CONTENT 5.1 SEISMIC BEHAVIOUR ... - CIB-W18
CONTENT 5.1 SEISMIC BEHAVIOUR ... - CIB-W18
CONTENT 5.1 SEISMIC BEHAVIOUR ... - CIB-W18
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34-16-3 A Mischler, A Frangi<br />
Pull-out tests on glued-in rods at high temperatures<br />
Summary<br />
Connections and reinforcements with glued-in steel rods are becoming<br />
more and more important in timber engineering. The load-carrying behaviour<br />
of this connection type at room temperature is investigated in many<br />
research projects.<br />
Not only the knowledge of the resistance at room temperature is needed<br />
but, in some cases, also the fire resistance of a connection. At present,<br />
there is only little information available about the fire resistance of this<br />
connection type. One problem is that the different adhesives are more or<br />
less sensitive to high temperature. Therefore, the fire resistance of these<br />
connections has to be investigated.<br />
This paper presents results of tests at different temperatures with axially<br />
loaded rods glued in glued laminated timber parallel to the grain.<br />
Conclusions<br />
Tests on screws and glued-in rods with oven heated specimen showed the<br />
influence of the temperature on the properties of the timber and the adhesive.<br />
Comparative tests with specimen subjected to ISO-fire and oven<br />
heated specimen showed, that the strength and stiffness values obtained in<br />
fire tests are smaller than the values measured on oven heated specimen.<br />
35-16-1 J König<br />
Basic and notional charring rates<br />
Summary<br />
In the Fire Part of Eurocode 5 basic and notional charring rates are given.<br />
In order to simplify the determination of the load bearing capacity of cross<br />
sections, a notional charring rate is given to be used on all sides of the<br />
cross section. It is shown that the same notional charring rate can be used<br />
also for very small or narrow cross sections with a great influence of twodimensional<br />
heat transfer, for example very narrow timber joists exposed<br />
on three sides.<br />
The basic charring rate is strictly valid only in the case of onedimensional<br />
heat flux and its use requires separate consideration of corner<br />
roundings of the char line. A criterion is derived to define when the notional<br />
charring rate should be applied.<br />
From the results of recent fire tests notional charring rates are derived<br />
to be applied to heavy laminated timber plates, such as nail laminated timber<br />
decks and walls where gaps may open between laminations due to drying<br />
in service.<br />
Conclusions<br />
It has been shown that the concept of notional charring rates is a tool that<br />
can be widely used to simplify the calculation of cross-sectional parameters<br />
by determining an equivalent rectangular residual cross-section. This<br />
is an option in order to simplify the calculation or when the real shape of<br />
the residual cross-section cannot be determined unless advanced heat<br />
transfer calculations are performed.<br />
37-16-1 J König<br />
Effective values of thermal properties of timber and thermal actions<br />
during the decay phase of natural fires<br />
Abstract<br />
For the thermal analysis of structural or non-structural timber members,<br />
using conventional simplified heat transfer models, thermal conductivity<br />
values of timber are normally calibrated to test results such that they implicitly<br />
take into account influences such as mass transport that are not included<br />
in the model. Various researchers and designers have used such effective<br />
thermal conductivity values, originally determined for standard fire<br />
exposure, to evaluate other fire scenarios such as natural fires. This paper<br />
discusses in qualitative terms some parameters that govern combustion of<br />
wood and their influence on effective conductivity values. Reviewing fire<br />
tests of timber slabs under natural fire conditions, it is explained why effective<br />
conductivity values, giving correct results for the ISO 834 standard<br />
fire scenario, should not be used in other fire scenarios. Therefore, the<br />
thermal properties of timber given in EN 1995-1-2 are limited to standard<br />
fire exposure. As shown by heat transfer calculations, the effective thermal<br />
conductivity of the char layer is strongly dependent on the charring rate<br />
and varies therefore during a natural fire scenario. It has also been shown<br />
that char oxidation during the decay phase in a natural fire has a significant<br />
influence on the temperature development in the timber member,<br />
<strong>CIB</strong>-<strong>W18</strong> Timber Structures – A review of meeting 1-43 5 SPECIAL ACTIONS page 5.35