کلیدواژهها
عنوان مقاله English
نویسندگان English
Based on experimental evidence and empirical models the proposed supplement to ASCE 41-
06 is developed for the purpose of updating provisions related to existing reinforced concrete
structural buildings. Several experimental research programs have demonstrated that many
older-type columns are capable of sustaining limited plastic deformation due to flexural
yielding prior to shear failure. This proposed supplement concentrates on this failure mode
and includes the categorization of columns based on failure mode, the selection of target
probabilities of failure for each failure mode and revisions to modeling parameters and
acceptance criteria for reinforced concrete columns. In this research, the effect of new
provisions on seismic evaluation of reinforced concrete moment resisting frame is
investigated. In this regard three medium ductile MRCRF structures with 4, 8 and 12 stories
and two direction median moment resisting frame systems are considered. These structures
initially have been analyzed and designed according to ‘Iranian Standard 2800, for seismic
design of buildings’ and ‘Iranian concrete code of practice’. Then nonlinear static analysis
and nonlinear time history analysis methods have been utilized to evaluate the seismic
performance of these structures. In nonlinear static analysis there are several methods for
determining target displacement among them some reliable methods are displacement
coefficient method (FEMA-356), Capacity spectrum method (ATC-40), and equivalent
linearization method and modifies coefficient method (FEMA-440). The target displacements
with these methods are compared with maximum displacement in nonlinear time history
analysis. It is observed that capacity spectrum method given by ATC-40 reports target
displacement values higher than time history analysis. Furthermore, results obtained from the
equivalent method and the modified coefficient methods suggested by FEMA-440 are closer
to time history analysis values. The performance levels of these structures have been
evaluated based upon target displacement of nonlinear static analysis that obtained from
FEMA-440 methods and maximum displacement in nonlinear time history analysis. The
effect of the variation of reinforced concrete columns modeling parameters and acceptance
criteria on performance levels of reinforced concrete structure is investigated. For this purpose
in nonlinear seismic design, the modeling parameters and acceptance criteria have been
considered with those from FEMA-356 for columns “controlled by flexure” and then with
those from proposed supplement to ASCE 41-06 for flexure failure (flexural yielding without
shear failure) and flexure-shear failure (shear failure following flexural yielding). The
obtained results indicate that these structures are to some extant conservative in their seismic
performance due to the modifications of ASCE41-06.
کلیدواژهها English
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