1,720,988 research outputs found
Valutazione della vulnerabilità sismica di edifici elettrici per reattori nucleari CPY tramite elementi shell multi-layered ed il Modello Fessurativo PARC_CL.
No full textNella presente memoria viene descritta la simulazione della prova su tavola vibrante di una struttura a pareti per l’alloggiamento di apparecchiature elettriche di una centrale nucleare tipo CPY realizzata nell’ambito del benchmark internazionale SMART2013. Tale simulazione è stata effettuata mediante modellazione con elementi shell multi-layered ed il modello “smeared” con fessure ad inclinazione fissa denominato PARC_CL. La modellazione ad elementi shell multi-layered si è dimostrata piuttosto efficace in quanto in grado di considerare indicatori di danno (Engineering Demand Parameter, EDP) sia locali che globali. I risultati della simulazione sono forniti in termini distribuzione delle tensioni, apertura di fessure e spostamenti a livello degli impalcati per la più severa delle analisi previste del benchmark (denominata Run#19, target PGA=1.7g). Lo stesso modello è stato poi utilizzato per un’analisi probabilistica della struttura; sono forniti esempi di curve di fragilità ottenute in funzione di diversi EDP e misure d’intensità (Intensity Measure, IM). Nonostante la modellazione con elementi shell e modello fessurativo PARC_CL abbia restituito buoni risultati e si sia rivelata efficiente nella valutazione degli EDP, rimangono aperte alcune questioni, come la corretta implementazione del damping, la possibile rottura all’interfaccia parete/fondazioni e la valutazione della robustezza dell’analisi probabilistica
Simulation of Smart 2013 shaking table test with shell elements and PARC_CL modeling
No full textIn the paper it is described the simulation of the Smart 2013 shaking table test by means of multi layered shell elements modeling and a total strain fixed crack model called PARC_CL. The shell modeling proved to be quite efficient for structural wall buildings as it can take into account global and local damage indicators. Results in terms of stresses contours, crack openings and floors displacements are then provided for a strong motion earthquake (Run #19 of the test). The same model was used also for the evaluation of fragility curves in Stage 4 of the test: examples are then provided both for linear and non linear runs. The multilayer shell elements modeling demonstrated to be a powerful tool although many issues like damping implementation, sliding shear walls failure mode and computational costs optimization require further studies
Simulation of Smart 2013 shaking table test with shell elements and PARC_CL modeling. WORKSHOP SMART2013
No full textBeyond design seismic assessment advanced methodologies for RC structures: PARC_CL for FEM analyses of nuclear power plants RC structures
No full textIn this paper it is presented the PARC_CL fixed crack model (implemented in the user subroutine UMAT.for in Abaqus Code), applied to the non-linear finite element analyses (NLFEA) of reinforced concrete (RC) structures used in nuclear power plants (NPP) under cyclic and dynamic loads. Applications of PARC_CL are presented in this paper: the cyclic analysis of a scaled model of a nuclear containment vessel and the dynamic simulation of a shaking table test of an electrical facility wall structure. The multi-layered shell elements modelling with PARC_CL demonstrated to adequately describe both global and local engineering demand parameters (EDP). Simulations results are provided in terms of displacements, strains and crack patterns. Although the simulations provided good results, some issues such as proper damping calibration in dynamic analysis, wall to foundation interface failure mode description and computational costs are open. Future developments of this research aim also to implement the new PARC_CL2.0 model with plastic strains and to extend it to other FEM codes
Verifiche sismiche di edifici storici tramite l’analisi cinematica lineare e non lineare
No full textNel presente articolo viene presentato un metodo per la valutazione del rischio sismico di edifici storici attraverso
analisi cinematica lineare e non lineare. Il livello di rischio sismico è stimato con un indice di sicurezza sismica
definito come il rapporto tra la capacità della struttura, in questo caso ricavata con analisi cinematica, e la domanda
sismica calcolata secondo le NTC 2008. In questa memoria è stata data particolare attenzione al metodo di verifica
proposto dalla normativa italiana per i meccanismi di danno locale, sottolineando alcune criticità. Nell’articolo
viene presentato un modello a fibre in grado di considerare gli effetti di alcune caratteristiche comunemente
riscontrabili nelle strutture in muratura sulla risposta strutturale. In particolare si tiene conto degli effetti dell’attrito
interno tra malta e laterizio, dell’attrito sviluppato tra una parete ribaltate e gli elementi strutturali degli impalcati e
l’effetto stabilizzante di porzioni di pareti trasversali che partecipano al meccanismo
Shell modelling of a 1/13 scaled RC containment vessel under cyclic actions with PARC_CL crack model.
No full textThe energetic resources exploitation became a big issue in present days. Globally 30 countries in the world are also exploiting Nuclear Power Plants (NPPs) for the generation of energy. In this case energy production issue is correlated to the requirements for population safeguard against radiation leakage and to safe nuclear waste storing. However, many of these NPPs, which are still producing a large amount of energy, need or will need in short times a renewal process. Reinforced concrete members are of strong importance for the safety and for the proper operation of NPPs. One of the most important structural elements is then the reinforced concrete containment vessel, RCCV, of the reactor. The correct prediction of the RCCV behavior under sever action is essential for the assessment of existing structure safety and for the design of new ones. In the paper it is described the modeling of a 1/13 scaled reinforce concrete containment vessel tested at the National Center for Research on Earthquake Engineering of Taipei, Taiwan, under cyclic loading. The RCCV was analyzed by means of non linear finite elements analysis using multi layered shell elements. A secant total strain fixed crack model called PARC_CL, implemented at the University of Parma in the user subroutine UMAT.for in ABAQUS code, has been used to evaluate the mechanical non-linearity of RC elements. The multi layered shell elements approach with PARC_CL crack model provided good results in terms of local and global EDPs and it was able to give a good estimation of the post cracking behavior until failure. Simulations results are provided in terms of displacements, strains and crack patterns. Although analyses provided good results, some issues like the modeling of the structure to foundation interface are still open
On the non linear behaviour of joint connections between precast members realized using steel dowel
No full textSIMULATION OF RC WALLS SEISMIC BEHAVIOUR WITH SHELL ELEMENTS AND PARC_CL MODELLING
No full textThe structural response of reinforced concrete (RC) wall system is usually characterized by low displacement values at the damage and ultimate limit states; such systems are then quite common in industrial and power plant buildings.
The paper presents for some case studies a brief review of experimental tests available in literature and non linear finite elements (NLFE) methods for pushover analysis. In particular, in the paper a multi-layered shell model based on the fixed crack approach PARC_CL (Physical Approach for Reinforced Concrete under Cyclic Loading condition) is presented. Advantages and critical aspects related to shell modelling of wall systems are highlighted by multi-level assessment; in particular by comparing NLFEA results, obtained with the proposed shell element modelling, with experimental observations, NLFEA results obtained with beam element modelling and analytical formulations prescribed by Eurocode 8 (EC8). In the paper it is demonstrated that multi-layered shell modelling can be a numerical tool for the analysis of different structural wall typologies, like ductile wall systems (coupled or uncoupled), dual systems (frame or wall equivalent) and squat or large wall system
The PARC_CL model for FEM analyses of RC structures subjected to cyclic loads
No full textIn the paper it is proposed a new version of the PARC_CL crack model for finite element analyses (NLFEA) of RC structures subjected to cyclic loads. The proposed model is an updated version of the previous PARC_CL model developed for loading-unloading and reloading conditions [1,2,3]. The secant unloading behavior implemented in the previous version of PARC_CL crack model was not able to adequately evaluate hysteretic cycles and plastic deformations. In the new PARC_CL2.0 version, proposed in the current paper, plastic deformations of elements subjected to plane stresses can be evaluated under alternate load cycles. The effectiveness of the model has been validated by comparing non-linear finite elements analyses (NLFEA) results with experimental tests on RC panels found in literature. NLFE analyses have been carried out by means of the ABAQUS code where PARC_CL model is implemented in the user subroutine UMAT.for
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