Search results for " scienza delle costruzioni"

Size effect in FRP-substrate material bonded joints

2008

Assessment of bonding defects in FRP reinforced structures via ultrasonic technique

2016

Fiber reinforced polymer (FRP) composite systems are widely used for the rehabilitation of concrete structures such as building that need to resist to seismic loads, bridges that have to carry heavier traffic loads. The technique consists in bonding the composite plate to the concrete surface element in order to increase the flexural capacity. A proper attachment of the FRP plate to the concrete surface is necessary for the efficiency of the load transfer between the reinforcement and the substrate. In this work, the quality of composite bonding is characterized through ultrasonic testing. The proposed technique is relative to a time domain analysis of the ultrasonic signals and couples the…

Elimination of spurious kinematic modes in hybrid equilibrium elements

2011

Hybrid stress elements are proposed as alternative to standard finite elements for linear and non linear analysis. Hybrid stress formulation is developed in a rigorous mathematical setting and an original approach for elimination of spurious kinematic modes is presented. Hybrid equilibrium method is compared to classical displacement based method by linear elastic analysis of some well known structural examples.

A Cohesive interface formulation in large displacements

2017

Mechanical interfaces are theoretical and computational tools able to properly reproduce the progressive decohesion along predefined surfaces. Scientific literature is rich of interface models, developed under very different conctitutive framework, but mostly developed in small displacements, whereas a few of them assess the problem in a geometrically nonlinear setting. In the present contribution interface formulation is rigorously developed in the large displacements regime. The relevant cohesive interface constitutive relations are defined in the local reference with normal and tangential axes to the middle surface in the current configuration. The interface is defined as a zero thicknes…

A proposal for improving the elastic behaviour of dogbone

2022

The Reduced Beam Section (RBS) connections are one of the prequalified connections approved by international standards and adopted to improve the seismic behaviour of steel Moment Resisting Frames (MRF) also protecting the joint between beams and columns. This goal is reached by locally reducing the resistance of a selected portion of the beam element by suitably trimming the flanges, to promote in that portion the onset of plastic deformations. In the framework of RBS, the most important typology proposed is the so-called dogbone (DB) connections that are widely diffused in seismic engineering. The essential advantages of DB are related to the protection of the welded cross section between…

Optimal design of structures under dynamic loading

2009

FRP-Substrate bonding quality investigation making use of ultrasonic waves

2016

Fiber reinforced polymer (FRP) composite systems are widely used to repair structurally deficient constructions thanks to their good immunity to corrosion, low weight and excellent mechanical properties. The quality of the FRP-substrate interface bond is a crucial parameter affecting the performance of retrofitted structures. In this framework, ultrasonic testing could be used to assess the quality of the bonding [1-2]. In the case of FRP laminates adhesively bonded to roughly inhomogeneous materials, such as concrete, high scattering attenuation occurs due to the presence of heterogeneities. The concrete behaves almost like a perfect absorber generating a considerable number of short-space…

A novel identification procedure from ambient vibration data for buildings of the cultural heritage

Ambient modal identification, also known as Operational Modal Analysis (OMA), aims to identify the modal properties of a structure based on vibration data collected when the structure is under its operating conditions, i.e., no initial excitation or known artificial excitation. This procedure for testing and/or monitoring historic buildings, is particularly attractive for civil engineers concerned with the safety of complex historic structures. However, since the external force is not recorded, the identification methods have to be more sophisticated and based on stochastic mechanics. In this context, this contribution will introduce an innovative ambient identification method based on appl…

Multicriterion design of frames with constraints on buckling

2011

The present paper is devoted to the optimal design of frame structures subjected to static and dynamic loading assuming the material behaviour as elastic perfectly plastic. The relevant optimal design problem is formulated as a minimum volume search problem. The minimum volume structure is determined under suitable constraints on the design variables as well as accounting for different resistance limits: the elastic shakedown limit and the instantaneous collapse limit, considering for each limit condition suitably chosen amplified load combinations. The effects of the dynamic actions are studied on the grounds of the dynamic features of the structure taking into account the structural perio…

A phase-field model for strain localization

2018

Strain localization in quasi-brittle materials occurs when a material is subjected to a high level of mechanical solicitations and inelastic strains develop in relatively narrow zone where micro-cracks appear. The gradual evolution of the micro-cracks results in the formation of localized bands up to the development of stress-free cracks. The localized zone or plastic band is generally associated to a faster growth of strain and is characterized by inelastic phenomena such as opening and propaga- tion of cracks, initiation and growth of voids. Conversely, outside of this zone, the material unloads elastically. Extensive research has been carried out to address issues related to the modeling…