DIC technique for experimental validation of higher order numerical models

This paper presents an adaptation to the Digital Image Correlation (DIC) technique to aid and improve standard measurement methods in experimental mechanics. The practical application is demonstrated by the validation of the Cosserat Continuum model, using small-scale masonry specimens. Numerical models, such as the Cosserat continuum, play an important role in the identification and description of the mechanical behaviour of structures. Especially when it comes to anisotropic and quasi-brittle materials like masonry, these models are needed to evaluate significant aspects like performance, safety, or the effects of various strengthening interventions. The experimental investigation to validate a numerical model is not always straightforward and several of them remain theoretical. Addressing this, the experimentation presented in this paper evaluates the Cosserat identification in shear, where along with simple shear deformation, rigid rotations, micro rotations and micro couples are also exhibited. With such complex deformations, conventional techniques, such as strain gauges, or extensometers can no longer be adopted. The adapted DIC allows the quantification of these deformation data and validates the numerical model

Dynamic investigation on the Mirandola bell tower in post-earthquake scenarios

After the seismic events of the 20th and 29th of May 2012 in Emilia (Italy), most of the monumental and historic buildings of the area were severely damaged. In a few structures, partial collapse mechanisms were observed (e.g. façade tilting, out-of-plane overturning of panels…). This paper presents the case-study of the bell tower of the Santa Maria Maggiore cathedral, located in Mirandola (Italy). The dynamic response of the structure was evaluated through operational modal analysis using ambient vibrations, a consolidated non-destructive procedure that estimates the dynamic parameters of the bell-tower. The dynamic tests were carried out in pre-intervention and post-intervention conditions in order to understand the sensitivity of dynamic measurements to safety interventions. Furthermore, a comparative study is made with similar cases of undamaged masonry towers up to the 6th mode. Finally, an investigation on the state of connections and of the building itself is carried out via FE model updating

First Evaluations on Structural Response of FRP Pultruded Applications Subjected to Seismic Actions

The present work proposes and analyses the solution for seismic behaviour of GFRP (Glass Fiber Reinforced Polymers) applications to evaluate the performances respect to dynamic actions considering the global effect on historical structures. The good strength-self-weight relationship defines the GFRP pultruded profile as an efficacious and innovative solution for structural rehabilitation of historical buildings. The composite material with polymeric matrix, FRP (Fiber Reinforced Polymers), is widely used in civil engineering as sheets, bars and strips. Recently a new technology was adopted to improve the structural response with limited increment of dead load with reversible and independent solution.</jats:p

Structural Performance of a New Column’s Prototype Made by FRP Pultruded Material and Light Concrete

This investigation presents some evaluation based on the experimental and numerical results obtained on the compression bearing capacity of new columns prototype made by FRP (Fibre Reinforced Polymer) material and concrete. In detail that is the junction due to the assembly between hollow FRP profiles made by pultrusion process with glass fibres and thermosetting matrix vinylestere, and very light concrete casting inside. To better understand the eventually influence related to the hollow shape employed, the study consider both the case of circular and square profile. Due to the novel of the research, a not negligible part of the research is dedicated to test previous the separate material, that is the plane concrete and the hollow GFRP profile, and then the prototype (concrete+GFRP) also considering two different way of load application. Particularly we applied in the first case the load to only the core of the sample, on the plane concrete, and then to the total cross section. This choice allows to evaluate the role and the influence of the bond strength along the length of each sample.</jats:p

Proposal of the concrete-GFRP interaction models

The results of an extensive experimental program aimed at understanding the structural performance of composite elements made of fiber-reinforced composite materials (fiber-reinforced polymers, FRPs) and concrete (C) are presented in this paper. The tests were carried out on pultruded unidimensional elements (beams and columns) made of glass fibers embedded in a hot-hardening vinyl-ether resin matrix, GFRP (glass fiber-reinforced polymers). These elements were coupled to concrete by means of either structural glues (based on polymeric resins). The constitutive law of the C-GFRP interface, with/without a structural glue, (a) was formulated on the basis of some specific experimental results, and (b) was instrumental in modeling the composite structural members, including their mutual mechanical interaction. On the whole, substantial agreement was found between the experimental and numerical results, this being a demonstration of the soundness of the proposed interface model that was implemented into an off-the-shelf FE code for nonlinear analysis, where each material of the composite members was independently modeled by means of six-node isoparametric brick elements