1,721,053 research outputs found
Elasticità di un materiale micro-strutturato modellato con elementi rigidi e relazione con un ortotropo di Cosserat
No full textThe macroscopic modelling of in-plane elastic behaviour of composite solids made with regular orthotropic texture is the object of the present study. In this field, a specific approach has been recently proposed by the author, based “rigid elements” whose mechanical characteristics are directly identified from the composite response without homogenization [1]. The theoretical relation between an orthotropic Cosserat continuum and the proposed rigid elements is explicitly given here. Then, referring to masonry-like textures, the elastic moduli of the corresponding Cosserat continuum are evaluated, and the passage to the rigid element model is performed. Depending on various factors, numerical results evidentiate the impact of the composite texture on the strain field map at the micro and macro-scale, with different shear responses of the vertical and horizontal joints and the local rotation of the blocks. Finally, the capability of the proposed rigid elements to discern at the macro-scale the different behaviour of composite materials as a function of their texture and the scale effects are pointed out
Modellazione ad Elementi Rigidi Piani di Facciate in Muratura
No full textNell'ambito delle analisi di vulnerabilità sismica di edifici storici si presenta una modellazione strutturale che sfrutta in modo determinante l'osservazione dei quadri di danno verificatisi nella realtà [Doglioni, 1994]. In particolare si studia il sistema facciata-parete laterale delle chiese [Casolo, 1997] dove i danneggiamenti sono dovuti generalamente alle flessioni fuori piano con lesioni che tendono a suddividere le facciate in zone quasi rigide e zone molto deformabili. La struttura viene modellata come un assemblaggio di elementi rigidi quadrilateri interconnessi attraverso interfacce collocate nei punti medi dei lati. L'analisi numerica è rivolta a stabilire in particolare il degrado delle singole interfacce con risultati in buon accordo con i quadri fessurativi rilevati in seguito a terremoti violenti
Significant groung motion parameters for evaluation of the seismic performance of slender masonry towers
No full textThe evaluation of seismic risk of masonry monuments requires to study the combination of vulnerability and hazard. In the present work, the global seismic response of slender masonry towers
has been studied by means of a specific 3-D fibre model. Accounting for the particular behaviour of such structures, the hazard should also be described by a suitable measure of intensity of the seismic action. A variety of different parameters relating with the ground acceleration recordings have been investigated for what regards their correlation with the damage indicators of the model.
The combination of the peak ground velocity of the horizontal component and of the significant duration is an effective measure of intensity. This measure can be improved by considering the accord of the frequency content of the ground motion with the dynamical characteristics of the tower. Since in some cases the effect of the vertical component proved to be important, a further improvement can be obtained by taking into account also the vertical ground motion intensity
Macro-scale modelling of the damage evolution of micro-structured material by a specific rigid element model
No full textA specific rigid element model for macro-scale dynamics of monumental masonry considering damage and micro-structure effects
No full textIn-plane dynamics of masonry walls by rigid elements: elastic behaviour and micro-structure effects
No full text
Macroscale modelling of microstructure damage evolution by a rigid body and spring model
No full textA mechanistic approach is presented for macroscale modelling of a structured solid material. The model consists of an assemblage of rigid mass-elements connected to each other by normal and shear line-springs at each side. The characteristics of these springs govern the macroscopic behaviour of the model that is able to incorporate an internal length and a polarity, in analogy with an orthotropic Cosserat solid material. The present numerical implementation addresses the in-plane modelling of a masonry-like composite whose main macroscopic constitutive aspects are: very low tensile strength, texture-dependent evolution of the damage, and orthotropy of shear strength and internal friction. The constitutive rules are assigned by following a heuristic approach, based on the main in-plane damage mechanisms that are identified at the mesoscale, on a representative volume element of the composite solid material. In particular, specific separate constitutive laws for the normal and the shear springs are adopted. Two numerical tests compare the present macroscale approach with a detailed finite element micromodelling, and demonstrate the capability of the proposed model to describe the main microstructure features of the damaging process with very few degrees of freedom
Modelling the out-of-plane seismic behaviour of masonry walls by rigid elements
No full textA computational model for evaluating the dynamical response and the degradation of masonry façades subjected to out-of-plane seismic actions is presented. The lateral actions are often the main cause of damage for the large plane walls of monuments subjected to strong earthquakes.
This is particularly evident for the façades and lateral walls of old masonry-built churches, where the crack patterns tend to subdivide the plane walls into a number of rigid blocks. The model assumes such walls as a series of quadrilateral plane rigid elements connected to each other in the middle of their adjoining sides. Only the out-of-plane displacements are considered, thence the connections are regarded as spherical elasto-plastic joints which allow rotations whose axis is in the plane of the undeformed wall. The hysteretic characteristics of these joints are defined so as
to approximate the brittle behaviour of masonry material and the degradation due to cyclic loadings. The numerical results obtained using a limited number of elements show that the global out-of-plane response of the masonry walls and the mechanical degradation at each connection are in accord with the observed behaviour of real churches hit by strong earthquakes
- …
