CONTENT 5.1 SEISMIC BEHAVIOUR ... - CIB-W18

of these frames is typically influenced by the connections used, adequate
connection design is of particular interest when these frames are used in
high-risk earthquake zones. Results from current research on seismic performance
and force modification factors for braced timber frames are presented
in this paper. Static and dynamic tests were conducted on a several
connection details with different diameter bolts and high strength glulam
rivets, with steel side plates. The resulting hysteresis loops were used to
develop non-linear mathematical models on a connection and frame level.
The models were then used in numerous non-linear time history dynamic
analyses, from which it was possible to determine the influence of different
connection details on seismic response of braced timber frames.
From the presented results, it is evident that the seismic response of
braced timber frames is heavily influenced by the behaviour of the connections.
The results suggest that braced frames with different connections
should not be assigned the same R-factor. Braced timber frames with mild
steel (ASTM A-307) bolted connections, with slenderness ratios (l/d) of 10
or higher showed far more adequate seismic performance than those
frames that utilized bolts with lower slenderness ratios. Further research is
needed, however, to study the effects of other parameters such as end distance,
spacing, number of rows number of bolts in a row etc., for the development
of general recommendations that will ensure ductile behaviour
of braced frames with bolted connections. Until such research is undertaken,
an R-factor of 1.5 appears to be reasonable for braced timber frames
with slender bolts.
On the other hand, glulam riveted connections showed promising results
when used for braced timber frames. They were the only connections
tested that consistently showed non-brittle deformations in the wood along
with yielding of the connectors even at large displacement levels. In addition,
riveted connections do not have as many parameters that influence
their cyclic behaviour, other than those implemented in the CSA086.1-94
design guidelines. Braced frames with glulam riveted connections designed
in rivet yielding mode may be assigned an R factor of 2.0, in
recognition of their higher and more consistent ductility capacity.
32-15-2 N Kawai
Application of capacity spectrum method to timber houses
Summary
Capacity spectrum method (CSM) is known as a convenient prediction
method for earthquake response of buildings, and is now discussed in Japan
as one of the procedures to confirm the seismic performance of buildings
in a technical standard under the revised Building Standard Law of
Japan. In this paper, the results of CSM are compared with the results of
time history analyses (THA), using one mass system models and two mass
system models with the load-displacement hysteresis model based on the
results of static cyclic loading tests on shear walls. The comparison of the
results for one mass systems model shows that equivalent linear response
tends to give a smaller prediction than the time history analysis when the
equivalent viscous damping ratio, heq, of first loop of cyclic loading protocol
proposed in ISO/TC165 is used. When heq is reduced to 80% of the
original in CSM, the prediction gives better agreement for one mass system
models in maximum response displacement. Also for two mass system
models, the results of CSM with 80% of heq agreed well with those of
THA in maximum response displacement. However, there was a case that
CSM gives smaller prediction of relative story displacement, which is 64%
of a result of THA.
Conclusions
The earthquake response predictions by capacity spectrum method were
compared with the results of time history analyses using one mass system
models and two mass system models, load-displacement relationships of
which are determined by those of shear wall(s). The results are summarized
as follows:
According to the results of the examination using one mass system
models, capacity spectrum method gives good prediction compared with
the results of time history analyses in maximum displacement, when the
equivalent viscous damping ratio reduced to 80% of the original is used.
Also for two mass system models, capacity spectrum method gave good
agreement in maximum story displacement with reduced values of equivalent
viscous damping to 80%.
However, it seems to be risky to use the result of capacity spectrum
method directly for the evaluation of maximum relative story displace-
CIB-W18 Timber Structures – A review of meeting 1-43 5 SPECIAL ACTIONS page 5.17