Papers by Athanatopoulou Asimina
Proceedings of the 17th World Conference on Earthquake Engineering 17WCEE 2020, 2021
The objective of the present work is to evaluate four procedures for selecting the sectional forc... more The objective of the present work is to evaluate four procedures for selecting the sectional forces for design purposes in the nonlinear range of behavior in case of multistorey buildings. For this purpose amultistorey asymmetric building designed using thefour procedures is analyzed by Nonlinear Response History Analysis (NRHA) underseven bi-directional earthquake ground motions. The two horizontal accelerograms of each ground motion are applied along horizontal orthogonal axes forming an angle θ=0°, 30°, 60°, …, …, 330° with the structural axes. Moreover, two different seismic intensity levels are considered by using two appropriate multipliers for each ground motion. For the evaluation of inelastic structural behavior the maximum interstorey drift ratio of the building is computed. The analyses results show that the overall damage state of the building is significantly affected by the procedure used to select the design sectional forces. The building designed using the procedure based on the maximum normal stress over all seismic incident angles shows the best seismic performance.
SN Applied Sciences, 2020
Most of the existing reinforced concrete (RC) buildings in India are either designed before the e... more Most of the existing reinforced concrete (RC) buildings in India are either designed before the existence of seismic design codes or without proper provisions to resist lateral loads. These structures generally possess low strength and limited ductility, thereby always prone to global failure and are a primary reason for causalities during an earthquake. Hence, seismic evaluation of these structures and strengthening, if necessary, is essential to prevent a disaster during its serviceable lifetime. In this investigation, a four-storied (G+3) RC building structure in Warangal city, Telangana State, India, has been selected as a case study. Furthermore, the structure is to be extended vertically by two stories above the existing configuration. The structural and material inputs to the analytical model are updated from visual inspection and nondestructive tests, followed by an analytical study. From the analytical study, the seismic capacity of the existing gravity load-designed structure itself is found to be inadequate for seismic requirements. Since the structure is to be extended vertically, the existing building needs to be strengthened appropriately to withstand additional loads and remain functional throughout its lifetime. The outcome of the seismic analysis is checked for conformity using demand and capacity requirement of the structural components of the six-storied (G+5) structure. This behavior mimics the current scenario of existing RC buildings in this locality, which needs to be appropriately strengthened. It has been observed from the analysis that the RC building was vulnerable to the seismic forces and needed retrofitting to remain functional during its service life.
Soil Dynamics and Earthquake Engineering
The present paper investigates the story-wise damage response and the seismic fragility of planar... more The present paper investigates the story-wise damage response and the seismic fragility of planar multistory R/C buildings with various masonry infills' distributions. In order to fulfil this purpose, six planar R/C buildings (three moment frames and three dual structural systems consisting of frames and walls) are studied. For each structure several different masonry infills' distributions are taken into account. Then, the buildings are subjected to a set of appropriately chosen real earthquake records for which nonlinear time history analyses are conducted and the story-wise IDA curves for each building and infill distribution are constructed. The quantification of the expected seismic damage state is accomplished through the calculation of the maximum interstory drift ratio. Subsequently, based on the results of the IDA curves, the fragilities of each buildings' story as well as of the whole buildings are calculated. The results of this study demonstrate the role of masonry infills on the story-wise seismic damage of R/C buildings. The presence of the masonry infills cannot be ignored, since they can signifficantly modify the damage response and the seismic fragility of buildings depending on the structural system and on the infills' distribution.
Soil Dynamics and Earthquake Engineering, 165: 107714, 2023
The present paper investigates the story-wise damage response and the seismic fragility of planar... more The present paper investigates the story-wise damage response and the seismic fragility of planar multistory R/C buildings with various masonry infills' distributions. In order to fulfil this purpose, six planar R/C buildings (three moment frames and three dual structural systems consisting of frames and walls) are studied. For each structure several different masonry infills' distributions are taken into account. Then, the buildings are subjected to a set of appropriately chosen real earthquake records for which nonlinear time history analyses are conducted and the story-wise IDA curves for each building and infill distribution are constructed. The quantification of the expected seismic damage state is accomplished through the calculation of the maximum interstory drift ratio. Subsequently, based on the results of the IDA curves, the fragilities of each buildings' story as well as of the whole buildings are calculated. The results of this study demonstrate the role of masonry infills on the story-wise seismic damage of R/C buildings. The presence of the masonry infills cannot be ignored, since they can signifficantly modify the damage response and the seismic fragility of buildings depending on the structural system and on the infills' distribution.
According to Eurocode 8, nonlinear time history analyses can be performed using a group of 7 grou... more According to Eurocode 8, nonlinear time history analyses can be performed using a group of 7 ground motions, applied using only one angle of incidence (ASI). Under these conditions, the mean value of the response under consideration can be used to represent seismic demand. Since it is known that, the smaller the group of ground motions, the larger the variability of the seismic demand, the variability of selected demand parameters is studied considering the effect of the number of bi-directional ground motions and the number of ASIs. Groups of ground motions of size 7 to 35 are involved in this analysis, all applied along 1 to 12 ASIs. Two demand parameters are examined and their variability is analysed in terms of acceptable risk, where risk corresponds to the probability of having a demand parameter outside preselected acceptable margins, which are defined with respect to a reference demand value. The results indicate that different demand parameters are influenced differently by the ground motion group size and the number of ASIs. Finally, it is demonstrated that an optimum combination of number of ground motions and ASIs can be selected depending on the acceptable margin that is selected.
Aristotle University of Thessaloniki, 2021
Spectral acceleration at the fundamental period of the structure Sa(T1) is the most widely used s... more Spectral acceleration at the fundamental period of the structure Sa(T1) is the most widely used structure-specific seismic Intensity Measure (IM) for the assessment of the structures’ seismic damage. The high correlation between Sa(T1)) and common seismic Response Measures (RMs) in low-rise structures has been extensively documented in present-day research. To further investigate the relation between spectral acceleration and the seismic response of the structure, the correlation between Sa(T) and a set of common RΜs was examined, not only at specific periods (such as T1, T2 etc.) but at the whole period range from 0 sec to 20 sec. This allows determining the characteristics of the “resonance” at the natural frequencies, such as the bandwidth of the main high-correlation lobe around T1, as well as the presence of secondary regions of high correlation. The response of a wide range of planar frames was simulated using the non-linear dynamic analysis (implemented with Opensees software), with a suite of 60 appropriately selected ground motion records. In total, 32 basic R/C frame configurations (moment frames and dual systems) were studied, both as bare and infilled frames, each one with 12 different infill types (in total 416 different models), for 10 different seismic intensity levels. For each model, a variety of local and global RMs were calculated, both at the storey level and globally. The chosen RMs are based on displacement demands (such as maximum and average interstorey drift), on local deformation demands (rotation/curvature ductility demands) and on the dissipated energy per element due to nonlinear response. The correlation between the above RMs and Sa(T) was calculated for a large number of periods, ranging from 0 sec to 20 sec, with a step of 0.01 sec.
In three-dimensional asymmetric buildings, the orientation of the applied forces with regard to t... more In three-dimensional asymmetric buildings, the orientation of the applied forces with regard to the structural system as well as the vertical distribution of the lateral forces affect the structural response. The proposed study addresses the determination of the critical angle of incidence of the lateral static forces that are needed to carry out lateral force analysis within the context of procedures for the seismic safety assessment of existing structures. For this purpose, an analytical methodology is developed to obtain the critical angle of incidence that leads to the maximum demand in terms of storey displacements. The procedure is based on the properties of the centre of stiffness and the principal directions of single storey buildings and can be straightforwardly applied to single storey and multi-storey isotropic buildings with an arbitrary in-plan configuration. Isotropic are buildings that have proportional horizontal stiffness matrices and, as a consequence, possess prin...
dist.unina.it
The vertical elastic axis and the horizontal principal axes of a building constitute the necessar... more The vertical elastic axis and the horizontal principal axes of a building constitute the necessary presupposition in order to apply the documented equivalent static method (simplified spectrum method) of seismic design. However, on the contrary to single-story ...
The present paper investigates the correlation between a number of structure-specific ground moti... more The present paper investigates the correlation between a number of structure-specific ground motion intensity measures and the damage state of 3D R/C buildings. To accomplish this purposefour 5-story R/C buildings are studied. The buildings are analyzed by nonlinear time history analysis using 20 bidirectional earthquake ground motions. The two horizontal accelerograms of each ground motion are applied along the structural axes of the buildings. The structural damage is expressed in terms of the maximum interstory drift as well as the overall structural damage index. For each individual pair of accelerograms the values of the aforementioned seismic damage measures are determined. Then, they are correlated with severalstrong motion intensity measures that take into account both earthquake and structural characteristics. The research identified certain intensity measures which exhibited strong correlation with the seismic damage of the four buildings. However, the degree of correlatio...
A key issue in seismic risk analysis within the context<br> of Performance-Based Earthquake... more A key issue in seismic risk analysis within the context<br> of Performance-Based Earthquake Engineering is the evaluation of<br> the expected seismic damage of structures under a specific<br> earthquake ground motion. The assessment of the seismic<br> performance strongly depends on the choice of the seismic Intensity<br> Measure (IM), which quantifies the characteristics of a ground<br> motion that are important to the nonlinear structural response. Several<br> conventional IMs of ground motion have been used to estimate their<br> damage potential to structures. Yet, none of them has been proved to<br> be able to predict adequately the seismic damage. Therefore,<br> alternative, scalar intensity measures, which take into account not<br> only ground motion characteristics but also structural information<br> have been proposed. Some of these IMs are based on integration of<br> spectral values over a range o...
Seismic Behaviour and Design of Irregular and Complex Civil Structures IV
Seismic Behaviour and Design of Irregular and Complex Civil Structures IV
An important area of research in seismic risk analysis is the evaluation of expected seismic dama... more An important area of research in seismic risk analysis is the evaluation of expected seismic damage of structures under a specific earthquake ground motion. Several conventional intensity measures of ground motion have been used to estimate their damage potential to structures. Yet, none of them was proved to be able to predict adequately the seismic damage of any structural system. Therefore, alternative, advanced intensity measures, which take into account not only ground motion characteristics but also structural information have been proposed. The adequacy of a number of advanced earthquake intensity measures in prediction of structural damage of 3D R/C buildings under seismic excitation which attacks the building with arbitrary incident angle is investigated in the present paper. To achieve this purpose a symmetric in plan and an asymmetric 5-story R/C building are studied. The two buildings are subjected to 20 bidirectional earthquake ground motions. The two horizontal accelerograms of each ground motion are applied along horizontal orthogonal axes forming 72 different angles with the structural axes. The response is computed by non-linear time history analysis. The structural damage is expressed in terms of the maximum interstory drift as well as the overall structural damage index. The values of the aforementioned seismic damage measures determined for incident angle 0o as well as their maximum values over all seismic incident angles are correlated with 9 structure-specific ground motion intensity measures. The research identified certain intensity measures which exhibited strong correlation with the seismic damage of the two buildings. However, their adequacy for estimation of the structural damage depends on the response parameter adopted. Furthermore, it was confirmed that the widely used spectral acceleration at the fundamental period of the structure is a good indicator of the expected earthquake damage level.
XI International Conference on Structural Dynamics
It is known that the slabs on soil constitute one of the most difficult types of structures despi... more It is known that the slabs on soil constitute one of the most difficult types of structures despite their apparent simplicity. It is not accidental that there are still no regulations on their proper construction. As main cause of their failure, someone could mention the restraints expressed either as differential settlements or, mainly, as hindrance of contractions and expansions. For the confrontation of restraints, solution can be given by the joints (contraction joints, construction joints, isolation joints, etc.). Because of the big density of joints, the slabs are manufactured as non-reinforced or fiber reinforced with small percentages of steel fibers because of the unfavorable influence of big percentages in workability of fiber reinforced concrete. Also, at the joint locations, the suitable placement of dowels is required to guarantee the collaboration of neighboring segments. Another weak point is also the fatigue of concrete, which acts catalytic for the slabs in question...
The scope of this work is the creation of a numerical FE model of an existing prestressed post-te... more The scope of this work is the creation of a numerical FE model of an existing prestressed post-tensioned RC box girder ductile ravine bridge and its updating, based on identified modal characteristics (eigenfrequencies). The challenge for this task rose from the fact that the identified modal characteristics were not adequate for the use of one of the advanced automated model updating methods that are available. In particular, the only usable parameters that were identified were some natural frequencies and their corresponding mode types but not eigenvectors. Safely assuming modern building conditions, the absence of localized structural damage and the linear behavior during the identification measurements, an empirical manual updating procedure is implemented for updating standard key parameters of the FE model. During the updating procedure the identified quantities are used to define the models uncertain parameters such as moduli of elasticity and boundary conditions, whilst robu...
Local site conditions generate large amplifications as well as spatial variations in the seismic ... more Local site conditions generate large amplifications as well as spatial variations in the seismic motions that must be accounted for in the earthquake resistant design of structures. The present paper aims to evaluate the influence of complex site effects on the non-linear response of irregular buildings. To achieve this purpose, site dependent ground motions are produced via Boundary Element Method (BEM). An ensemble of nine earthquakes recorded at the outcropping rock are considered as an input at the seismic bed of complex geological profiles, and acceleration time histories at the ground surface are computed. Several complex geological configurations are considered, taking into account the following key parameters: (i) canyon topography, (ii) layering and (iii) material gradient effect. Two 5-storey buildings are considered: a symmetric and an asymmetric in plan building. A series of Nonlinear Time History Analyses are conducted. The results of this study demonstrate that the pre...
The present paper examines the influence of complex site effects on the seismic response of plana... more The present paper examines the influence of complex site effects on the seismic response of planar multistorey R/C buildings with various masonry infills&#39; distributions. To accomplish this purpose, two planar R/C buildings (a moment frame building and a building with dual structural system) are studied. For each building a number of different distributions of masonry infills is considered. For the modeling of the masonry infills the single equivalent diagonal strut model is adopted. Site dependent ground motions are produced considering 2D analysis of the soil profile via the BEM numerical technique. Several complex geological configurations that account for canyon, layering and material gradient effects are taken into consideration. Next, the buildings are analyzed by means of nonlinear time-history analyses using nine recorded ground motions and the seismic damage state for each building is determined. The results of this study demonstrate the importance of local site conditions on the structural damage of masonry infilled R/C buildings. The presence of local site conditions cannot be ignored, since they influence the inelastic dynamic response of buildings.
The assessment of the seismic performance of a structure depends on the optimal choice of an eart... more The assessment of the seismic performance of a structure depends on the optimal choice of an earthquake Intensity Measure (IM). Given the fact that conventional IMs based only on ground motion information might not be able to successfully predict the seismic response of structures, several advanced structural-specific IMs have been proposed during the past years, taking into account not only earthquake characteristics but also structural information. Moreover, local site conditions may generate large amplifications as well as spatial variations in the ground motions, which influence the intensity measures and in most cases lead to important structural damage. Along these lines the objective of this paper is to study the correlation between well-known structure-specific intensity measures and the inelastic response of multi-story reinforced concrete planar frames taking into account site effects. First, site dependent ground motions are produced considering 2D analysis of the soil pr...
Coupled Site and Soil-Structure Interaction Effects with Application to Seismic Risk Mitigation
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Papers by Athanatopoulou Asimina