Limit Analysis for Historical Masonry Bridge with CFRP Reinforcements

The paper deals with the collapse behavior of a historical masonry arch bridge subject to combined seismic loads, by means of the limit analysis and shakedown theorems. The assessment of the collapse loads and shakedown multiplier have been analyzed using lower bound theorems of the limit analysis and shakedown theory. The retrofitting consists in the application of CFRP strips on the extrados of the arch with a significant increase of the collapses and shakedown multipliers. The results of a FEM analysis have been achieved with ANSYS code involving the non-linear material behavior and the structural role of the spandrel walls and filling

Equilibrium of masonry vaults and open stairs

In this paper the unilateral model for masonry is applied to explain the equilibrium of vaults. In particular, the present study is concerned with the application of the safe theorem of limit analysis to spiral vaults, that is, curved constructions modeled as continuous unilateral bodies. On allowing for singular stresses in the form of line or surface Dirac deltas, statically admissible stress fields concentrated on surfaces (and on their folds) lying inside the masonry, are considered. The unilateral restrictions require that the membrane surface lies in between the extrados and intrados surfaces of the vault and that the stress function, representing the stress, be concave. Such a constraint is, in general, not satisfied on a given shape for given loads: in such a case, the shape has to be modified to fit the constraint. A particular application, namely the double spiral stair of Sanfelice’ palace in Naples, is considered

Constitutive behaviour of quasi-brittle materials with anisotropic friction

This paper presents an approach to a constitutive model for anisotropic quasi-brittle materials, developed in the framework of rate independent softening plasticity, involving a yield criterion in which an anisotropic friction tensor is involved. It turns out to be useful for materials characterized by ultimate behaviour which varies according to the direction, such as composite materials, anisotropic rocks, textiles, masonry. A geometrical representation of the limit domain in the case of plane stress, together with the results of laboratory tests is presented and discussed

Out of plane behaviour of unreinforced masonry walls

The behaviour of unreinforced masonry walls has been widely investigated in order to assess the seismic vulnerability of masonry structures. Even if partial analyses are not sufficient for a full structural analysis under seismic actions, they can be used to have quick estimation of both collapse load and failure mechanisms. Simplified out-of-plane collapse mechanisms, taking into account connections with floor and transversal walls, are considered to evaluate the behaviour of masonry walls subjected to out of plane forces. In general cantilever walls and walls supported only at the top and bottom edges can be represented as equivalent SDOF system, in order to evaluate by simple static analysis the limit horizontal force at the threshold of rocking, assuming that the wall has cracked and hence the tensile strength of the mortar can be neglected. Similarly, the displacement at the threshold of overturning can be obtained from that simple kinematic model. The value of the collapse load and the consequent load-displacement behaviour is strongly related to the way of computing the displacements and to the way of cracking. This paper presents some remarks on the evaluation of the effective secant stiffness of an unreinforced masonry wall in out of plane loading. Comparisons with the Priestley model are shown

Seismic vulnerability reduction of existing masonry buildings. Modelling of retrofitting techniques

In many seismically active regions of the world there are large numbers of masonry buildings. Most of these buildings have not been designed for seismic loads. Recent earthquakes have shown that many such buildings are seismically vulnerable and should be considered for retrofitting. Different conventional and unconventional retrofitting techniques are available to increase the strength and/or ductility of unreinforced masonry walls. This paper reviews and discusses seismic retrofitting of masonry walls with emphasis on the conventional techniques. Retrofitting procedures are discussed with regard to a case study: a stone masonry building in Irpinia region, damaged by the 1980 earthquake. The interventions are evaluated by means of finite elements with a macroelement model obtained by means of an homogenization technique. Linear and nonlinear procedures are compared, and peculiarities of each procedure are shown

3D F.E.M. Analysis of a Roman Arch Bridge

The rehabilitation and conservation has shown in recent years the need of reliable methods for assessing masonry arch bridges: it is important not only to maintain ancient structures in good conditions, but also, when necessary, to be able to estimate their safety factor as accurately as possible. Starting from a real case, this paper presents the results of a 3D FEM analysis of a stone masonry arch bridge, performed involving non-linear material behaviour, in which the structural role of the spandrel walls and filling is involved

Influence of test conditions on mechanical properties of yellow tuff specimens

This paper describes an experimental investigation of strength properties of tuff specimens. Parameters involved in the testing procedure are shape, moisture conditions, friction between testing machine platen and specimen. The number of tests is enough to define the statistical dependence of compressive strength on the four test conditions performe