Nick Zygouris - Academia.edu (original) (raw)

Papers by Nick Zygouris

Earthquakes and Structures, 2015

ABSTRACT The application of the compressive force path method for the design of earthquake-resist... more ABSTRACT The application of the compressive force path method for the design of earthquake-resistant reinforced concrete structural walls with a shear span-to-depth ratio larger than 2.5 has been shown by experiment to lead to a significant reduction of the code specified transverse reinforcement within the critical lengths without compromising the code requirements for structural performance. The present work complements these findings with experimental results obtained from tests on structural walls with a shear span-to-depth ratio smaller than 2.5. The results show that the compressive force path method is capable of safeguarding the code performance requirements without the need of transverse reinforcement confining concrete within the critical lengths. Moreover, it is shown that ductility can be considerably increased by improving the strength of the two bottom edges of the walls through the use of structural steel elements extending to a small distance of the order of 100 mm from the wall base.

Technical Instructions concerning the structural design, the various different stages of construc... more Technical Instructions concerning the structural design, the various different stages of construction process and the quality control of concrete floors (slabs on ground) [avail. in Greek only].

Meccanica, 2014

The work presented is concerned with the application of the compressive force path (CFP) method f... more The work presented is concerned with the application of the compressive force path (CFP) method for the design of earthquake resistant reinforced concrete structural walls. It is based on a comparative study of the results obtained from tests on structural walls under cyclic loading mimicking seismic action. Of the walls tested, half have been designed in accordance with the CFP method and the remainder in accordance with the provisions of euro-codes 2 and 8. The results obtained show that both methods of design adopted lead to solutions which satisfy the requirements of current codes for structural performance in all cases investigated. Moreover, the solutions obtained from the application of the CFP method result in a significant reduction of the amount of stirrup reinforcement placed at the critical lengths of the walls' vertical edges. In fact, such reinforcement is not specified by the latter method for the case of walls with a span-to-depth ratio smaller than 2.5; for the case of walls with a shear span-to-depth ratio larger than 2.5, not only is it placed over a length which is considerably smaller, but also its spacing is significantly larger, than the code specified values. Keywords Earthquake-resistant design Á Compressive force path method Á Reinforced concrete Á Short walls Á Seismic performance

Magazine of Concrete Research, 2013

This paper reports on an investigation of the effect of the transverse reinforcement arrangement ... more This paper reports on an investigation of the effect of the transverse reinforcement arrangement on the effective ductility of short structural walls. The work described is based on a comparative study of the behaviour of three pairs of specimens, with different transverse reinforcement arrangements, tested under cyclic loading. Two of the reinforcement arrangements investigated are those specified by Eurocode 8 (EC8) for medium and high ductility levels and the third is that resulting from application of the compressive force path method, with the latter method, unlike EC8, not specifying confining reinforcement within the critical regions. The results obtained indicate that, in spite of the significant differences in the reinforcement arrangement, all specimens exhibited similar behaviour as regards ductility, load-carrying capacity and mode of failure, the latter being characterised by crushing of concrete and buckling of the flexural bars within the compressive zone at the base ...

ABSTRACT Most of the traditional greek buildings (new-classic ones or not, small or large), with ... more ABSTRACT Most of the traditional greek buildings (new-classic ones or not, small or large), with an age of more than 75 up to 250 yrs, are made of rubble stone masonry with a large volume of low strength lime mortars, while their floors/roofs are mainly made of timber. Their seismic assessment and redesign, based on recent conceptions and normative or informative code principles and criteria, is a challenging problem for the Structural Engineer, not to mention restrictions imposed due to the monumental character of almost all of these old buildings. To this end, the new “frame” of Euro-Codes, and especially of EC 6 and EC 8, is applied in general, as recently completed by the new Greek Codes on (Structural) Assessment and Interventions (nGCSI, 2012), fully harmonized with this “frame” of ECs but far beyond them and more detailed, with a lot of relative application rules. Several aspects are involved in structural assessment and redesign of such old buildings, as covered by the Codes and shortly presented/discussed in this paper, such as : Investigation and documentation of the geometrical and the mechanical data of the existing building, together with their reliability levels (DRLs), i.e. the so-called “knowledge levels”, influencing almost all phases and steps of the design; Quantitative assessment and documentation of any wear, deterioration or damage, of any kind, together with a practical but reliable and safe assessment of the residual me chanical characteristics, based on damage levels (DLs); Decision regarding the performance level (PL), i.e. the foreseen or expected degree of damage during the earthquake itself, probably different for the assessment or the redesign of the structural interventions; Aspects of mechanical behaviour of the masonry (and other) elements, out - of-plane and in -plane response, macro-models etc., before and after repair or/and strengthening, as well as Methods of analysis and dimensioning or redimensioning, linear and non - linear, checks in terms of force or of displacement, depending on PLs and based on skeleton curves. In this paper, most of the related issues are shortly covered, as faced during the structural design, while certain characteristic examples and applications are presented.

Technical Instructions concerning the properties and the use of Self-Compacting Concrete [avail. ... more Technical Instructions concerning the properties and the use of Self-Compacting Concrete [avail. in Greek only].

Magazine of Concrete Research

Developments in Artificial Intelligence for Civil and Structural Engineering, 1995

Most of the traditional greek buildings (new-classic ones or not, small or large), with an age of... more Most of the traditional greek buildings (new-classic ones or not, small or large), with an age of more than 75 up to 250 yrs, are made of rubble stone masonry with a large volume of low strength lime mortars, while their floors/roofs are mainly made of timber. Their seismic assessment and redesign, based on recent conceptions and normative or informative code principles and criteria, is a challenging problem for the Structural Engineer, not to mention restrictions imposed due to the monumental character of almost all of these old buildings. To this end, the new "frame" of Euro-Codes, and especially of EC 6 and EC 8, is applied in general, as recently completed by the new Greek Codes on (Structural) Assessment and Interventions (nGCSI, 2012), fully harmonized with this "frame" of ECs but far beyond them and more detailed, with a lot of relative application rules. Several aspects are involved in structural assessment and redesign of such old buildings, as covered by the Codes and shortly presented/discussed in this paper, such as :  Investigation and documentation of the geometrical and the mechanical data of the existing building, together with their reliability levels (DRLs), i.e. the so-called "knowledge levels", influencing almost all phases and steps of the design;  Quantitative assessment and documentation of any wear, deterioration or damage, of any kind, together with a practical but reliable and safe assessment of the residual mechanical characteristics, based on damage levels (DLs);  Decision regarding the performance level (PL), i.e. the foreseen or expected degree of damage during the earthquake itself, probably different for the assessment or the redesign of the structural interventions;  Aspects of mechanical behaviour of the masonry (and other) elements, out-of-plane and in-plane response, macro-models etc., before and after repair or/and strengthening, as well as  Methods of analysis and dimensioning or redimensioning, linear and non-linear, checks in terms of force or of displacement, depending on PLs and based on skeleton curves.

The application of the compressive force path method for the design of earthquake-resistant reinf... more The application of the compressive force path method for the design of earthquake-resistant reinforced concrete structural walls with a shear span-to-depth ratio larger than 2.5 has been shown by experiment to lead to a significant reduction of the code specified transverse reinforcement within the critical lengths without compromising the code requirements for structural performance. The present work complements these findings with experimental results obtained from tests on structural walls with a shear span-to-depth ratio smaller than 2.5. The results show that the compressive force path method is capable of safeguarding the code performance requirements without the need of transverse reinforcement confining concrete within the critical lengths. Moreover, it is shown that ductility can be considerably increased by improving the strength of the two bottom edges of the walls through the use of structural steel elements extending to a small distance of the order of 100 mm from the wall base.

The work presented is concerned with the application of the compressive force path (CFP) method ... more The work presented is concerned with the
application of the compressive force path (CFP) method
for the design of earthquake resistant reinforced
concrete structural walls. It is based on a comparative
study of the results obtained from tests on structural
walls under cyclic loading mimicking seismic action.Of
the walls tested, half have been designed in accordance
with the CFP method and the remainder in accordance
with the provisions of euro-codes 2 and 8. The results
obtained show that both methods of design adopted lead
to solutions which satisfy the requirements of current
codes for structural performance in all cases investigated.
Moreover, the solutions obtained from the
application of the CFP method result in a significant
reduction of the amount of stirrup reinforcement placed
at the critical lengths of the walls’ vertical edges. In fact,
such reinforcement is not specified by the latter method
for the case of walls with a span-to-depth ratio smaller
than 2.5; for the case of walls with a shear span-to-depth
ratio larger than 2.5, not only is it placed over a length
which is considerably smaller, but also its spacing is
significantly larger, than the code specified values.

This paper reports on an investigation of the effect of the transverse reinforcement arrangement ... more This paper reports on an investigation of the effect of the transverse reinforcement arrangement on the effective
ductility of short structural walls. The work described is based on a comparative study of the behaviour of three
pairs of specimens, with different transverse reinforcement arrangements, tested under cyclic loading. Two of the
reinforcement arrangements investigated are those specified by Eurocode 8 (EC8) for medium and high ductility
levels and the third is that resulting from application of the compressive force path method, with the latter method,
unlike EC8, not specifying confining reinforcement within the critical regions. The results obtained indicate that, in
spite of the significant differences in the reinforcement arrangement, all specimens exhibited similar behaviour as
regards ductility, load-carrying capacity and mode of failure, the latter being characterised by crushing of concrete
and buckling of the flexural bars within the compressive zone at the base of the specimens.

Most of the traditional greek buildings (new-classic ones or not, small or large), with an age of... more Most of the traditional greek buildings (new-classic ones or not, small or large), with an age of more than 75 up to 250 yrs, are made of rubble stone masonry with a large volume of low strength lime mortars, while their floors/roofs are mainly made of timber. Their seismic assessment and redesign, based on recent conceptions and normative or informative code principles and criteria, is a challenging problem for the Structural Engineer, not to mention restrictions imposed due to the monumental character of almost all of these old buildings. To this end, the new “frame” of Euro-Codes, and especially of EC 6 and EC 8, is applied in general, as recently completed by the new Greek Codes on (Structural) Assessment and Interventions (nGCSI, 2012), fully harmonized with this “frame” of ECs but far beyond them and more detailed, with a lot of relative application rules. Several aspects are involved in structural assessment and redesign of such old buildings, as covered by the Codes and shortly presented/discussed in this paper, such as :
 Investigation and documentation of the geometrical and the mechanical data of the existing building, together with their reliability levels (DRLs), i.e. the so-called “knowledge levels”, influencing almost all phases and steps of the design;
 Quantitative assessment and documentation of any wear, deterioration or damage, of any kind, together with a practical but reliable and safe assessment of the residual mechanical characteristics, based on damage levels (DLs);
 Decision regarding the performance level (PL), i.e. the foreseen or expected degree of damage during the earthquake itself, probably different for the assessment or the redesign of the structural interventions;
 Aspects of mechanical behaviour of the masonry (and other) elements, out-of-plane and in-plane response, macro-models etc., before and after repair or/and strengthening, as well as
 Methods of analysis and dimensioning or redimensioning, linear and non-linear, checks in terms of force or of displacement, depending on PLs and based on skeleton curves.
In this paper, most of the related issues are shortly covered, as faced during the structural design, while certain characteristic examples and applications are presented.

Earthquakes and Structures, 2015

Meccanica, 2014

Magazine of Concrete Research, 2013

Magazine of Concrete Research

Developments in Artificial Intelligence for Civil and Structural Engineering, 1995

This paper reports on an investigation of the effect of the transverse reinforcement arrangement ... more This paper reports on an investigation of the effect of the transverse reinforcement arrangement on the effective
ductility of short structural walls. The work described is based on a comparative study of the behaviour of three
pairs of specimens, with different transverse reinforcement arrangements, tested under cyclic loading. Two of the
reinforcement arrangements investigated are those specified by Eurocode 8 (EC8) for medium and high ductility
levels and the third is that resulting from application of the compressive force path method, with the latter method,
unlike EC8, not specifying confining reinforcement within the critical regions. The results obtained indicate that, in
spite of the significant differences in the reinforcement arrangement, all specimens exhibited similar behaviour as
regards ductility, load-carrying capacity and mode of failure, the latter being characterised by crushing of concrete
and buckling of the flexural bars within the compressive zone at the base of the specimens.

Most of the traditional greek buildings (new-classic ones or not, small or large), with an age of... more Most of the traditional greek buildings (new-classic ones or not, small or large), with an age of more than 75 up to 250 yrs, are made of rubble stone masonry with a large volume of low strength lime mortars, while their floors/roofs are mainly made of timber. Their seismic assessment and redesign, based on recent conceptions and normative or informative code principles and criteria, is a challenging problem for the Structural Engineer, not to mention restrictions imposed due to the monumental character of almost all of these old buildings. To this end, the new “frame” of Euro-Codes, and especially of EC 6 and EC 8, is applied in general, as recently completed by the new Greek Codes on (Structural) Assessment and Interventions (nGCSI, 2012), fully harmonized with this “frame” of ECs but far beyond them and more detailed, with a lot of relative application rules. Several aspects are involved in structural assessment and redesign of such old buildings, as covered by the Codes and shortly presented/discussed in this paper, such as :
 Investigation and documentation of the geometrical and the mechanical data of the existing building, together with their reliability levels (DRLs), i.e. the so-called “knowledge levels”, influencing almost all phases and steps of the design;
 Quantitative assessment and documentation of any wear, deterioration or damage, of any kind, together with a practical but reliable and safe assessment of the residual mechanical characteristics, based on damage levels (DLs);
 Decision regarding the performance level (PL), i.e. the foreseen or expected degree of damage during the earthquake itself, probably different for the assessment or the redesign of the structural interventions;
 Aspects of mechanical behaviour of the masonry (and other) elements, out-of-plane and in-plane response, macro-models etc., before and after repair or/and strengthening, as well as
 Methods of analysis and dimensioning or redimensioning, linear and non-linear, checks in terms of force or of displacement, depending on PLs and based on skeleton curves.
In this paper, most of the related issues are shortly covered, as faced during the structural design, while certain characteristic examples and applications are presented.