Experimental Analysis of Failure Mechanisms in Masonry-PFRP Profiles Connections

Fibre-reinforced polymer (FRP) profiles, with their low density, high durability, and ease of construction, are particularly suitable for the retrofit of traditional masonry structures, particularly historic constructions in seismic zones. However, a critical aspect of this new technology application is the connection between FRP profiles and masonry walls. So far, no research studies are available on this subject. The authors carried out a preliminary experimental campaign on different connection systems between masonry and pultruded glass-fibre-reinforced polymer (GFRP) profiles. The note presents the immediate results of this study, focusing on the performance and collapse mechanisms; the study may contribute to the development of an effective connection system between masonry and FRP profiles to be adopted in the retrofitting of existing building with juxtaposed FRP frames

Buckling of built-up columns of pultruded fiber-reinforced polymer C-sections

This paper presents the test results of an experimental investigation to evaluate the buckling behavior of built-up columns of pultruded profiles, subjected to axial compression. Specimens are assembled by using four (off the shelf) channel shaped profiles of E-glass fiber-reinforced polymer (FRP), having similar detailing to strut members in a large FRP structure that was executed in 2009 to start the restoration of the Santa Maria Paganica church in L’Aquila, Italy. This church had partially collapsed walls and no roof after the April 6, 2009, earthquake of 6.3 magnitude. A total of six columns are characterized with two different configurations for the bolted connections joining the channel sections into a built-up strut. Test results are discussed and a comparison is made with closed-form equation predictions for flexural buckling resistance, with buckling resistance values established from both eigenvalue and geometric nonlinear finite element analyses. Results show that there is a significant role played by the end loading condition, the composite action, and imperfections. Simple closed-form equations overestimate the flexural buckling strength, whereas the resistance provided by the nonlinear analysis provides a reasonably reliable numerical approach to establishing the actual buckling behavior

Multiscale Modeling and Simulation of Organic Solar Cells

In this article, we continue our mathematical study of organic solar cells (OSCs) and propose a two-scale (micro- and macro-scale) model of heterojunction OSCs with interface geometries characterized by an arbitrarily complex morphology. The microscale model consists of a system of partial and ordinary differential equations in an heterogeneous domain, that provides a full description of excitation/transport phenomena occurring in the bulk regions and dissociation/recombination processes occurring in a thin material slab across the interface. The macroscale model is obtained by a micro-to-macro scale transition that consists of averaging the mass balance equations in the normal direction across the interface thickness, giving rise to nonlinear transmission conditions that are parametrized by the interfacial width. These conditions account in a lumped manner for the volumetric dissociation/recombination phenomena occurring in the thin slab and depend locally on the electric field magnitude and orientation. Using the macroscale model in two spatial dimensions, device structures with complex interface morphologies, for which existing data are available, are numerically investigated showing that, if the electric field orientation relative to the interface is taken into due account, the device performance is determined not only by the total interface length but also by its shape

Dynamic Characterization of an All-FRP Bridge

The light weight and high deformability of bridges made with pultruded FRP (fiber-reinforced polymer) materials make them very promising, but, at the same time, vulnerable to dynamic loadings. As a consequence, the vibration serviceability limit state can govern their design. There is currently a lack of data about the dynamic characteristics of FRP bridges and of design guidelines for securing their vibration serviceability. The paper presents the results of dynamic testing and characterization of an all-FRP spatial footbridge. The main modal parameters of the bridge are evaluated by an experimental modal analysis and by comparison of experimental data with FE analysis results. The identified flexural and torsional modes of the bridge are characterized by relatively high values of frequencies and damping. Results of the dynamic characterization give useful information about the dynamic characteristics of this kind of structures and can contribute to the elaboration of future guidelines for providing them with the vibration serviceability

Evaluation of the structural response to the time-dependent behaviour of concrete: Part 2 - A general computational approach

The paper presents an integral-type general computational approach for the analysis of structural effects of timedependent behaviour of concrete, with particular regard to creep, based on the coupling of the finite elements method with a numerical solution of the hereditary Volterra integral equations of aging linear viscoelasticity ensuing from the application of the linear principle of superposition. This approach does not require the conversion to a rate-type form of the integral-type viscoelastic creep constitutive law adopted by most of current creep prediction models. Simple and complex structures (as non-homogenous structures realized through sequential construction procedures), can be modelled through the adoption of this general numerical approach. Two examples of application, relative to a cable-stayed bridge and to a multi-storey building, are presented

Structural joints made by FRP and steel: a new proposal of analysis based on the progressive damage approach

The work aims to investigate the nonlinear behavior of pultruded joints and the related dissipation capacity through a three-dimensional FE progressive failure analysis of different GFRP beam-column and column-base bolted connections. Different failure criteria are adopted in the analysis and the results are compared. The failure mechanisms of the joints are discussed and the dissipation capacity is evaluated through the computation of the equivalent viscous damping coefficient related to the nonlinear hysteretic behavior. For the column-base joint, the influence of the axial load on the joint's nonlinear behavior is also investigated. The adopted analysis approach appears able to realistically simulate the failure mechanism of the joints. The analysis of the joints subjected to hysteretic cycles evidences a low dissipation capacity, while the analysis of the column-base joint puts in evidence the significant influence of the axial load on the connection's behavior