The code provisions for design and construction of
structures using equivalent static load method are different depending on the
specific situation of each country.
This includes different parameters such as: the
expected horizontal ground acceleration, site effect (geology and types of
soil), importance factor of the structure, and the parameters relating the
structural response of buildings “ fundamental period of vibration of the structure
and force reduction factor or ductility factor”. In addition to that quality
control, level of detailing and construction techniques have also an effect.
Next, a brief description of the effect of applying different code
parameters on the values of the base shear coefficient.
The horizontal seismic forces at the base and
the base shear coefficient are calculated considering the following:
1-
The building height
a-
4
storeys
b-
10
storeys
2-
The structural system
a-
Ductile
moment resisting frame
b-
Moment
resisting frame
c-
Braced
frame
d-
Shear
wall
e-
Bearing
wall
3-
Construction Methods
Different construction methods were
considered for both 4 and 10 stories
4-
Codes Considered
The calculations for base shear coefficient
were done a ccording to different codes: Algeria, Argentina, Bulgaria, Chile,
China, Egypt, Hungury, India, Indonesia, Iran, Japan, Jordan, Mexico,
Newzeland, Romania, Turkey, United States of America (uniform building code
85, 94, and 97), and Former Yugoslavia.
It is known that each of the parameters and for each
code could have an effect on the values obtained for the base shear coefficient
(horizontal seismic force). To minimize the variation expected, the following
assumptions are adopted:
1-
The
Parameters relating the soil (site effect) horizontal ground acceleration, and
importance of structure are fixed.
2-
The
Parameters of the fundamental period and the nature of the structural response
which depend on the dimensions of the building, structural system, material used
and the method of construction are considered to be variable to find their
effect.
Considering the pre-mentioned different parameters
and applying different codes, the results were variable and can be described as
follows:
1-
There
is a variation in the results when applying a certain code “code formula” for the same building but
considering different structural types.
2-
The
results are also variable when applying different codes for the same building
and the same structural case.
3-
Big
variations in the results and sometimes up to double the values, between
different codes when considering methods of construction and material
variation.
4-
Generally,
the structural systems of moment resisting frame, ductile moment resisting
frames and reinforced concrete shear walls have no big variation in the results
between different codes considering the same site characteristics and
same level of excitation.
Preliminary studies of the vulnerability of buildings in West Bank and Gaza Strip were made as follows:
1-
Five
major cities were included in the assessment (expected seismic performance of
common buildings), they are Nablus, Jenin, Qulqilyah, Ramallah and Hebron.
2-
Many
factors were taken into consideration:
-
Soil
and foundation effects.
-
Architectural
configuration.
-
Soft
storey.
-
The
effect of using stone for decoration and its vulnerability.
-
Long
span loaded cantilevers.
-
Random
distribution of rigidities in both vertical and horizontal diaphragm.
(structural configuration)
-
Short
column effect.
-
Absence
of seismic joints.
-
Construction
on high slopes.
-
Others.