Design Considerations and Efficient Construction of HSR Structures

transcript

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]

March 4, 2011 Page 3

2. Loads And Actions Considered During HSR Structural Design

HSR Structures

LOADS AND ACTIONS

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

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.

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

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

3.3 Pre-Stressed Box

HSR Structures

PRE-STRESSED BOX

• Most widely used: monocelular – double track

• Box dimensions depend on bridge dimensions

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)

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

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

• Continuous structure

• Length: 1,755 meters

• Span No.: 22

• Pier height: 77.5m

• Spans: center (132m arch), sides (52.5m), others (66m).

Thank You

gonzalo.dediego@aecom.com

March 4, 2011

Design Considerations and Efficient Construction of HSR Structures

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