A displacement-based dislocation map has been used to build the eigenstress stress, which is the base of the structure’s limit analysis. The limit load has been calculated as the upper bound of any equilibrated stress that respects the compatibility inequalities by means of a linear optimization program. The eigenstress stress nodal parameters were assumed as the design variables, and the compatibility inequalities have been obtained from the Mises–Schleicher criterion, assuming that the stress belongs to the corresponding plastic domain. The numerical application has considered a linear secant representation of the domain, with a penalty factor on stresses, to correct the linearization error. Examples concerning a simply supported cantilever beam, a pipe section, and a plate with a circular hole highlighted the accuracy of the procedure with respect to the established literature. Moreover, the procedure has been applied to investigate plane structure examples. A square plate with variable elliptic holes has been analyzed, and the influence of ellipticity on the collapse load has been shown. The effects of porosity and heterogeneity of the structure with respect to the collapse load are shown considering the porous cantilever and representative volume element. The evaluation of the limit load along different element directions envisaged a point-wise calculation of the compatibility domain of the porous material to be used in the macro-scale analysis of the structures made of porous micro-cells.

The development of innovative early warning systems (EWS), structural health monitoring (SHM) and structural health monitoring and reinforcement (SHMR) systems is essential to prevent the occurrence of potentially dangerous events on engineering works, buildings and in the natural environment. Their effectiveness can be improved by using new generation sensors able to realize widespread, low-cost monitoring at increasing spatial and temporal resolution. The main aim of the research is, therefore, to develop a versatile strain transducer capable of monitoring elements of different nature such as slopes, buildings and linear infrastructures performing distributed real-time measurements. The paper introduces a new smart hybrid transducer (NSHT), a strain transducer belonging to the distributed optical fiber sensors family, appositely designed to overcome the drawbacks of traditional solutions. An experimental laboratory setup was arranged to test its reliability and a comparison between measurements retrieved by the NSHT and traditional devices were done. The results showed that the NSHT is able to perform strain monitoring with spatial resolution as high as 5 cm and accuracy comparable to that of the traditional devices. Finally, an integrated structural and geotechnical monitoring system architecture based on its use is proposed for the Petacciato site, where a deep-seated landslide affects the historical town and some infrastructures. To realize a single communication line in such a complex monitoring system, where multiple elements have to be monitored, a specific tool was also designed and tested, that allows the exact spatial identification of the various elements under observation. Although on-site validation is needed, these early results are encouraging and demonstrate that the NSHT is a low-cost transducer with great potential and that, looking forward, it can be used to increase the effectiveness of the existing EW, SHM and SHMR Systems. The development of systems involving NSHT also follows the new approach to innovation policy contributing to different points of the 2030 Agenda

This paper describes the Field Boundary Element Method (FBEM) applied to the fracture analysis of a 2D rectangular plate made of Functionally Graded Material (FGM) to calculate Mode I Stress Intensity Factor (SIF). The case study of this Field Boundary Element Method is the transversely isotropic plane plate. Its material presents an exponential variation of the elasticity tensor depending on a scalar function of position, i.e., the elastic tensor results from multiplying a scalar function by a constant taken as a reference. Several examples using a parametric representation of the structural response show the suitability of the method that constitutes a Stress Intensity Factor evaluation of Functionally Graded Materials plane plates even in the case of more complex geometries.

This work describes the application of a new transducer prototype for continuous monitoring in both the structural and geotechnical fields. The transducer is synthetically constituted by a wire of optical fiber embedded between two fiber tapes (fiberglass or carbon fiber) and glued by a matrix of polyester resin. The fiber optical wire ends have been connected to a control unit whose detection system is based on Brillouin optical time-domain frequency analysis. Three laboratory tests were carried out to evaluate the sensor’s reliability and accuracy. In each experiment, the transducer was applied to a sample of inclinometer casing sets in different configurations and with different constraint conditions. The experimental collected data were compared with theoretical models and with data obtained from the use of different measuring instruments to perform validation and calibration of the transducer at the same time. Several diagrams can compare the transducer and highlight its suitability for the monitoring and maintenance of structures. The characteristic of the transducer suggests its use as a mixed system for reinforcing and monitoring, especially in the lifetime maintenance of critical infrastructures such as transportation and service networks, and historical heritage.

Safety assessment of structures can be obtained employing limit design to overcome uncertainties concerning actual response due to inelastic constitutive behavior and more generally to non-linear structural response and loads’ random variability. The limit analysis is used for evaluating the safety of the structures, starting directly from load level without any knowledge of the load history. In the paper, the lower bound calculation is proposed where a new strain-based approach is used that allowed describing the residual stress and displacement in terms of permanent strain. The strategy uses the permanent strain as effective parameters of the procedure so that it is possible to assess the ductility requirements for the complete load program developed till collapse or shakedown. The procedure is compared to experimental results obtained on aluminum beams in shakedown.