Nikos Lagaros | National Technical University of Athens (original) (raw)
Papers by Nikos Lagaros
Proceedings of the 4th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2013), 2014
A number of articles have been published, studying the issue of torsional response of reinforced ... more A number of articles have been published, studying the issue of torsional response of reinforced concrete (RC) buildings [1], the majority of them were focused on the strength of the structural elements or the structure as a whole. In the work by Kan and Chopra [2] the Base Shear Torque (BST) surfaces have been proposed which provide a measure of the structural system’s strength reduction due to the torsion inflicted by earthquake loading. On the other hand, some other researchers examine the additional displacements caused on the structural system due to the torsional response. Paulay [3] suggested maximizing the ductility capacity in an effort to undertake the increased displacement due to the torsional response. Although a structural system can be assessed based on the above mentioned criteria, where the designer lacks the necessary design procedure to accomplish them. This can be achieved in a robust and reliable way through a structural optimization procedure [4]. In this work ...
Proceedings of the 3rd South-East European Conference on Computational Mechanics – SEECCM III, 2013
Proceedings of the 3rd South-East European Conference on Computational Mechanics – SEECCM III, 2013
III European Conference on Computational Mechanics
Case Studies in Structural Engineering, 2014
International Journal for Numerical Methods in Engineering, 2003
Computers & Structures, 2002
Frontiers in Built Environment
The coupled lateral-torsional response is observed in building structures subjected to dynamic ex... more The coupled lateral-torsional response is observed in building structures subjected to dynamic excitation due to lack of symmetry in terms of mass/stiffness in any of the stories’ plan views; such structural systems are called eccentric. Much damage and even collapse are concerned with building structures with asymmetric plan views. Combined torsional-translational vibration of their structural system results in higher ductility demands, especially to vertical structural elements located at the perimeter of the plan view. This study examines the minimization problem of the torsional response of an eccentric, multi-story reinforced concrete (RC) building by strengthening its vertical structural elements with RC jackets. The problem of minimizing the eccentricity between mass and rigidity centers for all story layouts and the corresponding minimization problem of the eccentricity between mass and strength centers for all stories are considered two separate formulations for the reducti...
International Journal for Simulation and Multidisciplinary Design Optimization, Oct 1, 2007
ABSTRACT In this work the uncertainty of a structural system is taken into account in the framewo... more ABSTRACT In this work the uncertainty of a structural system is taken into account in the framework of a structural Reliability based Robust Design Optimization (RRDO) formulation where probabilistic constraints are incorporated into the robust design optimization formulation. A robust design optimization problem is formulated as a multi-criteria optimization problem. The Pareto front representing the solution of the RRDO problem is composed by designs with a state of robustness, since their performance is the least sensitive to the variability of the uncertain variables. The cross section dimensions together with other structural parameters, such as the modulus of elasticity, the yield stress and the applied loading, are considered as random variables. For the solution of the RRDO problem, the non-dominant Cascade Evolutionary Algorithm is employed combined with a weighted Tchebycheff metric.
Frontiers in Built Environment, Mar 29, 2022
International Journal of Reliability and Safety, 2006
... Seismic hazard is represented by the EC8 spectrum where two uniform hazard spectra for the 2%... more ... Seismic hazard is represented by the EC8 spectrum where two uniform hazard spectra for the 2% and the 50% earthquakes are obtained using peak ground ... Llolleo 34 rock Pichilemu 24 rock Valparaiso UTFSM 28 rock Valparaiso Ventanas 28 soil Vina del Mar 30 soil ...
CISM International Centre for Mechanical Sciences, 2010
ABSTRACT This article presents recent applications of neural computations in the field of stochas... more ABSTRACT This article presents recent applications of neural computations in the field of stochastic finite element analysis of structures and earthquake engineering. The incorporation of Neural Networks (NN) in this type of problems is crucial since it leads to substantial reduction of the excessive computational cost. Earthquake- resistant design of structures using Probabilistic Safety Analysis (PSA) is an emerging field in structural engineering. The efficiency of soft computing methodologies is investigated when incorporated into the solution of computationally intensive earthquake engineering problems considering uncertainties.
Computers & Structures, Jun 1, 2011
ABSTRACT Cited By (since 1996): 1, Export Date: 13 December 2012, Source: Scopus
Engineering Structures, Aug 1, 2005
Structural and Multidisciplinary Optimization, Apr 27, 2006
IGI Global eBooks, Feb 5, 2013
Proceedings of the 4th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2013), 2014
A number of articles have been published, studying the issue of torsional response of reinforced ... more A number of articles have been published, studying the issue of torsional response of reinforced concrete (RC) buildings [1], the majority of them were focused on the strength of the structural elements or the structure as a whole. In the work by Kan and Chopra [2] the Base Shear Torque (BST) surfaces have been proposed which provide a measure of the structural system’s strength reduction due to the torsion inflicted by earthquake loading. On the other hand, some other researchers examine the additional displacements caused on the structural system due to the torsional response. Paulay [3] suggested maximizing the ductility capacity in an effort to undertake the increased displacement due to the torsional response. Although a structural system can be assessed based on the above mentioned criteria, where the designer lacks the necessary design procedure to accomplish them. This can be achieved in a robust and reliable way through a structural optimization procedure [4]. In this work ...
Proceedings of the 3rd South-East European Conference on Computational Mechanics – SEECCM III, 2013
Proceedings of the 3rd South-East European Conference on Computational Mechanics – SEECCM III, 2013
III European Conference on Computational Mechanics
Case Studies in Structural Engineering, 2014
International Journal for Numerical Methods in Engineering, 2003
Computers & Structures, 2002
Frontiers in Built Environment
The coupled lateral-torsional response is observed in building structures subjected to dynamic ex... more The coupled lateral-torsional response is observed in building structures subjected to dynamic excitation due to lack of symmetry in terms of mass/stiffness in any of the stories’ plan views; such structural systems are called eccentric. Much damage and even collapse are concerned with building structures with asymmetric plan views. Combined torsional-translational vibration of their structural system results in higher ductility demands, especially to vertical structural elements located at the perimeter of the plan view. This study examines the minimization problem of the torsional response of an eccentric, multi-story reinforced concrete (RC) building by strengthening its vertical structural elements with RC jackets. The problem of minimizing the eccentricity between mass and rigidity centers for all story layouts and the corresponding minimization problem of the eccentricity between mass and strength centers for all stories are considered two separate formulations for the reducti...
International Journal for Simulation and Multidisciplinary Design Optimization, Oct 1, 2007
ABSTRACT In this work the uncertainty of a structural system is taken into account in the framewo... more ABSTRACT In this work the uncertainty of a structural system is taken into account in the framework of a structural Reliability based Robust Design Optimization (RRDO) formulation where probabilistic constraints are incorporated into the robust design optimization formulation. A robust design optimization problem is formulated as a multi-criteria optimization problem. The Pareto front representing the solution of the RRDO problem is composed by designs with a state of robustness, since their performance is the least sensitive to the variability of the uncertain variables. The cross section dimensions together with other structural parameters, such as the modulus of elasticity, the yield stress and the applied loading, are considered as random variables. For the solution of the RRDO problem, the non-dominant Cascade Evolutionary Algorithm is employed combined with a weighted Tchebycheff metric.
Frontiers in Built Environment, Mar 29, 2022
International Journal of Reliability and Safety, 2006
... Seismic hazard is represented by the EC8 spectrum where two uniform hazard spectra for the 2%... more ... Seismic hazard is represented by the EC8 spectrum where two uniform hazard spectra for the 2% and the 50% earthquakes are obtained using peak ground ... Llolleo 34 rock Pichilemu 24 rock Valparaiso UTFSM 28 rock Valparaiso Ventanas 28 soil Vina del Mar 30 soil ...
CISM International Centre for Mechanical Sciences, 2010
ABSTRACT This article presents recent applications of neural computations in the field of stochas... more ABSTRACT This article presents recent applications of neural computations in the field of stochastic finite element analysis of structures and earthquake engineering. The incorporation of Neural Networks (NN) in this type of problems is crucial since it leads to substantial reduction of the excessive computational cost. Earthquake- resistant design of structures using Probabilistic Safety Analysis (PSA) is an emerging field in structural engineering. The efficiency of soft computing methodologies is investigated when incorporated into the solution of computationally intensive earthquake engineering problems considering uncertainties.
Computers & Structures, Jun 1, 2011
ABSTRACT Cited By (since 1996): 1, Export Date: 13 December 2012, Source: Scopus
Engineering Structures, Aug 1, 2005
Structural and Multidisciplinary Optimization, Apr 27, 2006
IGI Global eBooks, Feb 5, 2013