Earthquake Design - Response assessment of steel structures under earthquake effect
Authors
Kazakopoulos, Theodoros ; Fillippou, Filippos
Term
4. term
Education
Publication year
2020
Submitted on
2020-06-10
Pages
139
Abstract
Dette projekt designer og undersøger, hvordan en stålkonstruktion opfører sig under jordskælv, i overensstemmelse med Eurocode 8 (EC8), den europæiske standard for jordskælvssikring. Konstruktionen modelleres først i finit element-software (Robot). En modalanalyse bruges til at identificere konstruktionens naturlige svingningsformer, og dens geometriske regelmæssighed kontrolleres. Derefter anvendes to lineært elastiske metoder: modal responsspektrum-analyse og den ækvivalente statiske metode. Metoderne giver meget forskellige resultater; modal responsspektrum anses for mere pålidelig, og derfor baseres dimensioneringen på denne metode. Dernæst vurderes bygningens ydeevne med ikke-lineære analyser i programmet Seismostruct. En statisk ikke-lineær analyse bestemmer kapacitetskurver i de to vigtigste vandrette retninger—altså hvor stor kraft og forskydning konstruktionen kan tåle, før der opstår væsentlige skader. En dynamisk ikke-lineær tidsserieanalyse udføres også med tre forskellige accelerogrammer (registreringer af jordens acceleration under jordskælv). Responsen vurderes via forskydninger og plastiske deformationer (varige, inelastiske deformationer). Til sidst undersøges baseisolering. Elastomere lejer (gummilignende isolationslejer) tilføjes modellen, og der køres dynamiske ikke-lineære analyser. Resultaterne for den baseisolerede model sammenlignes med resultaterne for en model med fast base.
This thesis designs and examines how a steel building structure behaves during earthquakes, following Eurocode 8 (EC8), the European standard for seismic design. The structure is first modeled with finite element software (Robot). A modal analysis identifies the structure’s natural vibration modes, and its geometric regularity is checked. Two linear elastic methods are then applied: modal response spectrum analysis and the equivalent static method. These methods yield very different results; the modal response spectrum is considered more reliable, so the design is based on that method. Next, the building’s performance is assessed using nonlinear analyses with the Seismostruct program. A static nonlinear analysis determines capacity curves in the two principal horizontal directions—that is, how much force and displacement the structure can sustain before significant damage. A dynamic nonlinear time-history analysis is also performed using three accelerograms (records of ground acceleration during earthquakes). Structural response is evaluated through displacements and plastic deformations (permanent inelastic deformations). Finally, the study investigates base isolation. Elastomeric bearings (rubber-like isolation bearings) are added to the model, and dynamic nonlinear analyses are run. Results from the base-isolated model are compared with those from the fixed-base model.
[This abstract was generated with the help of AI]
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