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George Markou
Civil Engineering Department
Faculty of Engineering and Applied Sciences
PhD -          2011, National Technical University of Athens, Greece
Masters -   2005, National Technical University of Athens, Greece
Bachelor - 2004, National Technical University of Athens, Greece

 
Selected Publications
2013 - Generating Embedded Rebar Elements for Large-Scale RC Models
Authors: G. Markou
“Generating Embedded Rebar Elements for Large-Scale RC Models”, SEECCM III, 3rd South-East European Conference on Computational Mechanics, Kos Island, Greece, 12–14 June 2013”.
2013 - Numerical Investigation of a 3D Detailed Limit-State Simulation of a Full-Scale RC Bridge
Authors: G. Markou
“Numerical Investigation of a 3D Detailed Limit-State Simulation of a Full-Scale RC Bridge”, SEECCM III, 3rd South-East European Conference on Computational Mechanics, Kos Island, Greece, 12–14 June 2013.
2013 - Embedded reinforcement mesh generation method for large-scale RC simulations: Case study
Authors: G. Markou
“Embedded reinforcement mesh generation method for large-scale RC simulations: Case study”, AHU Journal of Engineering and Applied Sciences, 5(1), pp. 23-42, 2013.
2012 - Modeling of Reinforced Concrete Structures with 3d detailed finite element models
Authors: G. Markou and M. Papadrakakis,
“Modeling of Reinforced Concrete Structures with 3d detailed finite element models”, AHU Journal of Engineering and Applied Sciences, 4 (2), pp 47-63, 2012.
2012 - AN EFFICIENT GENERATION METHOD OF EMBEDDED REINFORCEMENT IN HEXAHEDRAL ELEMENTS FOR REINFORCED CONCRETE SIMULATIONS
Authors: G. Markou and M. Papadrakakis,
“AN EFFICIENT GENERATION METHOD OF EMBEDDED REINFORCEMENT IN HEXAHEDRAL ELEMENTS FOR REINFORCED CONCRETE SIMULATIONS”, Advances in Engineering Software ADES, 45 (1), pp. 175-187, 2012. (Journal)
2011 - Finite Element Analysis Software.
Authors: George Markou
“User’s Manual”, ReConAn FEA v1.00, Finite Element Analysis Software.
2011 - Modeling of Reinforced Concrete Structures.
Authors: George Markou
“Modeling of Reinforced Concrete Structures. Detailed Three-Dimensional Nonlinear Hybrid Simulation for the Analysis of Large-Scale Reinforced Concrete Structures”, LAP Lambert Academic Publishing (2011-09-01).
2011 - Non-Linear Simulation of Real-Scale RC Structures with Detailed and Hybrid Finite Element Models
Authors: G. Markou and M. Papadrakakis
7th GRACM International Congress on Computational Mechanics Athens, 30 June – 2 July 2011.
2010 - Finite Element Analysis Software.
Authors: George Markou
“User’s Manual”, ReConAn FEA Academic Version, Finite Element Analysis Software.
2010 - Detailed Three-Dimensional Modeling of Reinforced Concrete Structures
Authors: G. Markou and M. Papadrakakis,
9th HSTAM International Congress on Mechanics Limassol, Cyprus, 12 – 14 July, 2010.
2010 - Generating Embedded Reinforcement in Hexahedral Elements for Concrete Simulation
Authors: G. Markou and M. Papadrakakis
9th HSTAM International Congress on Mechanics Limassol, Cyprus, 12 – 14 July, 2010.
2010 - 3D Mesh Update Techniques in Fluid-Structure Interaction Problems
Authors: G. Markou and M. Papadrakakis
9th HSTAM International Congress on Mechanics Limassol, Cyprus, 12 – 14 July, 2010.
2007 - MESH UPDATE TECHNIQUES: ROBUSTNESS AND EFFICIENSY
Authors: G. Markou and M. Papadrakakis
“MESH UPDATE TECHNIQUES: ROBUSTNESS AND EFFICIENSY”, Int. Conf. on Computational Methods for Coupled Problems in Science and Engineering, COUPLED PROBLEMS 2007, Santa Eulalia, Ibiza, Spain.
2007 - The ortho-Semi-Torsional (OST) spring analogy method for 3D mesh moving boundary problems
Authors: G. Markou, Z.S. Mouroutis, D.C. Charmpis and M. Papadrakakis
“The ortho-Semi-Torsional (OST) spring analogy method for 3D mesh moving boundary problems”, Computer Methods in Applied Mechanics and Engineering, 196 (2007) 747-765.
2007 - An efficient mesh updating technique for fluid structure interaction problems
Authors: Mouroutis, G. Markou, D.C. Charmpis and M. Papadrakakis
International Journal of Computational Methods, Vol. 4, Issue 2, June 2007, pp.249-263.
2006 - Numerical study of four mesh update techniques
Authors: G. Markou and M. Papadrakakis
First South-East European Conference on Computational Mechanics SEECCM-06, June 28-30, 2006, Kragujevac, Serbia and Montenegro.
2005 - An efficient mesh updating technique for fluid structure interaction problems
Authors: Zacharias S. Mouroutis, G. Markou, Dimos C. Charmpis, Dimitris G. Koubogiannis and Manolis Papadrakakis
Zacharias S. Mouroutis, G. Markou, Dimos C. Charmpis, Dimitris G. Koubogiannis and Manolis Papadrakakis, “An efficient mesh updating technique for fluid structure interaction problems”, Int. Conf. on Computational Methods for Coupled Problems in Science and Engineering, COUPLED PROBLEMS, Santorini, May 2005.

 
Keynote address/Lectures
2010 – SPOLMIK (Civil Engineering Association of Cyprus) and Multisoft.
Lecture Title: “Eurocodes – Seismic Resistant Reinforced Concrete Structures – Implementation in Computational Mechanics”.
 
Graduate Students Supervision
BSc and MSc Thesis Supervision

1. Vasilomichelaki Stefania (2008), “Nonlinear Analysis of Steel Framed Structures with the Finite Element Method”, Diploma Thesis, National Technical University of Athens, Department of Civil engineering. [In Greek]
2.  Karakitsios Panagiotis (2009), “Nonlinear Analysis of Reinforced Concrete Framed Structures with the Finite Element Method”, Diploma Thesis, National Technical University of Athens, Department of Civil Engineering, Athens. [In Greek]
3. Vasilomichelaki Stefania (2010), “Parametric Investigation of Reinforced Concrete Framed Structures with the Finite Element Method”, Master’s Thesis, National Technical University of Athens. [In Greek]
4. Kleanthous Panagiotis (2011), “Non-Linear Analysis of Reinforced Concrete Structures with the Finite Element Method”, Diploma Thesis, Frederick University of Cyprus.
 
Research Interests/Areas
 Modeling of Structures with the Finite Element Method

Worldwide, Civil Engineers use software packages so as to analyze and design their structures. Furthermore, researchers of all engineering fields use numerical methods in order to solve different physical phenomena and predict approximate solutions that are used to derive significant conclusions. The Finite Element Method was proved to be the most efficient and numerically robust method that was able to provide the necessary numerical tools for accomplishing this task. Today, in their great majority, commercial and research software packages uses this method which is considered to be the basis of all numerical simulation.

After taking into consideration all the advances that this method provides to those that are able to implement it and given the research work performed during my Diploma and Master’s Thesis, the need for deeper investigation through an excessive involvement with this method was recognized thus the development of a general Finite Element Analysis (FEA) code was initiated. After a period of two years, the main code structure of ReConAn FEA was completed. The advances of this FEA software are found in its ability to model reinforced concrete (RC) structure through the use of different Finite Element (FE) types.

The most advanced types of modeling that ReConAn FEA incorporates are:

1. The Natural Beam-Column Flexibility-Based (NBCFB) FE: This element can simulate and analyze the nonlinear behavior of steel and RC structures by using the fiber approach so as to discretize each section of the structural members for the plastification distribution. It is also integrated with the natural mode method and the flexibility method which is used for the stiffness calculation. Finally, the use of a nonlinear state determination is performed for the internal state determination procedure at elemental level, making its numerical behavior extremely robust and accurate.

2. The 8-noded and 20-noded hexahedral elements which treat the phenomenon of cracking with the smeared crack approach and use 3D material models for concrete simulations. Reinforcement is modeled as embedded rebar elements and the ability of modeling these elements with truss or beam elements is provided.

3. A Hybrid model which combines the above two modeling types providing the required numerical tools of modeling the shear dominated structural members with the detailed model and the rest of the structure with the NBCFB element.

Through the development of ReConAn FEA algorithm, I’ve managed to enhance my research agenda and knowledge regarding all the main arithmetical parts which FEM deals with in order to create a complete FEA code:

I. FE formulations. Stiffness assemblage, internal forces computation and numerical behavior.

II. Solvers. Numerical handling of large-scale numerical problems. Different types of solution algorithm.

III. Mesh generation procedures. Main contribution to the embedded mesh generation procedure of steel rebar elements inside hexahedral elements used for concrete modeling.

IV. Nonlinear procedure. The solution of a nonlinear problem, either static or dynamic, requires special handling since numerical instabilities are excessive, especially in cases where the smeared crack approach is used, which induces numerical discontinuities in the numerical model when crack openings occur.

V. Connecting the numerical with the physical problem. The most difficult task in my opinion is to be able to derive whether a model is appropriate to predict realistically the mechanical behavior of a structure thus being able to confirm whether its numerical results are acceptable or not. This is why many believe that FEM is more an art than science.

VI. Visual representation of the results. For visualizing the crack propagation of a 3D detailed model, a post-processing software was developed so as to represent the predicted crack patterns and the deformation shape of the at hand numerical model.

VII. Development of object oriented FEA code. Dynamic handling of memory. Optimum and smart programming techniques.

Fluid-Structure Interaction / Dynamic mesh update

During my Diploma and Master Thesis, I performed research work on the numerical problem known as Fluid-Structure Interaction (FSI). Particularly, my research work was focused on the problem of the dynamic mesh update of the fluid domain which undergoes large displacements. After an excessive literature review and research through algorithmic implementations I’ve manages to develop an efficient and numerically robust mesh update technique which was designed to dynamically update 3D tetrahedral meshes that undergo large displacements.

The implementation of this type of modeling is widely used for the numerical modeling of aeronautical problems (aircraft flight, parachutes simulations, etc.), naval and marine applications, automobile applications (optimizing aerodynamics of an F1 car, etc.), war technology (optimization of fighting aircrafts, weapons aerodynamics, etc.), bioengineering (blood flow inside the human body) and any type of physical problem which involves the interaction between a fluid and a structural domain.

Finite Element Technology
In general Finite Element Technology (FET) is rapidly evolving and will evolve the next decades in an attempt of solving more complicated physical problems or providing more accurate and realistic results in predicting the mechanical behavior of different structural systems. This is also why modern researchers always try to include analyses models when performing an experiment, so as to confirm the correctness of their experimental setups, acknowledging the importance of using FEM as a validation tool in engineering science. Therefore, it is evident that the wide acceptance of using computational mechanics by scientists that perform experimental research is indisputable and underlines the significance of mastering the FEM and using it for future research projects.

This ability is provided since ReConAn FEA is a general software that can incorporate any type of FE, material model and solution procedure for simulating the mechanical behavior of different physical systems with a realistic manner and computational efficiency.

Research in Progress and Future Tasks

The main analyses conducted during my Ph.D. dissertation were monotonic nonlinear push over analysis thus the cyclic behavior is now under development. In addition to that, parametric investigations regarding the numerical behavior of the above models is investigated through the analysis of real-scale structures and improvement design technics are being developed so as to derive seismically resistant structures which will be able to transfer with safety the seismic forces that will be applied due to the design earthquake.

So as to model realistically the numerical behavior of RC and steel structural behavior in order to design and construct safer structures, soil material models are going to be incorporated for the modeling of the ground foundation, taking this way into account the soil-structure interaction. With the completion of this future task, we will be able of performing analyses for the cases of different real problems such as Tunnel-Soil Interaction, Foundation-Soil Interaction, Retaining Wall-Soil Interaction, Pile-Soil Interaction etc.

In addition to that, the algorithmic development of ReConAn FEA is also a research procedure which evolves with the above research work providing the ability of future enhancements of different types of FE modeling methods. It is important to state here that one of the most interesting engineering problems is the aerodynamics of structures especially in a time that high rise buildings and large scale cable or suspended bridges are being constructed. Since the wind loads whereas, wind dynamics, are known to be the largest applied load which these structures are designed to resist to, the Fluid-Structure Interaction problem in one of the most promising research areas, especially for developing more accurate formulae in wind load prediction and check the reliability of existing code provision regarding wind loads.

Finally, the scientific field of numerical modeling, analysis and design of fiber reinforced concrete (FRC) structures is rapidly evolving. Modeling these type of structures with 3D detailed models will provide us with the ability of investigating their mechanical behavior thus enabling us to propose design guidelines towards safer structures with a reduced construction cost. Therefore, the incorporation of this modeling method into ReConAn FEA code will be performed, for predicting the nonlinear behavior of FRC structures. Being able to use numerical models that objectively predict the mechanical behavior of FRC, then this technology can be directly applied for modeling retrofitted structures, a scientific area that still remains unexploited due to the complexity of the physical problem (modeling the existing corroded and newly applied materials, interaction at the interface, selection of the retrofitting geometry, etc.).


Research Projects
A.
Duration, Funding Ag. and Funding 2004 - 2005, (1 Years) Government funding (Greece).
Title Analysis of a Fluid Structure Interaction Problem with the Finite Element and Finite Volume Methods
Role and Contribution Researcher in Computational Mechanics – Programming – Running Analysis.


B.
Duration, Funding Ag. and Funding 2008 - 2011, (3 Years) National Technical University of Athens.
Title Analysis of Reinforced Concrete Structures with the Finite Element Method
Role and Contribution Young Researcher. Conduct the research project.


C.
Duration, Funding Ag. and Funding 2010 - 2011, (1 Years) Interserve Ltd - for MOD UK.
Title Seismic assessment of Reema Panel Buildings - Episcopi D- Block Pilot Study and Option Study
Role and Contribution Analysis through FEA software. Simulation and modeling consulting.
 

 
Honors/Awards
1. A three year scholarship from the J. Argyris foundation to a Ph.D. student for the completion of his thesis.
2. Award of Christou Papakipriakopoulou (mathematics).
3. Award of Nicolaou I. Kritikou.
4. Three Awards from the TEE (Technical Chamber of Greece) for his academic performance at the National Technical University of Athens, Department of Civil Engineering (1999-2000, 2000-2001 & 2002-2003).
5. Award from the Thomaidio Foundation for publishing a paper before a year has passed from my bachelors’ degree graduation.
 
Contact Details
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