Maria Favvata | University of Patras (original) (raw)

Papers by Maria Favvata

WIT Transactions on the Built Environment, Jun 29, 2015

In this study, the key parameters of structural pounding and their influence on the ductility and... more In this study, the key parameters of structural pounding and their influence on the ductility and shear requirements of reinforced concrete structures with different story heights are presented. The examined structures are multistory reinforced concrete (RC) frames with unequal total heights designed according to the codes EC2 and EC8. Results of an extensive investigation in this field indicate that the most vital issues for the seismic response of the RC structures with interaction problems are: the gap distance separation between the adjacent structures, the location of the point of the column that suffers the hit, the difference of the number of stories between the adjacent structures, the local response of the columns that suffer the impact, the local response of the RC beam-column joints at the level of the pounding the existence of masonry infill panels and their response. Each of these parameters is analysed and its importance on the seismic performance of the RC structures is evaluated. Further, initial results based on dynamic step by step analyses have shown that the seismic demand and the level of the seismic hazard are important parameters for the assessment of RC structures with pounding problems. These parameters could be used in the design process in order to eliminate the critically increasing local requirements of the structural members due to the pounding effect. In this view, it seems to be appropriate that the codes provisions for the evaluation of an adequate gap distance between adjacent RC structures take into account the seismic demand and the level of the seismic hazard.

WIT Transactions on the Built Environment, Jun 29, 2015

The interaction problem between adjacent multi-storey reinforced concrete structures with unequal... more The interaction problem between adjacent multi-storey reinforced concrete structures with unequal storey levels and different total heights at different limit states for three intensity levels of seismic hazard is evaluated. The seismic performance of the external column of the tall building that suffers the impact from the upper floor slab of the adjacent shorter structure is under consideration. The critical column's local requirements are checked at three different seismic demands according to the Eurocode 8-part 3: (a) demand for damage limitation limit state (b) demand for significant damage limit state and (c) demand for near collapse limit state. More than 252 nonlinear dynamic step by step analyses have been performed. The results indicate that the column that suffers the impact appears to be in a critical condition due to high ductility demands when the limit state for the assessment is increased from damage limitation to significant damage and to near collapse state. As expected, the column that suffers the hit is always in a critical condition due to shear action. The limit state that is adopted for the evaluation of the pounding effect on the maximum shear requirements of the column slightly altered the results. However, the level of the seismic intensity influences the number of times the shear demands of the column exceed the available strength during the analysis. An increase of the developing requirements for inter-storey drift is also observed in all the cases where the seismic intensity is increased and the limit state becomes more exigent. The minimum gap distance between the adjacent structures that is required in order to eliminate the shear demands of the column seems to be depended on the limit state and the level of the seismic hazard that is used for the evaluation.

Buildings

The effect of an intensity measure’s (IM’s) sufficiency property on the probabilistic assessment ... more The effect of an intensity measure’s (IM’s) sufficiency property on the probabilistic assessment of reinforced concrete (RC) structures due to floor-to-floor structural pounding conditions is examined. In the first part of this investigation, efficiency and sufficiency properties of 23 scalar IMs are verified. Then, the magnitude Mw and the distance Rrup are examined as elements in a vector with an efficient scalar IM to evaluate whether they have any significant effect on the structural response. Subsequently, probabilistic seismic demand models (PSDMs) are developed using linear regression analyses based on a scalar IM and a vector-valued IM. Fragility curves are developed based on these PSDMs, and the influence of Mw and Rrup on the evaluation of the minimum required separation gap distance dg,min due to the pounding effect is examined. More than two hundred nonlinear time history analyses are performed based on the Cloud Analysis method. Seismic displacement demands that control...

Applied Sciences

This Special Issue gathers 29 scientific papers that capture various open and challenging issues ... more This Special Issue gathers 29 scientific papers that capture various open and challenging issues in earthquake engineering for the assessment and design of structures [...]

The effect of infills on the global and local performances of a 6-storey reinforced concrete (RC)... more The effect of infills on the global and local performances of a 6-storey reinforced concrete (RC) frame structure is investigated at two different seismic demand levels, using dynamic step by step analyses procedures. Three different seismic excitations extracted from PEER’s database are considered and are scaled to fit the Eurocode 8 (EC8) elastic spectrum for low zone of seismic hazard and ground type B. The examined seismic demands are the Significant Damage and the Near Collapse limit state (EC8-part3). Two types of infilled RC frames are studied: (a) fully infilled and (b) pilotis type frame (without infills at the base floor). The case of bare frame is also included for comparison reasons. Results in terms of failure modes, interstory drifts, top displacements, base shear requirements, ductility requirements and infills local inelastic responses are presented. In this study, the influence of infills on the seismic response of the 6-storey frame is beneficial at the limit state...

WIT Transactions on The Built Environment, 2015

An innovative portable wireless real time structural health monitoring system that can detect the... more An innovative portable wireless real time structural health monitoring system that can detect the earthquake damage and the structural integrity of reinforced concrete members in seismic-prone regions is experimentally evaluated. Damage detection is achieved by the use of piezoelectric transducers (actuators/sensors) and the implementation of an integration analytical approach based on the electromechanical impedance method. In this direction, piezoelectric lead zirconate titanate (PZT) transducers are bonded on the surface of the steel reinforcing bars of two large-scale reinforced concrete beams. Tested beams subjected to typical flexural monotonic and cyclic loadings and damage monitoring was performed at different loading levels, before and after yielding, using the developed system. Comparisons of the response signals acquired from the bonded piezoelectric patches for the healthy and the damaged states showed a clear gradation of the examined damage levels and provide cogent evidence that the monitoring system is sensitive from an early stage of the performed tests. The effectiveness of this structural health Wireless impedance or Admittance Monitoring System (WiAMS) to detect concrete cracking and steel yielding due to seismic excitations is also commented on. First results showed that the use of PZTs for detecting earthquake damages in reinforced concrete structures by Earthquake Resistant Engineering Structures X 233

An effort for the detection of damages in the reinforcement bars of reinforced concret... more An effort for the detection of damages in the reinforcement bars of reinforced concrete members using PZTs is presented. The damage can be the result of excessive elongation of the steel bar due to steel yielding or due to local steel corrosion. In both cases the damage is simulated by considering reduced diameter of the rebar along the damaged part of its length. An integration approach based on both electromechanical admittance methodology and guided wave propagation technique is used to evaluate the artificial damage on the examined longitudinal steel bar. Two actuator PZTs and a sensor PZT are considered to be bonded on the examined steel bar. The admittance of the Sensor PZT is calculated using COMSOL 3.4a. Fast Furrier Transformation for a better evaluation of the results is employed. An effort for the quantification of the damage detec...

WIT Transactions on the Built Environment, 2005

In this study an analytical investigation and experimental verification of the influence of infil... more In this study an analytical investigation and experimental verification of the influence of infill panels on the seismic behavior of reinforced concrete frames is presented. The project includes three 1/3-scale, single-story, single-bay reinforced concrete frame specimens subjected to lateral cyclic loading; one infilled frame specimen with clay brick solid masonry and two bare frame specimens one with transverse steel in the form of common stirrups and one with continuous rectangular spirals of the same spacing. Special elements are employed for the modeling of the examined specimens. Beam and columns were modeled using elements with distributed plasticity. For the contribution of the behavior of the infill to the response of the frame the equivalent diagonal strut model is used. Two different types of elements were employed for this purpose. The first element is an inelastic truss element with bilinear brittle response. The second one is an inelastic element with response that can...

Abstract. The structural upgrading and rehabilitation procedure of a historic building representa... more Abstract. The structural upgrading and rehabilitation procedure of a historic building representative of 1920s construction in Thessaloniki, Greece is presented. The case study building is a listed three-storey reinforced concrete flat-slab frame structure sited in Nikis Avenue in front of the old seaside of the city of Thessaloniki. Reinforced concrete columns and beams frames along with wide infilled masonry walls are the load-bearing elements of the structure. The building was designed in 1925 without Seismic Code requirements and constructed in 1926. The ground floor was used for many years as a cinema, whereas the upper floors are areas where people may congregate since they are used as assembly halls (dining halls, reading and conference rooms). Concrete core tests and in-situ non-destructive tests were first performed to evaluate the compressive strength of the concrete and to detect determine the existing steel reinforcements of the reinforced concrete members. The concrete ...

XI International Conference on Structural Dynamics, 2020

Engineering Structures, 2021

Abstract The aim of this study is to incorporate the local inelastic demands of a multistory rein... more Abstract The aim of this study is to incorporate the local inelastic demands of a multistory reinforced concrete (RC) frame structure for the first time in the probabilistic seismic assessment of the pounding risk. Two distinct types of structural pounding are examined: a) the floor-to-floor structural pounding - Type A, and b) the inter-story (floor-to-column) structural pounding - Type B. Three different initial gap distances dg between the adjacent structures are considered. The seismic performance of the RC frame structure without the pounding effect is also estimated. The probabilistic evaluation of the pounding effect is performed through fragility curves in terms of global and local engineering demand parameters (EDPs) as a function of the peak ground acceleration (PGA). The first part of this research is focused on the development of global and local probabilistic seismic demand models (PSDMs) against pounding risk. For this purpose, linear and bilinear regression models have been used. Afterwards, the fragility assessment of the RC frame against pounding is performed (a) as a function of the separation gap distance dg, (b) based on the global seismic performances, and (c) based on the local seismic performances. A compounded fragility-based solution on evaluating the pounding risk at different performance levels is also presented and new performance levels thresholds are introduced. Results indicate that the local performances of the columns of the RC structure are crucial demand parameters for the probabilistic assessment of the pounding risk. The type of the structural pounding (Type A or Type B) that is occurred between the adjacent structures significantly alters the results of the probabilistic assessment when the local performances are considered. The compounded evaluation of the pounding risk clearly indicates that the RC frame structure exceeds the examined performance levels at a lower value of PGA when subjected to pounding in comparison to the corresponding cases without pounding. Finally, a decision method is presented as an approach to estimate the minimum separation gap distance dg,min between adjacent structures when global and local performances are incorporated in the fragility assessment process.

Proceedings of the 4th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2013), 2014

This study presents morphology, pathology, recording method, applied rehabilitation procedure and... more This study presents morphology, pathology, recording method, applied rehabilitation procedure and constructional problems of a four-storey masonry building in Alexandroupoli which today is partially collapsed. It was constructed before 1900 and enlarged in 1924 to be used as tobacco warehouse. From 1950s onwards, it has been neglected and because of the total lack of maintenance it has sustained structural and architectural deterioration; intervention works for its re-use as Municipal Library began in 2004. The first approved rehabilitation plan based on false strategy adopted the total removal of the interior structural members including wooden diaphragms, beams and columns and the construction of a new internal reinforced concrete frame structure. It proved to be catastrophic since in 2005 a sudden partial collapse of masonry and the roof was caused. The building has remained partially collapsed and difficult to approach due to the danger of a potential further collapsing. Recording of the present state has been based on photogrammetry. A proper intervention plan is applied. This work is a contribution in the field of structural rehabilitation of partially collapsed historic masonry buildings that constitute an extremely unsafe working environment.

Proceedings of the 4th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2013), 2014

The use of conventional and photogrammetric surveys is presented for the recording of two histori... more The use of conventional and photogrammetric surveys is presented for the recording of two historic masonry buildings in Greece. The first one is a four-storey traditional tobacco warehouse of the late 19th century in Alexandroupoli which has been partially collapsed in 2005 and constituted an extremely dangerous working environment. The second is an old customs house that is located in the old historic town of Nafplio and specifically in front of the central part of the port. It was built around the middle of the 19th century by the well-known Architect Stamatios Kleanthis. The architectural, structural and morphological characteristics along with the pathology of these buildings have been recorded through photogrammetric and conventional topographic surveys. This way, all the necessary information for the structures have been acquired with an appropriate accuracy in order to assist Engineers to choose the proper repairing and strengthening techniques for the renovation and the re-use of these historic buildings. The old tobacco warehouse in Alexandroupoli is planned to be the new Municipal Library, whereas the old customs house in Nafplio will be a museum for cultural exhibitions. The recording procedure used, combines the conventional topographic surveys and the photogrammetric image processing for the formation of all the façades' orthoimages. The orthoimages were used as background information to digitize details of the buildings façades in a CAD environment. The Photomodeler software and the freeware application Hugin has been used to create respectively a detailed 3D model and an interactive panorama file of the buildings.

Engineering Structures, 2017

The aim of this study is to correlate the seismic performance of a real RC frame structure at dif... more The aim of this study is to correlate the seismic performance of a real RC frame structure at different seismic demand levels with the separation gap that would be inadequate against pounding with an adjacent shorter and stiffer structure. In this direction 882 nonlinear step by step seismic analyses have been performed. The first part of this study includes the evaluation of the inter-story (floor to column) pounding problem at nine seismic demand levels, using for each level 14 seismic excitations that have been properly scaled. The examined cases are inter-story pounding cases between an 8-story RC frame and a 3-story RC frame-wall structure or a 3-story rigid barrier (very stiff structure) while the adjacent structures are considered to be in contact from the beginning. The seismic performances of the structures without the pounding effect have also been evaluated. The results of the assessment indicate that: (a) at all the examined levels of the seismic demand, the local performance of the external column of the tall building that suffers the impact from the upper floor slab of the adjacent shorter structure is the most important issue in the inter-story pounding phenomenon, (b) this column is always in a critical condition due to shear action and in the case of pounding with the 3-story rigid barrier this column appears to be critical due to high ductility demands as well, (c) the level of the seismic demand that is used to assess the pounding problem on the local performances of the critical column that suffers the hit, altered the developing requirements for flexural and shear capacity of the column. Thereafter, the minimum required gap distance against pounding between the adjacent structures has been estimated taking into account two different criteria: (a) avoidance of the shear failure in the critical column that suffers the hit and (b) complete avoidance of the contact between the adjacent structures. The separation gap is evaluated at all the seismic demand levels for both pounding cases. In comparison to the Eurocode 8 provisions the results of this study indicate less conservative separation gap distances between the adjacent structures at different levels of seismic demand.

Structural Engineering and Mechanics, 2009

ABSTRACT The seismic induced interaction between multistory structures with unequal story heights... more ABSTRACT The seismic induced interaction between multistory structures with unequal story heights (inter-story pounding) is studied taking into account the local response of the exterior beam-column joints. Although several parameters that influence the structural pounding have been studied sofar, the role of the joints local inelastic behaviour has not been yet investigated in the literature as key parameter for the pounding problem. Moreover, the influence of the infill panels as an additional parameter for the local damage effect of the joints on the inter-story pounding phenomenon is examined. Thirty six interaction cases between a multistory frame structure and an adjacent shorter and stiffer structure are studied for two different seismic excitations. The results are focused: (a) on the local response of the critical external column of the multistory structure that suffers the hit from the slab of the adjacent shorter structure, and (b) on the local response of the exterior beam-column joints of the multistory structure. Results of this investigation demonstrate that the possible local inelastic response of the exterior joints may be in some cases beneficial for the seismic behaviour of the critical column that suffers the impact. However, in all the examined cases the developing demands for deformation of the exterior joints are substantially increased and severe damages can be observed due to the pounding effect. The presence of the masonry infill panels has also been proved as an important parameter for the response of the exterior beam-column joints and thus for the safety of the building. Nevertheless, in all the examined inter-story pounding cases the presence of the infills was not enough for the total amelioration of the excessive demands for shear and ductility of the column that suffers the impact.

Earthquakes and Structures, 2014

ABSTRACT Nonlinear dynamic analyses are carried out to investigate the influence of the pinching ... more ABSTRACT Nonlinear dynamic analyses are carried out to investigate the influence of the pinching hysteretic response of the exterior RC beam-column joints on the seismic behavior of multistory RC frame structures. The effect of the pinching on the local and global mechanisms of an 8-storey bare frame and an 8-storey pilotis type frame structure is evaluated. Further, an experimental data bank extracted from literature is used to acquire experimental experience of the range of the real levels that have to be considered for the pinching effect on the hysteretic response of the joints. Thus, three different cases for the hysteretic response of the joints are considered: (a) joints with strength and stiffness degradation characteristics but without pinching effect, (b) joints with strength degradation, stiffness degradation and low pinching effect and (c) joints with strength degradation, stiffness degradation and high pinching effect. For the simulation of the beam-column joints a special-purpose rotational spring element that incorporates the examined hysteretic options developed by the authors and implemented in a well-known nonlinear dynamic analysis program is employed for the analysis of the structural systems. The results of this study indicate that the effect of pinching on the local and global responses of the examined cases is not really significant at early stages of the seismic loading and especially in the cases when strength degradation in the core of exterior joint has occurred. Nevertheless in the cases when strength degradation does not occur in the joints the pinching may increase the demands for ductility and become critical for the columns at the base floor of the frame structures. Finally, as it was expected the ability for energy absorption was reduced due to pinching effect.

Structural Engineering and Mechanics, 2013

ABSTRACT The seismic performance of reinforced concrete (RC) frame structures with irregularities... more ABSTRACT The seismic performance of reinforced concrete (RC) frame structures with irregularities leading to soft first floor is studied using capacity assessment procedures. The soft first story effect is investigated for the cases: (i) slab-column connections without beams at the first floor, (ii) tall first story height and (iii) pilotis type building (open ground story). The effects of the first floor irregularity on the RC frame structure performance stages at global and local level (limit states) are investigated. Assessment based on the Capacity Spectrum Method (ATC-40) and on the Coefficient Method (FEMA 356) is also examined. Results in terms of failure modes, capacity curves, interstory drifts, ductility requirements and infills behaviour are presented. From the results it can be deduced that the global capacity of the structures is decreased due to the considered first floor morphology irregularities in comparison to the capacities of the regular structure. An increase of the demands for interstory drift is observed at the first floor level due to the considered irregularities while the open ground floor structure (pilotis type) led to even higher values of interstory drift demands at the first story. In the cases of tall first story and slab-column connections without beams softstory mechanisms have also been observed at the first floor. Rotational criteria (EC8-part3) showed that the structure with slab-column connections without beams exhibited the most critical response.

Structural Engineering and Mechanics, 2005

The influence of the inter-story structural pounding on the seismic behaviour of adjacent multist... more The influence of the inter-story structural pounding on the seismic behaviour of adjacent multistory reinforced concrete structures with unequal total heights and different story heights is investigated. Although inter-story pounding is a common case in practice, it has not been studied before in the literature as far as the authors are aware. Fifty two pounding cases, each one for two different seismic excitations, are examined. From the results it can be deduced that: (i) The most important issue in the inter-story pounding is the local effect on the external column of the tall building that suffers the impact from the upper floor slab of the adjacent shorter structure. (ii) The ductility demands for this column are increased comparing with the ones without the pounding effect. In the cases that the two buildings are in contact these demands appear to be critical since they are higher than the available ductility values. In the cases that there is a small distance between the interacting buildings the ductility demands of this column are also higher than the ones of the same column without the pounding effect but they appear to be lower than the available ductility values. (iii) It has to be stressed that in all the examined cases the developed shear forces of this column exceeded the shear strength. Thus, it can be concluded that in inter-story pounding cases the column that suffers the impact is always in a critical condition due to shear action and, furthermore, in the cases that the two structures are in contact from the beginning this column appears to be critical due to high ductility demands as well. The consequences of the impact can be very severe for the integrity of the column and may be a primary cause for the initiation of the collapse of the structure. This means that special measures have to be taken in the design process first for the critically increased shear demands and secondly for the high ductility demands.

Case Studies in Construction Materials, 2016

The application of an innovative real-time structural health monitoring system is studied through... more The application of an innovative real-time structural health monitoring system is studied through tests performed on flexural and shear-critical reinforced concrete elements subjected to monotonic and cyclic loading. The test setup involves a Wireless impedance/ Admittance Monitoring System (WiAMS) that comprises specially manufactured smallsized portable devices to collect the voltage frequency responses of an array of smart piezoelectric transducers mounted on structural members of reinforced concrete constructions. Damage detection and evaluation is achieved using the in-situ measurements of the integrated piezoelectric sensors/actuators signals at the healthy state of the member and at various levels of damage during testing. Three different installations of Piezoelectric lead Zirconate Titanate (PZT) transducers are examined: (a) epoxy bonded PZTs on the surface of the steel reinforcing bars of the flexural elements, (b) PZTs embedded inside the concrete mass of the shear-critical beams and (c) externally epoxy bonded PZTs attached to the concrete surface of the tested elements. The smart piezoelectric materials have been pre-installed before testing based on the potential flexural and shear cracking of the elements. Quantitative assessment of the examined damage levels using values for the statistical damage index is also presented and discussed. Voltage signals and index values acquired from the PZTs' measurements using the proposed wireless monitoring technique demonstrated obvious discrepancies between the frequency response of the healthy and the examined damage levels for every tested element. These differences clearly indicate the presence of damage, whereas their gradation reveals the magnitude of the occurred damage. Promising results concerning the prediction of the forthcoming fatal failures at early damage stages have also been derived.

ABSTRACT The influence of the inter-story structural pounding on the seismic behavior of adjacent... more ABSTRACT The influence of the inter-story structural pounding on the seismic behavior of adjacent multistory reinforced concrete structures with unequal story heights is studied taking into account the local response of the infill panels. Results of more than one hundred dynamic analyses indicate that, the most important issue in the interaction between structures is the local response of the column of the tall structure that suffers the hit of the upper floor slab of the adjacent shorter and stiffer structure. This column appears to be in most of the times in a critical condition due to shear action. In this paper the influence of the infill panels on the pounding problem of adjacent structures is studied. Two types of masonry infilled structures are considered: (a) infilled frame and (b) infilled frame without infills at the base story (pilotis frame). Results in terms of interstorey drifts, shear requirements, ductility requirements and infill local seismic response are presented. The influence of the infill panels on the seismic performance of the critical column that suffers the hit led in all examined cases to an increase of the demands for shear and ductility, when compared to the corresponding values that are developed in the cases that the RC structure is studied without considering the infills. Thus, it can be demonstrated that in all examined inter-story pounding cases the presence of the infills was not enough for the amelioration of the excessive demands for shear and ductility of the column that suffers the impact. Nevertheless, the presence of the masonry infill panels has been proved as an important parameter for the safety of the building. Non-linear dynamic step-by-step analyses and special purpose elements are employed for the needs of this study.

WIT Transactions on the Built Environment, Jun 29, 2015

Buildings

Applied Sciences

WIT Transactions on The Built Environment, 2015

WIT Transactions on the Built Environment, 2005

XI International Conference on Structural Dynamics, 2020

Engineering Structures, 2021

Proceedings of the 4th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2013), 2014

Engineering Structures, 2017

Structural Engineering and Mechanics, 2009

Earthquakes and Structures, 2014

Structural Engineering and Mechanics, 2013

Structural Engineering and Mechanics, 2005

Case Studies in Construction Materials, 2016