Civil Engineering Reference
In-Depth Information
For a bar element as shown in
Figure 9.6
the displacement function is
(9.38)
By the method already explained earlier, the stiffness of the bar is
(9.39)
For simplicity, it is sometimes assumed that the bar elements are connected
to the planar elements in such a way that the bar elements do not occupy any
cross-sectional area of the planar elements and they are interconnected at the
nodes with perfect bonding (Nam and Salmon, 1974).
9.8
Point element or linkage element
At low stress level, perfect bonding between steel and concrete may exist.
As the stresses in the steel and concrete increase, cracking as well as
breaking of the bond will occur and there will be bond slip between the bar
and concrete (Ngo and Scordelis, 1967)
In order to account for the slip between concrete and steel a point
element or linkage (Figure 9.7) element may be used to connect the steel and
concrete elements. This can be considered to consist of two springs with
appropriate stiffnesses arranged in orthogonal directions, parallel to the axes
along the longitudinal direction of the bar and the normal direction. These
springs are considered to have negligible lengths and only their mechanical
Figure 9.7
Linkage element
