The performance of structures to resist seismic loading is the main aspect in earthquake engineering. The study investigates the seismic performance of two different types of steel structures: Building 1, designed according to Eurocode 8, and Building 2, design only for gravity loads. All the analyses are performed using the computer code SAP2000. Accurate numerical models of the two above-mentioned structures are developed. Bi-dimensional and three-dimensional models are both considered and mass eccentricity is introduced for the consideration of torsional effects. Nonlinear static and nonlinear dynamic analyses under bi-directional ground motion are carried out. Advanced nonlinear interactive plastic hinge PMM is established for the structure nonlinearity. Two real accelerograms, El Centro and Taft, are used in the numerical analyses. The retrofitting strategy is selected on the basis of the structural deficiencies, which are highlighted by numerical analyses. Retrofitting is mostly aimed: to increase the lateral stiffness, to improve the global ductility of the structure, to reduce the torsional component of the seismic response, and to introduce alternative connections. The effectiveness of seismic retrofitting techniques is also investigated in the numerical analyses. Conventional bracing system and braced ductile shear panel (BDSP), which are implemented to enhance stiffness and dissipate energy respectively, are used for both buildings. Compared with CBF, the seismic performance improvement is significant for the building equipped with BDSP. In addition, the weakening strategy of Reduced Beam Section (RBS) and strengthening strategy of Cover Plates (CP) are assigned for building 1. The aim of these two connection retrofitting techniques is shifting the beam plastic hinge away from the column face and prevent the damage of connections.
Il lavoro di tesi ha avuto per oggetto lo studio dell’efficacia di diverse tecniche di adeguamento per migliorare la risposta sismica di edifici in acciiao. Sono state considerate due diverse tipologie di strutture: la prima, progettata in accordo alle prescrizioni dell’Eurocodice 8, e la seconda, progettata principalmente per carichi verticali. Sono stati sviluppati diversi modelli numerici delle due tipologie di strutture e sono state eseguite analisi statiche e dinamiche nonlineari. Sono stati studiati modelli bidimensionali e tridimensionali delle strutture ed è stata considerata la presenza di eccentricità di massa per tenere conto di effetti torsionali. La nonlinearità del materiale è stata tenuta in conto introducendo cerniere plastiche alle estremità di travi e colonne. Le strategie e tecniche di adeguamento utilizzate sono state selezionate sulla base delle deficienze strutturali evidenziate dalle analisi numeriche sulle strutture originali. Gli obiettivi delle diverse tecniche di adeguamento sono stati il miglioramento della duttilità globale e della rigidezza della struttura, la riduzione della componente torsionale della risposta sismica e l’introduzione di connessioni alternative. I diversi interventi studiati sono stati simulati con appropriati modelli numerici. L’introduzione di controventi concentrici a X ha portato ad un aumento della rigidezza delle strutture, mentre il dispositvo BDSP, costituito da controventi e pannello duttile, ha permesso una maggiore dissipazione di energia. Il miglioramento della risposta sismica delle strutture è stato più evidente nel caso di strutture dotate di dispositivi BDSP. Per la tipologia di strutture progettate in accordo all’Eurocodice 8 sono state introdotte connessione alternative basate sull’indebolimento della sezione della trave o sul rinforzo mediante piastre. L'obiettivo è stato quello di proteggere la zona in corrispondenza della colonna allontanando la posizione di eventuali cerniere plastiche nelle travi.
Seismic performance improvement of steel structures using different methods
ZHANG, QIANG;CHENG, XI
2012/2013
Abstract
The performance of structures to resist seismic loading is the main aspect in earthquake engineering. The study investigates the seismic performance of two different types of steel structures: Building 1, designed according to Eurocode 8, and Building 2, design only for gravity loads. All the analyses are performed using the computer code SAP2000. Accurate numerical models of the two above-mentioned structures are developed. Bi-dimensional and three-dimensional models are both considered and mass eccentricity is introduced for the consideration of torsional effects. Nonlinear static and nonlinear dynamic analyses under bi-directional ground motion are carried out. Advanced nonlinear interactive plastic hinge PMM is established for the structure nonlinearity. Two real accelerograms, El Centro and Taft, are used in the numerical analyses. The retrofitting strategy is selected on the basis of the structural deficiencies, which are highlighted by numerical analyses. Retrofitting is mostly aimed: to increase the lateral stiffness, to improve the global ductility of the structure, to reduce the torsional component of the seismic response, and to introduce alternative connections. The effectiveness of seismic retrofitting techniques is also investigated in the numerical analyses. Conventional bracing system and braced ductile shear panel (BDSP), which are implemented to enhance stiffness and dissipate energy respectively, are used for both buildings. Compared with CBF, the seismic performance improvement is significant for the building equipped with BDSP. In addition, the weakening strategy of Reduced Beam Section (RBS) and strengthening strategy of Cover Plates (CP) are assigned for building 1. The aim of these two connection retrofitting techniques is shifting the beam plastic hinge away from the column face and prevent the damage of connections.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/81544