| dc.description.abstract | Stress-laminated timber (SLT) decks are a popular solution for the superstructure
of timber bridges. The aim of the research presented in this thesis was to increase
the knowledge on the behaviour of SLT decks. The timber beams that form a SLT
deck are compressed in the perpendicular to grain direction in order to work as a
plate. The stress is transferred by friction between the laminations. However, the
pre-stress level in the decks decreases during the lifetime of the bridges.
Therefore, the long-term behaviour of glulam loaded perpendicular to grain was
studied. Several compression perpendicular to grain experiments were performed
on glulam blocks in a climate controlled environment, keeping either the load or the
displacement constant, thereby resulting in creep and relaxation tests, respectively.
Hence, parameters describing the viscoelastic creep behaviour were determined, as
well as hygroscopic and mechanosorptive coefficients. Thus, the results of the longterm
tests helped the development and the validation of a material model for timber
under compression perpendicular to grain. The material model considers both time
and moisture content variations, describing thereby elastic, hygroscopic,
viscoelastic and mechanosorptive behaviour of timber. Moreover, the pith location
of each lamella is taken into account either by the use of effective properties, or by
defining the timber properties for each lamella in a cylindrical coordinate system
with origin in the pith.
Furthermore, the frictional behaviour between glulam elements was investigated in
an experimental campaign. The friction coefficient was evaluated in both of the
sliding directions (longitudinal and perpendicular to the grain) and with different
levels of compression stress. The results of the friction tests were thereafter
numerically modelled and employed in the subsequent study about the design of
SLT decks.
Finally, numerical simulations of SLT decks were performed in order to study the
influence of the butt joints distribution and the pre-stressing scheme on the
structural behaviour of SLT decks. Hence, the reduction of flexural stiffness for different butt joints configurations and the development of the stresses in the
perpendicular direction to the grain for three different pre-stressing patterns were
assessed. Furthermore, the influence of the geometrical layout of the anchor plates
on the perpendicular to grain compression of the outer deck beams in SLT decks was evaluated. | nb_NO |
