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1

Determining Frequency-Energy Dependencyof Nonlinear Normal Modes and Internal ResonancesUsing a Numerical Independent Approach

Ghariblou Arash, Mahmoudi Mussa

Computer Assisted Methods in Engineering and Science

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2022

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Vol. 29, no. 3

261--292

EN

Application of linear normal modes to the nonlinear area provides an in-depth investigation of structures. In this paper, a straightforward approach is proposed to investigatenonlinear normal modes (NNMs) thoroughly and focus on all possible solutions and bifurcations, independent of all initial assumptions and prior solutions. In this context, afterdiscretization of the response domain over an appropriate resolution, a periodicity algorithm is suggested to capture the solutions that meet the NNMs criteria. Afterward, thefrequency and energy of the system during accepted responses and degrees of freedom(DOFs)’ relations are derived. Finally, after verifying the proposed approach and acquir-ing new internal resonances, the frequency-energy plots and NNMs of a nonlinear elasticsystem with more substantial nonlinearities and a two-story steel structure with nonlinearmaterial are studied. It is worth noting that the periodicity algorithm and capturing allpossible solutions and bifurcations are among the apparent novelties of the current paper.

2

Seismic response characteristics of a base isolated cable-stayed bridge under moderate and strong ground motions

Javanmardi A., Ibrahim Z., Ghaedi K., Jameel M., Khatibi H., Suhatril M.

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 2

419--432

EN

In this study, the seismic behavior of an existing steel cable-stayed bridge equipped with lead-rubber bearing subjected to moderate and strong earthquakes is investigated. The bridge is located at high seismic zone and experienced an earthquake in 1988 which caused the failure of one of its anchorage plate of the support. Herein, the bridge was modeled in three dimensions and the base isolators implemented at the abutments and deck-tower connection. The bridge seismic responses were evaluated through nonlinear dynamic time-history analysis. The comparative analysis confirmed that the base isolation system was an effective tool in reducing seismic force transmit from substructure to superstructure. Furthermore, the overall seismic performance of cable-stayed bridge significantly enhanced in longitudinal and transverse directions. However, it is observed that the axial force of the tower in substructure increased due to the isolation system induced torsional deformation to the superstructure under transverse seismic loads.

3

Modelling of concrete buildings for practical nonlinear seismic response analysis

Fardis M.

Architecture Civil Engineering Environment

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2010

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Vol. 3, no. 1

31-46

EN

Member modelling for the practical evaluation of the seismic performance of real concrete buildings on the basis of nonlinear dynamic analysis in 3D is overviewed. Fibre Element modelling is highlighted and contrasted to simplified lumped inelasticity models of members, with parameters fitted to a wealth of cyclic test results. An application to a full-scale 3-storey structure in 3D subjected to seismic testing under two horizontal components of ground motion validates this latter type of modelling. Two further applications are presented, one to explain the partial collapse of a multi-storey building in the Athens (1999) earthquake and another for the seismic assessment and retrofitting of a theatre building. The applications, which demonstrate simple lumped inelasticity member models, with parameters fitted to test results, are cost-effective and reliable alternatives to prohibitive Fibre Element modelling.

PL

W artykule przedstawiono modelowanie (na bazie nieliniowej analizy dynamicznej w 3D) elementów rzeczywistych budynków betonowych, służące do praktycznej oceny wpływu oddziaływań sejsmicznych. Wyróżniono modelowanie elementami pasmowymi, w odróżnieniu od uproszczonych niesprężystych modeli skupionych elementów z parametrami dopasowanymi do dużej ilości wyników badań cyklicznych. Wykonanie trójwymiarowego, naturalnej wielkości modelu 3-kondygnacyjnej konstrukcji poddanej obciążeniu sejsmicznemu, w postaci dwóch poziomych składowych ruchu gruntu, uzasadnia zastosowanie tego drugiego typu modelowania. Przedstawiono również dwa dalsze zastosowania, pierwsze do wyjaśnienia częściowego zawalenia się wielokondygnacyjnego budynku w wyniku trzęsienia ziemi w Atenach (1999) i drugie do oceny sejsmicznej i modernizacji budynku teatru. Przedstawione zastosowania dowodzą, że proste, niesprężyste modele skupione, z parametrami dostosowanymi do wyników badań są ekonomicznie efektywne i stanowią pewną alternatywę dla modelowania elementami pasmowymi.