55,984 research outputs found
Literature review of the in-plane behavior of masonry walls: Theoretical vs. experimental results
No full textIn-plane strength of masonry walls is affected by the resistant mechanisms activated in the walls, i.e., related to flexural or shear behavior. The latter one can occur in the walls according to different failure modes depending on both mortar and unit strengths and on the type of assembling, i.e., ‘regular’ or ‘irregular’ texture. In this paper, a critical review of the existing design formulations for the in-plane strength of masonry walls is firstly presented, with important information on the achievable failure modes depending on the geometrical and mechanical features of the masonry fabric. Then, experimental tests are collected from the literature and a comparison between theoretical and experimental results is carried out. The presented analyses are aimed to highlight the differences between the existing formulations and to identify the most suitable ones
In-plane behaviour of masonry walls: Numerical analysis and design formulations
No full textThis paper presents the results of several numerical analyses aimed at investigating the in-plane resistance of masonry walls by means of two modelling approaches: a finite element model (FEM) and a discrete macro-element model (DMEM). Non-linear analyses are developed, in both cases, by changing the mechanical properties of masonry (compressive and tensile strengths, fracture energy in compression and tension, shear strength) and the value of the vertical compression stress applied on the walls. The reliability of both numerical models is firstly checked by means of comparisons with experimental tests available in the literature. The analyses show that the numerical results provided by the two modelling approaches are in good agreement, in terms of both failure loads and modes, while some differences are observed in their load-displacement curves, espe-cially in the non-linear field. Finally, the numerical in-plane resistances are compared with the theoretical formulations provided by the Italian building code for both flexural and shear failure modes and an amendment for the shape factor ‘b’ introduced in the code formulation for squat walls is proposed
Modelling Strategies for the In-plane Behaviour of Iron-framed Masonry Structures: Parametric Analysis on Simple Panels and a Church Façade
No full textAn atypical ‘baraccato’ system made of masonry walls encaged in iron frames was realized in the Ischia Island after the earthquake of 1883; an interesting example is represented by the Santa Maria Maddalena Church. Unfortunately, while several experimental and numerical studies can be found in the recent literature for traditional ‘baraccato’ systems (mixed timber and masonry elements), no information is available for iron-framed masonry structures. To fill this gap, the paper presents several parametric non-linear static analyses with reference to, firstly, simple iron-framed masonry panels and, successively, the façade of the Santa Maria Maddalena Church. All the numerical analyses were carried out by means of two modelling approaches with different levels of detail, i.e. finite element (FE) and discrete macro-element (DME) models. The numerical analyses allowed to: assess the reliability of the two models (FE and DME) into predicting similar results for the panels and the church façade with reference to both the unstrengthened and the iron-framed strengthened configurations; analyse the influence of the investigated parameters; evaluate the contribution of the iron frames on the overall behaviour of the strengthened masonry elements; and drive the choice of the most suitable modelling strategy for the whole church
Hart’s blind spot. The missing piece in The Concept of Law
No full textAl inicio de El Concepto de Derecho, Hart sugiere una asimilación errónea entre conducta que es «no opcional» y conducta que es «obligatoria» (i. e. conducta que o es forzada o sometida a una obligación). Esta asimilación vicia el argumento del libro en su conjunto, llevándole a Hart a descuidar las diferentes vías en las que el derecho monitorea, corrobora o constituye relaciones de poder. Es cierto y evidente que en The Concept of Law la atención se dedica a los poderes normativos, legales. Sin embargo, el poder social bruto, y las relaciones del derecho con él —el papel del derecho como una pieza en la maquinaria de los poderes sociales— están ampliamente ignorados. Éste es, de alguna manera, el ángulo muerto de Hart. Enuncio algunas de las vías, aparte de la coerción u obligación, en las que el derecho puede servir, corroborar o ser un instrumento de poder social. También muestro que el tratamiento de Hart de las relaciones entre el derecho y el poder político, en The Concept of Law, es insatisfactorio. Tanto su reconstrucción de la surgimiento ideal de un sistema jurídico desarrollado y el argumento que sustenta «el contenido mínimo del derecho natural» presuponen la idea de un grupo social en el que no subsisten relaciones de poder.At the beginning of The Concept of Law Hart suggests a mistaken assimilation between conduct that is «non-optional» and conduct that is «obligatory» (i. e. conduct that is either coerced or subject to an obligation). This suggested assimilation vitiates the argument of the whole book, leading Hart to neglect the different ways in which the law typically tracks, corroborates or constitutes power relations. It is true that, famously, attention is paid, in The Concept of Law, to normative, legal powers. Brute social power, and law’s relation to it —the role of law as a cog in the workings of social powers—, however, are largely overlooked. This is, in a way, Hart’s blind spot. I list some of the ways, other from coercion or obligation, in which the law may happen to serve, corroborate or be an instrument of social power. I also show that Hart’s treatment of the relations between the law and political power, in The Concept of Law, is unsatisfactory. Both his reconstruction of the ideal genesis of a developed legal system and the argument supporting a «minimal content of natural law» presuppose the idea of a social group in which no power relationships subsist
A Dynamic Subfilter-scale Stress Model for Large Eddy Simulations Based on Physical Flow Scales
No full textWe propose a new definition of the length scale in an eddy-viscosity model for large-eddy simulations (LES). This formulation extends and generalizes a previous proposal [Piomelli, Rouhi and Geurts, Proc. ETMM10, 2014], in which the LES length scale was expressed in terms of the integral length-scale of turbulence determined by the flow characteristics and explicitly decoupled from the simulation grid; this approach was named Integral Length-Scale Approximation (ILSA). As in the original ILSA, the model coefficient was determined by the user, and required to maintain a desired contribution of the unresolved, subfilter scales (SFS) to the global transport. We propose a local formulation (local ILSA) in which the model coefficient is local in space, allowing a precise control over SFS activity as a function of location. This new formulation preserves the properties of the global model; application to channel flow and backward-facing step verifies its features and accuracy
Large-eddy simulation of a separated flow with a sub-filter scale model based on the integral length-scale
No full textA new sub-filter scale model for large-eddy simulations, which uses a length-scale proportional to the integral scale of the turbulence instead of the grid resolution to parametrize the modelled stresses, will be assessed in the prediction of the flow of a boundary-layer over a rough surface, which includes separation and reattachment
Near Wall PIV-Measurements on the Windward Slope of a Hill
No full textThe turbulent flow over periodic hills was measured near to the wall, using planar Particle-Image-Velocimetry (PIV) at high spatial resolution. Our focus is on the near wall turbulence structure on the windward slope of the hill. For large-eddy simulation (LES) we suspect that, if this was not predicted accurately, it affects the prediction of the velocity profiles over the hill crest which in turn will affect the recirculation length downstream of the hill. Regarding the time averaged velocities, we were able to resolve the linear viscous region of the boundary layer. The velocity distribution and also the Reynolds stress does not comply with the law of the wall as it is valid for a turbulent boundary layer at equilibrium
Energy dissipation and flux laws for unsteady turbulence
No full textDirect Numerical Simulations of spatially periodic unsteady turbulence show that the high Reynolds number scalings of the instantaneous energy dissipation rate and interscale energy flux at intermediate wavenumbers are qualitatively different from the well-known cornerstone scalings of equilibrium turbulence where and are time-dependent rms velocity and integral length-scales. Instead, they both scale as where and are length and velocity scales characterizing initial/overall unsteady turbulence conditions
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