Showing 2 results for Poursha
Mehdi Poursha, Faramarz Khoshnoudian, Abdoreza S. Moghadam,
Volume 6, Issue 2 (June 2008)
Abstract
The nonlinear static pushover analysis technique is mostly used in the performance-based design of
structures and it is favored over nonlinear response history analysis. However, the pushover analysis with
FEMA load distributions losses its accuracy in estimating seismic responses of long period structures when
higher mode effects are important. Some procedures have been offered to consider this effect. FEMA and
Modal pushover analysis (MPA) are addressed in the current study and compared with inelastic response
history analysis. These procedures are applied to medium high-rise (10 and 15 storey) and high-rise (20 and
30 storey) frames efficiency and limitations of them are elaborated. MPA procedure present significant
advantage over FEMA load distributions in predicting storey drifts, but the both are thoroughly unsuccessful
to predict hinge plastic rotations with acceptable accuracy. It is demonstrated that the seismic demands
determined with MPA procedure will be unsatisfactory in nonlinear systems subjected to individual ground
motions which inelastic SDF systems related to significant modes of the buildings respond beyond the elastic
limit. Therefore, it’s inevitable to avoid evaluating seismic demands of the buildings based on individual
ground motion with MPA procedure.
M. Poursha,
Volume 11, Issue 2 (Transaction A: Civil Engineering, June 2013)
Abstract
Double- unsymmetric-plan medium-rise buildings subjected to bi-directional seismic excitation are complex structures where
higher-mode effects in plan and elevation are important in estimating the seismic responses using nonlinear static or pushover
analysis. Considering two horizontal components of the ground motions makes the problem more intricate. This paper presents
a method for nonlinear static analysis of double unsymmetric-plan low- and medium-rise buildings subjected to the two horizontal
components of ground motions. To consider bi-directional seismic excitation in pushover analyses, the proposed method utilizes
an iterative process until displacements at a control node (centre of mass at the roof level) progressively reach the predefined
target displacements in both horizontal directions. In the case of medium-rise buildings, continuous implementation of modal
pushover analyses is used to take higher-mode effects into account. To illustrate the applicability and to appraise the accuracy
of the proposed method, it is applied to the 4- and 10-storey torsionally-stiff and torsionally-flexible buildings as representative
of low- and medium-rise buildings, respectively. For the purpose of comparison, modal pushover analysis (MPA) is also
implemented considering the two horizontal components of the ground motions. The results indicate that the proposed method
and the MPA procedure can compute the seismic demands of double unsymmetric-plan low- and medium-rise buildings with
reasonable accuracy however, seismic responses resulting from the proposed method deteriorate at the flexible edge of the
torsionally-flexible buildings