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Strengthening reinforcement of basement. |
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Strengthening reinforcement of ground floor. |
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Strengthening reinforcement of 1st floor. |
Everyday Structural Engineering thoughts.
The 2nd Elementary school of Paschna is an existing reinforced concrete structure, built in 1975. The structural assesment using push-over analysis, showed inadequacies in the building's columns. Gunite Concrete has been proposed for the strengthening.
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Strengthening reinforcement of basement. |
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Strengthening reinforcement of ground floor. |
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Strengthening reinforcement of 1st floor. |
Κατά τη φάση σχεδιασμού των μεταλλικών κατασκευών, εκτός από τις διαφόρων ειδών φορτίσεις επί της κατασκευής (στατικά, σεισμού, ανέμου, χιονιού κλπ), πρέπει να λαμβάνονται υπόψη και φορτία πυρκαϊάς.
Βεβαίως, στην προκειμένη περίπτωση, όπου η φωτιά κατέστρεψε το 70% του φέροντος οργανισμού, ο σχεδιασμός έναντι πυρκαϊας ωφέλησε μόνο στην αποφυγή της κατάρρευσης.
This was really a very complex project to accomplish. Here are the most significant parts of the structural design we had to overcome:
1. Seismic absorbers design. Several analysis had to be done: time history analysis, responce spectrum analysis etc, using many hand calculations to verify the absorbers behavior. Viscous damping finally achieved, was about 18%. Most difficult aspect of the design was to correctly model the LRBs with non linear springs.
- Area springs should act only in compression. This means that a non linear analysis should be carried out, which will take more time to complete and more effort to check.
- At walls edges/corners, bending moments concentration/peak is noticed. It seems extremely difficult to suffiently describe the model behaviour in these areas whith finite elements.
- In most every day cases, the spring stiffness is estimated by experience. More stiff springs will lead to higher/concentrated stresses under walls/columns.
- The analysis of the superstructure should be done considering all vertical members (walls/columns) fixed at foundation level, unless specific reason exist. The design of the foundation should be done in a separate model, using springs. For this later analysis, superstructure results should be neglected.