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36-7-6 S Nakajima
Evaluation and estimation of the performance of the nail joints and
shear walls under dry/humid cyclic climate
Abstract
As shear walls installed in timber houses usually experience dry and humid
cyclic climate during their service life the effect of the humid and dry
climate on the performance of the nail joints was evaluated. Lateral nail
resistance tests were conducted after conditioning the test specimens in the
dry/humid/dry cyclic climate. The tests were conducted for all possible
combination of the surface grain direction of the studs and the sheathing
materials and the loading direction. The strength reduction of the shear
walls due to the dry and humid cyclic climate was estimated by the simplified
model.
Not only the conditioning schedule but also the final condition, i.e. the
condition of the test specimens during the test, affected the strength and
stiffness of the nail joints. The condition of the test specimens, i.e. wet or
dry, was supposed to be one issue that should be discussed in the process
of evaluating the stiffness and strength of the joints and the shear walls
that will be exposed to a certain humid climate.
Conclusion
The yield strength of the "plywood-lumber" nail joints was not reduced by
the humid and dry conditioning process and was almost same or approximately
15 % higher than that of the nail joints conditioned at the standard
climate. The reduction ratios of the initial stiffness of the "plywood - lumber"
nail joints due to the humid and dry conditioning process ranged from
53 % to 60 %.
Basically the yield shear strength of the "OSB - lumber" joint was reduced
to approximately 10 % by the humid and dry conditioning. The reduction
ratios of the initial stiffness of the "OSB - lumber" nail joints due
to the humid and dry conditioning process ranged from 48 % to 65 %.
Not only the conditioning schedule but also the final condition, i.e. the
condition of the test specimens during the test, affected the strength and
stiffness of the nail joints. The condition of the test specimens, i.e. wet or
dry, is supposed to be one issue that should be discussed when evaluating
the stiffness and strength of the joints and the shear walls that will be exposed
to a certain humid climate.
40-7-7 J W G van der Kuilen, A P M G Dias
Creep of timber and timber-concrete joints
Abstract
According to the EC5, the additional deformation of joints at long term
shall be calculated as the short term deformation multiplied by the deformation
factor kdef The short term deformation shall be determined based on
the slip modulus of the joint (Kser). The slip modulus of the joints may be
obtained either from the models given in Eurocode 5 for some types of
joints, or alternatively, from experimental tests in accordance with
EN26891. In experimental tests the long term deformation is related to the
short term deformation through the creep factor of the joints, and is determined
relative to the initial deformation. In this situation the deformation
factor from Eurocode 5 and the creep factor of the joints have an equivalent
meaning. An essential difference is the determination of the short term
deformation. In EC5 it is based on the joint slip modulus, while in the
creep tests it is usually taken the initial deformation. In the tests considered
here, the initial displacement was taken after 10 minutes after the
loads are applied.
In this paper a detailed analysis is made on the determination of joints
long term deformations in both situations: based on the creep factor determined
from creep tests and based on the Eurocode method. These results
are available from a large number of long term tests on timber-timber
and timber-concrete joints. These tests have been performed at Delft University
of Technology and at the University of Coimbra. Various types of
fasteners have been used and both climate-controlled and uncontrolled
conditions have been considered. The influence of climatic aspects on the
long term deformations is also discussed and a proposal for creep factors
for different duration of load classes is made.
CIB-W18 Timber Structures – A review of meeting 1-43 4 CONNECTIONS page 4.67