Doctoral School

Reading date: 15/10/2024

• GUANCHEZ REYES, EDINSON ASDRUBAL: ESTUDIO DE LA INFLUENCIA DE LOS FENÓMENOS DE INTERACCIÓN SUELO-ESTRUCTURA EN LA RESPUESTA SÍSMICA DE ESTRUCTURAS TÍPICAS DE ACERO CON ARRIOSTRAMIENTOS CONCÉNTRICOS
  
  Author: GUANCHEZ REYES, EDINSON ASDRUBAL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING
  Department: Department of Strength of Materials and Structural Engineering (RMEE)
  Mode: Normal
  Deposit date: 10/09/2024
  Reading date: 15/10/2024
  Reading time: 12:00
  Reading place: Defensa pública a la Sala Àgora del Campus Nord de la Universitat Politècnica de Catalunya
  Thesis director: SANCHEZ ROMERO, MONTSERRAT | WEYLER PEREZ, RAFAEL
  Committee:
       PRESIDENT: DEL COZ DÍAZ, JUAN JOSÉ
       SECRETARI: VELAZQUEZ AMEIJIDE, JUAN
       VOCAL: CITO, SALVATORE
  Thesis abstract: Steel concentrically braced frames (CBF) are considered efficient in resisting lateral forces because they provide high lateral strength and stiffness, which is particularly beneficial in seismic zones. However, this type of structure has a significant overstrength that is not considered during foundation design, which can lead to uplift of the footings under the braced members and to rocking mechanisms. On the other hand, soil-structure interaction (SSI) phenomena and foundation flexibility are generally not considered in performance-based analyses of new or existing structures.In this research, the influence of SSI phenomena on the seismic response of CBF is evaluated by considering the nonlinear response of embedded footings using the BNWF (Beam on Nonlinear Winkler Foundation) approach. To model the vertical stress-displacement behaviour of the footings, it is possible to define a backbone curve by combining the response of the compression zone in series with that of the tension zone.When uplift of the footing is allowed, it is shown that it is necessary to consider the horizontal stresses of the native soil in situ and the degree of compaction of the soil above the footing to avoid significant deviations between the analysis results and the real response. The tension zone in the response curves has been calibrated to take these parameters into account and, given the difficulty associated with their calibration, an estimate is reported which could also be used for practical applications.The implementation has been validated by various pushover analyses on a steel CBF archetype originally tested in the fixed base condition, and predictions for the flexible base condition have been made considering different soil types and footing embedment depths (Df). The results show a direct relationship between the nonlinear response of steel CBF and the uplift mechanism of embedded footings, with the embedment depth (Df) and the shape of the tension-displacement curve being the most important variables that influence the response.The model has been incorporated in various nonlinear time-history analyses considering a set of seismic records on a well-known steel CBF archetype. The results obtained suggest that, when analysing the response of steel CBF on a nonlinear flexible base condition, it is possible to report variations in the yielding sequence of the superstructure with respect to the fixed base condition. It is reported that the embedment depth (Df) of the footing, and hence its uplift stiffness, is able to modify the overall response of the superstructure. On the other hand, the cyclic response of the foundation determines a process of energy dissipation which is reflected in a reduction of the seismic force on the bracing system of the structure. The energy dissipation mechanism due to vertical response is more efficient for the supports located under the braced frames compared to those footings located under unbraced columns, and the effect is much more pronounced in soft or loose soils. The proposed model can be implemented as part of both static and dynamic analyses to have a more realistic prediction of the seismic response during performance-based designs of structures supported on embedded footings, particularly for the case of steel CBF.
  

Reading date: 17/10/2024

• BARRAJÓN RASTROLLO, JOSE LUIS: Navigating Organizational Change for Successful Implementation of HR Analytics
  
  Author: BARRAJÓN RASTROLLO, JOSE LUIS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN BUSINESS ADMINISTRATION AND MANAGEMENT
  Department: Department of Management (OE)
  Mode: Normal
  Deposit date: 19/09/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: FERNANDEZ ALARCON, VICENÇ | GALLARDO GALLARDO, EVA
  Committee:
       PRESIDENT: MARIN GARCIA, JUAN A.
       SECRETARI: PONS PEREGORT, OLGA
       VOCAL: ORTIZ DE URBINA CRIADO, MARTA
  Thesis abstract: Context: Numerous studies affirm the positive impact of Human Resources Analytics (HRA) on gaining a competitive edge and enhancing Human Resources (HR) strategic role therefore given the importance of knowing how to implement an HRA function in organizations successfully, this Ph.D. thesis brings relevant insights of the most critical variables, and the barriers to be faced during this process so that future researchers and practitioners have the enough knowledge and tools to address it with success.Purpose: The Ph.D. thesis is divided into two interrelated purposes: (1) identifying the most crucial factors through which organizations base their HRA implementation and (2) the learning barriers to face during the organizational change that suppose implementing those factors to become a data-driven decision-making organization.Method: For the culmination of both purposes, we have conducted an inductive/explorative study using semi-structured interviews as the qualitative data collection method. In this case, the sample consists of ten managers, seven HRA function leaders, and three from HR departments who had carried out analytics projects. Those ten leaders work for ten different organizations in distinct sectors and across varying levels of analytical maturity. We have based on a couple of frameworks, one of organizational learning and another of HRA to design and create our own to guide the research.Results: Through empirical qualitative research, we obtained the five key HRA factors highlighted in the literature: Data, Technology Support, Culture, People and Project Design. Additionally, we considered the analytical maturity level of our organization's sample and related to this, the results show that Data quality and accessibility are crucial in descriptive and predictive stages. On the contrary, prescriptive organizations seem to be more focused on Technology, to support advanced analytical models. As far as organizational change is concerned, our results show that the intensity of the learning barriers in HRA decreases as the organizations increase their analytical maturity level. Besides, communication problems seem to be in the descriptive organizations, especially with the Data and Technology departments and the management. On the other hand, in predictive organizations, HR and/or HRA departments seem to lack autonomy in accessing the Data, building their teams, and choosing the technology they need to mature the function. Finally, other factors, such as ethics, budget, and trust in the HR function, were shown in the results.Conclusions / Implications: This allows researchers and practitioners to design and implement an HRA function supported by a framework that guarantees success in the process.Originality: This Ph.D. thesis extends existing theory about HRA success factors (SSFF), as well as organizational learning, developing a new model including both disciplines for implementing HRA function in organizations successfully.
  

• LEI, JIANGTAO: A micromechanical investigation of pile set-up effect in sands
  
  Author: LEI, JIANGTAO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN GEOTECHNICAL ENGINEERING
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Normal
  Deposit date: 18/09/2024
  Reading date: 17/10/2024
  Reading time: 11:00
  Reading place: ETSECCPB. UPC, Campus Nord Building D2. Classroom: 216 C/Jordi Girona, 1-3 08034 Barcelona
  Thesis director: ARROYO ALVAREZ DE TOLEDO, MARCOS | CIANTIA, MATTEO
  Committee:
       PRESIDENT: BROWN, MICHAEL JOHN
       SECRETARI: ALONSO PEREZ DE AGREDA, EDUARDO
       VOCAL: GONZALEZ TEJADA, IGNACIO
  Thesis abstract: Driven piles in granular soils gain shaft capacity after installation in a phenomenon known as “pile set-up”. Set-up effects in sand have not been incorporated into design procedures largely because the underlying mechanisms are not well understood. This thesis reports a micromechanical investigation of pile set-up effect in sand using a newly developed fracture-based DEM model for simulating time-dependent behaviour in sand. Creep and stress relaxation around the pile have been widely discussed as possible underlying mechanism for pile set-up effect. Following the idea that creep and stress relaxation in sands are frequently accompanied by grain breakage, a new model based on the discrete-element method (DEM) to simulate creep/stress relaxation in sands was proposed. The model aims for conceptual simplicity, computational efficiency and ease of calibration. To this end a new form of normalized Charles power law is incorporated into a DEM model for rough crushable sands based on the particle splitting technique. The creep/stress relaxation time is advanced using an off-DEM ageing strategy. The model is validated by simulating creep/stress relaxation in quartz sands in oedometric and triaxial conditions. Model predictions are shown to compare favourably with experimental creep results in terms of creep strain, creep strain rates and particle breakage/GSD evolution, and with experimental stress relaxation results in terms of relaxed stress, stress relaxation rate, and GSD evolution.The fracture-based DEM model was then implemented to a centrifuge DEM chamber to simulated pile creep and pile set-up. Simulated pile creep settlements agree with observations in terms of pile creep parameter m and pile creep rate. Simulated pile set-up falls into the range of field observations for jacked piles. The results obtained indicate that particle breakage may play a significant role in set-up and represent the first validated modelling attempt of this complex phenomenon. To gain familiarity with DEM modelling of penetration problems, a DEM based CPT and SPT simulation on a volcanic sand was also conducted, using a virtual calibration chamber (VCC). The simulated CPT results are shown to capture well experiments from the literature over a range of density and confining stress. A good correlation between the energy-based equivalent SPT tip resistance with the CPT tip resistance can be observed if shaft resistance effects are discounted. SPT driven scheme may be used for simulating pile driven in the future study once proper driven parameters are determined.
  

• LUO, DA-SHUANG: Recovery of antimony and bismuth from copper metallurgical industry process streams
  
  Author: LUO, DA-SHUANG
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CHEMICAL PROCESS ENGINEERING
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 16/09/2024
  Reading date: 17/10/2024
  Reading time: 10:30
  Reading place: EEBE (Escola d'Enginyeria Barcelona), Sala Polivalent, Ed. A, Campus Diagonal - Besòs
  Thesis director: CORTINA PALLAS, JOSE LUIS | LÓPEZ RODRÍGUEZ, JULIO
  Committee:
       PRESIDENT: GIBERT AGULLO, ORIOL
       SECRETARI: CAMA I ROBERT, JORDI
       VOCAL: BRINGAS ELIZALDE, EUGENIO
  Thesis abstract: The pyrometallurgical industry faces challenges in maintaining copper purity due to increasing impurities in the primary resources (Sb, Bi, and As) that can reach the electrorefining unit forming insoluble minerals, compromising copper purity. To address this, the copper industry is developing actions to reduce the presence of such impurities along different stages of the process flow sheet acting at: i) the final stages of the electrorefining process or ii) the mineral concentration stages (e.g. flotation). The main target objective of this PhD thesis has been centred in the evaluation of technological solutions to reduce such impurities (Sb, Bi and As) by introducing a sustainability concept, where elements considered as critics for the European Union (i.e. Sb and Bi) are recovered. In the case of acting in the final stage of electrorefining, ion-exchange (IX) technology is employed at industrial scale to continually treat the copper electrolyte of the electrorefining stage, removing Sb and Bi and ensuring a high copper purity. Upon IX resin saturation, regeneration with 6 M HCl produces a concentrated eluate containing Sb, Bi (7–14 g/L each), and As (1–4 g/L). Currently, lime treatment removes these impurities producing large volumes of waste containing As, Sb and Bi. Therefore, two valoriaztion routes of the eluate were evaluated based on solvent extraction (SX) and selective precipitation. SX route was based on the use of a solvated mixture of alkylphosphine oxides (commercialized as Cyanex 923) dissolved in kerosene and 1-decyl alcohol (10%) as a phase modifier. The separation factors of Sb, Biand As were evaluated and optimized as a function of extractant concentration and aqueous to organic (A/O) phase ratio. The results showed that 39% Bi and 78% Sb could be extracted with low co-extraction of As (<2.5%) working at the lowest Cyanex 923 concentration (0.15 mol/L) and A/O ratio of 1/3. Using 8M HNO3 as a stripping agent, both Sb and Bi were easily recovered (>90%). During the direct precipitation of eluate, As(V) forms an insoluble antimony arsenate (SbAsO4(s)). Therefore, it is necessary to pre-treat the eluent with SO2(g) or NaHSO3(s) to reduce As(V) to the (+III) state valence state. In this case, antimony oxychloride (Sb4O5Cl2, purity >93%) and bismuth oxychloride (BiOCl, purity >95%) can be obtained sequentially using NaOH, NaHCO3 and/or Na2CO3 under appropriate pH control. The recovered high purity Sb4O5Cl2(s) and BiOCl(s), still containing a low content of As, could be converted into oxides in alkaline media, improving the final purity making them suitable for commercial use. The techno-economic implications of Sb and Bi showed that the recovery of BiOCl(s)/Sb4O5Cl2(s) and BiOCl(s)/Sb2O3(s) is economically feasible in copper metallurgy facilities, especially when Sb and Bi prices are higher than 8.5 and 9.5 €/kg, respectively. Overall, the results highlighted the economic and technical potential of implementing Sb and Bi recovery routes in copper metallurgy plants, in line with the ambitious circular economy targets set by the European Union.In the case of approaching the reduction of the presence of impurities in the mineral copper concentrates, tetrahedrite (Cu12Sb4S13(s)) was selected as case study. Selective leaching of antimony using microwave-assisted technology in a laboratory scale was investigated at different concentrations of Na2S and NaOH, solid/liquid ratio, temperature, and microwave power. Results indicated that Sb dissolution is highly dependent on the concentrations of leaching reagents (Na2S/NaOH) and the temperature. The Sb content in the copper concentrate was successfully reduced from 1.1% to less than 0.2%, making it suitable for copper concentrate metallurgy processing. A proposal of potential integration of both alkaline leaching and selective precipitation of the Sb could provide a sustainable solution, promoting the recovery of a critical raw material for the European industry
  

• WIERNA QUIROGA, PABLO NICOLÁS: A Novel Computational Homogenization Theory for Multilayered Plates: The Multiscale 2D+ Approach.
  
  Author: WIERNA QUIROGA, PABLO NICOLÁS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN STRUCTURAL ANALYSIS
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Normal
  Deposit date: 06/09/2024
  Reading date: 17/10/2024
  Reading time: 17:00
  Reading place: Sala O.C. Zienkievicz, Centre Internacional de Mètodes Numèrics a l'Enginyeria (CIMNE) C. Gran Capità, s/n, Mòdul C1, 2a planta/https://meet.google.com/gwt-ajmy-bdv
  Thesis director: OLIVER OLIVELLA, FRANCISCO JAVIER | LLOBERAS VALLS, ORIOL
  Committee:
       PRESIDENT: ARTEIRO, ALBERTINO
       SECRETARI: CANTE TERAN, JUAN CARLOS
       VOCAL NO PRESENCIAL: SANCHEZ, PABLO JAVIER
  Thesis abstract: This doctoral thesis presents a novel multiscale theory for the analysis of multilayered plate structures, termed the "Multiscale 2D+ approach" or, simply, "2D+". Based on the formalism of computational homogenization theory, this approach is specifically tailored to account for the mechanical behaviour of multilayered materials, which contain a heterogeneous distribution of thin layers across the thickness and often exhibit substantial non-linear material behavior. After identifying the macroscopic scale as the (2D) reference plane of the plate, the strategy models the through-the-thickness heterogeneity by means of a (1D) meso-scale filament, orthogonal to such plane and spanning the plate depth. At the macro-scale level, classical First Order Shear Deformation Theory (FSDT) kinematics is adopted. At the fine-scale level, the Representative Volume Element (RVE) kinematics is initially derived through the linearization of the macro-scale displacement field along the thickness, in accordance with the first-order computational homogenization theory. The RVE is then endowed with a fluctuating displacement field, which aims to capture the well-known (higher-order) zig-zag displacements observed across the thickness of composite laminates. The Hill-Mandel principle is used to establish the mechanical energy balance across both scales, resulting in a one-dimensional Boundary Value Problem (BVP) to be solved at the meso-scale level in terms of the fluctuating displacement field. Furthermore, the variational RVE-problem allows for the enforcement of an additional condition: the fulfillment of the linear momentum balance (equilibrium) equations at every point across the thickness. This yields a physically meaningful computational setting, in which both scales are represented through simple (degenerated) kinematic descriptions, accounting for the essential mechanical behavior observed at each level yet remaining computationally inexpensive. The Multiscale 2D+ approach can therefore be seen as a modern plate theory, where the through-the-thickness mechanical behavior of the plate is obtained upon the solution of the equilibrium problem of a meso-scale filament. Particularly well-suited for bending-dominated scenarios, it provides accurate stress distributions at the ply-level in non-linear simulations, close to those of full-3D models, at a computational cost similar to that of 2D models. The thesis comprises the development of both the formulation and the corresponding numerical multiscale model within the context of the finite element method. Through a series of representative simulations−including assessments of accuracy, computational performance, and non-linear material modeling− the merits of the 2D+ approach in successfully accounting for the mechanical behavior of multilayered plates are clearly evidenced in this contribution.