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Incremental launching
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SECONDINO VENTURA BRIDGE (ASTI) Incremental launching continuous beam
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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SECONDINO VENTURA BRIDGE Geographical positioning
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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SECONDINO VENTURA BRIDGE What could it have been the typical solution?
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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The typical l ti Th t i l solution f a railway for il deck is the use of simply supported beams
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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This common solution has the following features g Good speed of construction Computation simplicity Widely tested solution in term of rail traffic safety and passengers comfort Practically no p y problem of interaction between track and structure Necessity of accessibility from the bottom to the construction site (or utilization of high dimensions and expensive launching girders) High number of bearings and joints (with consequent problems of durability and substitution) Large width piles and capitals to accommodate t d t two rows of b i f bearings (3.0 m, 4.1 m) Non optimal distribution of the stresses and low slenderness L/h15 /
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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SECONDINO VENTURA BRIDGE A little history
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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A LITTLE HISTORY 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 made of steel Both the decks were supported by huge masonry piers that left very little free span between them them.
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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During the flooding the bridge presented: Insufficient hydraulic clearance: water reached the intrados of the th prestressed concrete d k t d t deck. Violent impacts of transported material against the upstream beam (and consequent damage) Drifting of material against the piles with consequent dam effect During post-flooding repair works of river Tanaro, the river bed in correspondence of the bridge has been enlarged. The two decks, road and railway, had then to be replaced
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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DESIGN RESTRAINTS Larger spans, to interfere as little as possible with the river and with th water fl ith the t flow (200 years return period) t i d) No significant variation of the railway level (railway station is nearby) Possibility of future reutilization of the rail deck as road deck, as a consequence of modification of railway line and transfer of the railway station in another zone Similar transverse section for deck radically different ( y (road deck and railway deck) Construction method able to guarantee the safety of the structure and working force during construction phases
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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SOLUTIONBoth 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/h20). Diaphragm piers with a transverse thickness of 150 cm.
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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BEARINGSFree Fixed Long. Long Free / Transv. fixed Transv Long. fixed / Transv. free
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Cross section of the two independent decks
Railway
Road + cycle track
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Cross section of the railway deck
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Comparison between construction techniques
Construction of one span (33 m) in ten days Lauching time: 3 hoursPolitecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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SECONDINO VENTURA BRIDGE Launching technique
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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a) Uplift ) p
) b) Trust
c) Down lift
d) Repositioning
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Geometrical limitations:In vertical plane horizontal circular linear i li ti li inclination circular In horizontal plane straight or circular straight circular i l circular
In the last two cases the projections on the horizontal plane are ellipse circles
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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NOSE DESIGNWe can assume Ln= nose length L = typical span of the bridge (temporary or final) qn = k Ln qn = dead weight of nose , , g k = 0,012 0,020 for road bridges 0,018 0,030 for rail bridges The ratio between dead weight of nose and deck can be assumed assumed, 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.Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
Ln 0 65 L 0,65
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For i lifi ti F simplification, as a fi t approach, we can analyze a continuous b first h l ti beam with ith an infinite number of spans and axial baricentric prestressing, to avoid the hyperstatic bending moments due to prestressing, which can assume different values for each bridge position position.
B BThe launching internal actions as a function of parameter = x/L, are x/L analyzed with: nose cantilevering 0 1-Ln/L nose on the pier pie 1-L 1 Ln/L 1
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Variation of MB during the launching for Ln/L = 0,80 and qn/q = 0,10 with the relative rigidity ratio EnIn/EI
Variation of MB during the launching for Ln/L = g 0,50 and qn/q = 0,10 with the relative rigidity ratio EnIn/EI
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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With qn/q = 0,10 the bending moment at maximum cantilevering is equal to EOL for Ln/L = 0,65 ,
Variation of MB for Ln/L = 0,65 and EnIn/EI = 0,200 as a function of the ratio qn/q. q
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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SECONDINO VENTURA BRIDGE Launching nose
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Launching nose anchoring systemLongitudinal section
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Section S120/20 L70cm welded to the plate
(interface with the nose)
Concrete bed for the plate Rck >45 MPa
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Section S3 (2m from the nose)
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Section S5 (4m from the nose)
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Section S7 (5m from the nose)
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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SECONDINO VENTURA BRIDGE Evaluation of the internal actions during launching and launching prestressing
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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INTERNAL ACTIONS DURING THE LAUNCHING: BENDING MOMENT Static scheme :
Definitive restraint Temporary restraint Actions: Self weight Temperature variation between intrados and extrados of 5 Maximum differential settlement between two consecutive bearings of 5 mmPolitecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Bending moment at end of launching (values in kN*10*m) g g
Step 95 Fase 95-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 -600.0 -500.0 -400.0 -300.0 -200.0 -100.0 0.0 0.0 100.0 100 0 200.0 300.0 400.0 500.0 600.0 700.0 20.0
Mg
M sett. Mced
M temp
M+
M-
Mtot+
Mtot-
40.0
60.0
80.0
100.0
120.0
140.0
160.0
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Bending moment during launching g g gFase Step 20-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 -600.0 -500.0 -400.0 -300.0 -200.0 -100.0 0.0 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
Mg
Msett. Mced
M temp
M+
M-
Mtot+
Mtot-
Fase 30 Step 30-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 -600.0 -500.0 -400.0 -300.0 -200.0 -100.0 0.0 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 20.0
Mg
Msett. Mced
M temp
M+
M-
Mtot+
Mtot-
40.0
60.0
80.0
100.0
120.0
140.0
160.0
Fase Step 40-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 700 0 -600.0 -500.0 -400.0 -300.0 -200.0 -100.0 0.0 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 20.0
Mg
Msett. Mced
M temp
M+
M-
Mtot+
Mtot-
Fase 50 Step 50-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 700 0 -600.0 -500.0 -400.0 -300.0 -200.0
Mg
Mced Msett.
M temp
M+
M-
Mtot+
Mtot-
40.0
60.0
80.0
100.0
120.0
140.0
160.0
-100.0 0.0 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
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Bending moment during launching g g gFase 60 Step 60-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 -600.0 -500.0 -400.0 -300.0 -200.0 -100.0 0.0 0.0 00 100.0 200.0 300.0 400.0 500.0 600.0 700.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
Mg
Msett. M temp Mced
M+
M-
Mtot+
Mtot-
Step 70 Fase 70-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 -600.0 -500.0 -400.0 -300.0 -200.0 -100.0 0.0 0.0 00 100.0 200.0 300.0 400.0 500.0 600.0 700.0 20.0
Mg
Msett. Mced
M temp
M+
M-
Mtot+
Mtot-
40.0
60.0
80.0
100.0
120.0
140.0
160.0
Fase 80 Step 80-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 -600.0 -500.0 -400.0 -300.0 -200.0 -100.0 0.0 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 20.0
Mg
Msett. Mced
M temp
M+
M-
Mtot+
Mtot-
Fase 90 Step 90-1200.0 -1100.0 -1000.0 -900.0 -800.0 -700.0 -600.0 -500.0 -400.0 -300.0 -200.0
Mg
Msett. Mced
M temp
M+
M-
Mtot+
Mtot-
40.0
60.0
80.0
100.0
120.0
140.0
160.0
-100.0 0.0 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
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As the bending moments are almost constant in all the sections and g the positive values are only half of the negative ones baricentric prestressing is introduced for the launching phases.
A [m2] 7.897
Enlargedsection Wsx,sup Wdx,sup Wsx,inf [m3] [m3] [m3] 2.828 2.631 2.171
Wdx,inf [m3] 2.237
A [m2] 6.458
Currentsection 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 g g gsupM+[MPa] (supM+)+prec 6.00 4.00 2.00 0.00 infM+[MPa] (infM+)+prec supM [MPa] (supM)+prec infM [MPa] (infM)+prec
[MPa]
2.00 4.00 6.00 8.00 8.00 10.00 12.00 14.00 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00
x[m]Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Shear at end of launching (values in kN*10*m) g
Fase 95 Step 95-300.0 -250.0
Vg
V sett. Vced
V temp
V+
V-
Vtot+
Vtot-
-200.0
-150.0
-100.0 100 0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
50.0
100.0
150.0
200.0
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Shear during launching g gFase 20 Step 20-300.0 -250.0
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
Fase 30 Step 30-300.0 -250.0
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
-200.0
-200.0
-150.0
-150.0
-100.0
-100.0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
50.0
50.0
100.0
100.0
150.0
150.0
200.0
200.0
Fase 40 Step 40-300.0 -250.0
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
Fase 50 Step 50-300.0 -250.0
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
-200.0
-200.0
-150.0
-150.0
-100.0
-100.0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
50.0
50.0
100.0
100.0
150.0
150.0
200.0
200.0
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Shear during launching g gFase 60 Step 60-300.0 -250.0
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
Fase 70 Step 70-300.0 -250.0
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
-200.0
-200.0
-150.0
-150.0
-100.0
-100.0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
50.0
50.0
100.0
100.0
150.0
150.0
200.0
200.0
Fase 80 Step 80-300.0 -250.0
Vg
Vsett. Vced
V temp
V+
V-
Vtot+
Vtot-
Fase 90 Step 90-300.0 -250.0
Vg
Vced Vsett.
V temp
V+
V-
Vtot+
Vtot-
-200.0
-200.0
-150.0
-150.0
-100.0
-100.0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
-50.0 0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
50.0 50 0
50.0 50 0
100.0
100.0
150.0
150.0
200.0
200.0
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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SECONDINO VENTURA BRIDGE SLS Verifications
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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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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Prestressing layout 1st span
19 T15 strands tendons
Couplers for 19T15
19 T15 strands tendons
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Prestressing layout section AASurface S f inclined 88 Live anchorage for 19 T15
Deck axis
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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section 11
Live anchorage for 19 T15
section 33
Bearings axis Live anchorage for 19 T15
19 T15 strands tendons
Bearings axis
19 T15 strands tendons
section 22 ti
Bearings axis
19 T15 strands tendons
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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section 55
Deck axis
19 T15 strands tendons Bearings axis
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Prestressing layout section BB
Deck i D k axis
19 T15 strands tendons
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Prestressing layout section CC
19 T15 strands tendons
Deck axis
Couplers for 19T15
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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section 44
Couplers for 19T15
19 T15 strands tendons
Live anchorage for 19 T15
Pier axis
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Prestressing layout 2nd span
Couplers for 19T15
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Prestressing layout section DD
Deck axis
19 T15 strands tendons
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Prestressing layout 3rd span
Couplers for 19T15
Live anchorage for 19 T15
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Prestressing layout section GG
Deck axis
19 T15 strands t d tendons
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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section 6619 T15 strands tendons
Live anchorage for 19 T15
Bearings axis
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Bending momentSelf weight Pesoproprio Permanent loads Permanentiportati25000 20000 15000 10000 5000
Prestressing Precompressione Temperature Gradiente gradient
Prestressing losses Caduteprecompressione
M[kNm m]
0 5000 10000 15000 20000 25000 30000 35000 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0
x[m]Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Internal actions (M,N) and relative stressesDEFINITIVE PRESTRESSING PRECOMPRESSIONE DEFINITIVAM[kNm]80000 70000 60000
N[kN]
sup[MPa]
inf[MPa]0.0 00 2.0 4.0 6.0 8.0 10.0 12.0 14.0 14.0 16.0 18.0 20.0
M[kNm], N[kN]
50000 40000 30000 20000 10000 10000 0 10000 20000 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0
160.0
x[m]Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Internal actions (M,N) and relative stressesS.L.E. IN ASSENZA DI PERMANENTI PORTATI) S.L.S. WITHOUT PERMANENT LOADS ( t = (t=)M60000 60000 50000 40000 40000
N
sup[MPa]
inf[MPa]0.0 2.0 40 4.0 6.0 8.0 10.0 12.0 14.0 16.0
M[kNm], ,N[kN]
30000 20000 10000 0 10000 20000 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0
160.0
x[m]Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
Stresses [MPa] Tensioni
Stresses [MPa] Tensioni
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Internal actions (M,N) and relative stressesS.L.S. QUASI-PERMANENT COMBINATION ( t ) S.L.E. - COMBINAZIONE QUASI PERMANENTE = (t=)M+ infM [MPa] inf M+[MPa]60000 50000 40000 30000 20000 10000 0 10000 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0
N supM sup M [MPa]
M infM inf M [MPa]
supM+[MPa]0.0 2.0 4.0 6.0 6 0 8.0 10.0 12.0 14.0 160.0
M M[kNm],N N[kN]
x[m]Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Internal actions (M,N) and relative stressesS.L.S. CHARACTERISTIC COMBINATION ( t = ) S.L.E. - COMBINAZIONE RARA (t=)M+ infM+[MPa] inf M+ [MPa]60000 50000 40000
N supM sup M [MPa]
M infM inf M [MPa]
supM+[MPa]0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0
M M[kNm],N N[kN]
30000 20000 10000 0 10000 20000 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0
160.0
x[m]Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
STensioni MPa] Stresses [M T
S Stresses [M Tensioni MPa]
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SECONDINO VENTURA BRIDGE ULS Verifications
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Bending moment diagram g g (excluded isostatic internal actions due to prestressing)S.L.U. - COMBINAZIONE UII(t=) U.L.S. COMBINATION ( (t=) )Msd[kNm]80000 60000 40000
Mrd[kNm]
M M[kNm],N[kN]
20000 0 20000 40000 60000 80000 100000 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
x[m]
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Ultimate limit state for shear and torsionUltimate 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 dont require shear reinforcements ( Rd c) is increased to take q (VRd,c into account the arch-tie resisting system.Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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VRd,c = [CRd,ck(100 l fck)1/3 + k1 cp] bwd Where:
CRd ,c =
0.18
c200 2 dWith d in millimeters
k = 1+
l =
As ,l bw d
k1 = 0.15With a minimum of: Where:Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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Resistance of web compression fi ld (VRd,max) i modified t t k i t R i t f b i fields is difi d to take into account the interaction between longitudinal and inclined compression: VRd,max = cw bw z 1 fcd/(cot + tan ) 1 = 0,6 1 = 0,9 fck /200 > 0,5 cw =1 cw = (1 + cp/fcd) cw = 1,25 cw =2 5 (1 - cp/fcd) =2,5 for fck 60 MPa for fck 60 MPa for non prestressed structure for 0 < cp 0,25 fcd for 0,25 fcd < cp 0,5 fcd for 0 5 fcd < cp < 1,0 fcd 0,5 10
Prestressing reinforcement can also be used to carry the increment of g y the tensile force in the tensed chord due to shear.Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design
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References CEB FIP CEB-FIP Model Code 1990 Thomas Telford 1990 1990, Eurocode 2 Design of concrete structures, Part 1-1: general rules and rules for buildings - 2003 Eurocode 2 D i of concrete structures P t 2: concrete E d Design f t t t Part 2 t bridges - 2004
Politecnico di TorinoDepartment of structural and geotechnical engineering Bridge design