Institute of Earthquake Engineering and Engineering Seismology

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    Analysis of exponent K based on “SHARE” project data and its implications on importance factors of EN 1998–1
    (Springer Science and Business Media LLC, 2022-02-08)
    Dragojević, Dejan
    ;
    Šalić Makreska, Radmila
    ;
    Milutinović, Zoran
    This contribution deals with seismic activity represented by a hazard curve through a single parameter–exponent k as given in EN 1998–1 and its implications on importance factors. We used the SHARE project dataset to calculate exponent k for the wider European area, and a limited number of separate national studies for comparison of the results since comparison to the SHARE results on the same dataset resulted in values of exponent k smaller by 1–1.5. The results indicate that the recommended value of exponent k of 3 is rather an exception than an expected value in seismically active regions and that, with the exclusion of the Vrancea zone, for the majority of Europe, exponent k is well below that assumed in EN 1998–1, which consequently indicates that the importance factors for these locations should be higher than those recommended in EN 1998–1.
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    Genealogy of development and codification of Yugoslavian earthquake resistant design
    (Springer Science and Business Media LLC, 2022-08-30)
    Milutinovic, Zoran
    ;
    Salic Makreska, Radmila
    ;
    Tomic, Daniel
    ;
    Trajcevski, Jovan
    This contribution aims to clarify for exposure modelers and vulnerability and seismic risk assessors the basis on which seismic lateral loads have been established in all Yugoslavian seismic design codes since 1948. The particular focus is on JUS39/64 and JUS31/81 seismic design codes since they controlled the seismic safety of Macedonian (and Yugoslavian) exposure for 16 and 41 years, respectively. The analyses and discussions are centered on lateral force coefficients as a primary factor for representing the features of each design level. Presented is in all detail the developed K-Quotient method that efficiently compares inter-code lateral force levels. The method provides the closed solution for simplified lateral load calculation applicable to “stiff” buildings (T ≤ 0.5 s). The presented results are indicative of flexible buildings requiring further research on the subject.
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    Effectiveness of tune mass damper in the reduction of the seismic response of the structure
    (2012-02-26)
    Rakicevic, Z.T. and Bogdanovic, A. and Jurukovski, D. and Nawrotzki, P.
    A shaking table testing of a 16.6 t five storey steel frame structure with and tuned mass damper (TMD) named as Tuned Mass Control System (TMCS) installed at the top has been carried out in the Dynamic Testing Laboratory at the Institute of Earthquake Engineering and Engineering Seismology (IZIIS) in Skopje, Republic of Macedonia. For estimation of the effectiveness of Tuned Mass Control System (TMCS) large number of shaking table experiments have been performed. Simulating different earthquake time histories on the model structure with and without TMCS it has been demonstrated that this system is capable to reduce the responses in order from 10% to more than 50% depending on the frequency content of the seismic input and the corresponding sensitivity of the structure. Given a high quality analytical model of a structure and a dynamic absorber, a series of variant analyses have been performed within the study to investigate the effect of the individual parameters and evaluate the efficiency of the dynamic absorber. The analyses have been performed to define the effect of the location of the absorber, also, upon the dynamic behaviour of the structure in the case the absorber is installed at the different level (storey) of the structure. Comparative analysis of the structure with TMCS having optimally tuned its mechanical properties versus structure that has TMCS having the same mechanical properties as tested specimen showed that the TMCS additionally improves the structural behaviour, depending on frequency content of earthquake excitation.
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    A European Association for the Control of Structures joint perspective. Recent studies in civil structural control across Europe
    (2014-03-12)
    Basu, B. and Bursi, O.S. and Casciati, F. and Casciati, S. and Del Grosso, A.E. and Domaneschi, M. and Faravelli, L. and Holnicki-Szulc, J. and Irschik, H. and Krommer, M. and Lepidi, M. and Martelli, A. and Ozturk, B. and Pozo, F. and Pujol, G. and Rakicevic, Z. and Rodellar, J.
    Structural control has been comprehensively studied over the world as a multidisciplinary research field. The present work is motivated by an attempt to give a common frame to the recent research and applications of structural control technology in civil engineering across Europe. They include novel passive dampers, functional materials and semi-active dampers, active control systems, and their performance investigations. Design methods for the vibrations reduction of buildings, bridges, and wind turbines are discussed with reference to case studies. Control algorithms and dimension reduction techniques are also studied. Adaptation strategies and techniques based on the potential offered by piezoelectricity are reviewed. Copyright © 2014 John Wiley & Sons, Ltd.
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    Shake table tests and numerical investigation of a resilient damping device for seismic response control of building structures
    (2019-08-25)
    Bogdanovic, A. and Rakicevic, Z. and Noroozinejad Farsangi, E.
    In this study, shake table tests of a multistory steel frame structure designed according to Eurocodes 3 and 8 with and without the newly developed prestressed viscous damper (PVD) have been carried out at the Institute of Earthquake Engineering and Engineering Seismology in Macedonia. An array of strong ground motion records has been applied to the reduced-scale test structure to assess the efficiency and seismic performance of the equipped building with PVDs. It has been revealed that with the implementation of this system, the structural responses were suppressed in the range of 10% to 70%. Series of sensitivity analyses have been performed within the study to investigate the effect of the individual parameters and evaluate the effectiveness of the proposed system. Besides the experimental investigations, extensive numerical simulations of the structure without PVDs versus structure with three different damper placements were performed in ANSYS nonlinear platform, and part of the results that are presented in this paper confirms the remarkable structural performance improvement when using this system. The results also exhibit that the developed finite element models are properly verified through the experimental results and have the capabilities to further investigate the proposed system. It is likely that the proposed control strategy can be used for practical implementations into full-scale buildings to improve the urban seismic resilience.
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    Deformable polyurethane joints and fibre grids for resilient seismic performance of reinforced concrete frames with orthoblock brick infills
    (2020-11-30)
    Rousakis, T. and Ilki, A. and Kwiecien, A. and Viskovic, A. and Gams, M. and Triller, P. and Ghiassi, B. and Benedetti, A. and Rakicevic, Z. and Colla, C. and Halici, O.F. and Zaj?c, B. and Hojdys, ?. and Krajewski, P. and Rizzo, F. and Vanian, V. and Sapalidis, A. and Papadouli, E. and Bogdanovic, A.
    The behaviour of reinforced concrete frames with masonry wall infills is influenced a lot by the stiffness and strength difference between the frame and the infill, causing early detrimental damage to the infill or to the critical concrete columns. The paper reports the results from shake table seismic tests on a full-scale reinforced concrete (RC) frame building with modified hollow clay block (orthoblock brick) infill walls, within INMASPOL SERA Horizon 2020 project. The building received innovative resilient protection using Polyurethane Flexible Joints (PUFJs) made of polyurethane resin (PU), applied at the frame-infill interface in different schemes. Further, PUs were used for bonding of glass fibre grids to the weak masonry substrate to form Fibre Reinforced Polyurethanes (FRPUs) as an emergency repair intervention. The test results showed enhancement in the in-plane and out-of-plane infill performance under seismic excitations. The results confirmed remarkable delay of significant infill damages at very high RC frame inter-story drifts as a consequence of the use of PUFJs. Further, the PUFJ protection enabled the resilient repair of the infill even after very high inter-story drift of the structure up to 3.7%. The applied glass FRPU system efficiently protected the damaged infills against collapse under out-of-plane excitation while they restored large part of their in-plane stiffness.
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    Item type:Publication,
    A hybrid seismic isolation system toward more resilient structures: Shaking table experiment and fragility analysis
    (Elsevier BV, 2021-06)
    Rakicevic, Zoran
    ;
    Bogdanovic, Aleksandra
    ;
    Noroozinejad Farsangi, Ehsan
    ;
    Sivandi-Pour, Abbas
    The effectiveness of various vibration control strategies has always been a debate among structural engineers. Seismic base isolation systems and passive dampers are recognized as two of the most economical devices which have passive mechanisms in reducing the structural vibration and responses. To this end, comprehensive biaxial shake table testings have been carried out on a building frame with and without a proposed base isolation system. The proposed device has a novel combined isolation mechanism at the structure's base. By different methods of testing, natural frequencies and viscous damping for the frame model with and without the proposed system were identified. Both structures were intensively tested under various earthquake motions, and various structural responses were recorded. The experimental results indicated that the newly proposed system is very effective in controlling the vibration of building structures and can be used to increase the seismic resilience metrics. As a complementary investigation, the incremental dynamic analysis (IDA) was conducted to develop the seismic fragility curves under both near-field and far-field strong ground motions (SGMs). The fragility estimations indicated that the proposed system has a higher collapse margin ratio (CMR) compared to conventional fixed-base frames.