By now it is well known that the rotation angle of the ground motion has a not negligible influence on several engineering demand parameters (EDPs), especially in case of near-fault excitations. Several current seismic codes require that at least two horizontal ground motion components should be considered for three-dimensional response history analysis of structures. However, they do not contain accurate provisions about the directions of application and only recently they have included provisions about the near-fault cases. Therefore the designer has the task of evaluating all the “relevant” directions or the “most critical” conditions adapted to each case, in order to evict the underestimation of structural demand prediction. Moreover, given that the critical angle for a specified EDP varies with fundamental period, model type and the level of inelastic behaviour, its estimation is quite difficult. Indeed it is necessary to use a three-dimensional structural nonlinear modelling to evaluate the critical angle for each structural case, with a large amount of computational efforts. The main objective of this work is to assess the ability of simple models, i.e. linear and nonlinear two-Degree of Freedom (2DOF) systems, to predict the most critical incidence angle. To this aim a reinforced concrete eight story building, designed according to a past Italian code, has been selected to represent a realistic building located in Italy. The effect of directionality on the building has been investigated by means on non-linear dynamic analyses considering 124 pairs of near-fault ground motion records oriented along eight incidence angles, whose values are between 0 and 180 degrees, with an increment of 22.5 degrees. Afterwards, the effect of directionality has been studied considering single models (2D) of the building. The results have shown that the equivalent linear and nonlinear 2DOF models may be adequate to predict the most critical angle of incidence.
Simple models to predict the most critical incidence angle for buildings under bi-directional near-fault excitations / Sebastiani, PAOLO EMIDIO; Liberatore, Laura; Lucchini, Andrea; Mollaioli, Fabrizio. - ELETTRONICO. - (2014). (Intervento presentato al convegno Second European Conference on Earthquake Engineering and Seismology tenutosi a Istanbul, Turkey nel August 25-29).
Simple models to predict the most critical incidence angle for buildings under bi-directional near-fault excitations
SEBASTIANI, PAOLO EMIDIO;LIBERATORE, Laura;LUCCHINI, Andrea;MOLLAIOLI, Fabrizio
2014
Abstract
By now it is well known that the rotation angle of the ground motion has a not negligible influence on several engineering demand parameters (EDPs), especially in case of near-fault excitations. Several current seismic codes require that at least two horizontal ground motion components should be considered for three-dimensional response history analysis of structures. However, they do not contain accurate provisions about the directions of application and only recently they have included provisions about the near-fault cases. Therefore the designer has the task of evaluating all the “relevant” directions or the “most critical” conditions adapted to each case, in order to evict the underestimation of structural demand prediction. Moreover, given that the critical angle for a specified EDP varies with fundamental period, model type and the level of inelastic behaviour, its estimation is quite difficult. Indeed it is necessary to use a three-dimensional structural nonlinear modelling to evaluate the critical angle for each structural case, with a large amount of computational efforts. The main objective of this work is to assess the ability of simple models, i.e. linear and nonlinear two-Degree of Freedom (2DOF) systems, to predict the most critical incidence angle. To this aim a reinforced concrete eight story building, designed according to a past Italian code, has been selected to represent a realistic building located in Italy. The effect of directionality on the building has been investigated by means on non-linear dynamic analyses considering 124 pairs of near-fault ground motion records oriented along eight incidence angles, whose values are between 0 and 180 degrees, with an increment of 22.5 degrees. Afterwards, the effect of directionality has been studied considering single models (2D) of the building. The results have shown that the equivalent linear and nonlinear 2DOF models may be adequate to predict the most critical angle of incidence.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
