On Safety Assessment and Base Isolation of Heavy Non-structural Monolithic Objects

Abstract Under seismic actions heavy non-structural objects, which are usually placed at the top of existing constructions, may constitute a danger to human lives and a considerable loss for world heritage. In this contribution, safety assessment of non-structural monolithic objects is discussed through the illustration of a case study, which concerns seismic protection of eleven ancient marble decorative pinnacles placed at the top of a three-arched masonry city gate in Ferrara (ITALY). A method for assessing the safety of the underlying masonry structure under the action of seismic excitations is outlined and the amplification of the ground motions due to the presence of such structure is evaluated

On the analysis of membranes stretched over a unilateral support by B.E.M.

The resolution of membranes stretched over a unilateral, frictionless, rigid (or deformable obstacle) is considered by employing BE methods and performing a suitable domain discretization of the unknown support reaction. As in the case of domain-type techniques algebraic formulations in the form of a linear complementarity problem are obtained, whose coefficient matrices are shown to be symmetric negative definite 'up to the discretization errors'. The problem could also be solved by making a constrained Trefftz functional stationary, from which, by means of an indirect BE method, a linear complementarity problem with a symmetric coefficient matrix follows directly

A finite element multifield model for critical loads of composite laminated plates

Fibre-reinforced plates and shells are finding an increasing interest in engineering applications, because they are light-weight and provide a high stiffness over weight ratio. Consequently, efficient and robust computational tools are required for the analysis of such structural models. It should be remarked that because of their slenderness these structural elements require a careful evaluation of their safety with reference to buckling phenomena

Verifiche sperimentali di prodotti industriali a base cementizia rinforzati con microfibre polimeriche

In questo lavoro si presentano i risultati sperimentali di una ricerca volta a valutare il comportamento meccanico di malte rinforzate mediante l’inserimento di fibre corte polimeriche da utilizzarsi in processi di produttivi industriali di estrusione. Un’estesa campagna prove di cui si è riferito in precedenza ha reso possibile la valutazione delle miscele, fibrorinforzate con fibre polimeriche, più prestanti nella realizzazione di prodotti estrusi tramite processi di tipo industriale. Infatti poiché la produzione industriale si basa usualmente su un processo di estrusione vengono nella pratica utilizzati rapporti sabbia-cemento molto più grandi di quelli in genere riportati nella letteratura tecnica sugli ECC. La campagna di prove viene completata con ulteriori prove di flessione e con prove di compressione e trazione diretta. Nello svolgimento delle prove, ove possibile, si è fatto riferimento alle normative esistenti. Scopo della ricerca è inoltre verificare se l’approccio proposto dalla CNR DT 204 proposta per calcestruzzi fibrorinforzati con fibre metalliche e gettati in opera, è ancora utilizzabile per elementi ottenuti mediante processi industriali e rinforzati con fibre polimeriche. A tal fine i modelli semplificati proposti nella letteratura tecnica vengono utilizzati per simulare i risultati della prova di flessione e risultano dare indicazioni attendibili sul comportamento di manufatti allo Stato Limite Ultimo

Fast kinematic limit analysis of FRP-reinforced masonry vaults. II: Numerical simulations

A new approach for limit analysis of masonry vaults retrofitted with fiber-reinforced polymers (FRPs) based on an upper bound formulation is presented. Part I of this paper was devoted to detailing the theory on which this approach relies. The main idea consists of exploiting properties of nonuniform rational b-spline (NURBS) functions to develop a computationally efficient adaptive limit analysis procedure, which allows quick evaluation of the collapse load multiplier of any given FRP-reinforced masonry vault starting from its three-dimensional (3D) model, which can be generated within any free-form modeler natively working with NURBS entities. A suitably devised genetic algorithm (GA) governs mesh adaption. The present Part II is devoted to validating and discussing through numerical simulations the proposed GA-NURBS procedure. Several structural examples of masonry vaults, including two distinct arches (a straight parabolic barrel vault and a skew parabolic arch, respectively), a hemispherical dome, and both cloister and cross vaults are investigated. Each example is analyzed considering both the unreinforced configuration and the presence of FRP reinforcements. Moreover, comparisons with both nonlinear finite-element (FE) simulations and data collected from experiments (where existing) are presented to assess the proposed GA-NURBS limit analysis procedure. It is shown that, for all cases analyzed, this model allows reliable prediction of both collapse mechanisms and failure loads. The present GA-NURBS approach turns out to be a promising tool that may be conveniently used by practitioners who seek a quick and reliable way to evaluate the outcome of restoration interventions based on the application of FRP composites

Danneggiamento non locale con il metodo degli elementi di contorno

A nonlocal integral formulation for elastic-damaged materials is presented. The approach offers the possibility to simulate the mechanical behaviour of history-dependent materials, irreversibly degenerating under mechanical loads. The model is briefly introduced by the aid of thermodynamical considerations. The Boundary Element Method (BEM) is applied in order to obtain numerical results. This numerical strategy avoids the appearance of stress oscillation patterns occurring for certain Finite Element models

A F.E. Limit analysis software for FRP-reinforced masonry buildings subjected to Horizontal loads

A 3D homogenized FE limit analysis software for the prediction of collapse loads and failure mechanisms of masonry buildings reinforced with FRP strips is presented. A two step approach is adopted: in step I masonry failure surfaces are obtained through a kinematic FE approach in the representative element of volume (REV), constituted by a brick interconnected with its six neighbors. 8-noded rigid infinitely resistant parallelepiped elements interconnected with interfaces with frictional behavior and limited tensile and compressive strength are utilized to model the REV. A linear programming problem in few variables is obtained, suitable to predict masonry failure surfaces. Homogenized surfaces are implemented in the FE kinematic limit analysis software for an inexpensive evaluation of collapse loads of entire buildings. Delamination is considered, giving FRP masonry interfaces a limited resistance in agreement with Italian code CNR-DT-200. Six noded rigid infinitely resistant 3D wedge shaped elements are used to model the homogenized masonry, whereas for FRP three noded rigid elements are utilized. A two story small masonry house reinforced with FRP strips is analyzed to evaluate the increase of the load bearing capacity of the entire building due to the FRP