Evaluation of Seismic Demand for Substandard Reinforced Concrete Structures

Nicholas Kyriakides1, *, Ahmad Sohaib2, Kypros Pilakoutas2, Kyriakos Neocleous1, Christis Chrysostomou1, Elia Tantele1, Renos Votsis1
1 Cyprus University of Technology Civil Engineering and Geomatics Limassol 0035725002356 Achilleos 1 Building, 3rd floor, Saripolou 2-8, 3036, Limassol, CY, Cyprus
2 University of Sheffield Department of Civil and Structural Engineering Sir Frederick Mappin Building Mappin Street, Sheffield, S1 3JD Sheffield, S1 3JD, UK

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© 2018 Kyriakides et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address Correspondence to this author at the Cyprus University of Technology, Civil Engineering and Geomatics Limassol 0035725002356, Achilleos 1 Building, 3rd floor, Saripolou 2-8, 3036, Limassol, CY, Cyprus; Tel: +35728002351; E-mail:



Reinforced Concrete (RC) buildings with no seismic design exhibit degrading behaviour under severe seismic loading due to non-ductile brittle failure modes. The seismic performance of such substandard structures can be predicted using existing capacity demand diagram methods through the idealization of the non-linear capacity curve of the degrading system, and its comparison with a reduced earthquake demand spectrum.


Modern non-linear static methods for derivation of capacity curves incorporate idealization assumptions that are too simplistic and do not apply for sub-standard buildings. The conventional idealisation procedures cannot maintain the true strength degradation behaviour of such structures in the post-peak part, and thus may lead to significant errors in seismic performance prediction especially in the cases of brittle failure modes dominating the response.


In order to increase the accuracy of the prediction, an alternative idealisation procedure using equivalent elastic perfectly plastic systems is proposed herein that can be used in conjunction with any capacity demand diagram method.


Moreover, the performance of this improved equivalent linearization procedure in predicting the response of an RC frame is assessed herein.


This improved idealization procedure has been proven to reduce the error in the seismic performance prediction as compared to seismic shaking table test results [1] and will be further investigated probabilistically herein.

Keywords: Seismic demand predictions, Capacity-demand diagram methods, Degrading systems, Energy balance, Hysteretic behaviour, Cyclic.