squat silos containing grain-like material subjected to shaking ...Stefano Silvestri...
Transcript of squat silos containing grain-like material subjected to shaking ...Stefano Silvestri...
S E R I E S
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES
FOR EUROPEAN SYNERGIES
COMMISSION OF THE EUROPEAN COMMUNITIES
FP7- INFRASTRUCTURES-2008-1
SP4-Capacities
“Analysis of the dynamic behavior of
squat silos containing grain-like material
subjected to shaking-table tests”
Dora Foti [email protected]
Tomaso Trombetti
Stefano Silvestri [email protected]
Salvador Ivorra Chorro
Colin Taylor [email protected] Matt Dietz [email protected]
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
PRESENTATION LAYOUT • The test set-up
• The scientific background • The shaking-table tests performed and the first results
• The comparison with theory expectations
OBJECTIVES
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
• To find out the pressure that the grain-like material produces on
the silo walls due to time constant acceleration (for the
experimental verifications of the analytical findings obtained in
Silvestri et al., BEE 2012);
• To evaluate the influence of the base input (earthquake vs.
sinusoidal)
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
SPECIMEN DATA
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
Session 1 Sessions 2 and 3
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
SPECIMEN GEOMETRY
SILO SPECIMEN
(scale 1:10)
INSERTION OF BALLOTTINI
PARAMETERS
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
INSTRUMENTATION
• mono-directional accelerometers located
at the shaking-table foundation, glued to
the silo walls and placed inside the
Ballottini glass;
• vertical and horizontal strain gauges
positioned on the exterior side of the
walls at four different heights;
• LVDT placed at the top of the structure;
• film and Flexi Force pressure sensors
placed on the interior side of the walls, in
order to measure pressures
INSTRUMENTATION VIEW
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
FROM REALITY TO IDEALIZATIONS
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
A
• Flexible
• Compressible
grain
• Earthquake input
B1
• Flexible
• Uncompressible
grain
• Earthquake input
B2
• Flexible
• Uncompressible
grain
• Sinusoidal input
C
• Infinitely stiff
• Uncompressible
grain
• Constant input
REAL CASE IDEAL MODEL
z
yx
z
yx
z
yx
TEST SPECIMEN
z
yx
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
THE SPECIMEN MODEL IS SITUATED IN A CENTRAL POSITION
WITH RESPECT TO THE REAL CASE AND THE IDEAL MODEL:
1. The silo walls are considered not infinitely stiff but with some
flexibility associated to the acceleration profile;
2. The grain particles of the ensiled material are considered
uncompressible;
3. The inputs used are:
▫ Sinusoidal at low frequency that is comparable with the
constant input used for the theory;
▫ Un-scaled Earthquake closer to the real silo conditions
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
PROBLEM FORMULATION
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
20-22 August 2012:
• Silo with smooth walls (grain-wall friction coefficient ) and
filled with Ballotini glass up to a height of 120 cm.
• Input – white noises (ampl. 0.05g, 0.1g, 0.2g, 0.3g), sinusoidal (low
frequency) and earthquake accelerograms along Y direction.
Objective:
Analyze the behavior of the silo specimen under the specific conditions presented
above with respect to the theory expectation
0.30GW
SESSION 1
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
29-31 January 2013: • Silo with roughened walls (grain-wall friction coefficient ) and filled with
Ballotini glass up to a height of 60 cm.
• Input – white noises, sinusoidal at 1Hz and 2Hz along Y and Z directions and
earthquake accelerograms (South Iceland records).
Objective:
Analyse the repeatability and the initial conditions of the silo and monitor the effect of a
lower slenderness ratio
0.45GW
SESSION 2
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
1-2 February 2013:
• Silo with roughened walls (grain-wall friction coefficient ) and filled
with Ballotini glass up to a height of 120 cm.
• Input – systematic sinusoidal input (ampl. 0.1g-0.6g) at 1Hz and 2Hz along Y
direction.
Objective:
Analyze the behavior of the silo specimen under the specific conditions presented
above with respect to the theory expectation and the results of the first session
with particular attention on the effect of the increased roughness and the changed
internal friction coefficient of the ensiled material.
0.45GW
SESSION 3
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
ACCELERATION RESULTS
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
Session 1 – test S9
0 5 10 15 20 25 30 35 40-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Accelerometers y=0.6(LEFT)- test - S9 - a =0.339g
Time (s)
Ho
rizo
nta
l A
ccele
rati
on
(g
)
h=0
h=0.44
h=0.84
h=1.24
h=1.54
0 5 10 15 20 25 30 35 40-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Accelerometers y=-0.6(RIGHT)- test - S9 - a =0.339g
Time (s)
Ho
rizo
nta
l A
ccele
rati
on
(g
)
h=0
h=0.44
h=0.84
h=1.24
h=1.54
-2 -1.5 -1 -0.5 0 0.5 1 1.5 20
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
max/min horizontal accelerations. Filtered t=0- test - E17 - a =0.415g
Acceleration (g)
h (
m)
max y=0.6(LEFT)
min y=0.6(LEFT)
max y=-0.6(RIGHT)
min y=-0.6(RIGHT)
-2 -1.5 -1 -0.5 0 0.5 1 1.5 20
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
max/min horizontal accelerations. Filtered t=0- test - S9 - a =0.339g
Acceleration (g)
h (
m)
max y=0.6(LEFT)
min y=0.6(LEFT)
max y=-0.6(RIGHT)
min y=-0.6(RIGHT)
EARTHQUAKE
INPUT
SINUSOIDAL
INPUT
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
ACCELERATION RESULTS
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
Session 2– test S50
0 5 10 15 20 25-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Accelerometers y=0.6(LEFT) test S50 a = 0.2747 g
Time (s)
Ho
rizo
nta
l A
ccele
rati
on
(g
)
h=0
h=0.44
0 5 10 15 20 25-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Accelerometers y=-0.6(RIGHT) test S50 a = 0.2747 g
Time (s)
Ho
rizo
nta
l A
ccele
rati
on
(g
)
h=0
h=0.44
-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.50
0.1
0.2
0.3
0.4
0.5
0.6
max/min horizontal accelerations. Filtered t=0 test S50 a = 0.2747 g
Acceleration (g)
h (
m)
max y=0.6(LEFT)
min y=0.6(LEFT)
max y=-0.6(RIGHT)
min y=-0.6(RIGHT)
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
Session 3 – test S4
ACCELERATION RESULTS
0 5 10 15 20 25 30 35 40-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Accelerometers y=0.6(LEFT) test S4 a = 0.325 g
Time (s)
Ho
rizo
nta
l A
ccele
rati
on
(g
)
h=0
h=0.44
h=0.84
h=1.24
h=1.54
0 5 10 15 20 25 30 35 40-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Accelerometers y=-0.6(RIGHT) test S4 a = 0.325 g
Time (s)
Ho
rizo
nta
l A
ccele
rati
on
(g
)
h=0
h=0.44
h=0.84
h=1.24
h=1.54
-2 -1.5 -1 -0.5 0 0.5 1 1.5 20
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
max/min horizontal accelerations. Filtered t=0 test S4 a = 0.325 g
Acceleration (g)
h (
m)
max y=0.6(LEFT)
min y=0.6(LEFT)
max y=-0.6(RIGHT)
min y=-0.6(RIGHT)
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
STRAIN RESULTS
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
Session 1 – test S9
Session 2– test S50
0 5 10 15 20 25 30 35 40-80
-60
-40
-20
0
20
40
60
80
100
Vertical strain-gauges, y=0.6(LEFT) filt. t=0- test - S9 - a =0.339g
Time (s)
Vert
ical m
icro
-str
ain
h=0.18m
h=0.32m
h=0.62m
h=0.92m
0 5 10 15 20 25 30 35 40-150
-100
-50
0
50
100
150
200
250
Vertical strain-gauges, y=-0.6 filt. t=0- test - S9 - a =0.339g
Time (s)
Vert
ical m
icro
-str
ain
h=0.18m
h=0.32m
h=0.62m
h=0.92m
0 5 10 15 20 25-30
-20
-10
0
10
20
30
Vertical strain-gauges, y=0.6(LEFT) filt. t=0 test S50 a = 0.2747 g
Time (s)
Vert
ical m
icro
-str
ain
h=0.18m
h=0.32m
h=0.62m
0 5 10 15 20 25-100
-80
-60
-40
-20
0
20
40
60
80
Vertical strain-gauges, y=-0.6 filt. t=0 test S50 a = 0.2747 g
Time (s)
Vert
ical m
icro
-str
ain
h=0.18m
h=0.32m
h=0.62m
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
STRAIN RESULTS
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
Session 3 – test S4
COMMENTS
For all the sessions the maximum vertical strain is reached at height 0.18 m
(the lowest one), on the contrary the lowest vertical strain is set for height of
0.92 m. This is concordant with the behavior of the silo under a sinusoidal
input. Moreover the behavior of the two parts of the silo seems to be not
identical; this may be due to a squeezing of Ballottini glass along the
junction between the two polycarbonate semicircles
0 5 10 15 20 25 30 35 40-250
-200
-150
-100
-50
0
50
100
150
200
250
Vertical strain-gauges, y=0.6(LEFT) filt. t=0 test S4 a = 0.325 g
Time (s)
Vert
ical m
icro
-str
ain
h=0.18m
h=0.32m
h=0.62m
h=0.92m
0 5 10 15 20 25 30 35 40-250
-200
-150
-100
-50
0
50
100
150
200
250
Vertical strain-gauges, y=-0.6 filt. t=0 test S4 a = 0.325 g
Time (s)
Vert
ical m
icro
-str
ain
h=0.18m
h=0.32m
h=0.62m
h=0.92m
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
STRAIN RESULTS
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
Squeezing of Ballottini glass
along the junction between
the two polycarbonate
semicircles
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
PHYSICAL BEHAVIOR FOR A CHANGE
IN THE PGA o by looking at the mean plot (black line - Figure 1a), there is a clear change in the
physical behaviour for a value of PGA around 0.35 g.
o the same also for the case of input in Y and Z direction (Figure 1 b)
o Figure 1 c shows that for the case of rough walls surface the change in the
physical behavior seems to appear around 0.25g.
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
100
200
300
400
500
600
PGA [g]
max
[]
1Hz sinusoid (Y) - HBallottini
= 1.2 m
1pos
1neg
9pos
9neg
mean
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
50
100
150
200
250
PGA [g]
max
[]
1Hz sinusoid (Y&Z) - HBallottini
= 0.6 m
3pos
3neg
15pos
15neg
mean
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
100
200
300
400
500
600
PGA [g]
max
[]
1Hz sinusoid (Y) - HBallottini
= 1.2 m
3pos
3neg
15pos
15neg
mean
Figure 1b Figure 1c Figure 1a
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
INTERPRETATION OF
EXPERIMENTAL RESULTS The interpretation of the experimental results basically concerns the comparison between:
• the experimental bending moment at the base of the silo, as reconstructed from the strain values of the vertical strain gauges placed at a height z = 0.14 m from the table;
• the predicted value of the base bending moment, as given by the analytical formulations proposed by the authors (Silvestri et al. 2012);
• the Eurocode 8 prescribed values
The methodologies applied to reconstruct the experimental bending moment at the base of the silo (at a height z = 0.14 m) directly integrates the base vertical stresses multiplied by the corresponding lever arm over the whole circumferential cross-section.
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
METHODOLOGY
2
exp i i i
i
M t t A r
i polycarbonate it E t
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
x
y
30°
15°
42,43
44
4
3
43
16
15
42
2
41
14
60
57,96
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
Form the reconstruction of the experimental base bending moment
it is possible to note that the wall-grain friction coefficient strongly
affects the experimental base bending moment. This does not match
with Eurocode 8 prescriptions which do not take into account the wall-
grain friction coefficient at all.
0 5 10 15 20 25 30 35 40-1.5
-1
-0.5
0
0.5
1
1.5x 10
4 M(t) as re-constructed from base strains - a =0.33g
t [s]
M [kgcm]
first session: smooth walls
third session: roughened walls
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
INTERPRETATION OF THE RESULTS:
ROUGHENED
WALLS
SMOOTH
WALLS
All same
conditions,
except for the
wall-grain friction
coefficient
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
For h = 120 cm of the ensiled material the reconstructed experimental
bending moment is much closer to the prediction given by the
analytical formulas provided by the authors (Silvestri et al. 2012) than
the Eurocode 8 provision.
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”
INTERPRETATION OF THE RESULTS:
0 5 10 15 20 25 30 35 40-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1x 10
4
0.891
2.4
3
0.951
2.6
3.2
Mpos/Mneg =1.1
M(t) as re-constructed from base strains - S2- a =0.101g
t [s]
M [kgcm]
M experimental
mean M experimental
M ns prediction
M EC8 simplified
M EC8 accurate
0 5 10 15 20 25 30 35 40-4
-3
-2
-1
0
1
2
3
4x 10
4
0.68
1
1.8
2.3
0.68
1
1.9
2.3
Mpos/Mneg =1
M(t) as re-constructed from base strains - S4- a =0.325g
t [s]
M [kgcm]
M experimental
mean M experimental
M ns prediction
M EC8 simplified
M EC8 accurate
0 5 10 15 20 25 30 35 40-6
-4
-2
0
2
4
6x 10
4
0.55
1
1.5
1.8
0.59
1
1.6
2
Mpos/Mneg =1.1
M(t) as re-constructed from base strains - S6- a =0.54g
t [s]
M [kgcm]
M experimental
mean M experimental
M ns prediction
M EC8 simplified
M EC8 accurate
0 5 10 15 20 25-2
-1.5
-1
-0.5
0
0.5
1
1.5
2x 10
4
0.831
2.3
2.8
0.781
2.1
2.6
Mpos/Mneg =0.94
M(t) as re-constructed from base strains - S10- a =0.162g
t [s]
M [kgcm]
M experimental
mean M experimental
M ns prediction
M EC8 simplified
M EC8 accurate
SEISMIC ENGINEERING RESEARCH INFRASTRUCTURES FOR EUROPEAN SYNERGIES
END
Final Meeting – ISPRA 28-30 May 2013 D. Foti - “Analysis of the dynamic behavior of squat silos…”