Artículos (Mecánica de Medios Continuos y Teoría de Estructuras)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11397

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3D analysis of railway induced vibrations on skew girder bridges including ballast track–bridge interaction effects
(Elsevier, 2023-03) Sánchez-Quesada, Juan Carlos; Romero Ordóñez, Antonio; Galvín, Pedro; Moliner, Emma; Martínez-Rodrigo, María Dolores; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; Generalitat Valenciana; Universitat Jaume I; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
This work is devoted to the analysis of the vibratory response of High-Speed (HS) multi-track railway bridges composed by simply-supported spans. In particular, it aims to investigate the influence of three geometrical aspects usually disregarded in numerical models used to evaluate the Serviceability Limit State of traffic safety in such structures: (i) the deck obliquity, (ii) the presence and correct execution of transverse diaphragms at the supports, and (iii) the number of successive simply-supported spans weakly coupled through the ballast track layer. The influence of these aspects is analysed from the correlation of a detailed numerical model and experimental measurements on an in-service High Speed (HS) multi-track railway bridge. From the reference model, a set of variants accounting for different levels of deck obliquity and diaphragm configurations are envisaged and the maximum transverse acceleration over the platform is determined under railway excitation. The analysis is extended to bridges with an increasing number of successive spans. Special attention is paid to the particular location of the maximum response and to the participation of modes different from the longitudinal bending one. Finally, a numerical–experimental comparison of the bridge response under two train passages is presented for the straight and oblique models, and the response adjustment along with the actual bridge performance are assessed.
3D non-linear time domain FEM-BEM approach to soil-structure interaction problems
(Elsevier, 2013) Romero Ordóñez, Antonio; Galvín, Pedro; Domínguez Abascal, José; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Economía y Competitividad (MINECO). España
Dynamic soil-structure interaction is concerned with the study of structures supported on ﬂexible soils and subjected to dynamic actions. Methods combining the ﬁnite element method (FEM) and the boundary element method (BEM) are well suited to address dynamic soil-structure interaction problems. Hence, FEM-BEM models have been widely used. However, non-linear contact conditions and non-linear behaviour of the structures have not usually been considered in the analyses. This paper presents a 3D non-linear time domain FEM-BEM numerical model designed to address soil-structure interaction problems. The BEM formulation, based on element subdivision and the constant velocity approach, was improved by using interpolation matrices. The FEM approach was based on implicit Green’s functions and non-linear contact was considered at the FEM-BEM interface. Two engineering problems were studied with the proposed methodology: the propagation of waves in an elastic foundation and the dynamic response of a structure to an incident wave ﬁeld.
3D printed energy harvesters for railway bridges-Design optimisation
(Elsevier, 2023-05) Cámara Molina, Javier Cristóbal; Moliner, Emma; Martínez Rodríguez, María Dolores; Connolly, David P.; Yurchenko, D.; Galvín, Pedro; Romero Ordóñez, Antonio; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Spanish Ministry of Science, Innovation and Universities project PID2019-109622RB; FEDER Andalucía 2014–2020 US-126491; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
This paper investigates the optimal design of 3D printed energy harvesters for railway bridges. The type of harvester studied is a cantilever bimorph beam with a mass at the tip and a load resistance. These parameters are adjusted to find the optimal design that tunes the harvester to the fundamental frequency of the bridge. An analytical model based on a variational formulation to represent the electromechanical behaviour of the device is presented. The optimisation problem is solved using a genetic algorithm with constraints of geometry and structural integrity. The proposed procedure is implemented in the design and manufacture of an energy harvesting device for a railway bridge on an in-service high-speed line. To do so, first the methodology is validated experimentally under laboratory conditions and shown to offer strong performance. Next the in-situ railway bridge is instrumented using accelerometers and the results used to evaluate energy harvesting performance. The results show the energy harvested in a time window of three and a half hours (20 train passages) is E=109.32 mJ . The proposed methodology is particularly useful for bridges with fundamental mode shapes above 4.5 Hz, however optimal design curves are also presented for the most common railway bridges found in practice. A novelty of this work is the use of additive manufacturing to 3D print energy harvesters, thus maximising design flexibility and energy performance.
A 2.5D coupled FE–BE methodology for the dynamic interaction between longitudinally invariant structures and a layered halfspace
(Elsevier, 2010-04) François, S.; Schevenels, M.; Galvín, Pedro; Lombaert, G.; Degrande, G.; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. TEP295: Ingeniería de las Estructuras
This paper presents a general 2.5D coupled finite element–boundary element methodology for the computation of the dynamic interaction between a layered soil and structures with a longitudinally invariant geometry, such as railway tracks, roads, tunnels, dams, and pipelines. The classical 2.5D finite element method is combined with a novel 2.5D boundary element method. A regularized 2.5D boundary integral equation is derived that avoids the evaluation of singular traction integrals. The 2.5D Green’s functions of a layered halfspace, computed with the direct stiffness method, are used in a boundary element method formulation. This avoids meshing of the free surface and the layer interfaces with boundary elements and effectively reduces the computational efforts and storage requirements. The proposed technique is applied to four examples: a road on the surface of a halfspace, a tunnel embedded in a layered halfspace, a dike on a halfspace and a vibration isolating screen in the soil.
A 2.5D coupled FE-BE model for the prediction of railway induced vibrations
(Elsevier, 2010) Galvín, Pedro; François, S.; Schevenels, M.; Bongini, E.; Degrande, G.; Lombaert, G.; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Junta de Andalucía; Ministerio de Educación y Ciencia (MEC). España
Ground vibrations induced by railway traffic at grade and in tunnels are often studied by means of two-and-half dimensional (2.5D) models that are based on a Fourier transform of the coordinate in the longitudinal direction of the track. In this paper, the need for 2.5D coupled finite element-boundary element models is demonstrated in two cases where the prediction of railway induced vibrations is considered. A recently proposed novel 2.5D methodology is used where the finite element method is combined with a boundary element method, based on a regularized boundary integral equation. In the formulation of the boundary integral equation, Green's functions of a layered elastic halfspace are used, so that no discretization of the free surface or the layer interfaces is required. In the first case, two alternative models for a ballasted track on an embankment are compared. In the first model, the ballast and the embankment are modelled as a continuum using 2.5D solid elements, whereas a simplified beam representation is adopted in the second model. The free field vibrations predicted by both models are compared to those measured during a passage of the TGVA at a site in Reugny (France). A very large difference is found for the free field response of both models that is due to the fact that the deformation of the cross section of the embankment is disregarded in the simplified representation. In the second case, the track and free field response due to a harmonic load in a tunnel embedded in a layered halfspace are considered. A simplified methodology based on the use of the full space Green's function in the tunnel–soil interaction problem is investigated. It is shown that the rigorous finite element-boundary element method is required when the distance between the tunnel and the free surface and the layer interfaces of the halfspace is small compared to the wavelength in the soil.
A 2.5D time-frequency domain model for railway induced soil-building vibration due to railway defects
(Elsevier, 2019-05) Connolly, David P.; Galvín, Pedro; Olivier, B.; Romero Ordóñez, Antonio; Kouroussis, G.; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
A new hybrid time-frequency modelling methodology is proposed to simulate the generation of railway vibration caused by singular defects (e.g. joints, switches, crossings), and its propagation through the track, soil and into nearby buildings. To create the full source-to-received model, first the force density due to wheel-rail-defect interaction is calculated using a time domain finite element vehicle-track-soil model. Next, the frequency domain track-soil transfer function is calculated using a 2.5D boundary/finite element approach and coupled with the force densities to recover the free-field response. Finally, the soil-structure interaction of buildings close to the line is computed using a time domain approach. The effect of defect type, train speed and building type (4-storey office block and 8-storey apartment building) on a variety of commonly used international vibration metrics (one-third octaves, PPV, MTVV) is then investigated. It is found that train speed doesn't correlate with building vibration and different defect types have a complex relationship with vibration levels both in the ground and buildings. The 8-storey apartment building has a frequency response dominated by a narrow frequency range, whereas the modal contribution of the 4-storey office building is over a wider frequency band. This results in the 8-storey building having a higher response.
A 3-D boundary element model for the dynamic analysis of arch dams with porous sediments
(WIT Press, 2001) Aznárez, J. J.; Maeso, O.; Domínguez Abascal, José; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras
A three-dimensional boundary element technique for dynamic analysis of arch dams including dynamic interaction and sediments on the bottom of the reservoir is presented. The dam and the foundation rock are assumed to be viscoelastic domains with linear behaviour. The water is assumed to be compressible and the sediment is considered as a two-phase poroelastic material according to Biot's theory. The four domains (dam, foundation rock, water and bottom sediments) are discretized and the interaction between them is rigorously represented. The effects of sediments on the dynamic response of arch dams are evaluated for rigid and compliant foundation. Upstream, vertical and cross-stream excitation are considered. The influence of the degree of saturation of the sediment is analysed. Other modelling of the sediment as a single-phase scalar medium are considered in order to reduce the degrees of freedom of the system.
A 3D Numerical Mode for HST Induced Vibrations
(Multi-Science Publishing, 2010) Galvín, Pedro; Domínguez Abascal, José; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras
A general numerical model for the analysis of soil motion due to high-speed train passage and effects on nearby surface and underground structures is presented in this paper. In contrast to other existing approaches, effects on a particular structure and the influence of non-uniform soil conditions along the track can be evaluated. Numerical results are obtained for different situations and some of them are compared with existing experimental records. The experimental values are to a large extent reproduced by the present numerical approach.
A 3D time domain numerical model based on half-space Green's function for soil-structure interaction analysis
(Springer, 2014) Galvín, Pedro; Maestre Torreblanca, José María; Romero Ordóñez, Antonio; ; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería de Sistemas y Automática; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
This paper presents a numerical method based on a three dimensional boundary element-finite element (BEM- FEM) coupled formulation in the time domain. The proposed model allows studying soil-structure interaction problems. The soil is modelled with the BEM, where the radiation condition is implicitly satisfied in the fundamental solution. Half-space Green's function including internal soil damping is considered as the fundamental solution. An effective treatment based on the integration into a complex Jordan path is proposed to avoid the singularities at the arrival time of the Rayleigh waves. The efficiency of the BEM is improved taking into account the spatial symmetry and the invariance of the fundamental solution when it is expressed in a dimensionless form. The FEM is used to represent the structure. The proposed method is validated by comparison with analytical solutions and numerical results presented in the literature. Finally, a soil-structure interaction problem concerning with a building subjected to different incident wave fields is studied
A common framework for the robust design of tuned mass damper techniques to mitigate pedestrian-induced vibrations in lively footbridges
(Elsevier Ltd, 2021) Jiménez Alonso, Javier Fernando; Soria, José M.; Díaz, Iván M.; Guillén González, Francisco Manuel; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ecuaciones Diferenciales y Análisis Numérico; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
The dynamic response of modern slender footbridges is usually sensitive to both the pedestrian actions and the uncertainties associated with their inherent structural behavior. Thus, tuned mass dampers have been widely integrated in the design of these structures to guarantee the fulfillment of the vibration serviceability limit state during their overall life cycle. Three different techniques of tuned mass dampers (active, semi-active and passive) are usually considered for this purpose. Although there are algorithms for the robust design of each particular technique, however, this specificity makes difficult the implementation of all these techniques in practical en gineering applications. Herein, the motion-based design method under uncertainty conditions is proposed and further implemented to create a common framework for the robust design of all these techniques when they are employed to mitigate pedestrian-induced vibrations in slender footbridges. According to this method, the design problem may be transformed into the combination of two sequential sub-problems: (i) a reliability multi objective optimization sub-problem; and (ii) a decision-making sub-problem. Subsequently, the performance of this proposal has been validated through a numerical case study in which the dynamic response of a steel footbridge has been controlled by three different tuned mass damper techniques designed according to the proposed common framework.
A continuum large-deformation theory for the coupled modeling of polymer–solvent system with application to PV recycling
(Elsevier, 2023-06) Liu, Zeng; Marino, Michele; Reinoso Cuevas, José Antonio; Paggi, Marco; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 861061 – Project NEWFRAC; Consejería de Economía y Conocimiento of the Junta de Andalucía (Spain) contract US-1265577-Programa Operativo FEDER Andalucía 2014–2020; Spanish Ministerio de Ciencia, Innovación y Universidades, Spain grant PID2019-109723GB-I00; Consejería de Economía y Conocimiento of the Junta de Andalucía (Spain) grant P2-00595; Ministerio de Ciencia e Innovación of Spain TED2021-131649B-I00; Universidad de Sevilla. TEP131: Elasticidad y Resistencia de Materiales
Nowadays recycling of photovoltaics (PV) using the solvent method is becoming a very hot topic as massive products deployed in the last century have approached the end of their service lifetime. The key problem in the recycling of end-of-life PV modules is the nondestructive recovery of precious silicon wafers for the manufacturing of new products. However, the attempt to comprehensively understand the polymer–solvent system in the PV recycling process is completely lacking. In this work, a thermodynamically consistent large-deformation theory is proposed to model the coupled behavior of this system. The development of continuum theory accounts for the solvent permeation, swelling and elastic deformation, as well as shrinking effects due to the initial crosslinking of ethylene-co-vinyl acetate (EVA). The crosslinking of EVA influences the stiffness of the polymer network, and interacts with the diffusive kinetics of solvents. Also, given the effects of mechanical constraint, the two-way coupling between the EVA deformation and solvent diffusion is established on the basis of thermodynamic arguments. The proposed modeling method is firstly applied to simulate the swelling experiments of cylindrical EVA samples in solvents Toluene, Tetrahydrofuran, and Octane, and good agreement has been achieved between the numerical prediction and available testing data. Then the second example demonstrates the capability of this modeling framework to describe the influences of initial crosslinking and mechanical constraints on the time history evolution of swelling and elastic deformation. Finally, the complete PV laminate in the 3D setting is modeled for the investigation of solvent penetration induced deformation in the silicon cell layer during the PV recycling process, and comparison has been made to showcase the spatial distribution of maximum principal stress of the silicon cell layers in solvents with different solubility parameters and molar volumes. With this computational tool at hand, it is possible to provide guidance to the design of suitable experimental procedures for the structure-intact recovery of silicon wafers in PV recycling with the solvent method.
A coupled approach to predict cone-cracks in spherical indentation tests with smooth or rough indenters
(Elsevier, 2023-09) Marulli, Maria Rosaria; Bonari, Jacopo; Reinoso Cuevas, José Antonio; Paggi, Marco; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 101086342 – Project DIAGONAL; Universidad de Sevilla. TEP131: Elasticidad y Resistencia de Materiales
Indentation tests are largely exploited in experiments to characterize the mechanical and fracture properties of the materials from the resulting crack patterns. This work proposes an efficient theoretical and computational framework, whose implementation is detailed for 2D axisymmetric and for 3D geometries, to simulate indentation-induced cracking phenomena caused by non-conforming contacts with indenter profiles of an arbitrary shape. The formulation hinges on the coupling of the MPJR (eMbedded Profile for Joint Roughness) interface finite elements which embed the indenter profile to efficiently solve the contact problem between non-planar bodies, and the phase-field model for brittle fracture to simulate crack evolution and nonlocal damage in the substrate. The novel framework is applied to predict cone-crack formation in the case of indentation tests with smooth spherical indenters, with validation against experimental data. Then, the methodology is employed for the very first time in the literature to assess the effect of surface roughness superimposed on the shape of the smooth spherical indenter. In terms of physical insights, numerical predictions quantify the dependencies of the critical load for crack nucleation and the crack radius on the amplitude of roughness in comparison with the behavior of smooth indenters. Again, the consistency with available experimental trends is noticed.
A critical study on the experimental determination of stiffness and viscosity of the human triceps surae by free vibration methods
(Sage, 2013-09) París García, Federico; Barroso Caro, Alberto; Cañas Delgado, José; Ribas Serna, Juan; París Carballo, Federico; Universidad de Sevilla. Departamento de Fisiología Médica y Biofísica; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. TEP131: Grupo de Elasticidad y Resistencia de Materiales
Muscles and tendons play an important role in human performance. Their mechanical behaviour can be described by analytical/numerical models including springs and dampers. Free vibration techniques are a widely used approach to the in vivo determination of stiffness and viscosity of muscle–tendon complexes involved in sport movements. By considering the data reported in the literature, it appears that the visco-elastic properties of the triceps surae muscle–tendon complexes are independent of the modality in which free vibration is induced as well as they do not depend on the composition of the population of subjects submitted to the experiments. This research will critically discuss this important aspect focussing in particular on two studies documented in the literature. For this purpose, two equipments will be developed to reproduce literature experiments under the assumption that the oscillating part of the body behaves as a single-degree-of-freedom system: The governing degree of freedom is associated with the vertical displacement of the lower leg or with the rotation of the foot around the ankle articulation. Unlike literature, measurements are now conducted on the same population of subjects in order to draw more general conclusions on the real equivalence of results and validity of the mechanical properties determined experimentally. Free vibration tests are accurately simulated by analytical models describing the response of each vibrating system. It is found that if the two measurement protocols are applied to the same population of individuals as it is done in this study, values of visco-elastic properties of muscle–tendon complexes extracted from experimental data are significantly different, the differences presenting a convincing consistency. This result is in contrast with the literature and confirms the need to evaluate results of free vibration techniques by taking homogeneous bases of comparison.
A crowd-structure interaction model to analyze the lateral lock-in phenomenon on footbridges
(WIT Press, 2018) Jiménez Alonso, Javier Fernando; Sáez Pérez, Andrés; Caetano, Elsa; Cunha, Álvaro; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
In this paper a simplified biomechanical crowd-structure interaction model is proposed and validated in order to analyse the lateral lock-in phenomenon on real footbridges. The proposed crowd-structure interaction model is organized in three levels: (i) pedestrian-structure interaction; (ii) interaction among pedestrians in the crowd; and (iii) interaction between the crowd and the structure. To this end, first, the human-structure interaction of each pedestrian is modelled via a simplified two degrees of freedom system. Second, the interaction among pedestrians inside the crowd is simulated using a multi-agent model. The considered model simulates the movement of each pedestrian from the dynamic equilibrium of the different social forces that act on him/her. Finally, the crowd-structure interaction is achieved modifying the behaviour of the pedestrians depending on the comfort level experienced. For this purpose, the recommendations established by the French standards have been considered. The integration of the three levels in an overall model is achieved by the implementation of a predictive– corrective method. The performance of the proposed model is validated correlating the numerical and experimental dynamic response of the Pedro e Inês footbridge during the development of a lateral lock-in pedestrian test. As the first lateral natural frequency of the footbridge is inside the range that characterizes the walking pedestrian step frequency in lateral direction, numerical and experimental studies were performed to analyse its behaviour under pedestrian action. The agreement between the numerical and experimental results is adequate. However, further studies are recommended in order to generalize the proposed approach and facilitate its use during the design project of future footbridges.
A direct pedestrian-structure interaction model to characterize the human induced vibrations on slender footbridges
(Consejo Superior de Investigaciones Científicas, CSIC: Instituto Eduardo Torroja, 2014) Jiménez Alonso, Javier Fernando; Sáez Pérez, Andrés; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
Although the scientific community had knowledge of the human induced vibration problems in structures since the end of the 19th century, it was not until the occurrence of the vibration phenomenon happened in the Millennium Bridge (London, 2000) that the importance of the problem revealed and a higher level of attention devoted. Despite the large advances achieved in the determination of the human-structure interaction force, one of the main deficiencies of the existing models is the exclusion of the effect of changes in the footbridge dynamic properties due to the presence of pedestrians. In this paper, the formulation of a human-structure interaction model, addresses these limitations, is carried out and its reliability is verified from previously published experimental results.
A finite element implementation of phase-field approach of fracture for nonlinear solid shells including inelastic material behavior
(ELSEVIER, 2024) Valverde González, Ángel de Jesús; Asur Vijaya Kumar, Pavan Kumar; Quintanas Corominas, Adrià; Reinoso Cuevas, José Antonio; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP-131:Elasticidad y Resistencia de Materiales
The parametrization of shell structures using the so-called solid shell concept has been widely exploited in the last decades. This trend is mainly attributed to the relatively simple kinematic treatment of solid shells in the corresponding finite element formulation in conjunction with the use of unmodified three-dimensional material laws, among other aspects. In the present investigation, we provide a comprehensive finite element implementation of solid shells incor- porating: (i) the use of Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) methods to prevent locking issues, (ii) the phase-field approach for triggering fracture events, and (iii) some representative inelastic material models. The current modular implementation has been integrated into the FE package ABAQUS via the user-defined routine UEL. Several representative examples demonstrate the applicability of the present formulation.
A finite element implementation of phase-field approach of fracture for nonlinear solid shells including inelastic material behavior
(Elsevier, 2024-06) Valverde González, Ángel de Jesús; Asur Vijaya Kumar, Pavan Kumar; Quintanas-Corominas, Adria; Reinoso Cuevas, José Antonio; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP131: Elasticidad y Resistencia de Materiales
The parametrization of shell structures using the so-called solid shell concept has been widely exploited in the last decades. This trend is mainly attributed to the relatively simple kinematic treatment of solid shells in the corresponding finite element formulation in conjunction with the use of unmodified three-dimensional material laws, among other aspects. In the present investigation, we provide a comprehensive finite element implementation of solid shells incorporating: (i) the use of Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) methods to prevent locking issues, (ii) the phase-field approach for triggering fracture events, and (iii) some representative inelastic material models. The current modular implementation has been integrated into the FE package ABAQUS via the user-defined routine UEL. Several representative examples demonstrate the applicability of the present formulation.
A Finite Element‑Based Methodology for the Thermo‑mechanical Analysis of Early Age Behavior in Concrete Structures
(SpringerOpen, 2019) Cifuentes-Bulté, Héctor; Montero Chacón, Francisco de Paula; Galán, J; Cabezas, Joaquín; Martínez de la Concha, Antonio; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Economía y Competitividad (MINECO). España
This paper presents a general procedure based on fracture mechanics models in order to analyze the level of cracking and structural safety in reinforced concrete elements at early ages, depending on the stripping time. Our procedure involves the development of a thermo-mechanical numerical model based on the finite element method that accounts for the change in the mechanical properties of concrete with time. Moreover, fracture mechanisms are analyzed by means of a material damage model, which is characterized via specific experimental results obtained for standard specimens and notched beams under three-point bending testing. The loading conditions are both thermal and mechanical, and are obtained from the hydration process for a given concrete dosage. The presented methodology allows for the determination of the optimal stripping time, whereas it helps assessing the analysis of the cracking and the stress states of the elements under consideration. A practical application, namely the analysis of a retaining wall, is used to validate our methodology, showing its suitability in engineering practice.
A framework for the analysis of fully coupled normal and tangential contact problems with complex interfaces
(Elsevier B.V., 2021) Bonari, Jacopo; Paggi, Marco; Reinoso Cuevas, José Antonio; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia, Innovación y Universidades (España); European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Consejería de Economía y Conocimiento de la Junta de Andalucía (España); Universidad Bundeswehr de Múnich (Alemania); Erasmus+; Deutscher Akademischer Austauschdienst (DAAD).; Ministerio italiano de Educación, Universidad e Investigación (MIUR)
An extension to the interface finite element with eMbedded Profile for Joint Roughness (MPJR interface finite element) is herein proposed for solving the frictional contact problem between a rigid indenter of any complex shape and an elastic body under generic oblique load histories. The actual shape of the indenter is accounted for as a correction of the gap function. A regularised version of the Coulomb friction law is employed for modeling the tangential contact response, while a penalty approach is introduced in the normal contact direction. The development of the finite element (FE) formulation stemming from its variational formalism is thoroughly derived and the model is validated in relation to challenging scenarios for standard (alternative) finite element procedures and analytical methods, such as the contact with multi-scale rough profiles. The present framework enables the comprehensive investigation of the system response due to the occurrence of tangential tractions, which are at the origin of important phenomena such as wear and fretting fatigue, together with the analysis of the effects of coupling between normal and tangential contact tractions. This scenario is herein investigated in relation to challenging physical problems involving arbitrary loading histories.
A frequency-domain approach to model vertical crowd-structure interaction in lightweight footbridges
(Elsevier, 2023-08) Gallegos-Calderón, Christian; Naranjo Pérez, Javier; Renedo, Carlos M.C.; Muñoz Díaz, Iván; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (Spain) and 10.13039/501100011033 FEDER, European Union grant PID2021-127627OB-I00
Load models that account for Human-Structure Interaction (HSI) may be preferable to accurately predict the dynamic response of lightweight footbridges subjected to pedestrian actions. Representing each person within a crowd may not be practical in engineering design calculations as time-variant models with a large number of degrees of freedom have to be managed. In addition, high computational time may be required to achieve the steady-state response. In this sense, this paper proposes a novel approach to calculate the vertical steady-state response of footbridges from a time-invariant coupled crowd-structure system. Considering the model of the structure and a feedback model of the crowd, a total closed-loop Transfer Function (TF) of the coupled system is derived. Based on this frequency-domain interacting methodology, a step-by-step procedure is set to asses the vibration serviceability of lightweight footbridges due to harmonic excitations through simple algebraic operations. The proposal is used to study a Fibre Reinforced Polymer footbridge subjected to two streams of walking pedestrians. For this structure, a good compromise between experimental and numerical results is obtained in terms of vertical vibrations and TFs. To further validate the proposed approach, a pre-stressed concrete laboratory facility is also analysed, obtaining a satisfactory agreement between the experimental and numerical TFs. Thus, the proposed approach allows to evaluate lightweight footbridges under crowd-induced loads considering HSI in a simple and accurate manner, which is clearly geared to practice.

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