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Recent Italian earthquakes have shown the seismic vulnerability of many typical historical masonry churches characterized by one nave and wooden roofs. Under transverse earthquake, the nave transverse response of this kind of churches can be influenced by the geometrical and material features. To increase the seismic performance, strengthening interventions aimed to pursue the global box-behavior by the realization of dissipative roof-structure represent a valid strategy, especially to avoid out-of-plane mechanisms. In this way, the roof structure must be able to represent a tool for the damped rocking of the perimeter walls. Cross-laminated timber (CLT) panels with calibrated metal connections have been recently adopted in experimental tests as a valid solution to obtain a roof-diaphragm with ductile behavior, satisfying the conservative restoration criteria at the same time. In this paper, after a description of the numerical approach for the damped rocking mechanism for one nave configuration church, the effectiveness of different CLT based roof-diaphragms in the nave transverse response is investigated for four historical churches. The seismic responses are performed by comparative dynamic nonlinear analyses and the results are shown in terms of displacements and shear actions transferred to the façade. The influence of the geometrical features of the churches on the nave transversal response is deepened by sensitivity analyses with the aim to predict the displacements and shear variations under the same earthquake excitation.

The repair of historical masonry columns damaged by earthquakes is a complex engineering procedure. In most cases, these elements support important vertical loads, and, for this reason, the repairi...

Recently, the engineering interest about the durability of existing reinforced concrete structures has significantly increased as confirmed by the conspicuous scientific literature. The results of these studies are influencing the development of new structural codes. Among the wide range of existing reinforced concrete structures, motorway viaducts stand out for their strategic relevance. Most of these structures were built between ’60 and ’70 years and, nowadays, the materials degradation phenomena are leading to strength capacity reduction, either in serviceability condition or in presence of exceptional loads such as the seismic action. In order to evaluate the degradation phenomena effects on the seismic vulnerability of motorway viaducts, this paper shows an efficient procedure to evaluate the seismic performance of reinforced concrete bridges starting from the modelling of the materials degradation, according to several scenarios, and by carrying out multimodal pushover analyses.

This paper deals with an experimental and numerical dynamic characterization of two steel wind turbines currently located in Italy. The considered steel turbines are onshore and were originally built more than 20 years ago with 65 m of height (from the ground level to the hub). Five years ago, they were unmounted and reassembled in the present location. During this phase, due to local and national environmental prescriptions, they were shortened to about 45 m (hub height). Unfortunately, this procedure generated a huge problem in their structural behaviour: the fundamental frequency of vibration of both the “shorter” steel turbines become close to the working frequency of their rotors, causing a resonance problem. To evaluate exactly the turbine frequencies and modal shapes, structural monitoring involving several accelerometers has been implemented. Then, numerical finite element models (FEM) have been developed to investigate the influence of the soil-structure interaction (SSI) on the dynamic behaviour of these structures. Finally, two practical solutions to overcome the resonance problem are proposed and discussed. Since the investigated problems can arise for any worldwide wind turbine, the proposed solutions are of general validity and can be extended to many other different cases.

In this study the Construction Stage Analysis (CSA) of a new mixed structure building is discussed in order to identify the best timing and execution activities scheduling. The building is part of a new university campus that will be realized close to the center of the city. The CSA is carried out by the implementation of two models: the finite element model for the structural analyses and the BIM model for controlling the sequence of the construction phases. Once fixed the structural model, in the preliminary design phase, different sequences are analyzed in order to optimize the construction management in terms of timing and costs. Moreover, the optimization of the construction phases is set by considering the creep and shrinkage of the concrete material.

The structural safety and durability of existing reinforced concrete bridges can be considered as one of the current most important research topics in structural engineering, especially after the numerous collapses that have occurred in recent years. Considering the Italian context, it is important to highlight that most of these structures were built in the 1960s and 1970s and, consequently, the effects of materials degradation phenomena have reduced their vertical and horizontal load-bearing capacity. This paper presents an efficient procedure for the collapse mechanism evaluation of existing reinforced concrete motorway bridges under horizontal loads, considering the corrosion effects due to carbonation through a simplified model that takes into account the steel rebars reduction and applying a multi-modal pushover analysis approach. In this study, three different (slight, moderate and high) corrosion scenarios are considered for two existing reinforced concrete bridges characterized by frame piers. The results of the numerical analyses, which consider both brittle and ductile failure mechanisms, highlight a significant decrease of the seismic capacity of the structures as the corrosion level increases, especially for brittle collapse mechanisms that are strongly affected by the bridge maintenance condition. Such a procedure allows identifying the first structural elements reaching the collapse, providing useful information for the maintenance of existing bridges in terms of repair and strengthening interventions.

The evaluation of the seismic behaviour of shallow multi-propped underground structures (e.g. metro stations, parking, etc.) can be considered as one of the most important and actual research topics in structural earthquake engineering. Over the last decades, different types of analysis approaches have been proposed, but several issues are still open, especially for multi-propped structures embedded in granular soils. In this paper, the main limitations of the decoupled approach are investigated and discussed through a large set of numerical simulations involving: i) a multi-propped underground structure; ii) five natural and one synthetic accelerograms; iii) four different soil profiles characterized by the same mechanical properties but different values of the shear modulus that are related to the shear wave velocity ranging between 360 m/s and 750 m/s. The results, in terms of bending moment acting on RC retaining walls, obtained through the decupled approach are discussed in comparison with those obtained through the coupled approach (non-linear dynamic analysis), highlighting the main differences and limitations. This study shows that the decoupled approach provides consistent results only for soil profiles characterized by low values of stiffness due to the main assumptions underlying the approach.

In the seismic retrofitting of historical churches, the realisation of new foundations of collapsed elements represents an important aspect for the interaction with both the underground pre-existing structures and the new structural elements to be rebuilt. For the specific case study of the Basilica di Collemaggio, after an accurate geometrical survey and onsite geotechnical tests, a specific mixed structure foundation system is proposed in order to fulfil the seismicsafety requirements and the Cultural Heritage Office's conservation prescriptions. Nonlinear analyses are performed considering the interaction between the soil and the foundation system, together with the new couple of main pillars and the triumphal arch. The analyses are aimed to verify the capabilities of the new foundation system to bear the transversal seismic actions. The analyses are also completed by some experimental tests on micropiles, which represent the main underground-to-elevation connection elements.

The paper concerns a tuned mass dumper (TMD) design to improve the seismic response of an historical chimney located in an important Italian hydraulic plant. The chimney, built at the beginning of XX century, has about 50 m total height and its structure is completely in masonry. To understand the chimney’s dynamic response and evaluate the TMD characteristics (in terms of optimum mass, stiffness and damping values) to improve the seismic response, some numerical analysis are carried out by Finite Elements Models (FEM) represented two configurations, respectively: the “chimney” (Type A) and “chimney with TMD” (Type B). Both of the configurations are investigated by two different kind of FEMs: a FEM-Model 1 characterized by beam elements and a FEM-Model 2 characterized by solid elements. In the FEMs, observing the Italian Buildings Code, the local earthquake has been applied by a spectrum-compatible accelerograms by performing a “time history” analysis. The mechanical characteristics of the masonry (elastic modulus and compressive strength) implemented in the FEMs has been already determined by a set of experimental tests. Finally, optimizing the TMD characteristics, the seismic improvements in terms of base shear, compressive/tensile stresses and top displacements are shown.

In this paper the Vibration Control by the Tuned Mass Dumper (TMD), in important and symbolic constructions, are illustrated. Some TMD optimization procedures are discussed for different types of constructions (new tall buildings, an existing masonry chimney and a new footbridge) for the seismic and wind actions. By the TMDs, the structural behaviors improvements are shown, either for the Ultimate Limit State (ULS), either for the Serviceability Limit State (SLS). To appreciate the structural improvements by TMD installation, for each types of constructions, structural analysis by finite elements model (FEM) are carried out with and without TMD. Finally, for each TMDs, a design hypothesis are showed pointing out the installation procedures and the related costs.

An original architecture based on composite configurations of printed-circuit hybrid rings is developed for flexible signal-processing functionalities in advanced monopulse radar applications. The modularity of the proposed topology, together with proper design choices, strongly simplifies the structure of the beam forming network, reducing the relevant ohmic losses, and consequently improving the antenna gain. The circuit also allows us to manage only two radio frequency channels (instead of the conventional three), combining the delta- and omnidirectional channel functions. The principles of the structure are presented, and a specific layout is designed. Stripline prototypes are fabricated and tested for L-band applications. The compared results of simulations and measurements fully confirm the interesting performance of this device. The versatility of the architecture is illustrated further considering alternative circuit implementations. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1663–1670, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27647

International audience; A novel compact, light-weight, and low-loss printed circuit based on hybrid rings is developed and tested for processing functionalities in radar applications. The circuit modularity and the design choices enable for the reduction both of the topological complexity of the beam forming network and of the relevant ohmic losses with consequent improvements in the antenna gain. At the same time, this circuit allows us to manage only two RF channels (instead of the conventional three) combining Delta and Omnidirectional channels with the possibility to modulate Omni-channel signal. After the design and simulation processes, two components have been built and measured, showing the expected valid performance.

This algorithm consists in the design of robust technique for the management of the antenna beam pointing, able to optimize the overall antenna main performances especially when small compact antenna and/or phase shifter with a reduced number of bits are used. The idea was born under the need to guarantee acceptable antenna features with the use of small and cheap phased array (in which the electronic steering is demanded to low cost components) for the Civilian and Military market In many applications such type of solution provides under similar overall performances some advantages on operating maintainability, failures management and economic impacts.