Page 27 - Riem-Vol6_nº3

379 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
P. F. SCHWETZ | F. P. S. L. GASTAL | L. C. P. SILVA F°
3.1.2 The Frame Element
The Frame Element is a tridimensional element with six de-
grees of freedom per node: three degrees of freedom for
translation and three degrees of freedom for rotation. It is
used for two or three dimensional modeling of frames, trusses
and grids.
The formulation of the Frame element includes the determina-
tion of biaxial bending, torsion, axial and shear stress, through
the integration of the tensions along the section. Those stresses
are determined at the ends of each element and at points along
the element chosen by the user.
In the FE model of the waffle slab under study, which is shown in
Fig. 8, the top slab, the ribs, the edge beams and the solid slab
regions were modeled using shell elements, totaling approxi-
mately 23,000 elements, and the columns were modeled with
frame elements. A nonlinear analysis of the structure was car-
ried out, applying three types of loads in the following sequence:
self-weight, a masonry load applied directly on the edge beams
and the additional dead load. The numerical results correspond-
ing to the experimental load were considered as being the differ-
ence between the values obtained from the numerical analysis
at the first and the last stages of the additional dead load ap-
plication (Fig. 9).
Figure 7 – (a) Unevenly distribution of the load and (b) Slab totally loaded
A B
Figure 8 – Finite element model
Figure 9 – Vertical displacements of instrumentation
point PC concerning the loads applied on SAP2000