On the inelastic seismic response of asymmetric buildings under bi-axial excitation

Abstract

SUMMARYThe elastic and inelastic seismic response of plan-asymmetric regular multi-storey steel-frame buildings has been investigated under bi-directional horizontal ground motions. Symmetric variants of these buildings were designed according to Eurocodes 3 and 8. Asymmetric buildings were created by assuming a mass eccentricity in each of the two principal directions. The torsional response in the elastic and inelastic range is qualitatively similar with the exception of the sti edge in the strong direction of torsionally sti buildings and the sti edge in the weak direction of torsionally exible buildings. The response is in uenced by the intensity of ground motion, i.e. by the magnitude of plastic deformation. In the limiting case of very strong ground motion, the behaviour of initially torsionally sti and initially torsionally exible buildings may become qualitatively similar. A decrease in sti ness due to plastic deformations in one direction may substantially in uence the behaviour in the orthogonal direction. The response strongly depends on the detailed characteristics of the ground motion. On average, torsional e ects are reduced with increasing plastic deformations, unless the plastic deformations are small. Taking into account also the dispersion of results which is generally larger in the inelastic range than in the elastic one, it can be concluded that (a) the ampliÿcation of displacements determined by the elastic analysis can be used as a rough estimate also in the inelastic range and (b) any favourable torsional e ect on the sti side of torsionally sti buildings, which may arise from elastic analysis, may disappear in the inelastic range. The conclusions are limited to fairly regular buildings and subject to further investigations.

Collapse behavior evaluation of asymmetric buildings subjected to bi‐directional ground motion

“…This complicated phenomenon specific to asymmetric structures has also been reported by others previously (e.g. Marušić and Fajfar, 2005). Moreover, Tables 5 and 6 demonstrate that the SSF reduces as the plan eccentricities increases.…”

On the inelastic torsional response of single-storey structures under bi-axial excitation

“…to regular (along the height) structures with lateral load-carrying elements having similar deformation shapes (all frames or all walls). It is encouraging that in a companion study on such multi-storey buildings [3] very similar ÿndings were obtained, although the global characteristics of the structural system and the loading were very di erent. Moreover, the main ÿndings were conÿrmed also in a study made for a realistic 3-storey reinforced concrete building with sti ness and strength eccentricity [4].…”

“…Although extensive parametric studies have been performed (only some of them are presented in this paper), and a very simple single-storey structural model was used, it was possible to explore only a very limited number of cases. Nevertheless, together with the companion paper [3], several combinations of input parameters have been I. PERU Ä S AND P. FAJFAR investigated and some consistent trends have been observed. Based on the results of these studies, the following conclusions, important for the development of simpliÿed procedures, can be drawn:…”

“…The number of test examples has to be limited for practical reasons. (In the companion paper by MaruÄ sià c and Fajfar [3] intentionally multi-storey buildings with very di erent global characteristics were investigated with the aim of complementing the results presented in this paper.) Two di erent sets of systems with periods in two di erent regions of the response spectrum were investigated in order to explore the potential di erence between sti and moderately exible structures.…”

Inelastic Parametric Analysis of Seismic Responses of Multistorey Bidirectional Eccentric Structure

“…Currently, the available investigations primarily concentrate on the dynamic analysis of these regularly asymmetrical multistorey buildings. Marus ić et al [15] studied the elastic and inelastic seismic response of a multistorey regular eccentric steel frame structure under bidirectional earthquake motions. They found that the reduction in lateral stiffness due to plastic deformations in a certain direction may considerably influence the lateral load-resisting member in the orthogonal direction.…”