Strength and Ductility Demand A Case Study of Ethiopian Design Practice to Seismic Loads
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Date
2009-09
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Addis Ababa University
Abstract
This thesis is conducted to investigate the relationship between strength and
ductility demand. The base shear and the story displacement ductility were used as
parameters to establish the relationship and a five story and ten story reinforced
concrete shear frames were used to this end. Eighteen shear frames with different
combinations of ductility class and sub-soil class, according to the Ethiopian Building
Code Standard EBCS 8, 1995, were considered. Each model was subjected to one linear
static with EBCS 8, 1995 base shear distribution, two linear response spectrum EBCS 8,
1995 and EC 8, 2004, two non-linear static and one non-linear time-history analyses
cases using the computer program SAP 2000 Ver.12.
A range of base shear values were applied on each model to study the post-yield
displacement ductility demands imposed on it. From the analyses results, different
curves showing the relationship between the reduced (%) base shear yield strength and
ductility demand were produced. To this effect, the non-linear static or the pushover
analysis method was used as a tool. Two types of non-linear properties were considered
for all the models; the first, material non-linearity following the recommendations by
Federal Emergency Management Agency FEMA 356 Pre-standard and Commentary for
Seismic Rehabilitation of Buildings and Applied Technology Council ATC 40 Seismic
Evaluation and Retrofit of Concrete Buildings and the second Geometric non-linearity
by implementing the iterative P-D analysis procedure included in SAP 2000 Ver.12.
The influence of undermining the design base shear on ductility demand and the
validity of permitted reductions by EBCS8, 1995 of design base shear through a
behavior factor for each ductility class for the five and ten story shear frames was
assessed by making use of theses curves. Finally the implementation of the relationship
between these two important seismic design parameters in the current seismic design
practice of Ethiopia was investigated by conducting a case study on an existing building
located in Debre Birhan.
Key words: Base shear yield strength; Ductility demand; Pushover analysis
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Civil Engineering