BR(Bs to mu+ mu-) as an electroweak precision test

Using an effective-theory approach, we analyze the impact of BR(Bs to mu+ mu-) in constraining new-physics models that predict modifications of the Z-boson couplings to down-type quarks. Under motivated assumptions about the flavor structure of the effective theory, we show that the bounds presently derived from BR(Bs to mu+ mu-) on the effective Z-boson couplings are comparable (in the case of minimal flavor violation) or significantly more stringent (in the case of generic partial compositeness) with respect to those derived from observables at the Z peak.Comment: 8 pages, 1 figure. v3: minor textual modifications; minor update in the numerics; no change in results. Matches journal version (PLB

ADVANCES IN RELIABILITY METHODS FOR REINFORCED CONCRETE STRUCTURES

L'abstract è presente nell'allegato / the abstract is in the attachmen

SEISMIC PERFORMANCE OF BRIDGES ISOLATED WITH DCFP DEVICES

The paper analyzes the influence of double concave friction pendulum (DCFP) isolator properties on the seismic performance of isolated bridges. The behavior of these systems is analyzed by employing an eight-degree-of-freedom model accounting for the first five vibra-tional modes of the pier and the presence of a rigid abutment, whereas the DCFP isolator behaviour is described combining two single FPSs in series. The uncertainty in the seismic input is taken into account by considering a set of natural records with different character-istics. The variation of the statistics of the response parameters relevant to the seismic per-formance is investigated through an extensive parametric study carried out for different sys-tem properties

MODEL UNCERTAINTIES IN NLFEAS OF RC SYSTEMS UNDER CYCLIC LOADS

This work is focused on the resistance model uncertainties in non-linear finite element anal-yses (NLFEAs) for reinforced concrete structures under cyclic loading conditions. In detail, different walls experimentally tested are numerically reproduced by means of appropriate plane stress finite elements (FE) structural models within different assumptions and numeri-cal codes. After that, the values of the global resistances computed through numerical simu-lations are compared to the experimental outcomes to evaluate the influence of the different assumptions on the mechanical behaviour of reinforced concrete members subjected to cy-clic loads

Comparison between non-linear numerical models for R.C. shear walls under cyclic loading

The non-linear behaviour of concrete structures is the result of a series of phenomena, as material non-linear constitutive law and cracking process. As a consequence, in order to understand the behaviour of reinforced concrete members from elastic field to ul-timate condition, is necessary to use instruments able to simulate the material damaging evolution under growing loads. Commer-cial non-linear finite elements codes are generally able to simulate concrete behaviour with good approximation when a progressive incremental load is applied. However, the same result could not be reached under a cyclic loading. In this work two commercial non-linear finite element codes have been considered in order to assess the skill of these codes to simulate non-linear concrete be-haviour under cyclic loading. The results of six laboratory tests on shear walls have been compared with the ones obtained by means of numerical models and some conclusions on the numerical predictions are presented. / Il comportamento non lineare delle strutture realizzate in calcestruzzo è il risultato di una serie di fenomeni, come la non linearità della legge costitutiva del materiale ed il processo di fessurazione. Al fine di comprendere il comportamento degli elementi struttura-li in calcestruzzo armato è necessario disporre di strumenti in grado di simulare il progressivo danneggiamento del materiale in pre-senza di carichi crescenti. In generale, i codici di calcolo presenti in commercio sono in grado di cogliere abbastanza bene il compor-tamento delle strutture in cemento armato soggette a carichi monotoni crescenti. Risulta invece più complesso seguire il compor-tamento strutturale in presenza di un carico ciclico. In questo lavoro sono stati considerati due diversi codici di calcolo non lineare agli elementi finiti al fine di verificare la loro capacità nel simulare il comportamento di pareti a taglio soggette a un carico ciclico. Sono stati considerati i risultati di sei prove di laboratorio disponibili in letteratura; tali risultati sono stati confrontati con quelli otte-nuti numericamente per trarre delle conclusioni sull’affidabilità dei modelli numerici

SEISMIC PERFORMANCE OF BRIDGES ISOLATED BY DCFP DEVICES: A PARAMETRIC ANALYSIS

The present investigation examines how the properties of the double concave friction pendulum (DCFP) devices influence the seismic performance of isolated multi-span continuous deck bridges. The numerical simulations are carried out using an eight-degree-of-freedom model to reproduce the elastic behavior of the pier, associated to the assumption of both rigid abutment and rigid deck, and the non-linear velocity-dependent behavior of the two surfaces of the double concave friction pen-dulum isolators under a set of natural records with different characteristics. The results in terms of the statistics related to the relevant response parameters are computed in non-dimensional form with respect to the seismic intensity considering different properties of both DCFP isolators and bridge

Influence of Slenderness on the Evaluation of Epistemic Uncertainty Related to Non-Linear Numerical Analysis of RC Columns

This investigation is devoted to quantify the epistemic uncertainty related to the nonlinear analysis of reinforced concrete columns characterized by high slenderness using numerical codes. The adoption of refined numerical tools, which are able to consider both mechanical and geometric non linearities, implies to perform assumptions and approximations with respect to reality. Whit reference to reliability analysis, these simplifications lead, inevitably, to additional uncertainties which are of epistemic nature. In fact, these uncertainties may be reduced by the engineers/analysts by increasing the level of refinement of the numerical model and/or increasing knowledge about parameters associated to material models. However, also numerical model established by expert engineers/analysts are affected by this kind of epistemic uncertainty. Accepting that the level of uncertainty associated to the experimental tests set are minimized, the epistemic uncertainty associated to non-linear numerical simulations can be quantified characterizing the model uncertainty random variable comparing the outcomes of numerical results to the associated experimental ones. The present investigation proposes the quantification of the model uncertainty related to non-linear numerical simulations of slender RC columns. A total number of 40 experimental results known from literature are herein selected in coherence with current Eurocodes specifications. The experiments are reproduced adopting non-linear numerical analysis differentiating between several modelling hypotheses (i.e., numerical code; materials models). The comparison between experimental and numerical results is adopted to characterize the most suitable probabilistic model for the model uncertainty random variable associated to non-linear numerical simulations of RC columns subjected to significant slenderness. The outcomes of the research are useful to provide background to the characterization of partial safety factor for model uncertainty in non-linear numerical analysis using the approach of the global resistance format for safety verifications

Prediction of Cracking Induced by Indirect Actions in RC Structures

Cracking of concrete plays a key role in reinforced concrete (RC) structures design, especially in serviceability conditions. A variety of reasons contribute to develop cracking and its presence in concrete structures is to be considered as almost unavoidable. Therefore, a good control of the phenomenon in order to provide durability is required. Cracking development is due to tensile stresses that arise in concrete structures as a result of the action of direct external loads or restrained endogenous deformations. This paper focuses on cracking induced by indirect actions. In fact, there is very limited literature regarding this particular phenomenon if compared to its high incidence in the construction practice. As a consequence, the correct prediction of the crack opening, width and position when structures are subjected to imposed deformations, such as massive castings or other highly restrained structures, becomes a compelling task, not so much for the structural capacity, as for their durability. However, this is only partially addressed by commonly used design methods, which are usually intended for direct actions. A set of non-linear analysis on simple tie models is performed using the Finite Element Method in order to study the cracking process under imposed deformations. Different concrete grades have been considered and analysed. The results of this study have been compared with the provisions of the most common codes

SEISMIC PERFORMANCE OF BRIDGES EQUIPPED WITH FPS

The scope of the present study is focused on the evaluation of the seismic response of bridges iso-lated by single concave sliding pendulum isolators (FPS) for the different structural properties when the presence of the rigid abutment is considered or neglected (i.e., isolated viaducts). In this way, they have been defined two specific multi-degree-of-freedom (mdof) models to simulate the elastic behavior of the reinforced concrete pier in combination to the infinitely rigid presence of the deck and to the presence of the rigid abutment if considered. Both the numerical models also account for the non-linear velocity-dependent behavior of the FPS bearings. Considering the alea-tory uncertainty in the seismic input by means of several natural records with different character-istics, a parametric analysis is developed for several structural properties. The relevant results ex-pressed as the statistics in non-dimensional form with respect to the seismic intensity have permit-ted to study the differences between the two numerical models in relation to the effectiveness of the seismic isolation

Seismic reliability-based design of hardening structures equipped with double sliding devices

This study deals with seismic reliability-based design (SRBD) relationships in terms of beha-vior factors and displacement demands for hardening structures equipped with double fric-tion pendulum system (DFPS) bearings. An equivalent 3dof system having a hardening post-yield slope is adopted to describe the superstructure behavior, whereas velocity-dependent laws are assumed to model the responses of the two surfaces of the DFPS. The yielding cha-racteristics of the superstructures are defined for increasing behavior factors in compliance with the seismic hazard of L’Aquila site (Italy) and with NTC18 assuming a lifetime of 50 years. Considering several natural seismic records and building properties under the hypo-thesis of modelling the friction coefficients of the two surfaces of the DFPS as random variables, incremental dynamic analyses are performed to evaluate the seismic fragility and the seismic reliability of these systems. Finally, seismic reliability is evaluated and seismic relia-bility-based design (SRBD) curves for the two surfaces of the double sliding devices are de-scribed