Sustainable Construction A Life Cycle Approach in Engineering

Numerical simulations of ash pegs tested under shear loads were carried out to validate previous
results and to calibrate the shear properties of ash.
Different shear length were considered in order to evaluate the reliability of the implemented
model to predict both flexural and shear failure modes observed after tests.
The finite element models of the pegs were implemented with reference to the part under shear
deformations.
On the basis of the calibrated material properties, the finite element model of the double shear
joint was implemented.
Due to the symmetry, only a quarter of the joint was modeled in the finite element analysis.
Three dimensional elements with a plane stress formulation were used to model timber pegs
and plates. In particular, continuum shell elements SC8R were used. The interaction between
the different parts were modeled using surface-to-surface contacts. These contacts were applied
at the interface of the pin with the hole. Contact was modeled using the pin as master surface
and the hole as slavery surface. Frictionless behaviour of contacts was assumed and small sliding
formulation was selected.
As far as ash, the calibrated mechanical properties were assumed. The properties of fir material
were defined on the basis of values reported in the literature. In particular, the fir characteristics
in terms of longitudinal tensile and compressive strength were taken from the experimental results
given by Ceraldi et al. 2008. Other parameters were set according to the literature.
As far as boundary conditions, full restraints were considered at one end of the connection. The
model was loaded under displacement control at the other end of the joint.
The response of the finite element model was compared with the experimental results given by
Ceraldi et al. 2008.
In general, a good agreement of experimental and numerical results was found for the selected
timber joint.
In particular, the predicted strength of connection fits well experimental results. However, some
differences in terms of stiffness were observed.
The calculated distribution of stresses is shown in Figure 4. The model of connection attains the
ultimate load for the shear failure of the peg, according to experimental tests. In particular, the
distribution of damage predicted by the finite element model shows that the collapse is due to
the achievement of tensile strength in the matrix.
a) b)
Figure 4. a) Deformed shape of a quarter of the double shear joint and distribution of stresses at collapse
load; b) Detail of the distribution of tensile and compressive matrix damage in the peg.
On the basis of obtained results, it can be concluded that the implemented finite element model
is a reliable numerical tool that can be further developed. The generated numerical model could
be used to support experimental investigation on selected connections and to extend test results
by parametric analysis.
5 CONCLUSIONS
This paper focus on the problem of deconstruction as a sustainable method to reduce construction
waste and to encourage the recycle and the reuse of structural materials. To perform a cor-
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