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• Synergistic effects of tubular halloysite clay and zirconium phosphate on thermal behavior of intumescent coating for structural steel

  Y. Lee, F. Ahmad, S. Kabir, P. Masset, E. Oñate, G. Yeoh

  Journal of Materials Research and Technology (2022). Vol. 18, pp. 4456-4469

  
  

  Abstract

  Zirconium phosphate (ZrP) recently introduced in intumescent fire protective coating has shown improvement in developing ceramic layer. The tubular halloysite clay (THC) due to its unique molecular structure can be combined with ZrP to enhance fire resistance by developing a strong silica network on the char surface. This study is aimed to investigate the synergistic effects of tubular halloysite clay and zirconium phosphate fillers to improve the thermal performance of the intumescent coating. The control coating formulation and a range of coating formulations using a combination of weight percentage of THC and ZrP were developed to study the influences of fillers on fire performance. The char expansion and fire resistance tests of the coatings were conducted using furnace fire test and Lab scale fire jet. Thermal stability of the coating was determined by TGA and char was characterized by FESEM, XRD, FTIR and XPS. Water-resistance test of the coating was performed according to ASTM D-870. Results showed that the reinforcement of THC-ZrP showed promising improvement on the performance of IFC and substrate temperature was far below the critical temperature, 550 °C. Sample HZ 5 showed the least backside steel substrate temperature of 219 °C. Expansion rate of char was found reduced with the addition of THC but improved the char compactness. The addition of THC and ZrP in IFC improved 18% fire resistance performance and 5% residual wt. Of char. Char morphology showed silica network, XRD and FTIR confirmed the presence of silicon. Water absorption test showed 95% less water absorption (HZ-5) compared to control coating. Post water immersion, fire test showed 7% increase in substrate temperature which is 18% less than control coating after water immersion fire test.

  Abstract
  Zirconium phosphate (ZrP) recently introduced in intumescent fire protective coating has shown improvement in developing ceramic layer. The tubular halloysite clay (THC) [...]

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• Adaptive breakwaters with inflatable elements for coastal protection. Preliminary numerical estimation of their performance

  P. Ryzhakov, F. Hermosilla, P. Ubach, E. Oñate

  Ocean Engineering (2022). Volume 251, 110818

  
  

  Abstract

  Excessive erosion of sand beaches defines a serious problem worldwide and is particularly pronounced in the Mediterranean region. One of the typical measures for alleviating this erosion consists in building rigid breakwaters in the vicinity of the coast for diminishing sand transport. This solution, however, is often accompanied by undesirable alteration of the coastline. In this work we address the viability of using conceptually new structures with inflatable elements striving to improve the control over the sediment transport. The aim of the inflatable element is to adapt the breakwater configuration to the sea state. A preliminary design is proposed and tested in a number of storm scenarios using an in-house finite element/level set model. Influence of various breakwater design parameters upon its functionality is studied. Transmission coefficients and maximum pressures exerted upon the breakwater are estimated. Numerical study performed shows that for the considered range of storm scenarios the proposed design is characterized by transmission coefficients below 0.5. It is also shown that the use of inflatable elements facilitates adaptation of the breakwater functionality to a given sea state.

  Abstract
  Excessive erosion of sand beaches defines a serious problem worldwide and is particularly pronounced in the Mediterranean region. One of the typical measures for alleviating [...]

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• Numerical simulation of particle impact drilling (PID) systems: a one-way coupled approach

  G. Casas, I. de-Pouplana, R. Gandikota, E. Oñate

  Computational Particle Mechanics (2022). pp. 1-23

  
  

  Abstract

  A numerical technique based on a CFD-DEM method is presented for the analysis of particle impact drilling (PID) systems. The method is built from a preexisting finite element Navier–Stokes solver for the fluid phase and a discrete element method module for the steel particles which this drilling technology utilizes to enhance the penetration rate. We provide a detailed description of the most relevant implementation issues, including our choice of the hydrodynamic forces appropriate for power-law fluids. We also discuss several critical aspects related to the validity of the simplifying assumptions that will be helpful to simulation engineers. We apply our simple, one-way coupled approach on designs provided by an industrial partner to illustrate its potential as an analysis tool for this promising drilling technology. The goal of this work is, on the one hand, to provide evidence for the usefulness of the numerical approach as a design tool for PID systems, as well as a detailed discussion of the different aspects to be assessed for an effective simulation campaign. On the other hand, a series of modeling aspects that require further work are identified. The focus of the simulation campaign presented is on the particles and fluid flow characteristics within the drill bit.

  Abstract
  A numerical technique based on a CFD-DEM method is presented for the analysis of particle impact drilling (PID) systems. The method is built from a preexisting finite element [...]

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• A FIC-FEM procedure for the shallow water equations over partially wet domains

  M. Maso, I. de-Pouplana, E. Oñate

  Computer Methods in Applied Mechanics and Engineering (2022). Volume 389, 114362

  
  

  Abstract

  We present a stable finite element formulation for the shallow water equations using the finite increment calculus (FIC) procedure. This research is focused on the stability properties of the FIC technique and uses linear triangles for the spatial discretization with an equal order of interpolation for all the variables. The extension to higher order polynomial interpolation functions and different geometries is straightforward. The present FIC-FEM procedure is also able to introduce artificial viscosity for an adequate shock capturing. An implicit time integration has been used. Special attention has been payed to the dry domain in order to solve the moving boundaries with a fixed mesh Eulerian approach. Three academic examples are included in order to test the capabilities of the FIC-FEM procedure: the global stabilization, the shock capturing technique and the dry-wet interface. An experimental benchmark tests the overall accuracy of the present formulation.

  Abstract
  We present a stable finite element formulation for the shallow water equations using the finite increment calculus (FIC) procedure. This research is focused on the stability [...]

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• Combination of the finite element method and particle-based methods for predicting the failure of reinforced concrete structures under extreme water forces

  E. Oñate, A. Cornejo Velázquez, F. Zarate, K. Kashiyama, A. Franci

  Engineering Structures (2022). Vol. 251, Part B, 113510

  
  

  Abstract

  We present a combination of the Finite Element Method (FEM), the Particle Finite Element Method (PFEM), and the Discrete Element Method (DEM) for modeling and analyzing the failure of reinforced concrete structures under impulsive wave forces originating from free-surface flows in critical water hazards. The free-surface water flow is modeled with the PFEM, while the structural behavior and the fractures induced by the water forces in the structure are modeled with a coupled FEM–DEM technique. The concrete material behavior is simulated with a standard isotropic damage model. The reinforcing bars are modeled by a rule of mixtures procedure, for simplicity. The possibilities of the new integrated PDFEM approach for predicting the evolution of free-surface tsunami-type waves and their devastating effect on constructions are validated with experiments on the failure of reinforced concrete plates under large impacting waves, performed in a laboratory facility in Japan.

  Abstract
  We present a combination of the Finite Element Method (FEM), the Particle Finite Element Method (PFEM), and the Discrete Element Method (DEM) for modeling and analyzing the [...]

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• Virtual reality stories for construction training scenarios: the case of social distancing at the construction site

  F. Rivera, J. Mora-Serrano, E. Oñate

  WIT Transactions on The Built Environment (2022). Vol. 205, pp. 37-47

  
  

  Abstract

  The architecture, engineering, construction and operation industry has high accident rates, and its workers are susceptible to certain risks due to the variability of their worksites, the tasks they perform and the equipment they use. Of particular interest is the coexistence of workers and heavy machinery in the same space, which is one of the main causes of high accident rates. Increasing digitisation also incorporates the use of new systems (e.g. UAVs, autonomous vehicles, robotic devices), which must function while preserving worker safety. As such, worker training is also essential in these contexts. Research indicates that occupational risk prevention training in construction is not satisfactory. Traditional methods based on lectures (where the student does not take an active role) and traditional test-type assessments do not result in significant learning and fail to create a culture of prevention among workers. In the context of the COVID-19 pandemic, the construction industry has had to incorporate new prevention measures to continue projects while protecting workers’ health and safety. Virtual reality has demonstrated advantages in adapting to different contexts, allowing for the agile development of training experiences with immersive characteristics and more significant learning than traditional methods. This research shows the application and agile development of a training experience for social distancing at construction sites to prevent COVID-19 transmission, based on virtual reality and building information modelling and using serious games as a teaching strategy.

  Abstract
  The architecture, engineering, construction and operation industry has high accident rates, and its workers are susceptible to certain risks due to the variability of their [...]

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• Factors influencing Safety on Construction Projects (fSCPs): Types and categories

  F. Rivera, J. Mora, E. Oñate

  Int. J. Environ. Res. Public Health (2021). Vol. 18(20), 10884

  
  

  Abstract

  Due to the fact of activity, environment and work dynamics, the construction industry is characterised by high accident rates. Different initiatives have emerged to reduce these figures, which focus on using new methodologies and technologies for safety management. Therefore, it is essential to know the key factors and their influence on safety in construction projects (fSCPs) to focus efforts on these elements. Through a systematic literature review, based on PRISMA methodology, this article identifies, describes and categorises 100 factors that affect construction safety. It thus contributes by providing a comprehensive general framework, unifying previous studies focused on specific geographic areas or case studies with factors not considered or insufficiently disaggregated, along with an absence of classifications focused on understanding where and how factors affect the different dimensions of construction projects. The 100 factors identified are described and categorised according to the dimensions and aspects of the project in which these have an impact, along with identifying whether they are shaping or immediate factors or originating influences for the generation of accidents. These factors, their description and classification are a key contribution to improving the systematic creation of safety and generating training and awareness materials to fully develop a safety culture in organisations.

  Abstract
  Due to the fact of activity, environment and work dynamics, the construction industry is characterised by high accident rates. Different initiatives have emerged to reduce [...]

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• The P-DNS method applied to the numerical simulation of turbulent multiphase flows

  J. Giménez, S. Idelsohn, E. Oñate

  Mecánica Computacional (2021). Vol. 38 (30), 1177-1177

  
  

  Abstract

     The Pseudo-Direct Numerical Simulation (P-DNS) method is a numerical approach to solve multiscale fluid dynamics phenomena overcoming the computational burden associated with direct numerical resolution of the governing equations. In P-DNS, both the coarse scale and the fine scale are solved numerically. The most expensive part of the computations, the solutions of the fine scale, are parametrized to be performed offline and store their results in dimensionless databases. This latter allows us to construct synthetic models to emulate the fine scale behavior when coarse scale solutions are computed. In this work, a multiphase representative volume element (RVE) is designed for the specific case of a dispersed flow of heavy particles in air. Making use of high performance computing facilities, a set of numerical experiments for a wide range of volume fractions, particle distribution sizes, and inertial forces introduced as shear loads are carried out. Quantitative results of the statistically stationary turbulent state are obtained. This brings insights into the turbulence modulation phenomenon, i.e. the change of the kinetic energy of the carrier flow due to the presence of the particles. The database of RVE results is stored in an artificial neural network to facilitate its use in general flow solvers via a fast interpolation technique. Global case studies of particulate flows are analyzed, highlighting the differences and similarities found using the fine-scale model developed vis-a-vis a standard turbulence modeling.

  Abstract
     The Pseudo-Direct Numerical Simulation (P-DNS) method is a numerical approach to solve multiscale fluid dynamics phenomena overcoming the computational burden [...]

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• Simulation of the burning and dripping cables in fire using the particle finite element method

  J. Marti, B. Schartel, E. Oñate

  Journal of Fire Sciences (2022). Vol. 40(1), pp. 3-25

  
  

  Abstract

  The behavior of the cable jacket in fire characterized by the tendency to melt and drip constitutes a major source of fire hazard. The reason is that the melted material may convey the flame from one point to another, expanding fire and contributing to the fire load. In this article, the capability of a new computational strategy based on the particle finite element method for simulating a bench-scale cables burning test is analyzed. The use bench-scale test has been previously used to simulate the full-scale test described in EN 50399. As the air effect is neglected, a simple combustion model is included. The samples selected are two cables consisting of a copper core and differently flame retarded thermoplastic polyurethane sheets. The key modeling parameters were determined from different literature sources as well as experimentally. During the experiment, the specimen was burned under the test set-up condition recording the process and measuring the temperature evolution by means of three thermocouples. Next, the test was reproduced numerically and compared with a real fire test. The numerical results show that the particle finite element method can accurately predict the evolution of the temperature and the melting of the jacket.

  Abstract
  The behavior of the cable jacket in fire characterized by the tendency to melt and drip constitutes a major source of fire hazard. The reason is that the melted material may [...]

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• A multiscale approach for the numerical simulation of turbulent flows with droplets

  J. Giménez, S. Idelsohn, E. Oñate, R. Lohner

  Archives of Computational Methods in Engineering (2021). Special Issue: Modeling and Simulation of Infectious Diseases

  
  

  Abstract

  A multiscale approach for the detailed simulation of water droplets dispersed in a turbulent airflow is presented. The multiscale procedure combines a novel representative volume element (RVE) with the Pseudo Direct Numerical Simulation (P-DNS) method. The solution at the coarse-scale relies on a synthetic model, constructed using precomputed offline RVE simulations and an alternating digital tree, to characterize the non-linear dynamic response at the fine-scale. A set of numerical experiments for a wide range of volume fractions, particle distribution sizes, and external shear forces in the RVE are carried out. Quantitative results of the statistically stationary turbulent state are obtained, and the turbulence modulation phenomenon due to the presence of droplets is discussed. The developed synthetic model is then employed to solve global scale simulations of flows with airborne droplets via the P-DNS method. Improved predictions are obtained for flow conditions where turbulence modulation is noticeable.

  Abstract
  A multiscale approach for the detailed simulation of water droplets dispersed in a turbulent airflow is presented. The multiscale procedure combines a novel representative [...]

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