IRIS - UNIRSM (Univ. degli Studi della Repubblica di San Marino)
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A numerical model for the dynamic analysis of inclined pile groups
No full textThe paper presents a numerical model for the dynamic analysis of pile groups with inclined piles in horizontally layered soil deposits. Piles are modelled with Euler-Bernoulli beams, while the soil is supposed to be constituted by independent infinite viscoelastic horizontal layers. The pile-soil-pile interaction as well as the hysteretic and geometric damping is taken into account by means of two-dimensional elastodynamic Green's functions. Piles cap is considered by introducing a rigid constraint; the condensation of the problem permits a consistent derivation of both the dynamic impedance matrix of the soil-foundation system and the foundation input motion. These quantities are those used to perform inertial soil-structure interaction analyses in the framework of the substructure approach. Furthermore, the model allows evaluating the kinematic stress resultants in piles resulting from waves propagating in the soil deposit, taking into account the pile-soil-pile interactions. The model validation is carried out by performing accuracy analyses and comparing results in terms of dynamic impedance functions, kinematic response parameters and pile stress resultants, with those furnished by 3D refined finite element models. To this purpose, classical elastodynamic solutions are adopted to define the soil-pile interaction problem. The model results in low computational demands without significant loss of precision, compared with more rigorous approaches or refined finite element model
Un' “Armonia” discordante. Alcune puntualizzazioni sul (P. Dura 10) Diatessaron di Taziano
No full textKinematic Bending Moments in Square Pile Groups
No full textThis paper describes kinematic seismic interaction analysis of square pile groups in homogeneous soil deposits, focusing on bending
moments induced by the transient motion. Analyses were performed by means of a three-dimensional (3D) numerical procedure able to
account for both pile–soil–pile interaction and radiation damping. The seismic motion was defined by an artificial accelerogram at the outcropping
bedrock, and one-dimensional (1D) propagation analyses were performed to define the free-field motion within the deposits. An extensive
parametric study was conducted to determine the effects of different variables, such as the soil properties, the bedrock location, the number of
piles, and the pile spacing, on the dynamic response of pile-group foundations. Bending moments obtained from the analyses of the pile group,
both at the pile head and at the interface separating soil layers, were normalized with respect to the single-pile bending moments, allowing for
the proposal of a new design formula for the estimation of the kinematic bending moments in the most stressed pile of the group, starting from
the knowledge of the single-pile response. The proposed formula was used, in conjunction with some simplified approaches that allow estimation
of the single-pile response, to evaluate bending moments in the analyzed pile groups. The adequacy of the formula for design purposes is
demonstrated
A fuzzy lot-sizing problem with two-stage composite human learning
No full textDue to the repetitive nature of inventory planning over the planning horizon, the operator in charge has to perform planning tasks repetitively, and consequently s/he becomes more familiar with the tasks over time. Familiarity with the tasks suggests that learning takes place in inventory planning. Even though the operator’s learning over time might improve his/her efficiency, prior research on fuzzy lot-sizing problems mostly overlooked the effect of human learning in their models and its impact on the operator’s performance. To close the research gap in this area, this paper models the operator's learning in a fuzzy economic order quantity model with backorders. The paper models a situation where the operator applies the acquired knowledge over the cycles in setting the fuzzy parameters at the beginning of every planning cycle, where his/her learning ability includes the cognitive and motor capabilities of a human being. Subsequently, a mathematical model which takes account of a two-stage human learning over the planning cycles is developed, which is then analytically investigated using sample data-sets. The results indicate that both operator’s capabilities, cognitive and motor, affect the efficiency of the fuzzy lot-sizing inventory model, but the influence of the cognitive capability is more profound, which in turn suggests the importance of training programmes for the workforces. The results of the sensitivity analysis also draw some managerial insights for the case that some model parameters vary over the planning horizon
Laminated Composite Doubly-Curved Shell Structures I. Differential Geometry. Higher-Order Structural Theories
No full textThe title, “Laminated Composite Doubly-Curved Shell Structures. Differential Geometry and Higher-order Theories” illustrates the theme treated and the prospective followed during the composition of the present work. The aim of this manuscript is to analyze the static and dynamic behavior of thick and moderately thick composite shells through the application of the Differential Quadrature (DQ) method.
The book is divided into two volumes wherein the principal higher order structural theories are illustrated in detail and the mechanical behavior of doubly-curved structures are presented by several static and dynamic numerical applications. In particular, the first volume is mainly theoretical, whereas the second one is mainly related to the numerical DQ technique and its applications in the structural field.
The starting point to analyze higher-order structural theories is given by the so-called Carrera Unified Formulation (CUF), which allows to consider and study several kinematic models in a unified manner. Both the Equivalent Single Layer (ESL) and Layer-Wise (LW) approaches are presented. A particular attention is paid to composite materials, due to their increasing development and use in many engineering fields during the last years
Assessing performance of Workload Control in High Variety Low Volumes MTO job shops: A simulative analysis
No full textThis paper deals with Workload Control (WLC), one of the best techniques to control Work In Process (WIP) and to stabilize Lead Time (LT) in job-shop systems. Our focus is on the job release strategy and, specifically, on the selection and dimensioning of suitable norms; a challenging problem, which is often the cause of the little industrial use of WLC. Specifically, our aim is to assess whether or not the use of easy to implement norms, appealing also from an operating point of view, may be enough to boost performance of a productive system. To this aim, a thorough discrete events simulation was made, considering a realistic job-shop environment in different operating conditions. Job release was subjected by WLC, regulated by two consolidated norms (i.e., Shop-Load and Bottleneck-Load) and by a novel one, which leverages on the grouping of jobs into families. Obtained outcomes are highly satisfactory, since good performances, in terms of WIP minimization and Due Dates compliance can be obtained, especially in highly constrained productive environments
Quali formatori per la sicurezza sul lavoro?
No full textIl saggio analizza la recente disciplina della qualificazione dei formatori in materia di sicurezza sul lavoro.
Dopo aver esaminato anche criticamente i vari criteri previsti nel decreto del 6 marzo 2013, il saggio
focalizza alcune questioni legate alle responsabilità del datore di lavoro nel caso in cui non osservi le regole
del decreto. In conclusione si formulano alcune proposte per migliorare il quadro della qualificazione dei
formatori in materia di sicurezza sul lavoro
LA NOSTRA ESPERIENZA PRESSO L’AMBULATORIO DI COMPLICANZE DA FILLER ALLA SAPIENZA UNIVERSITÀ DI ROMA
No full textCon il termine “filler”, (dall’inglese “to fill”=riempire) si definisce una sostanza, di varia natura,
che può essere iniettata nei tessuti molli al fine di migliorare i volumi e gli effetti
dell’invecchiamento L’utilizzo di tali materiali è aumentato notevolmente negli anni. L’incremento
del numero di utilizzatori, del numero e varietà di sostanze, l’assenza di protocolli di uso
standardizzati e l’aumento dei casi di effetti avversi e complicanze legato all’uso dei filler ci ha
spinto all’apertura, presso il nostro ambulatorio di Chirurgia Plastica Sapienza Università di Roma
di un centro di riferimento dedicato al trattamento delle complicanze da filler. Nei 15 anni di attività
di questo ambulatorio abbiamo potuto fare alcune considerazioni. Spesso i pazienti si avvicinano a
questi trattamenti con estrema superficialità, non considerandoli procedure mediche associate a
possibili complicanze. In molti casi, i pazienti non sono a conoscenza del materiale iniettato e non
sono in grado di contattare il professionista che ha eseguito il trattamento. Inoltre alcuni pazienti
hanno riferito l’utilizzo di materiali e/o ambienti non idonei, arrivando addirittura all’autoinoculazione.
Vengono riportati alcuni dei casi giunti alla nostra osservazion
Accurate Inter-Laminar Recovery for Plates and Doubly-Curved Shells with Variable Radii of Curvature Using Layer-Wise Theories
No full textThe present work illustrates a general formulation for higher-order Layer-Wise (LW) theories. It aims to analyze doubly-curved laminated shells and panels when soft-core properties are selected. The present approach has its own roots in the Carrera Unified Formulation (CUF) for which the stretching effect of each layer is not neglected. CUF allows to take the kinematic expansion order as a free parameter for the representation of any higher order formulation. This paper shows the explicit fundamental operators for the LW approach when static analysis is investigated. The mathematical problem is solved using a strong formulation approach, termed Generalized Differential Quadrature (GDQ) method. Moreover, the so-called Generalized Integral Quadrature (GIQ) method is used for evaluating the through-the-thickness quantities of the theory such as the stiffness constants, computed layer by layer. Numerical applications are related to the recovery of the inter-laminar stresses and strains that have been compared to reference solutions obtained by a commercial three-dimensional (3D) FEM code
