Evangelos J. Sapountzakis

Evangelos J. Sapountzakis
National Technical University of Athens | NTUA · School of Civil Engineering

Professor

About

268
Publications
35,009
Reads
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2,857
Citations
Citations since 2017
80 Research Items
1118 Citations
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2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Introduction
• Linear and Nonlinear Theory of Elasticity • Advanced Beam Theories • Static and Dynamic Analysis of Structures • Seismic Isolation • Νovel absorption and isolation concepts. Applications to Buildings, Bridges and Wind Turbine Towers
Additional affiliations
September 1985 - present
National Technical University of Athens

Publications

Publications (268)
Article
Full-text available
In this study, a negative stiffness‐based passive vibration absorber is developed and implemented as a seismic retrofitting measure for typical reinforced concrete (RC) residential buildings. The device, namely, the extended KDamper for retrofitting (EKD‐R), is introduced at the base of the structure, between the foundation level and the first stor...
Article
Full-text available
Locally resonant metamaterials (LRMs), with unit-cells exhibiting local resonance, present extraordinary wave propagation properties as a result of their spatial periodicity. However, these structures present certain limitations when wide bandgaps are sought, such as the need of heavy resonating masses. In this paper, a simple dynamic directional a...
Article
Full-text available
A KDamper oscillator is proven to be a more effective alternative to conventional Tuned Mass Damper (TMD) approaches and Quazi Zero Stiffness (QZS) or negative stiffness isolators. In this paper, an extended version of the KDamper (EKD) concept is employed to control the dynamic responses of an undamped (or low damper) SDoF system subjected to vari...
Article
Full-text available
One of the most effective approaches for seismic protection of structural systems is isolation. The majority of existing seismic protection systems are related to horizontal ground motion and only few focus on vertical seismic components, as this would require vertical flexibility, a feature conflicting with the need for sufficient support of the i...
Article
Full-text available
The application of dynamic vibration absorbers (DVA) to Wind Turbine (WT) towers has the potential to significantly improve the damping of the tower and the nacelle dynamic responses, increasing thus the reliability of WTs. The Tuned Mass Damper (TMD) is limited by the requirement of large masses, in association to its installation location. In thi...
Article
PurposeIn this paper, a radically new concept of a Stiff Seismic Base Absorber (SBA) is proposed for seismic protection of multistory building structures.Methods An inerter is first implemented, connecting directly the structure to the ground. This results in the decrease of the natural frequency of the structure, without decreasing its structural...
Article
Full-text available
Conventional base isolation (BI) techniques require a great reduction in the fundamental frequency of the system in order to mitigate the structural dynamic responses due to earthquake excitations. However, the resulting base displacements are large and can cause utility connection problems, rendering BI inadequate for retrofitting. This paper prop...
Conference Paper
Full-text available
This paper introduces a passive vibration absorption system, based on the extension of KDamper (EKD), for seismic protection of multi-story building structures. So far, KDamper is implemented for the seismic protection of structures as a seismic absorption base. In this paper, the EKD is implemented between each floor of the examined multi-story bu...
Conference Paper
The central concept of negative stiffness isolators is to significantly reduce the natural frequency of the primary structure even at almost zero levels, below the predominant energy-containing frequencies of earthquake ground motions, and thus mitigate the superstructure dynamic responses. This paper proposes a novel stiff seismic base absorber th...
Conference Paper
Full-text available
The KDamper is a novel passive vibration isolation and damping concept, based essentially on the optimal combination of appropriate stiffness elements, which include a negative stiffness element. The KDamper concept ensures the static stability of the structure, does not require heavy masses and can achieve better dynamic characteristics, compared...
Article
Seismic isolation is proven to be an effective technology for seismic protection of building structures, equipment, and industrial facilities. The majority of the existing isolation systems and techniques are related to horizontal ground motions, whereas there are only a few vertical isolation systems. The main reason is because of the conflict con...
Article
In this paper, an extended KDamper (EKD) concept is proposed, for implementation as a seismic base absorber. The complexity of the EKD renders the conventional minmax (H∞) approaches ineffective. For this reason, a dedicated constrained optimization problem is proposed for the selection of the optimal system parameters. The EKD is designed accordin...
Chapter
Throughout the past decades, seismic isolation of structures has attracted the attention of civil engineers and scientists. Research around this field has progressed tremendously, starting from the use of simple elastomeric bearings for the decoupling of the superstructure from the foundation and moving toward the invention of more complex devices...
Chapter
Contemporary seismic isolation systems for bridge structures provide (A) horizontal isolation from the effects of ground motion and (B) an energy dissipation mechanism to reduce displacements. Throughout the years many kinds of seismic isolation mechanisms have been developed, with the concept of introducing negative stiffness being the most promis...
Chapter
The KDamper is a novel passive vibration isolation and damping concept, based essentially on the optimal combination of appropriate stiffness elements, which include a negative stiffness element. The KDamper concept ensures the static stability of the structure, does not require heavy masses, and can achieve better dynamic characteristics, compared...
Book
This book presents the select proceedings of the 14th International Conference on Vibration Problems (ICOVP 2019) held in Crete, Greece. The volume brings together contributions from researchers working on vibration related problems in a wide variety of engineering disciplines such as mechanical engineering, wind and earthquake engineering, nuclear...
Preprint
This paper proposed a radically new concept of a Stiff Seismic Base Absorber (SBA).
Preprint
This paper proposed a radically new concept of a Stiff Seismic Base Absorber (SBA).
Article
The KDamper is a novel passive vibration absorption concept based essentially on the optimal combination of appropriate stiffness elements, one of which has a negative value. In this paper, the implementation of the KDamper as a seismic Absorption Base (KDAB) is considered. The performance of the KDAB is assessed in three characteristic test cases,...
Conference Paper
Full-text available
Throughout the past decades, seismic isolation of structures has been studied rigorously as an approach to reduce seismic demand and mitigate structural damage. Research in this field has progressed significantly, starting from the use of simple elastomeric bearings for the decoupling of the superstructure from the base to more complex devices that...
Conference Paper
The KDamper is a novel passive vibration absorption concept, based essentially on the optimal combination of appropriate stiffness elements, which include a negative stiffness element. In this paper, the implementation of the KDamper as a seismic Absorption Base (KDAB) is considered. The paper proceeds to the assessment of the performance of the KD...
Article
In this paper an advanced 32 × 32 stiffness matrix and the corresponding nodal load vector of a 3-D beam element of arbitrary cross section taking into account shear deformation, generalized warping (shear lag effects) and distortional effects due to both flexure and torsion is presented. Nonuniform distortional/warping distributions are taken into...
Conference Paper
Full-text available
Both Euler-Bernoulli and Timoshenko beam theories maintain the assumptions that neither out-of-plane (warping) nor in-plane (distortion) deformation contribute to beams response. To account for shear lag effects, the inclusion of non-uniform warping is necessary, relaxing the assumption of plane cross section. The shear flow associated with non-uni...
Article
In this paper, a higher order beam theory is developed for the analysis of beams of homogeneous cross-section, taking into account warping and distortional phenomena due to axial, shear, flexural and torsional behavior. The beam can be subjected to arbitrary axial, transverse and/or torsional concentrated or distributed load, while its edges are re...
Article
In this paper, a higher order beam theory is employed for linear local buckling analysis of beams of homogeneous cross-section, taking into account warping and distortional phenomena due to axial, shear, flexural, and torsional behavior. The beam is subjected to arbitrary concentrated or distributed loading, while its edges are restrained by the mo...
Article
Contemporary seismic isolation systems for bridge applications provide a) horizontal isolation from earthquake shaking effects, and b) energy dissipation mechanisms to reduce displacements. Throughout the years, many kinds of seismic isolation mechanisms have been developed, with those incorporating negative stiffness elements being the most promis...
Article
Full-text available
Comparing Euler-Bernoulli or Tismoshenko beam theory to higher order beam theories, an essential difference can be depicted: the additional degrees of freedom accounting for out-of plane (warping) and in-plane (distortional) phenomena leading to the appearance of respective higher order geometric constants. In this paper, after briefly overviewing...
Conference Paper
Throughout the last decades, earthquake engineering and seismic codes focus on innovative methods and techniques for infrastructure earthquake protection. In this context, seismic isolation has been introduced as a promising alternative to conventional practice, as its fundamental aim is the reduction of seismic forces imposed on a structure instea...
Article
Full-text available
This work aims to introduce a new layered approach to the nonlinear analysis of initially straight Euler-Bernoulli beams by the Boundary Element Method (BEM). The beam is studied in the context of both geometrical and material nonlinearity. The governing differential equations, derived by applying the principle of minimum total potential energy, ar...
Conference Paper
Full-text available
During the last decades, various mechanical devices and configurations have made their appearance in an effort to mitigate the effects of seismic excitations on bridge structures through controlling their response. Elastomeric bearings, lead rubber bearings, roller bearings or tuned mass dampers (TMDs) are characteristic examples of such devices. I...
Article
Full-text available
Toward improving conventional beam elements in order to include distortional effects in their analysis, in this paper, independent parameters have been taken into account. Beam’s behavior becomes more complex, especially for eccentric loading, due to the coupling between warping and distortion. Thus, the importance of including higher-order phenome...
Article
Contemporary seismic isolation systems for bridge applications provide (a) horizontal isolation from the effects of earthquake shaking, and (b) an energy dissipation mechanism to reduce displacements. Throughout the years many kinds of seismic isolation mechanisms have been developed, with two concepts being the most promising ones: the introductio...
Book
Matrix Methods for Advanced Structural Analysis covers in detail the theoretical concepts related to rockbursts, and introduces the current computational modeling techniques and laboratory tests available. The second part is devoted to case studies in mining (coal and metal) and tunneling environments worldwide. The third part covers the most recen...
Article
Towards improving conventional beam elements in order to include distortional effects in their analysis, independent parameters have been taken into account in this study. Curved beam’s behavior becomes more complex, even for dead loading, due to the coupling between axial force, bending moments and torque that curvature produces. Thus, the importa...
Article
This paper presents a general formulation for the distortional analysis of beams of arbitrary cross section under arbitrary external loading and general boundary conditions. The nonuniform distortional/warping distributions along the beam length are taken into account by employing independent parameters multiplying suitable deformation modes accoun...
Conference Paper
Full-text available
In this paper a novel design methodology for seismic isolation of bridges is presented employing the KDamper passive system and the Harmony Search (HS) optimization algorithm. The implementation of the KDamper concept to the absorption of seismic excitation of bridge structures requires the solution of a linear dynamic problem during which the basi...
Article
Curved beam structures have been used in many civil, mechanical, aircraft, and aerospace constructions. The analysis is mainly based on solid and plate models due to the fact that traditional curved beam elements do not include nonuniform warping effects, especially in the dynamic analysis. In this article, independent warping parameters have been...
Article
In this paper a Hybrid Domain Boundary Element Method is developed for the geometrically nonlinear dynamic analysis of inelastic Euler-Bernoulli beams of arbitrary doubly symmetric simply or multiply connected constant cross-section, resting on viscous inelastic Winkler foundation. The beam is subjected to the combined action of arbitrarily distrib...
Article
In this paper, the Isogeometric tools, either integrated in the Finite Element Method (FEM) or in a Boundary Element based Method (BEM) called Analog Equation Method (AEM), are employed for the vibration analysis of homogeneous beams of arbitrary cross section (thin- or thick- walled) taking into account nonuniform warping and shear deformation eff...
Article
The finite element method is employed for the flexural-torsional linear buckling analysis of beams of arbitrarily shaped composite cross-section taking into account generalized warping (shear lag effects due to both flexure and torsion). The contacting materials, that constitute the composite cross section, may include a finite number of holes. A c...
Article
In this paper, the Analog Equation Method (AEM), a boundary element based method, is employed for the analysis of homogenous beams of arbitrary cross section (thin- or thick-walled) taking into account nonuniform warping and shear deformation effects (shear lag due to both flexure and torsion), considering a B-spline approximation for the fictitiou...
Article
In this paper a general formulation for the nonuniform warping dynamic analysis of beams of arbitrary simply or multiply connected cross section, under arbitrary external loading and general boundary conditions is presented taking into account the effects of rotary and warping inertia. The nonuniform warping distributions are taken into account by...
Article
In this paper a boundary element method (BEM) is developed for the torsional vibration problem of bars of arbitrary doubly symmetric constant cross section, taking into account the nonuniform warping and secondary torsional shear deformation effects (STSDE). The bar is subjected to arbitrarily distributed or concentrated dynamic torsional loading a...
Article
In this paper, the analysis of homogenous curved beams of arbitrary cross section (thin- or thick-walled) taking into account the coupling of extension, flexure and torsion, nonuniform warping as well as shear deformation effects (shear lag due to both flexure and torsion) has been studied. The curved beam is subjected to the combined action of arb...
Conference Paper
Full-text available
In this paper, the analysis of homogenous curved beams of arbitrary cross section (thin-or thick-walled) taking into account the coupling of extension, flexure and torsion, nonuniform warping as well as shear deformation effects (shear lag due to both flexure and torsion) has been studied. The curved beam is subjected to the combined action of arbi...
Article
The objective of this paper is to present an efficient beam formulation based on the boundary element method (BEM), for the nonlinear dynamic analysis of wind turbine towers of variable cross section founded either on surface or on monopile foundation system. The whole structure may undergo moderately large displacements, taking into account the ef...
Article
In this paper, an advanced 20 × 20 stiffness matrix and the corresponding nodal load vector of a member of arbitrary composite cross section is developed taking into account shear lag effects due to both flexure and torsion (the case of the three-dimensional beam element of arbitrary homogeneous cross section is treated as a special one). The compo...
Article
In this paper, the analog equation method, a boundary element-based method, is employed for the nonuniform torsional problem of bars of arbitrary constant cross section, considering a quadratic B-spline approximation for the fictitious loads of a substitute problem. The fictitious loads are established using a boundary element method-based techniqu...
Article
In this paper a Boundary Element Method (BEM) is developed for the geometrically nonlinear inelastic analysis of Timoshenko beams of arbitrary doubly symmetric simply or multiply connected constant cross-section, resting on inelastic tensionless Winkler foundation. The beam is subjected to the combined action of arbitrarily distributed or concentra...
Article
In this paper a general formulation for the nonuniform shear warping analysis of composite beams of arbitrary simply or multiply connected cross section with at least one axis of symmetry, under general boundary conditions is presented. The beam is subjected to the combined action of arbitrarily distributed or concentrated transverse loading passin...