Design Considerations and Efficient Construction of HSR Structures

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

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

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

(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

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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Thank You

[email protected]

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Design Considerations and Efficient Construction of HSR Structures

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