Francesco Potenza

An Integrated Approach to the Design of Wireless Sensor Networks for Structural Health Monitoring

Wireless Sensor Networks are a promising technology for the implementation of Structural Health Monitoring systems, since they allow to increase the diffusion of measurements in the structure and to reduce the sensor deployment effort and the overall costs. In this paper, possible benefits and critical issues related with the use of Wireless Sensor Networks for structural monitoring are analysed, specifically addressing network design strategies oriented to the damage detection problem. A global cost function is defined and used for the definition of possible design methodologies. Among the various approach, the use of an integrated strategy, able to take advantage of a preliminary structural analysis is considered. Moreover, the implementation of a distributed processing is an explored strategy for an overall improvement of system performances. Benefits of this methodology are finally demonstrated through the analysis of a representative case study, the IASC-ASCE benchmark problem.

Serviceability and Damage Scenario in Irregular RC Structures: Post-Earthquake Observations and Modeling Predictions

AbstractThe catastrophic earthquake that struck the city of L’Aquila in early April 2009 caused extensive damage to buildings at the University of L’Aquila. Among these edifices are those of the Engineering Faculty, which, in particular, suffered large structural displacements and accelerations that resulted in failures of nonstructural elements (infills, false ceilings, door and window frames), the breakage of wiring and piping systems, and the destruction of furniture and machinery. Of these buildings, the so-called Edifice A presents the most critical damage scenario, requiring a significant rehabilitating intervention. The structural behavior of this building, composed of seven independent RC substructures, is the object of intensive investigation; this is in part because irregularities among these substructures, in terms of geometry, stiffness, and weight distribution, provide a rich case study for interpreting different structural and nonstructural damage scenarios. The paper interprets the observed...

Distributed Structural Monitoring for a Smart City in a Seismic Area

The concept of Smart City (SC) has been introduced to categorize the vast area of activities to enhance the life quality of citizen, which are characterised by a pervasive use of Information and Communication Technologies (ICT), to help cities, with various urban domains, making better use of their resources. Monitoring the structural behaviour of strategic buildings and monuments may be desirable for citizens, which have recently experienced a destructive earthquake in their own town, such as the case of L’Aquila. The paper deals with the design of a distributed structural monitoring network for a selected set of strategic structures belonging to the city of L’Aquila. Preliminary design criteria are discussed on the basis of previous authors’ experiences in this context. Specific attention has been dedicated to analyse the expected acceleration response measurements induced by small seismic excitations for the general purpose of monitoring.

Ecosmart Reinforcement for a Masonry Polycentric Pavilion Vault

In the cultural life of modern societies great importance has acquired the preservation of existing and, in particular, ancient architectural heritage. With the inherent historical aspects, the economic implications have to be taken into account as well. Indeed, especially European cities and countries receive significant economic advantages by the existence of monuments and ancient suburbs. In this context, structural maintenance, strengthening and monitoring has gained an important academic and professional impulse. The present paper aims to present the results of a real scale experimental work regarding the application of an innovative seismic retrofitting technique for masonry walls and vaults by Hydraulic Lime Mortar strengthened by Glass Fiber Reinforced Polymer textile grids (HLM-GFRP) embedding new sensing systems as fiber optical sensors. The real scale specimen is a masonry polycentric pavilion vault that was damaged during the L’Aquila earthquake of April 2009. The need of eco compatibility of bonding material with masonry support implies the use of HLM-GFRP as strengthening system. On the other hand, the use of Fiber Bragg Grating (FBG) has a large number of advantages in opposite to electrical measuring methods. Example are: small sensor dimensions, low weight as well as high static and dynamic resolution of measured values, distributed sensing feature allowing to detect anomalies in load transfer between reinforcement and substrate and the location of eventual cracking patterns. A suitable Finite Element (FE) model is developed both to assess the effectiveness of the HLM-GFRP strengthening layers in retrofitting of the masonry vault and to define the strain field essential to the design of the FBG sensors network.

Semiactive Control Using MR Dampers of a Frame Structure under Seismic Excitation

The paper approaches the multifaceted task of semiactively controlling the seismic response of a prototypal building model, through interstorey bracings embedding magnetorheological dampers. The control strategy is based on a synthetic discrete model, purposely formulated in a reduced space of significant dynamic variables, and consistently updated to match the modal properties identified from the experimental response of the modeled physical structure. The occurrence of a known eccentricity in the mass distribution, breaking the structural symmetry, is also considered. The dissipative action of two magnetorheological dampers is governed by a clipped‐optimal control strategy. The dampers are positioned in order to deliver two eccentric and independent forces, acting on the first‐storey displacements. This set‐up allows the mitigation of the three‐dimensional motion arising when monodirectional ground motion is imposed on the non‐symmetric structure. Numerical investigations on the model response to natura...

Elasto-Static Model for Point Mass Sagged Cable-Suspended Robots

In this paper, a model is presented for the elasto-static problem of planar point mass robots suspended by m-cables . In particular, each cable configuration is described by an elastic catenary and static equations and compatibility conditions for the system are given, thus the 2m force reaction unknowns can be evaluated. The proposed formulation has been used to solve the direct problem and it is suitable for investigating the influence of elastic catenary on the end-effector exact positioning. The model allows evaluating the relation between end-effector position and the involvement of each cable in sustaining the payload.

Seismic Retrofitting and Structural Health Monitoring of a Masonry Vault by using GFRP Grids with Embedded FBG Sensors

Fiber reinforced polymer (FRP) materials are currently used for strengthening of masonry structures. The behavior of this retrofit technique depends on the bond characteristics of the FRP to the external surface of the structure. A promising method to control the durability of the FRP reinforced structures is to incorporate fiber optical sensors (FOSs) in the composite material during its application or manufacture. The research leads to design of composite systems for the seismic retrofitting of an ancient masonry vault. The reinforcement technique involves the use of composite systems made up by FRP integrated with FOSs. The FOSs are employed as diagnostic tool for structural health monitoring. doi: 10.12783/SHM2015/202

Design of Damper Viscous Properties for Semi-active Control of Asymmetric Structures

A method to design semi-active control strategies of asymmetric structures is presented. The method is based on the optimal sizing of an equivalent Kelvin-Voight model describing the constitutive behavior of semi-active magneto-rheological devices, through the evaluation of the maximum achievable modal damping when they work in passive modality. The complex eigenvalue loci of the passively-controlled system versus the device mechanical characteristics are spanned for symmetric and asymmetric frame structures. A coherent representation of the reference effect ensured by an optimized linear active feedback on the eigenvalues loci is selected to drive the design of the adjustable properties of the semi-active device. A clipped-optimal control algorithm is used in a prototype experimental application whose performance are highlighted by the presented design method.

Monitoring and Maintenance of Customized Structures for Underground Environments: The Case of Gran Sasso National Laboratory

In recent years, the monitoring and maintenance of underground structures has received increasing attention. This chapter presents a structural analysis of two customized prototypes necessary for conducting experimental research within the underground halls of the Gran Sasso National Laboratory (LNGS). These structures consist primarily of a steel-framed structure built within a water tank. Different models representing the fluid–structure interaction are also discussed. The structural monitoring is carried out through dynamic experimental tests in different configurations (prototype empty or filled with water) and load conditions (release, hammer, and environmental). The experimental modal information is used to perform manual updating of the numerical finite element models. Finally, a possible structural monitoring system is proposed, which consists primarily of a distributed fiber optic sensing system for the vaults of the experimental halls of the LNGS.