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Abdelmegeed M.M.,Fayoum University | Badogiannis E.,National Technical University of Athens | Kotsovos G.,Lithos Consulting Engineers | Vougioukas E.,National Technical University of Athens
International Journal of Conservation Science | Year: 2015

The work presented is concerned with the rehabilitation of a typical traditional masonry building built in Athens in the late 18th early 19th century. The building has suffered significant damage primarily in the form of vertical and inclined splitting of the bearing walls and fragmentation of the mortar used to bind together the masonry stones as a result of seismic excitation, lack of maintenance, construction defects, etc. The paper describes the damage suffered and investigates its causes through the use of numerical analysis techniques. It is found that the causes of damage are predominantly linked with structural deficiencies such as lack of diaphragmatic action and bracing and restoration methods are proposed. The latter include a reinforced-concrete layer at the wall crowning, strengthening (or replacement wherever necessary) of the floor timber beams and bracing in the form of external and internal reinforced concrete strips at the level of the basement floor.


Kotsovos G.M.,Lithos Consulting Engineers | Vougioukas E.,National Technical University of Athens | Kotsovos M.D.,National Technical University of Athens
Magazine of Concrete Research | Year: 2015

The work presented concerns an investigation of the effect of bond between concrete and longitudinal reinforcement on the behaviour of reinforced concrete beams, without transverse reinforcement, subjected to transverse loading combined with an axial force in selected cases. The results showed that the development of bond anywhere within the shear span inevitably leads to inclined cracking, which is the cause of 'shear' failure. Similarly, eliminating bond throughout the beam's span was also found not to safeguard against premature failure. On the other hand, allowing the development of bond only within the shear-free region of the beam was found not only to prevent failure within the shear span, but also to allow the calculation of flexural capacity as for the case of beams with steel bonded to concrete throughout their span.


Kotsovou G.M.,Heriot - Watt University | Kotsovos G.M.,Lithos Consulting Engineers | Vougioukas E.,National Technical University of Athens
Computers and Concrete | Year: 2016

The work is intended to demonstrate that the loss of bond between concrete and flexural steel which led in recent years a number of flat-slab structures to punching collapse under service loading conditions is also relevant to ultimate limit-state design. It is based on a comparative study of the results obtained from numerical experiments on flat slab-column sub-assemblages. The slabs were designed for punching either in compliance with the EC2 code requirements, which do not allow for such loss of bond, or in accordance with the compressive force-path method which considers the loss of bond between concrete and the flexural reinforcement in tension as the primary cause of punching. The numerical experiments are carried out through the use of a nonlinear finite element analysis package for which, although ample published evidence of its validity exists, additional proof of its suitability for the purposes of the present work is presented. Copyright © 2016 Techno-Press, Ltd.


Zygouris N.S.,Lithos Consulting Engineers | Kotsovos G.M.,Lithos Consulting Engineers | Cotsovos D.M.,Heriot - Watt University | Kotsovos M.D.,National Technical University of Athens
Meccanica | Year: 2014

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. © 2014, Springer Science+Business Media Dordrecht.


Abdelmegeed M.M.,Fayoum University | Badogiannis E.,National Technical University of Athens | Kotsovos G.,Lithos Consulting Engineers | Vougioukas E.,National Technical University of Athens
International Journal of Conservation Science | Year: 2014

Historical buildings demand a full characterization of the materials used for their construction, before any rehabilitation action. The assessment of the mechanical characteristics of the masonry materials is based on visual observation, sampling of the construction materials and laboratory testing of the samples. The work described is concerned with the rehabilitation of a traditional masonry house in Athens which over the years suffered damage due to various causes. The paper describes the early preliminary stages of the rehabilitation work concerned with the description of the structural system, the mapping of damage and the documentation of the materials used.


Kotsovou G.M.,University of Edinburgh | Kotsovos G.M.,Lithos Consulting Engineers
Computers and Concrete | Year: 2016

The present work is concerned with a numerical investigation of the behaviour of reinforcedconcrete beams with non-bonded flexural tension reinforcement. The numerically-established behaviour of such beams with and without transverse reinforcement is compared with its counterpart of similar beams with bonded reinforcement. From the comparison, it is found that the development of bond anywhere within the shear span inevitably leads to inclined cracking which is the cause of 'shear' failure. On the other hand, the lack of bond within the shear span of the beams is found, not only to prevent cracking within the shear span, but, also, to lead to a flexural type of failure preceded by the formation of horizontal splitting of concrete in the compressive zone. It is also found that delaying the extension of horizontal splitting through the provision of transverse reinforcement in the beam mid span can lead to flexural failure after yielding of the tension reinforcement. Yielding of the tension reinforcement before the horizontal splitting of the compressive zone may also be achieved by reducing the amount of the latter reinforcement. © 2016 Techno-Press, Ltd.


Zygouris N.S.,Lithos Consulting Engineers | Kotsovos G.M.,Lithos Consulting Engineers | Kotsovos M.D.,National Technical University of Athens
Earthquake and Structures | Year: 2015

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. © 2015 Techno-Press, Ltd.

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