CONTENT 5.1 SEISMIC BEHAVIOUR ... - CIB-W18

24-15-3 M Yasumura
Seismic behaviour of wood-framed shear walls
Abstract
Wood-framed shear walls sheathed with plywood and gypsum boards
were subjected to the reversed cyclic lateral loading, and it was found that
the reversed cyclic loading affects more on the shear strength of gypsumsheathed
panels than that of plywood-sheathed panels. From the results of
time-history earthquake response analysis of these panels, the behaviour
factor "q" of 2.5 to 3.0 is proposed for the wood-framed shear walls.
Conclusion
Summarizing the results of this study, the following conclusions are lead.
(1) The reversed cyclic loading affected very little on the ultimate properties
of plywood-sheathed shear walls, and there were no decrease of
ultimate load by the cyclic loading of lower load level.
(2) The reversed cyclic loading made a serious influence on the shear
strength of gypsum-sheathed shear walls, and the ultimate load was
decreased 27% comparing to that in monotonic loading test.
(3) The elastic limit of plywood-sheathed shear walls may be defined by
the shear deformation angle of 1/300 which corresponds to 50 to 60%
of the ultimate load, and the yield load may be defined by multiplying
by 1.5 the elastic limit which corresponds to 80% of the ultimate load.
(4) In the gypsum-sheathed panel, the shear load at the second and third
cycles of 1/300 decreased to 87 and 83% respectively comparing to
the first cycle, and it was shown that the elastic limit of gypsumsheathed
panel might be smaller than 1/300 of shear deformation angle.
The yield load of gypsum-sheathed shear walls may be defined by
the shear deformation angle of 1/300 considering the effect of cyclic
loading.
(5) The equivalent viscous damping of plywood-sheathed panel was in a
15% at the first cycle and 12% at the second and third cycle. That of`
sheathed panel was in average 18.5% at the first cycle and 15% at the
second and third cycles, and showed higher values than those of the
plywood-sheathed panel.
(6) The ductility factor of 5.0 which corresponds to the shear deforms angle
of 1/40 gives the Au/Ay value of 3.0 for the plywood-sheathed
shear walls.
(7) The ductility factor of 5.0 which corresponds to the shear deformation
angle of 1/60 gives the Au/Ay value of 2.5, and the ductility factor of
which corresponds to the shear deformation angle of 1/40 gives the
Au/Ay value of 3.0 for the gypsum-sheathed shear walls.
(8) The ductility factor response of plywood-sheathed shear walls varied
from 1.1 to 5.9 which corresponded to the shear deformation angle of
1/270 to 1/53 when the accelerograms were linearly scaled for
300cm/sec 2 and mg/Ay=3.0.
26-15-2 K Becker, A Ceccotti, H Charlier, E Katsaragakis, H J Larsen, H
Zeitter
Eurocode 8 - Part 1.3 - Chapter 5 - specific rules for timber buildings in
seismic regions
Introduction
This paper presents the pertinent state of the drafting and redrafting work
on the timber chapter in Eurocode 8 'Buildings in seismic regions'.
As there are still possibilities to complement necessary provisions in
the code text or in the 'National Application Document' (NAD) every
comment and criticism is very welcome. The paper is aimed at opening of
a discussion to provide substantial information.
On one hand it is very important to give guidance and rules for an adequate
analysis, design and detailing for timber structures in seismic regions.
The experience showed both during last earthquakes, an excellent
behaviour as well as failures and more or less heavy damages on timber
structures. The minority, the failures, originated from almost completely
avoidable mistakes in modelling, design and mostly detailing. The development
of a new code gave the possibility to elaborate the corresponding
provisions with all the knowledge and experience of several seismic regions
in the world.
One the other hand the use of timber for building purposes is to be
strengthened face to face with other materials wherever possible. As the
reasons for that engagement are well known, it is obvious to avoid huge
masses of provisions, rules and prohibitions as for example the concrete
part of Eurocode 8 takes almost the same size as the Eurocode 2. Designers,
architects and engineers will stand away from timber, when they are
exceptionally dealing with a seismic hazard and therefore confronted with
too much confinement. For these reasons the code provisions should be
CIB-W18 Timber Structures – A review of meeting 1-43 5 SPECIAL ACTIONS page 5.12