Geminiano Mancusi

A numerical evaluation of the interlaminar stress state in externally FRP plated RC beams

The present work deals with the structural plating of reinforced concrete beams with composite materials. Some numerical results obtained via finite element method (FEM) are given. The FEM analysis has been performed by using a suitable mechanical model introduced by the authors in previous steps of the research. This model allows to accurately predict the actual stress state at the interface between concrete core and reinforcing plate. Such interfacial stresses play a fundamental role in the mechanics of plated beams, because they can produce a sudden and premature failure. A simplified procedure for verifying the interfacial stress state is also presented.

On the statical behaviour of fibre-reinforced polymer thin-walled beams

The work deals with the formulation of a one-dimensional kinematical model that is able to study the static behaviour of fibre-reinforced polymer thin-walled beams. The proposed model allows us to take into account the effects of shear deformability. Some numerical results obtained via the finite element method are provided and comparisons with the results obtained by Vlasovs classical theory are also presented.

Failure Criteria for FRP Adhesive Lap Joints: A Comparative Analysis

In this paper the debonding of adhesive lap joints between FRP adherents is analyzed with regard to the influence of the chosen interface failure criterion. In particular, the results obtained by using the well-known criteria of Hutchinson and Suo, Xu and Needleman, and Camacho and Ortiz, are compared. Due to the mathematical formulation of such cohesive interface models, the examined mechanical problem is non linear, although the adherents are supposed to be linear elastic up to failure. Furthermore, shear deformability of the adherents is taken into account. The numerical results of a finite element analysis are presented and discussed. Suggestions for the design of adhesive lap joints are also given.

Axial/Bending Coupled Analysis for FRP Adhesive Lap Joints

In this paper a finite element analysis of the behavior of adhesive joints between FRP (fiber-reinforced polymers) adherents is presented. In particular, double-lap joints, in the case of both normal and shear/flexure stresses, are considered. The problem is nonlinear due to the mathematical formulation of the cohesive laws introduced to model the interfacial interactions. On the contrary, the adherents are supposed to be linear elastic up to failure. The common approach of analyzing shear/flexure behavior separately from extensional behavior, as well as disregarding the mutual effects between the normal and tangential stresses acting at the joint interfaces, has been updated. The paper takes into account the coupling effects between shear/flexure and extensional equilibrium problems. As highlighted in literature, only a coupled analysis can be considered correct when the mechanical characteristics of the adherents are quite different, as usually occurs in practice. Furthermore it also has been assumed that the adherents are shear deformable. The numerical results obtained by such an approach are presented, discussed and compared with others available in literature.

A Refined Finite Element Formulation for the Microstructure-Dependent Analysis of Two-Dimensional (2D) Lattice Materials

A finite element approximation is proposed for the dynamic analysis of two-dimensional (2D) lattice materials. The unit cell is modeled by means of a defined number of shear deformable micro-beams. The main innovative feature concerns the presence of a microstructure-dependent scale length, which allows the consideration of the so called size-effect that can be highly relevant, due to the characteristics of the lattice at the local scale. Some numerical results show the influence of the microstructure parameter on the dynamic behavior of two-dimensional lattice materials.

Concrete Open-Wall Systems Wrapped with FRP under Torsional Loads

The static behavior of reinforced concrete (RC) beams plated with layers of fiber-reinforced composite material (FRP) is widely investigated in current literature, which deals with both its numerical modeling as well as experiments. Scientific interest in this topic is explained by the increasing widespread use of composite materials in retrofitting techniques, as well as the consolidation and upgrading of existing reinforced concrete elements to new service conditions. The effectiveness of these techniques is typically influenced by the debonding of the FRP at the interface with concrete, where the transfer of stresses occurs from one element (RC member) to the other (FRP strengthening). In fact, the activation of the well-known premature failure modes can be regarded as a consequence of high peak values of the interfacial interactions. Until now, typical applications of FRP structural plating have included cases of flexural or shear-flexural strengthening. Within this context, the present study aims at extending the investigation to the case of wall-systems with open cross-section under torsional loads. It includes the results of some numerical analyses carried out by means of a finite element approximation.

Time-Dependent Behavior of Reinforced Polymer Concrete Columns under Eccentric Axial Loading

Polymer concretes (PCs) represent a promising alternative to traditional cementitious materials in the field of new construction. In fact, PCs exhibit high compressive strength and ultimate compressive strain values, as well as good chemical resistance. Within the context of these benefits, this paper presents a study on the time-dependent behavior of polymer concrete columns reinforced with different bar types using a mechanical model recently developed by the authors. Balanced internal reinforcements are considered (i.e., two bars at both the top and bottom of the cross-section). The investigation highlights relevant stress and strain variations over time and, consequently, the emergence of a significant decrease in concrete’s stiffness and strength over time. Therefore, the results indicate that deferred effects due to viscous flow may significantly affect the reliability of reinforced polymer concrete elements over time.

Fabric-Reinforced Cementitious Matrix (FRCM): A New Italian Guideline under Development

In addition to Fibre-Reinfoced composite materials, which are made of long glass/carbon/aramid fibers embedded in a polymer matrix (FRP), the use of FRCM composites (Fabric-Reinforced Cementitious Matrix) is becoming more and more widespread. As far as this specific case, the inorganic matrix guarantees many advantages, especially when dealing with masonry substrates, including a good compatibility from both a physical and a chemical point of view and the possibility of wet lay-up application. Despite their wide use in technical applications, the constitutive behavior and the failure mechanisms of FRCMs have not been adequately studied. As a consequence, a final assessment upon which criteria have to be used for verification and qualification of FRCMs is still missing. In the context of a recent experimental program-still under development-cooperated by many Italian academic laboratories, that is aimed at detecting the main features of the constitutive behavior of these materials, a discussion seems to be appropriate on the initial experimental results obtained at Salerno University on many FRCM specimens tested under uniaxial tensile loads.

STRUCTURAL ANALYSIS OF ADHESIVE BONDING FOR THICK-WALLED TUBULAR COMPOSITE PROFILES

Abstract A mechanical model for predicting the response of a GFRP tubular truss member glued to terminal (nodal) devices is presented. The given model captures shear deformation and simulates adhesion between the composite tube and the nodal devices via an appropriate cohesive interface. A comparison between theoretical and experimental results highlights a very good theory-experiment matching in terms of failure load and global displacements.

2D LATTICE STRUCTURES - A PARAMETRIC ANALYSIS

As discussed in a number of papers, both the static and the dynamic response of square lattice materials are strongly affected by the inner microstructure. It is worth noting that results obtained without considering this influence are totally misleading, especially if non-uniform changes in terms of stresses and strains are concerned at the local scale. Within this context, the present work focuses on a parametric analysis aimed at evaluating the influence of the main mechanical properties of RUC on the dynamic response of a 2D square lattice, thus extending previous results towards the condition of a possible different nonuniform mass density distribution over the RUC configuration. The existence of the band gaps within the low frequency region is searched as well as the position and width of the existing gaps are evaluated by means of a numerical strategy already developed and tested. 4986 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 4986-4999