CONTENT 5.1 SEISMIC BEHAVIOUR ... - CIB-W18

ment, as there was a case that gives smaller prediction, which is 64% of a
result of time history analysis.
33-15-2 N Kawai
Prediction of earthquake response of timber houses considering shear
deformation of horizontal frames
Summary
Related to the revision of Building Standard Law of Japan, the application
of capacity spectrum method (CSM) is discussed as a convenient prediction
method for the earthquake response of structures. For the application
of CSM, there are some problems in the procedure to replace the structure
to a single degree of freedom model, such as distribution of external forces,
assumption of damping, and so on.
In this paper the predictions by CSM were compared with the results of
time history analysis (THA) against ten artificial waves, using horizontally
lumped mass system models, in which the shear deformation of horizontal
frames are considered. The models of one-storied houses were used, which
has 3 rows of shear walls in x-direction and 4 rows in y-direction, and the
earthquake load is applied in y-direction. Vertical frames (rows of shear
walls) and the parts of horizontal frames are modelled as shear panels,
which have load-displacement hysteresis model based on the cyclic loading
tests on a plywood sheathed shear wall.
As a whole, the predictions by CSM agreed well with the results of
THA when the modified value of damping is used, which is calculated using
80 % of equivalent viscous damping corresponding to the first loop
under the cyclic loading protocol of ISO/WD16670. And the CSM using
damping calculated with 100 % of equivalent viscous damping corresponding
to the stabilized loop seemed to give the upper limit of maximum
displacement obtained by THA. However, CSM sometimes gives different
distribution of response displacement from THA, in case the deformation
by torsional behaviour and horizontal shear deformation is relatively large.
For a solution of this problem, modification of CSM is proposed to use the
distribution of external force with adding torsional moment corresponding
to the existing eccentric moment. When the distribution of external forces
with 20 % of eccentric moment in CSM, correlation of the predicted maximum
response displacement between THA and CSM was improved.
Conclusions
To confirm the applicability of Capacity Spectrum Method (CSM) to timber
houses 1 shear deformation in horizontal frames, predictions of maximum
response displacement CSM were compared with the results of time
history analysis (THA) using 21 type horizontally lumped mass system
models. The predictions by CSM agreed well with results of THA when
the modified value of damping is used, which is calculated using 80 % of
equivalent viscous damping corresponding to the first loop under the cyclic
loaf protocol of ISO/WD16670. And the predictions by CSM using
damping ratio corresponding to stabilized loop were near to the upper limit
of predictions by THA. However, CSM sometimes gives different distribution
of response displacement from THA in case the deformation by torsional
behaviour and horizontal shear deformation is relatively large. For
this problem, a modification to use external force to which torsional moment
is added is proposed. When the 20% of existing eccentric moment is
added for the model with eccentricity with asymmetrically distributed
masses, the prediction by the modified CSM gives better agreement with
THA in the distribution of maximum rest displacement including torsional
behaviour.
34-15-3 M Yasumura
Evaluation of damping capacity of timber structures for seismic design
Introduction
Linear equivalent response method is one of the seismic design methods to
ensure the structural safety of buildings against severe earthquake motion.
This design method was introduced to Japanese new building codes in
June 2000. Different from the equivalent energy method, it does not need
the behaviour factor (q) which depends on a lot of experiences and highly
engineering judgements. The major parameter required for the linear
equivalent response method is a force-displacement relationship and the
equivalent damping of the structure. The equivalent viscous damping ratio
obtained from the static reversed cyclic test is generally applied to determine
the equivalent damping of the structure.
The structural behaviour of wood-framed construction against horizontal
loads is highly dependent on those of shear walls. Therefore, monotonic
and reversed cyclic loading tests were conducted on wood-framed shear
walls to obtain the parameters for determining the hysteretic model of
CIB-W18 Timber Structures – A review of meeting 1-43 5 SPECIAL ACTIONS page 5.18