RSSV 4 2013.indd - Stazione Sperimentale del Vetro

4-2013
studies
studi
Rivista della Stazione Sperimentale del Vetro
Robustness
To verify the robustness of composite steel-glass
beams, additional set of experiments was carried
out. Test set-up as well as the length and crosssection
of the test specimens were the same. Beams
were subjected to 4-point bending, where the lateral
support in the middle of the span was arranged to
avoid lateral-torsion buckling effects. Some of the
test specimens were loaded till the glass failure to
obtain the ultimate load level which is comparable
with dates and results of previous experiments. Next
part of test specimens was used for investigation of
robustness. Before the load introduction, one glass
pane was broken and consequently the beam was
loaded by the serviceability level of load for 48
hours, see Fig. 5. Vertical deflection of the beam and
stress in steel flanges and glass web were measured
during whole 48 hour long period.
Robustness was tested on specimens with the web
composed from 5 glass panes. Before the load introduction,
one pane was broken and then the hybrid
beam was loaded by constant couple of forces
F const
= 4,8kN (i.e. M const
= 5,0kNm in the middle)
for 48 hours. After 48 hours the test specimen was
unloaded and then loaded again continuously to the
glass failure. 2 test specimens were used to verify
the robustness. Once, glass pane in the middle of
the span was broken before the load introduction to
weaken the beam in the part with maximum bending
moment, see Fig. 6. Next time, the first pane near
the support was broken to weaken the place, where
the maximal shear force is acting, see Fig. 7.
In term of robustness, hybrid beams fulfil all requirements,
if used adhesive has the value of initial
shear modulus at least 40 - 50MPa. For safety design
overlapped joint between glass panes is more
Figure 5. Robustness tests
Figure 6. Results for 48 hour robustness test of the beam with destroyed mid-span panel
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