design considerations and efficient construction of hsr structures
DESCRIPTION
Design Considerations and Efficient Construction of HSR Structures. Gonzalo de Diego Barrenechea. March 4, 2011. 1. World HSR Development . SPANISH EXPERIENCE. World HSR rank [expected by end of 2010] 1st China: 1,929 miles [3,105 km] 2nd Japan: 1,352 miles [2,176 km] - PowerPoint PPT PresentationTRANSCRIPT
Design Considerations and Efficient Construction of HSR Structures
Gonzalo de Diego Barrenechea
March 4, 2011
1. World HSR Development
HSR Structures
SPANISH EXPERIENCE
• World HSR rank [expected by end of 2010]– 1st China: 1,929 miles [3,105 km] – 2nd Japan: 1,352 miles [2,176 km]– 3rd Spain: 1,200 miles [1,932 km]
• Spain has more than 24 years of HSR experience (first construction started 1986)
• More than US$ 85 billion invested in HSR since the 90s
• Estimated construction cost: US$ 20 million/km for new lines
• Only China and Spain designed HSR infrastructure for 220 mph [350 km/h] operations Speed matters
• AECOM-Spain (legacy INOCSA) has provided HSR design services for more than 625 miles (1,000 km) [including PE-15%, PE-30%, and Final Design]
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2. Loads And Actions Considered During HSR Structural Design
HSR Structures
LOADS AND ACTIONS
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TYPE OF ACTIONS Unique HSR considerations
PERMANENT- CONSTANT VALUE (self weight, removable weights)NO
PERMANENT- VARIABLE VALUE (pre-stressed, reological, ground)NO
VARIABLE ACTIONS – CLIMATE ACTIONS (wind, snow, temperature)NO
COMBINED TRACK/STRUCTURE ACTIONS SOME
ACCIDENTAL ACTIONS [derailments, impacts, seismic] NO
VARIABLE ACTIONS – TRAFFIC LOADS• VERTICAL LOADS• DYNAMIC EFFECTS• HORIZONTAL FORCES• AERODYNAMIC EFFECTS
YES
2.1 Vertical and Horizontal Loads
HSR Structures
VERTICAL & HORIZONTAL LOADS
VERTICAL
• Static analysis: UIC-71 load model
• Dynamic analysis: Specific model for HSR HSLM (High Speed Load Model) [for trains exceeding 200 km/hr- 125 mph]
HORIZONTAL
• Traction & breaking forces are significant
• Centrifugal forces increase significantly in curved structures.
• Combined response of the structure and track– Longitudinal forces over track
(acceleration, starting, breaking)– Different deformation between deck &
slab– Resulting load transfer between track
and ballast through fixingsMarch 4, 2011 Page 7
2.2 Dynamic Effects
HSR Structures
• Static stresses and deformations induced in a bridge are increased and decreased under the effects of moving traffic by:– Rapid rate of loading due to the speed of traffic
crossing the structure and the inertial response Specific Dynamic Analysis IMPACT COEFFICIENT [ v > 220 KM/H- 125 mph]
– Passage of successive loads with uniform spacing which can excite the structure and under certain circumstances create RESONANCE (where the frequency of excitation matches a natural frequency of the structure)
– Variation in wheel loads resulting from track or vehicle imperfections.
• These stresses and deformations might cause fatigue so a proper fatigue analysis should also be done.
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DYNAMIC EFFECTS
2.3 Aerodynamic Effects
HSR Structures March 4, 2011 Page 11
AERODYNAMIC EFFECTS
• Passing trains Aerodynamic effect– Must be taken into consideration
when designing structures adjacent to railway tracks.
• Aerodynamic effect Wave alternating pressure and suction – At 300 km/hr this pressure can
be up to 6 times that at 120 km/h
2.4 Combined Response
COMBINED RESPONSE OF STRUCTURE AND TRACK TO VARIABLE ACTIONS
March 4, 2011HSR Structures Page 13
(1) Track(2) Superstructure (a single deck comprising two spans and a single deck with one span
shown)(3) Embankment(4) Rail expansion device (if present)(5) Longitudinal non-linear springs reproducing the longitudinal load / displacement
behaviour of the track(6) Longitudinal springs reproducing the longitudinal stiffnes K of a fixed supporte to the
deck taking into account the stiffness of the foundation, piers and bearings etc.
• Continuous rails + discontinuities in the support to the track (e.g between bridge structure and embankment) structure of the bridge (bridge decks, bearings and substructure) + track (rails, ballast, etc) JOINTLY resist the longitudinal actions due to traction or braking.
• Where continuous rails restrain the free movement of the bridge deck– Deformations of the bridge deck (e.g due to terminal variations, vertical loading, creep and
shrinkage ) produces longitudinal forces in the rails and in the fixed bridge bearings.– Continuous bridges require rail expansion devices
3. Efficient Structure Construction
HSR Structures
SPANISH EXPERIENCE
• Know-how evolves maximum bridge span increases optimum bridge typology evolves
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Inaugurated Line Design speed (km/h)
Max. Bridge Length (m)
Max. Bridge Span (m)
1992 Madrid-Sevilla 250 1,000 <40
2008 Madrid-Barcelona 350 3,000
Average > 50
Exceptional > 100
End - 2010 Madrid-Valencia 350 > 3,000
Average > 70
Exceptional > 200
SPAN (recommended) BRIDGE TYPE CROSS SECTION
Less than 30 meters PRECAST BEAM BRIDGE
SLAB BRIDGE (pre-stressed slabs)
More than 30 meters PRE-STRESSED BOX
3.1 Precast Beam Bridges
HSR Structures
PRECAST BEAM BRIDGES• Beams produced at the factory transported to the site
• Once beams are on deck concrete slab is applied
• Usual height/span ratio: 1/14
• Typology:– Double T beams no longer in use due to lack of torsion stiffness Track warping
problems– U shaped beams in use (below)
• Bridge type:– Mostly applied to simply – supported bridges. Also valid for continuous structure
• Constructive methods:– Cranes– Beam launching– Transversal shifting– Lifting
• Maximum span: 35 m (exceptionally 40 meters)March 4, 2011 Page 17
3.2 Slab Bridges
HSR Structures
SLAB BRIDGES
• Pre-stressed best beam depth/span ratios [1/16 – 1/20]
• Appropriate for urban-semiurban areas
• Types– Depending on slab depth
• Depth < 90 cm. solid slab• Depth > 120 cm voiled slab• Depth 90 cm – 120 cm varies
– Depending on span• < 30 meters: constant depth slab• Span 30-50 meters: variable depth slab
• Construction method Conventional centering
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3.3 Pre-Stressed Box
HSR Structures
PRE-STRESSED BOX
• Most widely used: monocelular – double track
• Box dimensions depend on bridge dimensions
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STRAIGHT EDGE CURVED EDGE
Span length < 50 meters > 50 meters Depth/ span
ratio 1/11-1/15 (center&sides) 1/11-1/15 (sides) 1/22-1/30 (center)
Minimim thickness top side
30 cm 30 cm
Minimim thickness
bottom side 30 cm 30 cm
Max. Side 3.50 m 3.50 m
3.4 Constructive Methods
HSR Structures
CONSTRUCTIVE METHODS (SPAN)
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METHOD STRAIGHT EDGE
CURVED EDGE
SPAN MOSTLY USED
CONVENCIONAL CENTERIN YES YES < 30 m (máx 50m) Slabs
PUSHED DECK YES NO 40-60 meters (máx 80 m)
• Box section • Bridges > 600 m • Performance: 20
meters / week
LAUNCHING GIRDER YES YES < 70 meters
Bridges > 600 meters
SEGMENTAL BRIDGE YES YES 70-100 meters
Not widely used for rail bridges (due
to shorter span)
HSR Structures
SIMPLY SUPPORTED VS. CONTINUOUS STRUCTURE
• Significant vertical loads + high speed Dynamic effects
• Need to impose strict deformation limits for:
- Rotation- Settlement
• To increase comfort & safety and reduce fatigue
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WITH RAIL EXPANSION DEVICE WITHOUT RAIL EXPANSION DEVICE BRIDGE LENGTH SIMPLY
SUPPORTTED SPAN
CONTINOUS STRUCTURE SIMPLY SUPPORTTED SPAN CONTINOUS STRUCTURE
L ≤ 350 feet (105 meters)
350 ≤ L ≤ 700 feet
0.14 ≤ L ≤ 0.75 miles
210 ≤ L ≤ 1,210 meters
0.75 ≤ L ≤ 1.5 miles
1,210 ≤ L ≤ 2,420 meters
CONTINUOS BEAMS SIMPLY SUPPORTTED BEAMS SUITED FOR HS STRUCTURES
Better response to breaking forces
3.5 Special HSR Bridge Typology
HSR Structures
Rombach Type Bridge: Viaducto del SOTO (Spain)• Designed: INOCSA – AECOM
Spain
• Continuous structure
• Length: 1,755 meters
• Span No.: 22
• Pier height: 77.5m
• Spans: center (132m arch), sides (52.5m), others (66m).
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