Ioannis Kavvadias

Democritus University of Thrace | DUTH · Department of Civil Engineering

I am delighted to share that I am serving as a Guest Editor for a Special Issue entitled: "FRC and FRP Materials in Seismic Design and the Retrofitting of Reinforced Concrete and Masonry Structures" that will be published in the open-access journal Fibers published by MDPI. The publication of this Special Issue will contribute to the advancement o...

To access additional information regarding the special issue, click on the following link: https://www.mdpi.com/journal/applsci/special_issues/N774W7KZI2

A variety of structural members and non-structural components, including bridge piers, museum artifacts, furniture, or electrical and mechanical equipment, can uplift and rock under ground motion excitations. Given the inherently non-linear nature of rocking behavior, employing machine learning algorithms to predict rocking response presents a nota...

The idea of separating the structure from the horizontal motion of the ground using kinematic bearings that may uplift and rock under severe ground excitations can be considered equally as a seismic isolation technique. However, the seismic demand reduction on the superstructure due to the uplift of the kinematic bearings presents an inversely prop...

The assessment of rocking response is a challenging task due to its high nonlinearity. The present study investigates two methodologies to evaluate finite rocking rotations and overturn of three typical rocking systems. In particular, fuzzy linear regression (FLR) with triangular fuzzy numbers and a hybrid model combining logistic regression and fu...

Recently developed Machine Learning (ML) interpretability techniques have the potential to explain how predictors influence the dependent variable in high-dimensional and non-linear problems. This study investigates the application of the above methods to damage prediction during a sequence of earthquakes, emphasizing the use of techniques such as...

During intense ground motion excitations, the pounding between adjacent buildings may result in extensive structural damage. Despite the provision of regulations regarding the minimum separation gap required to prevent structural collisions, the majority of existing structures are poorly separated. The modern seismic design and assessment of struct...

Computational approaches could provide a viable and cost-effective alternative to expensive experiments for accurately evaluating the nonlinear constitutive behavior of cementitious nanocomposite materials. In the present study, the mechanical properties of cement paste reinforced with multi-wall carbon nanotubes (MWCNTs) are examined experimentall...

This study investigates the interpretability of machine learning (ML) models applied to cumulative damage prediction during a sequence of earthquakes, emphasizing the use of techniques such as SHapley Additive exPlanations (SHAP), Partial Dependence Plots (PDPs), Local Interpretable Model-agnostic Explanations (LIME), Accumulated Local Effects (ALE...

Structures that can uplift and rock under severe seismic excitations present remarkable stability without exhibiting damage. As such, rocking-response-based structural systems constitute a promising design practice. Due to the high nonlinearity of the rocking response, the seismic performance of this class of structures should be evaluated probabil...

Advanced machine learning algorithms have the potential to be successfully applied to many areas of system modelling. In the present study, the capability of ten machine learning algorithms to predict the structural damage of an 8-storey reinforced concrete frame building subjected to single and successive ground motions is examined. From this poin...

Our paper "Seismic response of elastic multidegree of freedom oscillators placed on the top of rocking storey" published in Earthquake Engineering & Structural Dynamics journal has been recognized as "Top Cited Article 2020-2021".

Advanced machine learning algorithms, have the potential to be successfully applied to many areas of system modelling. In the present study the capability of ten machine learning algorithms in predicting the structural damage of an 8-storey reinforced concrete frame building subjected to single and successive ground motions is examined. From this p...

For the first time, the thermoelectric properties of cement/single-walled carbon nanotube (SWCNT) nanocomposites with over 3, 7, 14 and 28 days of hydration are reported, while a thermoelectric generator device (TEG) is fabricated utilising the material with the highest achieved power factor (PF). SWCNTs with inherent p-type semiconductor character...

Rocking podium structures (RPSs) refer to a wide class of structural systems in which the base storey consisting of freestanding columns that can uplift during seismic excitations. Due to the rocking response, the base storey can be considered as a base isolation system on the condition that a rocking overturn is prevented. In the present study, th...

Advanced machine learning algorithms, such as neural networks, have the potential to be successfully applied to many areas of system modelling. Several studies have been already conducted on forecasting structural damage due to individual earthquakes, ignoring the influence of seismic sequences, using neural networks. In the present study, an ensem...

Additive manufacturing is at the forefront of research activities worldwide, as the commercial exploitation of this technology is expected to displace some traditional manufacturing methods over the next few years. The aim of this research is the identification of the dynamic characteristics of three-dimensional printing specimens. The specific spe...

In the present study the effect of impact modeling on the seismic response of multi-storey structures placed on the top of a rocking storey is examined. For this purpose, two impact models are introduced, where the energy dissipation is treated using the angular momentum-impulse theorem combined with different assumptions regarding the post-impact...

In this study the effect of ground motion characteristics on the response of an isolated base using double friction pendulum bearings (DFPBs) is presented. Planar nonlinear time history analyses are performed considering one horizontal and the corresponding vertical component of natural ground motion records. Both far-fault and near-fault ground mo...

A storey comprised of free-standing columns that may uplift under ground motion excitations can be regarded as a seismic isolation technique. These columns are referred to the literature as "kinematic bearings" and have been used in Russia and the wider region of the former Soviet Union over the past 40 years. Despite the extensive use of kinematic...

In the present study the seismic response of elastic single degree of freedom oscillators placed on the top of a rocking storey is examined. A storey comprised of columns that may uplift under ground motion excitations can be regarded as an innovative and cost effective base isolation technique. Regarding the podium structural systems, apart from s...

In the present study, the seismic response of multistorey structures placed on the top of a rocking storey is examined. For this purpose, an analytical model that allows the interaction of all vibration modes of the superstructure with the rocking base is introduced. As uplift of the rocking base modifies the dynamic properties of the superstructur...

Στην παρούσα εργασία πραγματοποιείται συσχέτιση μεταξύ σεισμικών παραμέτρων έντασης και ολικών δεικτών βλάβης σε κατασκευές οπλισμένου σκυροδέματος. Για αυτόν τον σκοπό, χρησιμοποιήθηκαν καταγραφές πραγματικών σεισμών, από τις οποίες υπολογίστηκαν παράμετροι, που χαρακτηρίζουν ένα επιταχυνσιογράφημα και προτάθηκαν εναλλακτικές τους. Στη συνέχεια μέ...

Στην παρούσα εργασία πραγματοποιείται συσχέτιση μεταξύ σεισμικών παραμέτρων έντασης και ολικών δεικτών βλάβης σε κατασκευές οπλισμένου σκυροδέματος. Για αυτόν τον σκοπό, χρησιμοποιήθηκαν καταγραφές πραγματικών σεισμών, από τις οποίες υπολογίστηκαν παράμετροι, που χαρακτηρίζουν ένα επιταχυνσιογράφημα και προτάθηκαν εναλλακτικές τους. Στη συνέχεια μέ...

The seismic response evaluation of free standing building contents, has become a challenging task for the structural engineers. Artistic assets, which are placed on museums, are subjected to the floors' acceleration signal. In this view, it is obvious that the seismic action that affect the response of the floors non-structural contents is affected...

In the present study the seismic response of elastic single degree of freedom oscillators placed on the top of a rocking story are examined. A story comprised by columns that may uplift under ground motion excitations can be assumed as an innovative and cost effective base isolation technique. Regarding the podium structural systems, except of the...

Intensity measures (IMs) that incorporate structural information are intended to have strong interrelation with the structural performance. Numerous IMs which are calculated by the response spectra of elastic SDOF oscillators have been presented in the literature. The definition of spectral IMs based on the rocking response seems to be essential fo...

The seismic protection of cultural heritage artifacts has become a challenging objective the last decades. Artistic assets, which are placed on museums, are subjected to the floors' acceleration signal. The actual seismic action is affected by the seismic response of the host building. The contents are usually standing unanchored on the base, and a...

The seismic sequence may be devastating for structures which are damaged during the main event. Thus, the seismic performance of structural systems subjected to successive ground motions receives increasing attention the last years. In this view, the present study investigates the effect of the aftershock characteristics on the seismic response of...

In the present study, the definition of constant ductility high damping spectra, which are suitable for estimating the response of structural systems with supplemental linear viscous damping, is presented. First, damping reduction factors (B) are introduced to generate high damping elastic demand spectra. Given the elastic spectra, the inelastic pe...

In the present study a capacity spectrum method based on constant ductility inelastic spectra to estimate the seismic performance of structures equipped with elastic viscous dampers is presented. As the definition of the structures' effective damping, due to the damping system, is necessary, an alternative method to specify the effective damping ra...

The seismic response of rigid rocking structural systems is investigated. Specifically, the response of monumental structures, is examined in this study. These structures, such as free standing columns, colonnades and masonry arches, consist representatives of rigid rocking SDOF oscillators. The original scientific contribution of the present thesi...

In this study a spectral ground motion intensity measure (IM) is presented. The proposed IM is calculated throughout the rocking spectrum which is illustrated as a 3D surface diagram, with the slenderness α and the period T, the two horizontal axes. Thus, the IM is defined as the volume under the rocking spectrum, evaluated throughout integration....

Base isolation is a modern strategy to decrease the effects of earthquakes on buildings of high significance. The general principle is that the structure is decoupled from the horizontal components of the earthquake ground motion by interposing a layer with low lateral stiffness between the structure and the foundation. One of the major devices to...

A numerical study of the seismic response of base isolated free standing monolithic ancient column is presented in this paper. These rocking structural systems are analyzed standing free on an isolated base supported on friction pendulum (FP) bearings. Specifically, the implementation of multi-spherical friction bearings is examined. The rocking co...

This study examines the seismic response of free-standing, monolithic rocking columns, taking into account different ground motion intensity measures (IMs). The primary scope of this article is to investigate the effect of the IMs, among 23 considered, on the rocking response of the examined structural system. The seismic vulnerability of the exami...

Strengthening reinforced concrete slabs with a central cutout using FRP composites is analytically investigated in this paper. Introducing an opening in existing slabs inRCbuildings due to functional changes is commonly required. In comparison to traditional strengthening methods, the application of FRP laminates is very suitable not only because o...

In this study the seismic response of free standing, rocking columns and frames is investigated taking into account different intensity measures (IMs) of the seismic excitations. The seismic vulnerability of the examined structural systems is based on the probabilistic seismic demand model (PSDM), in which the degree of uncertainty is depended on t...

The aim of this paper is to examine the efficiency of retrofitting with passive energy dissipative systems on the seismic performance of existing reinforced concrete buildings designed according to the old seismic Greek Codes. Specifically, is investigated the response of two 3-strorey frame structures. Both structural systems have tall first story...

This paper presents a numerical investigation of the seismic response of monolithic and multidrum columns. The effect of the column size and the effect of the input motion char-acteristics on the dynamic response of free standing columns are studied. Single columns and two columns coupled with an architrave subjected to a set of 20 ground motions a...

In early 2014, strong earthquakes occurred on the Island of Cephalonia and buildings with significant design errors were heavily damaged. The building that is being studied is a two-storey reinforced concrete building, which was affected by the specific earthquakes. The structural model of the building is regular in plan as it consists of parallel...