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SECONDINO VENTURA BRIDGE (ASTI) Incremental launching continuous beam
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SECONDINO VENTURA BRIDGE Geographical positioning
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SECONDINO VENTURA BRIDGE Geographical positioning
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SECO SECOND NDIN INO O VENT VENTUR URA A BR BRID IDGE GE What could it have been the typical solution?
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e typ ca so ut on or a ra way deck is the use of simply supported beams
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This common solution has the followin features •
Good speed of construction
•
Necessity of accessibility from the
• •
•
utilization of high dimensions and expensive launching girders)
Widely tested solution in and passengers comfort
•
Practicall no roblem of interaction between track and structure
High number of bearings and joints (with consequent problems of durability and substitution)
•
Large width piles and capitals to accommo a e wo rows o ear ngs (3.0 m, 4.1 m) stresses and low slenderness L/h≤15
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SECONDINO VENTURA BRIDGE A little history
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… •
Flooding in Piedmont in 1994 concerned principally Tanaro basin with a flow measured in Alessandria of about 3800 m3 /s
•
Old Corso Savona bridge in Asti was made of a upper way road deck, realized with 4 prestressed precast concrete beams with cast in situ slab of about 20 m span, and a lower railway deck
•
Both the decks were supported by huge masonry piers that left .
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During the flooding the bridge presented:
Insufficient hydraulic clearance: water reached the intrados of t e prestresse concrete ec . Violent impacts of transported material against the upstream Drifting of material against the piles with consequent dam effect During post-flooding repair works of river Tanaro, the river bed in . The two decks, road and railway, had then to be replaced
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•
Larger spans, to interfere as little as possible with the river and wit t e water ow 200 years return perio
•
No significant variation of the railway level (railway station is
•
Possibility of future reutilization of the rail deck as road deck, as a railway station in another zone
•
Similar transverse section for deck radically different (road deck and railway deck)
•
Construction method able to guarantee the safety of the structure and working force during construction phases
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Both road and railway decks made of prestressed concrete. Two continuous beams with 5 spans each (end spans 29.70 m and central spans 33.20 m), Incremental launching. Total depth of the beams = 165 cm (l/h≈20). Diaphragm piers with a transverse thickness of 150 cm.
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. Fixed
.
Long. fixed / Transv. free
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Railway
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Road + cycle track
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•
Construction of one span (33 m) in ten days
•
Lauching time: 3 hours
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SECONDINO VENTURA BRIDGE Launching technique
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a U lift
c) Down lift
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b Trust
d) Repositioning
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Geometrical limitations: In vertical plane
In horizontal plane
horizontal
straight or circular
circular
straight
near nc na on
c rcu ar
circular
circular
In the last two cases the projections on the horizontal plane are ellipse circles
Polit ecnico di Torino Depart ment of structural and geotechnical engineering “ Bridge design”
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NOSE DESIGN We can assume n
,
Ln= nose length L = typical span of the bridge (temporary or final) qn = k Ln² qn = dead weight of nose k = 0 012 ÷ 0 020 for road brid es 0,018 ÷ 0,030 for rail bridges ,
at a first approximation, as: qn /q = 0,10
The effect of relative flexural rigidity EnIn /EI on the limitation of stress variation during the launching should be evaluated. Polit ecnico di Torino Depart ment of structural and geotechnical engineering “ Bridge design”
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or s mp ca on, as a rs approac , we can ana yze a con nuous eam w an infinite number of spans and axial baricentric prestressing, to avoid the hyperstatic bending moments due to prestressing, which can assume different .
B B , analyzed with: • nose cantilevering • nose on e p er
0
≤
-
n
α
≤
1-Ln /L α
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Variation of MB during the launchin for L /L = 0 80 and qn/q = 0,10 with the relative rigidity ratio n n
Variation of MB during the launching for L n/L = 0,50 and qn/q = 0,10 with the relative rigidity ratio EnIn/EI
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With qn/q = 0,10 the bending moment at maximum cantilevering is equal to EOL for L /L = 0,65
Variation of MB for Ln/L = 0,65 and EnIn/EI = 0,200 as a function of the ratio / .
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SECONDINO VENTURA BRIDGE Launching nose
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Longitudinal section
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Section S1 φ20/20 L70cm
welded to the plate
Concrete bed for the plate Rck >45 MPa
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(interface with the nose)
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Section S3 (2m from the nose)
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Section S5 (4m from the nose)
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Section S7 (5m from the nose)
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SECONDINO VENTURA BRIDGE Evaluation of the internal actions during launching and launching prestressing
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INTERNAL ACTIONS DURING THE LAUNCHING: BENDING MOMENT •
Definitive restraint Tem orar restraint • Actions:
Temperature variation between intrados and extrados of ± 5° bearings of 5 mm
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Bending moment at end of launching (values in kN*10*m)
Step 95 Fase 95
Mg
M sett. Mced
M temp
M+
M-
Mtot+
Mtot-
-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 -600.0 -500.0 -400.0 -300.0 -200.0 -100.0 0.0
20.0
40.0
60.0
80.0
100.0
0.0 . 200.0 300.0 400.0 500.0 . 600.0 700.0
Polit ecnico di Torino Depart ment of structural and geotechnical engineering “ Bridge design”
120.0
140.0
160.0
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As the bending moments are almost constant in all the sections and the positive values are only half of the negative ones baricentric prestressing is introduced for the launching phases.
Enlarged section Wsx,sup Wdx,sup Wsx,inf [m3] [m3] [m3] ‐2.828 ‐2.631 2.171
A [m2] 7.897
Wdx,inf [m3] 2.237
A [m2] 6.458
Current section Wsx,sup Wdx,sup Wsx,inf [m3] [m3] [m3] ‐2.498 ‐2.290 1.590
Wdx,inf [m3] 1.629
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Longitudinal stresses during launching sup M+ [MPa]
inf M+ [MPa]
sup M‐ [MPa]
inf M‐ [MPa]
σ
σ
σ
σ
(σsup M+) + σprec
(σinf M+) + σprec
(σsup M‐) + σprec
(σinf M‐) + σprec
6.00 4.00 2.00 0.00
] a P M [
2.00
‐
4.00
‐
6.00
‐
8.00
‐
10.00
‐
12.00
‐
14.00
‐
0.00
20.00
40.00
60.00
80.00
100.00
x [m] Polit ecnico di Torino Depart ment of structural and geotechnical engineering “ Bridge design”
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180.00
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Shear during launching Fase Step60 60
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
Fase70 70 Step
-300.0
-300.0
-250.0
-250.0
-200.0
-200.0
-150.0
-150.0
-100.0
-100.0
-50.0
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
-50.0 0.0
20.0
40 .0
6 0.0
8 0.0
10 0.0
1 20.0
1 40.0
160 .0
0.0
0 .0
20 .0
40 .0
6 0.0
80.0
1 00.0
120 .0
140 .0
16 0.0
0.0
50.0
50.0
100.0
100.0
150.0
150.0
200.0
200.0
Fase Step 80 80
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
Fase90 90 Step
-300.0
-300.0
-250.0
-250.0
-200.0
-200.0
-150.0
-150.0
-100.0
-100.0
-50.0
Vg
Vced Vsett.
V temp
V+
V-
Vtot+
Vtot-
-50.0 0.0
20.0
40 .0
6 0.0
8 0.0
10 0.0
1 20.0
1 40.0
0.0
160 .0
0 .0
20 .0
40 .0
60.0
80.0
1 00.0
120 .0
140 .0
16 0.0
0.0
.
.
100.0
100.0
150.0
150.0
200.0
200.0
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SECONDINO VENTURA BRIDGE SLS Verifications
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•
4 3/ 6 6
Static scheme:
• Actions:
Self weight
Prestressing (considering anchorage draw in and friction)
Prestressing losses
Permanent loads
Termic variation between intrados and extrados of ± 5°
Traffic loads
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–
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st
19 T15 strands tendons
19 T15 strands tendons
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Couplers for 19T15
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– Surface inclined 88° Live Deck axis
for 19 T15
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I ncremental launching Live anchorage for 19 T15
section 11
Bearings axis
anchorage for 19 T15
Live anc orage or 19 T15
19 T15 strands tendons
sec on
Bearings axis
19 T15 strands tendons
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Bearings axis
19 T15 strands tendons
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section 55
Deck axis
19 T15 strands tendons Bearings axis
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–
Deck axis
19 T15 strands tendons
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–
19 T15 strands tendons
Deck axis
Couplers for 19T15
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section 44
Couplers for 19T15
19 T15 strands tendons
Live anchorage for 19 T15
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Pier axis
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–
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nd
Couplers for 19T15
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–
Deck axis
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19 T15 strands tendons
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–
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rd
Couplers for 19T15
Live anchorage for 19 T15
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–
Deck axis
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19 T15 strands tendons
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section 66
for 19 T15
19 T15 strands tendons
Live anchorage for 19 T15
Bearings axis
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Bending moment Self weight Peso proprio Permanentportati loads Permanenti ‐
25000
‐
20000
‐
15000
‐
10000 ‐
Prestressing Precompressione Temperature Gradiente gradient
Prestressing losses Cadute precompressione
5000
] 0 m N 5000 k [ M 10000 15000 20000 25000 30000 35000 0.0
20.0
40.0
60.0
80.0
100.0
x [m]
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180.0
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Internal actions (M,N) and relative stresses DEFINITIVE PRESTRESSING PRECOMPRESSIONE DEFINITIVA M [kN m]
N [kN]
σ
sup [MPa]
σ
inf [MPa] .
‐
70000
‐
2.0
60000
‐
4.0
] ‐50000 N k [ ‐40000
‐
6.0
‐
‐
] a P 8.0 M [ i ‐10.0 n s e o i s s s ‐12.0 n e r e t T ‐
N , ] ‐30000 m N k [ ‐20000
M‐10000
‐
14.0 .
0
‐
16.0
10000
‐
18.0
20000
‐
20.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
S
160.0
x [m]
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Internal actions (M,N) and relative stresses S.L.E. IN ASSENZA PERMANENTI PORTATI (t= S.L.S. WITHOUTDI PERMANENT LOADS (t=∞ ) ∞) M
N
σ
sup [MPa]
σ
inf [MPa]
‐
60000
0.0 .
‐
50000
‐
2.0
‐
] N ‐30000 k [
] a P M [ i ‐8.0 n s e o i s s s n e ‐10.0 r e t T 6.0
‐
N ] ‐20000 m N k [ ‐
.
‐
10000
M
S
0
‐
12.0
10000
‐
14.0
20000
‐
16.0
0.0
20.0
40.0
60.0
80.0
100.0
x [m]
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160.0
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Internal actions (M,N) and relative stresses S.L.S. QUASI-PERMANENT COMBINATION ( t = (t= ∞) ∞) S.L.E. - COMBINAZIONE QUASI PERMANENTE M+ σ inf M+ MPa
N σ
M‐ σ inf M‐ MPa
su M‐ MPa
σ
sup M+ [MPa]
‐
60000
0.0
‐
50000
‐
2.0
] ‐40000 N k [
4.0
‐
‐
‐
.
‐
, ] m N ‐20000 k [
8.0
‐
10000
‐
10.0
0
‐
12.0
10000
‐
14.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
] a P [ i n s e o i s s s n e r e t T
160.0
x [m]
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Internal actions (M,N) and relative stresses S.L.S. CHARACTERISTIC COMBINATION ( t)= ∞) S.L.E. - COMBINAZIONE RARA (t=∞ M+ σ inf M+ MPa
N σ
M‐ σ inf M‐ MPa
su M‐ MPa
σ
sup M+ [MPa]
‐
60000
0.0
‐
50000
‐
‐
40000
‐
2.0 4.0
] N k [ ‐30000
] a P [ i ‐8.0 n s o e i s s s n ‐10.0 e r e t T 6.0
‐
, ] ‐20000 m N k [ ‐10000
S
0
‐
12.0
10000
‐
20000
‐
14.0 16.0
0.0
20.0
40.0
60.0
80.0
100.0
x [m]
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140.0
160.0
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SECONDINO VENTURA BRIDGE ULS Verifications
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Bending moment diagram (excluded isostatic internal actions due to prestressing) S.L.U. - COMBINAZIONE UII(t= (t= U.L.S. COMBINATION ∞∞ )) Msd [kN m]
Mrd [kN m]
80000
‐
‐
40000
‐
] N ‐20000 k [
0 N , ] m 20000 N k [
60000 80000 100000 0.0
20.0
40.0
60.0
80.0
100.0
x [m]
Polit ecnico di Torino Depart ment of structural and geotechnical engineering “ Bridge design”
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140.0
160.0
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Ultimate limit state for shear and torsion Ultimate verification for shear of prestressed elements can be very complicated because of the necessity to take into account the interaction between compression fields due shear and prestressing. The EN1992 simplify the approach, using a formulation that, in general case, is on the safe side. Practically shear coming from prestressing (in an statically determined structure it is coincident to the vertical component of prestressing force) is subtracted to the shear due to the external actions. The limit resistance of the elements that don’t re uire shear reinforcements V
,
is increased to take
into account the arch-tie resisting system. Polit ecnico di Torino Depart ment of structural and geotechnical engineering “ Bridge design”
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Rd,c
Rd,c
l ck
1/3
1
cp
w
Where: C Rd , c
=
k = 1 +
ρ l = k 1
0.18 γ c 200 d
≤2
With d in millimeters
As ,l bw ⋅ d
= 0.15
With a minimum of: Where: Polit ecnico di Torino Depart ment of structural and geotechnical engineering “ Bridge design”
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