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4.17 TRADITIONAL JOINTS
41-7-4 C Faye, P Gatcia, L Le Magorou, F Rouger
Mechanical behaviour of traditional timber connections: Proposals for
design, based on experimental and numerical investigations. Part I:
Birds mouth
Introduction
Due to the development of CNC (Computer Numerically Controlled) machines,
traditional timber connections become economically competitive.
Consequently, the use of these wooden connections in construction is increasing.
In this context, it is necessary to provide appropriate design rules taking
account of the specific geometry of these connections.
Indeed, failure of the birds mouth connections occurs according to two
phenomena:
– shear failure in the notch, for low skew angles. In this case, criteria using
the average shear stress are not adequate because high peak stresses
are not taken into account;
– failure in compression with an angle to grain in contact zones for higher
skew angles. In this case, non linear distribution of the compression
stress has to be determined.
In order to solve these issues, an experimental and numerical study on
the instantaneous mechanical behavior of birdsmouth connections was investigated.
Summary
This paper describes:
1/ an experimental study: birdsmouth connections were tested for glued
laminated beams in eight geometric configurations varying the values of
skew angle 0, notch depth t and notch length l. The experimental and designed
values were compared.
2/ a finite element modeling taking account of contact with friction between
timber surfaces. The model allows the determination of shear and
compression stresses with angle to grain profiles respectively in the notch
and contact wooden zones.
3/ formulation of design proposals on the basis of experimental and numerical
results.
CIB-W18 Timber Structures – A review of meeting 1-43 4 CONNECTIONS page 4.89