that the performance of the identification method is still quite good. Contrasting to the simpler structure, the improved accuracy of a large complex structure is even greater. Moreover, the accuracy of the NS can be greatly increased even though the model error is increased. By tuning the initial values of constitutive parameters, the negative influence of model error is decreased to further improve the precision of the NS. By observing the specimen, it is found that the thin-walled hollow section specimen is a bending-shear type damage mode and finally damaged due to the tensile rupture of the stirrup.

The integral abutment bridge (IAB) constituted by the superstructure and the substructure can achieve a composite action responding as a single structural unit by eliminating or reducing expansion joints and bearings. Accordingly, the construction and maintenance costs can be reduced. Therefore, the IAB concept has recently become a topic of remarkable interest among bridge engineers, not only for newly built bridges but also during refurbishment processes. The research topic concerns the retrofit of existing bridges with the IAB concept. In order to investigate the retrofitting technique with the IAB concept, the literature survey on the practical applications of this approach in worldwide was carried out firstly, including retrofitting motivations, detailed processes and structural performance after retrofitting. Besides, another literature review on the critical issues of analysis on the IAB, such as soil-structure interactions, modelling approaches and plastic hinge simulations, was conducted in order to find out the most suitable method in modelling. The case study of a simply supported prestressed concrete bridge (named Viadotto Serrone) with three spans constructed in 1972 was analyzed, which has some durability problems nowadays. The finite element model was built, involving soil-structure interactions, non-linear behaviors and retrofitting processes. The original and updated Italian design codes are compared through static analysis and seismic analysis. Another investigation was conducted to prove the necessity of considering soil-structure interactions in the IAB. Based on the appropriate finite element model, a large number of static sensitive analyses were carried out, taking thermal actions; bridge types; soil conditions and substructure heights as parameters. Through analysing the responses of girders, piers, abutment stems and piles, some important factors and the corresponding influence were found, which could be adopted to guide the retrofitting technique with the IAB concept. Then, the verification was conducted in order to check if the existing sections could be reused without any changes and point out the most critical components, which need to be repaired or replaced. Moreover, the dynamic performance of bridge before and after retrofitting was investigated preliminarily through modal analysis and response spectrum analysis.

The research hereinafter describes aims at mechanically characterize the behavior of timber framed buildings, with particular focus on their behaviour in seismic zones. An extensive experimental campaign divided into three phases has been completed in order to achieve this objective. In the first phase tests on the connection between sheating panels and timber studs were conducted. Subsequently the behavior of the connections used for anchoring the walls to the foundation were investigated. In the second stage the full scale timber framed walls were subjected to tests. The walls were realized using different materials and different type of connections to the ground. The results have allowed the study of the individual structural components which constitute an entire building, from the single connector to the entire wall. In order to understand the behavior of the components themselves in a real building, and thus their interaction with each other in case of an earthquake, in the third step a shaking table test of a three-story building has been done. All tests have permitted to collect a wealth of data with which to populate a database to be used both to understand in detail the structural behavior of the timber framed building system and in also to validate the proposed formulations. From the analytical point of view, an equation able to provide the horizontal displacement of a wall subject to a horizontal force has been developed. This equation was then successfully validated by comparing the results with those obtained from laboratory tests. For the execution of the tests have been created procedures and set-up ad hoc, that could be used also in the future to carry out similar tests. An important work has been done to achieve a configuration suitable to test full scale timber framed walls through well controlling the boundary conditions.

In Europe about one third of total annual energy consumption is used in both residential and commercial buildings. In many countries already a building regulation exists to ensure the reduction of energy needs for DHW and space heating. Hence, the interest in reducing summer energy demand has grown in the last few years. The summer behavior of buildings is mostly non-stationary and, therefore, the reliability of simple quasi steady state model predictions can not be taken for granted. Since detailed hourly energy simulations emulate the dynamic interaction between environment, building structure, occupants and indoor conditions, they have the potential to provide relevant information about the building summer behavior and to indicate the possible conservation measures for the reduction of energy consumptions. However, one of the limits for the application of enhanced simulation methods, that sometimes can undermine the reliability of their results, is the difficulty to gather reliable input data. Moreover, if dynamic simulation are used in order to compare different choices, decisions are often suboptimal because of the insufficient knowledge of data that has a large consequence on results. Consequently, in order to broaden the use of building simulation in the design process, it is essentially to clarify some aspects. For instance, one of the biggest objection versus the use of detailed procedure is: "to what extent these methods are meaningful if input data are not reliable?" For this reason, the emphasis of this thesis is on the uncertainties of model predictions. In particular, the research is divided in two parts: the investigation of climate issues and the uncertainty analysis of heat transfer estimation, especially for massive wall. The purpose of the research is to support AE in the choice of the characteristics to which the model predictions are more sensitive. In fact, the results of sensitivity and uncertainty analyzes allow to know the robustness of simulation models and make AE aware if the wrong specifications can lead to uncertain results.

This document presents a part of the wide research carried out on modern timber buildings by the timber research group of the University of Trento. In the last five years several experimental and numerical analysis have been performed on crucial structural topics about multistorey timber construction. The efforts have been focused on the traditional light timber framed system (LTF) and on the log-house system (LH). Concerning the LTF, different aspects of the structural behaviour to the lateral load bearing structure such as walls and connection devices were investigated through experimental tests from the single component up to the full-scale building tested on shake table. The goals of these capstone tests, carried out on three-storey buildings, were the investigation of peculiar aspects which especially for the European constructive tradition were not sufficiently discussed. The same layout was follow for the traditional log-house system. In a first step of the research campaign the behaviour of single components (joints, reinforce elements) was tested and analysed in order to form the basis of the second part that was dedicated to the full scale shear walls tests and analysis. The thesis is organized in two main parts. In the opening chapters, after a brief introduction to the constructive system, the seismic behaviour of light timber framed constructions is analysed. The validation of the predictive models and the mechanical characterization of the gypsum fibreboard sheathing material are presented. Different steps of the S.E.R.I.E.S. project are summarized (tests on connection and real scale walls - shake table tests). The aim of the discussion is the deeper understanding of the boundary condition and the reliability of the tests on the single component on the real scale model. In the second part, the mechanical characterization of modern timber log-house building through experimental tests is presented. The strong cooperation among Rubner Haus Company and the timber research group of the University of Trento made possible a detailed experimental campaign organized on two steps. The first is focused on the evaluation of the corner joints proprieties by means of analysis of small portion of walls. The second part deals with the behaviour of full-scale walls with vertical loads in different geometries (corner joints types, length and presence of openings). The two innovative test setup were designed to reproduce the boundary condition of the structural elements of the building, and to minimize the effects of the test pparatus on the results. The outcomes of the tests show a complex interaction between contributions provided by different mechanisms. In the last chapters, a simplified model suitable to predict the overall load displacement curves of the wall is introduced.

The use of pre-fabricated concrete components and their related coupling systems in seismic engineering constitutes a subject of wide and deep interest among researchers, practitioners and manufacturers all over the world, as demonstrated by a large number of studies conducted, among other Countries, especially in Japan, New Zealand and United States since the early ‘80s and, in relatively more recent times, in Italy. A key issue is given by the possibility to apply the typical benefits of the pre-fabrication not only to low rise industrial/commercial structures, but also to multi-storey frames for public and strategic buildings such as schools, hospitals and many others, as well as to high-rise residential premises built in areas characterized by a medium to high seismic intensity. On the basis of what stated above, an original structural system made by prefabricated composite steel truss-concrete beams and centrifuged high-strength concrete columns is presented in the following. Specifically designed joints are provided to couple the different structural components in order to guarantee an overall ease of construction with reduced tolerance problems and self-bearing capacity during temporary erection phases, with a consequent reduction in schedule and costs. The use of high performance concrete for columns allows for a high bearing capacity with limited overall dimensions and the consequent maximization of the commercial or saleable space. The original layout of the system proposed has led to the need to perform an intensive theoretical and experimental research activity. The finite element model of the structural system was calibrated upon both static and cyclic testing evidence carried out on full scale samples built in Italy and tested at the Tongji University-Shanghai, China. On the basis of the data collected, the tuned model was used to carry out further analyses and to deepen the specific knowledge on several further aspects, as specified in the following. Firstly, an estimation of the joint’s strength domain, suitable for everyday’s design was carried out based on a component-approach. Then, a structural optimization on the component used to guarantee hogging and sagging bending moment resistance to the joint, was carried out in order to achieve the minimization of the construction material employed. Furthermore, the estimation of the seismic performance of the joint, based on the evaluation of a purposely defined vulnerability parameter, supplied encouraging results with reference to the applicability of the investigated technology over most of the National territory. Finally an improved layout of the joint, with reference to confined concrete and the related possibility to achieve a suitable seismic response also at edge joints, is presented.