Ricerc@Sapienza

An experimental investigation was conducted to evaluate both residual capacity and the damage of the concrete material in previously damaged RC columns. Three circular columns, each caged to provide low, medium, and high level of confinement, were axially loaded to failure. All damaged columns were then cut into three pieces, and two cored cylinders were taken from each piece. The first core was prepared and instrumented for compression, whereas the second was sliced into a number of 25-mm disks for permeability testing.

Instability failure (also referred to as out-of-plane instability) has been observed in several experimental studies conducted on seismic performance of rectangular structural walls under in-plane loading. Observation of this failure pattern in some well-confined modern walls during the 2010 Chile and the 2011 Christchurch earthquakes has raised concerns about the reliability of current design code provisions.

Since 2010, twelve post-tensioned timber (Pres-Lam) buildings have been constructed throughout the world. The technology relies on unbonded post-tensioning tendons to provide moment capacity to beam-column, wall-foundation, or column-foundation connections. Supplemental energy dissipation can be introduced by mild steel bars or replaceable damping devices when designing buildings for high seismic risk areas. Creep within the timber elements leads to losses in post-tensioning force over time.

Fiber Reinforced Polymers (FRP) material are proposed and implemented for civil engineering applications for both retrofitting of existing structures and building of new facilities. In new construction realizations, FRP elements are frequently manufactured using pultrusion that represents a high rate manufacturing method, however characterized by a prevalent longitudinal fiber orientation with consequently weakness along the directions different than the longitudinal one.

It is well known that the incidence angle of seismic excitation has an influence on the structural response of buildings, and this effect can be more significant in the case of near-fault signals. However, current seismic codes do not include detailed requirements regarding the direction of application of the seismic action and they have only recently introduced specific provisions about near-fault earthquakes. Thus, engineers have the task of evaluating all the relevant directions or the most critical conditions case by case, in order to avoid underestimating structural demand.

A nonlocal damage-plastic model is proposed to investigate the mechanical response of masonry elements, under static and dynamic actions. The adopted constitutive relationship is able to capture degrading mechanisms due to propagation of microcracks and accumulation of irreversible strains. Moreover, the stiffness recovery, due to re-closure of tensile cracks when material undergoes compression strains, is taken into account to properly simulate the masonry cyclic response.

In this paper, identification of energy dissipation in the joints of a lab-scale structure is accomplished. The identification is carried out by means of an energy flow analysis and experimental data. The devised procedure enables to formulate an energy balance in the vicinity of the joints to obtain local energy dissipation. In this paper, a damping matrix based on the locally identified damping coefficients is formulated. The formulated damping matrix is later used in a five-degrees-of-freedom (5DOF) system for validation.

This paper describes the simulation of RC members with a three-dimensional (3D), 2-node beam finite element (FE) that includes warping of the cross section. A previously proposed FE formulation is extended to allow the description of structural members with softening material behavior. The governing equations are derived from an extended four-field Hu-Washizu variational principle, with independent interpolation of the warping displacement field from the rigid section displacement, the generalized section deformation, and the material stress fields.

In this work the multi-mode vibration absorption capability of a nonlinear metamaterial beam is investigated. A Euler–Bernoulli beam is coupled to a distributed array of nonlinear spring–mass subsystems acting as local resonators/vibration absorbers. The dynamic behavior of the metamaterial beam is first investigated via the classical approach employed for periodic structures by which the frequency stop bands of the single cell are determined.

We present a finite element discrete model for pantographic lattices, based on a continuous Euler–Bernoulli beam for modeling the fibers composing the pantographic sheet. This model takes into account large displacements, rotations and deformations; the Euler–Bernoulli beam is described by using nonlinear interpolation functions, a Green–Lagrange strain for elongation and a curvature depending on elongation. On the basis of the introduced discrete model of a pantographic lattice, we perform some numerical simulations.