Proiectarea bazata pe performanta. Consolidarea cladirilor vulnerabile seismic.

Autor/autori: Drd. ing. Adrian Manolache, Prof. dr. ing. Mircea Ieremia

Rezumat: De o buna perioada de vreme, a aparut cu prioritate in multe tari cu risc seismic ridicat necesitatea evaluarii vulnerabilitatii constructiilor existente. Aceasta evaluare este necesara pentru a stabili consecintele producerii unui seism intr-o anumita zona si a se identifica cladirile cu cea mai mare sensibilitate la un cutremur in perspectiva unei consolidari a structurii de rezistenta. In acest sens, vulnerabilitatea trebuie sa fie exprimata sub o forma compatibila cu notiunea de alee seismica, astfel incat sa se poata estima impactul asupra unei zone construite. Normele paraseismice au considerat din totdeauna actiunea seismica ca o forta, iar raspunsul calculat al unei structuri s-a determinat pe baza principiului fundamental al Dinamicii. In consecinta, dimensionarea sau verificarea structurii la seism revenea la a se echilibra aceste forte. In realitate, actiunea seismica se limiteaza la o deplasare impusa la baza constructiei. Forta seismica mentionata de norme nu este decat o consecinta (reactiunea) acestei deplasari. Atata timp cat deplasarea si forta respectiva sunt legate printr-o relatie liniara, analiza dinamica prin aproximarea in forte echivaleaza cu o analiza in deplasari. Aceasta echivalenta inceteaza insa a mai fi valabila in momentul in care comportarea materialului nu mai este liniar-elastica. In acest caz se recurge la aproximarea in forte apeland fie la metode de calcul numerice capabile sa traduca pas cu pas comportamentul structural fizic neliniar, fie la coeficienti de reducere a efortului respectiv (coeficienti de comportare), iar prevederile constructive impuse de proiectant asigura structurii ductilitatea corespunzatoare. In concluzie, cand se dimensioneaza sau se verifica o structura prin noile norme de proiectare paraseimica se urmareste sa se controleze deplasarile si nu sa se echilibreze fortele provocate de seism. In plus, actiunea seismica poate fi reprezentata in mod natural printr-o deplasare si nu printr-o forta sau o simpla acceleratie.

Cuvinte cheie: cercetare seismica, cutremur, deformare postelastica, rigiditate, disipare de energie, comportare ductila, actiune seismica.

Abstract: For a long period of time has emerged as a priority in many countries with high seismic risk, need to assess the vulnerability of existing buildings. This assessment is needed to determine the consequences of an earthquake in a given area and to identify buildings with the greatest sensitivity to an earthquake with a view to reinforcing the structure. In this respect, the vulnerability must be expressed in a form compatible with the concept of seismic path, so you can estimate the impact of construction areas. Paraseismic rules have always been considered as a seismic action force and the calculated response of a structure was determined based on the fundamental principle of dynamics. Consequently, sizing or check was for the seismic structure to balance these forces. In fact, the action is limited to a seismic shift in the construction required. Seismic force that rule is not merely a consequence of (reaction) in this movement. As long as the movement and strength that are linked by a linear relationship, the dynamic analysis by approximating the force equivalent to a movement analysis. This equivalence, however, cease to be valid when the behavior is not linear elastic material. In this case we resort to approximating the forces calling numerical calculation methods are able to translate physical step nonlinear structural behavior, or the factors that reduce effort (attitude factors) and structural requirements imposed by the designer ensure adequate ductility structure. In conclusion, when a structure sized or verified by the new rules paraseimic design seeks to control the movements and not to balance the forces caused by earthquake. In addition, seismic action can be naturally represented by a shift and not by mere force or acceleration.

Keywords: seismical research, earthquake, postelastic deformation, stiffness, energy dissipation, ductile behavior, seismic action.

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