http://hdl.handle.net/10256/4388 2013-06-19T22:38:41Z 2013-06-19T22:38:41Z Ribera Roget, Albert http://hdl.handle.net/10256/7912 2013-06-14T00:01:14Z 2013-03-20T00:00:00Z

El salario a rendimiento en el sector de la construcción. Modelo para determinar el precio óptimo y el precio máximo a pagar por un trabajo a destajo Ribera Roget, Albert This doctoral thesis explores HR management through systems of production incentives in the construction sector which has been instrumental to the Spanish economy. The transformation of a time-based payment system to a performance or production-based payment system is difficult if you consider the complexity of the calculation and the environment in which prices are negotiated. In any case, before agreeing to a piece-rate determined price it is imperative that the person responsible for negotiating on behalf of the company knows the relationship of this piece rate compared to expected labour costs as an objective in the opening plans. The main objective of this thesis is to propose an algorithm in flowchart form that facilitates —from the data found in the costs study— knowledge about the price range within which the economic incentive for piece-rate compensation for any work should be established by applying a few simple conversion coefficients proposed by the model itself; Aquesta tesi doctoral es centra en la gestió dels recursos humans a través dels sistemes d'incentius a la producció. La transformació d'un sistema de pagament per temps a un sistema de pagament per rendiment o per producció no és senzill si es té en compte la complexitat del càlcul i l'entorn en el qual es pacten els preus. És imprescindible que abans d'acordar un determinat preu fet, el responsable de la negociació, conegui la relació d'aquest preu respecte els costos de mà d'obra que té previstos com a objectiu en el pressupost de producció. El principal objectiu d'aquesta tesi és proposar un algoritme que faciliti —a partir de les dades contingudes en l'estudi de costos—, conèixer l'interval de preus dins del qual s'hauria d'establir l'incentiu econòmic de remuneració a preu fet d'un treball qualsevol, mitjançant l'aplicació d'uns simples coeficients de conversió que proposa el propi model

2013-03-20T00:00:00Z Maimí, Pere Camanho, Pedro P. Mayugo Majó, Joan Andreu Dávila, Carlos G. http://hdl.handle.net/10256/7898 2013-06-07T00:00:40Z 2006-01-01T00:00:00Z

A Thermodynamically Consistent Damage Model for Advanced Composites Maimí, Pere; Camanho, Pedro P.; Mayugo Majó, Joan Andreu; Dávila, Carlos G. A continuum damage model for the prediction of damage onset and structural collapse of structures manufactured in fiber-reinforced plastic laminates is proposed. The principal damage mechanisms occurring in the longitudinal and transverse directions of a ply are represented by a damage tensor that is fixed in space. Crack closure under load reversal effects are taken into account using damage variables established as a function of the sign of the components of the stress tensor. Damage activation functions based on the LaRC04 failure criteria are used to predict the different damage mechanisms occurring at the ply level. The constitutive damage model is implemented in a finite element code. The objectivity of the numerical model is assured by regularizing the dissipated energy at a material point using Bazant’s Crack Band Model. To verify the accuracy of the approach, analyses of coupon specimens were performed, and the numerical predictions were compared with experimental data NASA/TM-2006-214282

2006-01-01T00:00:00Z Mayugo Majó, Joan Andreu Camanho, Pedro P. Maimí, Pere Dávila, Carlos G. http://hdl.handle.net/10256/7897 2013-06-07T00:00:39Z 2006-01-01T00:00:00Z

A Micromechanics-Based Damage Model for [± θ / 90n ]s Composite Laminates Mayugo Majó, Joan Andreu; Camanho, Pedro P.; Maimí, Pere; Dávila, Carlos G. A new damage model based on a micromechanical analysis of cracked [± θ / 90n ]s laminates subjected to multiaxial loads is proposed. The model predicts the onset and accumulation of transverse matrix cracks in uniformly stressed laminates, the effect of matrix cracks on the stiffness of the laminate, as well as the ultimate failure of the laminate. The model also accounts for the effect of the ply thickness on the ply strength. Predictions relating the elastic properties of several laminates and multiaxial loads are presented NASA/TM-2006-214285

2006-01-01T00:00:00Z Turon Travesa, Albert Dávila, Carlos G. Camanho, Pedro P. Costa i Balanzat, Josep http://hdl.handle.net/10256/7896 2013-06-07T00:00:42Z 2005-01-01T00:00:00Z

An Engineering Solution for using Coarse Meshes in the Simulation of Delamination with Cohesive Zone Models Turon Travesa, Albert; Dávila, Carlos G.; Camanho, Pedro P.; Costa i Balanzat, Josep This paper presents a methodology to determine the parameters used in the simulation of delamination in composite materials using decohesion finite elements. A closed-form expression is developed to define the stiffness of the cohesive layer. A novel procedure that allows the use of coarser meshes of decohesion elements in large-scale computations is proposed. The procedure ensures that the energy dissipated by the fracture process is correctly computed. It is shown that coarse-meshed models defined using the approach proposed here yield the same results as the models with finer meshes normally used in the simulation of fracture processes NASA/TM-2005-213547

2005-01-01T00:00:00Z Torres Llinàs, Lluís Cahís Carola, Francesc Xavier López Almansa, Francisco Bozzo Rotondo, Luis http://hdl.handle.net/10256/7883 2013-06-06T00:00:42Z 2003-01-01T00:00:00Z

Modelo de comportamiento en sevicio para estructuras reticulares de hormigón. Parte II: Diagrama tensión- deformación para elementos fisurados a flexión Torres Llinàs, Lluís; Cahís Carola, Francesc Xavier; López Almansa, Francisco; Bozzo Rotondo, Luis This paper presents a general methodology to adjust the coefficients defining a constitutive law for tensioned concrete to simulate, under serviceability conditions, the behaviour of cracked concrete members subjected to simple and combined bending (with axial compressive forces). Although experimental results could be used to obtain the mentioned objective, in this work the models proposed by the CEB are utilized, in order to obtain more general conclusions not subjected to specific experiments. A numerical parametrical analysis is performed to determine the more significant variables influencing the Tension-Stiffening effect and simplified closed-form solution is derived for rectangular sections. A systematic study has been to verify the ability of the method to simulate long-term effects. The methodology can be implemented as an initial process in a general model of analysis like the one presented in Part I; Se presenta una metodología general para ajustar los coeficientes que definen una ley constitutiva para modelizar el comportamiento en condiciones de servicio de secciones fisuradas de hormigón, sometidas a flexión simple o acompañada de compresión. Aunque para este fin pueden emplearse datos experimentales, el trabajo se centra en la utilización de los modelos propuestos para el CEB, de manera que se obtienen conclusiones más generales no circunscritas a ensayos determinados. Mediante un estudio paramétrico se determinan las variables que tienen más incidencia en el efecto de Tesión-Stiffening y se halla una expresión simplificada válida para secciones rectangulares. Asimismo se ha realizado un estudio sistemático de la capacidad del método para predecir los efectos a largo plazo. La metodología puede ser implementada como un proceso inicial en un modelo general de cálculo como es presentado en la Parte I

2003-01-01T00:00:00Z Torres Llinàs, Lluís Cahís Carola, Francesc Xavier López Almansa, Francisco Bozzo Rotondo, Luis http://hdl.handle.net/10256/7882 2013-06-06T00:00:41Z 2003-01-01T00:00:00Z

Modelo de comportamiento en sevicio para estructuras reticulares de hormigón. Parte I: Descripción del modelo y ejemplos de aplicación Torres Llinàs, Lluís; Cahís Carola, Francesc Xavier; López Almansa, Francisco; Bozzo Rotondo, Luis A general method for instantaneous and time-dependent serviceability analysis of plane concrete frames is presented. The methodology is based in an extension of the classic matrix formulation for bars. The main aspects influencing the behaviour of the structural concrete are considered: cracking, creep, shrinkage or prestress losses. To simulate the effect of cracking a smeared model (developed in Part II) based on the modification of the tensile branch of the concrete stress-strain relationship is adopted. The general approach considered permits the application to different materials and constitutive laws. Sequential construction (sectional and structural), incorporation of reinforcement, consideration of the loads history; placing and removing shores, and restraining or releasing in boundary conditions are considered. Some examples are included to highlight the capabilities of the model; Se presenta un modelo general para el análisis en servicio instantáneo y diferido, de estructuras reticulares planas de hormigón estructural. El desarrollo se basa en una extensión de la formulación matricial para análisis de barras en la que se tienen en cuenta los principales aspectos que influyen en el comportamiento estructural del hormigón como son fisuración, fluencia, retracción o pérdidas de pretensado. Se adopta un modelo de fisuración distribuida (desarrollado en la Parte II) basado en la modificación del diagrama constitutivo del hormigón. El planteamiento general permite su aplicación a distintos materiales y leyes de comportamiento. Se contempla la construcción evolutiva (seccional y estructural) con posibilidad de incorporación de refuerzos, consideración de la historia de cargas, de los procesos de cimbrado y deseimbrado o de la restricción o liberación de grados de libertad. Se incluyen ejemplos para mostrar las posibilidades del modelo

2003-01-01T00:00:00Z Cahís Carola, Francesc Xavier Torres Llinàs, Lluís Bozzo Rotondo, Luis http://hdl.handle.net/10256/7881 2013-06-06T00:00:39Z 2001-01-01T00:00:00Z

Nuevo disipador para edificación sismorresistente. 2ª parte: comportamiento de estructures duales de un grado de libertad con disipadores Cahís Carola, Francesc Xavier; Torres Llinàs, Lluís; Bozzo Rotondo, Luis The behaviour of a new elastoplastic shear link dissipator has been analysed in the first part of this paper. The second part describes experimental and numerical studies for a SDOF non-standard dual system protected with shear dissipators. High and intermediate stiff deal systems with this Device have presented smaller values of the shear base force and the interstory drift when compared to linear and elastic systems response. It has been appreciated that most of introduced energy is dissipated when a low ratio between the main frame stiffness and dissipation system stiffness is hold. It has been also observed that a higher ratio between the dissipator yielding force and the total mass drives to a more reduced structural response. Finally is has been appreciated than the absorbed energy might be predicted using the velocity pseudo-spectra and an effective fundamental period, that has been defined by using the minimum secant stiffness of dual system; La primera parte de éste artículo analizaba el comportamiento de un nuevo disipador de energía elastoplástico. En ésta segunda parte se estudia experimental y numéricamente, la respuesta de un sistema dual de un grado de libertad que lo incluye. El disipador ha demostrado su efectividad en sistemas de rigidez elevada e intermedia, ofreciendo valores del cortante de base y del desplazamiento de entrepiso significativamente menores a los observados en sistemas lineales y elásticos. Se ha observado que una relación baja entre las rigideces de los subsistemas flexible y rígido permite disipar una mayor cantidad de la energía introducida al sistema y minimizar su respuesta estructural. También se ha apreciado que los sistemas más rígidos, para minimizar su respuesta estructural, deben mantener una relación más elevada entre su fuerza de plastificación y la masa total del sistema. Finalmente se ha observado que la energía absorbida por los disipadores puede ser predecida a partir del pseudoespectro de velocidades y del periodo fundamental efectivo, definido a partir de la rigidez secante mínima del sistema

2001-01-01T00:00:00Z Cahís Carola, Francesc Xavier Torres Llinàs, Lluís Bozzo Rotondo, Luis http://hdl.handle.net/10256/7880 2013-06-04T00:00:40Z 2001-01-01T00:00:00Z

Nuevo disipador para edificación sismorresistente. 1ª parte: caracterización y modelos de predicción Cahís Carola, Francesc Xavier; Torres Llinàs, Lluís; Bozzo Rotondo, Luis A new energy dissipator, based on yielding of steel under shear response, has been developed and recently tested. It is H shaped and web stiffened. Yielding moin part is mechanized from one piece of rectangular shoped steel bar. Its conception let obtain thin and well-stiffened web cross sections without welded parts. Main experimentally obtained charecteristics are a yielding point near 0.5 mm of displacement, yielding loads between 14 kN and 20 kN and a dissipated energy, before damage appears in the web, from 10 kJ to 21 kJ. All tested specimens have developed large deformations without web buckling. Whe web degradation appers, flanges and stiffeners keep dissipating an important amount of energy. Proposed numerical models and simple mathematical expressions offer well correlated results when compared to the experimental ones; Se ha desarrollado y ensayado un nuevo disipador de energia basado en la plastificación del acero por esfuerzo cortante. Su cuerpo disipativo dispone de una sección transversal en I, fabricada por fresado de una barra rectangular de acero laminado. Su concepción permite almas con espesores particularment reducidos. Los resultados experimentales obtenidos han revelado desplazamientos de plastificación del orden de los 0.5 mm, Asociados a un cortante comprendido entre 14 y 20 kN, y energies absorbides entre 10 y 21 kJ antes que su alma empiece a desgradar. Todos los especímenes ensayados histeréticamente han mostrado, pese a las elevades deformaciones plásticas, un comportamiento estable sin abolladura. Al dañarse el alma, las ales y los rigidizadores han continuado disipando na importante cantidad de energia. Completan el articulo varios modelos de predicción, analíticos y numéricos, manifiestando en un conjunto una buena correlación con los resultados experimentales

2001-01-01T00:00:00Z Cruz Hidalgo, Raúl Pagonabarraga Mora, Ignacio http://hdl.handle.net/10256/7621 2013-03-21T01:00:37Z 2008-01-01T00:00:00Z

Driven fragmentation of granular gases Cruz Hidalgo, Raúl; Pagonabarraga Mora, Ignacio The dynamics of homogeneously heated granular gases which fragment due to particle collisions is analyzed. We introduce a kinetic model which accounts for correlations induced at the grain collisions and analyze both the kinetics and relevant distribution functions these systems develop. The work combines analytical and numerical studies based on direct simulation Monte Carlo calculations. A broad family of fragmentation probabilities is considered, and its implications for the system kinetics are discussed. We show that generically these driven materials evolve asymptotically into a dynamical scaling regime. If the fragmentation probability tends to a constant, the grain number diverges at a finite time, leading to a shattering singularity. If the fragmentation probability vanishes, then the number of grains grows monotonously as a power law. We consider different homogeneous thermostats and show that the kinetics of these systems depends weakly on both the grain inelasticity and driving. We observe that fragmentation plays a relevant role in the shape of the velocity distribution of the particles. When the fragmentation is driven by local stochastic events, the long velocity tail is essentially exponential independently of the heating frequency and the breaking rule. However, for a Lowe-Andersen thermostat, numerical evidence strongly supports the conjecture that the scaled velocity distribution follows a generalized exponential behavior f (c)~exp (−cⁿ), with n ≈1.2, regarding less the fragmentation mechanisms

2008-01-01T00:00:00Z Pujol i Sagaró, Toni Comas, Bruna http://hdl.handle.net/10256/7613 2013-03-16T01:00:38Z 2011-01-01T00:00:00Z

Analytical expressions for the flame front speed in the downward combustion of thin solid fuels and comparison to experiments Pujol i Sagaró, Toni; Comas, Bruna We derive analytical expressions for the propagation speed of downward combustion fronts of thin solid fuels with a background flow initially at rest. The classical combustion model for thin solid fuels that consists of five coupled reaction-convection-diffusion equations is here reduced into a single equation with the gas temperature as the single variable. For doing so we apply a two-zone combustion model that divides the system into a preheating region and a pyrolyzing region. The speed of the combustion front is obtained after matching the temperature and its derivative at the location that separates both regions.We also derive a simplified version of this analytical expression expected to be valid for a wide range of cases. Flame front velocities predicted by our analytical expressions agree well with experimental data found in the literature for a large variety of cases and substantially improve the results obtained from a previous well-known analytical expression

2011-01-01T00:00:00Z