Page 127 - Çevre Şehir İklim İngilizce - Sayı 4

Cenk Alhan - Mert Hacıemiroğlu

coefficient of friction (μ) are used for curved surface friction isolators in
order to determine the largest possible displacement demand and the
most unfavorable situation in terms of stability in these calculations.
In the calculation of the loads affecting the isolators, the upper limit
properties, which are the most unfavorable scenario for this situation,
are used.

5. The design of the superstructure and the calculation of the horizontal
force acting on the superstructure to be used for this design are
performed at the rare, standard design earthquake ground motion
level (DD2), which is a lower earthquake level, with a recurrence period
of 475 years. When taking into account the variations that may occur
in the isolator parameters, the upper limit values of the parameters of
the isolators mentioned in Article 4 are considered this time in order
to obtain the maximum value of the horizontal force acting on the
superstructure in order to stay in a safe direction.
6. Nominal floor accelerations are taken into account in the calculation of
floor accelerations.
7. Since the superstructure of buildings with seismic isolation will exhibit
linear behavior to a large extent as a result of the design approach;
according to the regulation, the superstructure and infrastructure can be
modeled as linear elastic, while isolators need to be modeled for non-
linear behavior. Besides, effective cross-sectional rigidity multipliers
should be used when modeling the structural elements that make up
the superstructure and infrastructure, the values of these multipliers are
also higher than those of a fixed-base building.
8. The design should be made in such a way to avoid, as far as possible,
any tensile force on the isolators. This is more difficult to achieve in
vulnerable and light buildings. In addition, there may be problems in
cases where very high accelerations occur in the vertical components of
near-fault earthquakes. Although special quality isolators can be used
in such cases, it must be confirmed by tests if these isolators can meet
the resulting tensile forces. There are quite low number of laboratories
in the world capable of performing horizontal drift tests under tension.
9. It is not preferred for the structure to move too much under the wind
load in terms of the comfort of the inhabitants. Therefore, the maximum
relative drift that will occur at the insulation interface under wind load
should be limited and should not exceed the relative storey drift value
that emerges at the level of ground motion of the DD-2 earthquake on
the superstructure.

116 The Journal of Environment, Urban and Climate