Implementing Vibration and Rail Gap Controls in Preliminary Design of Sound Transit Lynnwood Rail Link Extension

Transcription

1 Implementing Vibration and Rail Gap Controls in Preliminary Design of Sound Transit Lynnwood Rail Link Extension APTA RAIL CONFERENCE JUNE 2016

2 Project Location Lynnwood, WA

3 Lynnwood Link Typical LRT Aerial Structures

4 Preliminary Design Considerations Strength and Safety Passenger Comfort Site Constraints Maintenance Durability Cost Speed of Consideration Constructability Aesthetics Construction Impacts Client Preferences Contract Packaging

5 Typical & Maximum Span Length Strength (load support capacity) Accelerations/Vibrations Deflections/displacements Allowable rail gap length Construction methods Costs of superstructure vs. substructure

6 Light Rail Aerial Structure Performance Factors impact performances: Vibration Deformation Rail Gap

7 Light Rail Aerial Structure Preliminary Design Performances Safety Passenger comfort Durability Fasteners, etc. Resonance, etc.

8 Vibration & Deflection Compact form of matrix equation: [M] { x } + [C] { x } + [K] { x } = { f } for Preliminary Design?

9 Light Rail Aerial Structure Preliminary Design Allowable Performance Limits Vibration Deformation Rail Gap Structure Characteristics

10 Vibration & Deflection Control Criteria Project specific design criteria Euro Codes Other agencies AASHTO a = f (ω² ) For sinusoidal function ω = 2πf

11 Vibration & Deflection - Project Criteria DCM VIBRATION DEFLECTION First mode of natural frequency fn >= 2.5 Hz Deflection <= L/1,000 (LL + Dynamic) Vehicle and structure interaction analysis required if above criteria not met

12 Natural Frequency (Hz) Project Criteria - DCM DCM lower bound 2.5 Hz min Simple Span Length (ft)

13 Vibration (fn), Acceleration (a) & Deflection ( ) EURO CODES: Acceleration Safety: a <= 16.4 f/s² Acceleration Comfort: a <= 3.3 ~ 6.6 f/s² CALIFORNIA HSR: Natural frequency limit: fn >= L where L = effective span length (feet) Acceleration a Natural Frequency fn = g (L) EN :2003, Figure 6.10

14 Natural Frequency Limits vs. Span Length Euro Code The light rail guideway design frequency CA-HSR ST DCM lower bound 2.5 Hz Min. L = 138 ft.

15 Frequencies (fn) vs. Resonant Speeds (Vr) Natural frequency fn => 2.5 Hz Resonant speed Vr => 156 mph, >> 55 mph (design speed)

16 Vibration (fn), Acceleration (a) & Deflection ( ) a = f (ω² ), where ω = 2πf Level of comfort Very Good: a = 3.28 ft/s² Ratio L / is given in EN A1:2005 Figure A2.3

17 Span Length / Deflection L / Project Criteria - DCM 99.4 mph 74.6 mph 66 ft. 98 ft. 131 ft. 164 ft. Simple Span Length (m)

18 Rail Gap Design Criteria: Maximum rail gap <= 2 inches +/-

19 Major Factors that Influence Rail Gap Concrete strength (f c) Young s modulus of concrete (Ec) and rail (Es) Temperature range (TU) Rail fastener friction (Ff) & spacing (Sf) Rail vehicle acceleration/deceleration Supporting structure movement (Δ)

20 Rail Gap (Δ) Challenge A FOUR SPAN CONTINUOUS STRUCTURE ft ft ft ft. = Total length ft

21 Rail Internal Stresses & Gap

22 Rail Internal Stresses & Gap

23 Rail Gap MAXIMUM RAIL GAP (should the rail break) Total Δ (rail stresses, temperature, structural move, etc.) = 2.3 inches Accepted under this special condition (Long Span)

24 Preliminary Design Considerations Strength and Safety Passenger Comfort Site Constraints Maintenance Durability Cost Speed of Consideration Constructability Aesthetics Construction Impacts Client Preferences Contract Packaging

25 Aesthetics Related Structural Topics Superstructure (girders) type Typical sections Pier shapes & sizes Span lengths & layouts

26 Design Baseline Structural Type Baseline Segmental Box Girders Alternative Precast Tub Girders

27 PT Tub Girder Curve Affects Span Length Span Radius (ft.) (ft.) e (in.) - Eccentricity due to Curve

28 PT Tub Girder Curve Affects Span Length Span Radius (ft.) (ft.) e (in.) - Eccentricity due to Curve

29 PT Tub Girders Twin Boxes Web slant ratio 7:1 Girder Depth 8 ft. +/-

30 Segmental Box Girder Typical depth = 8 feet Convenience for maintenance works Suitable for typical span length Proportional to the deck width (twin tracks) Deck width (twin tracks) = 28-8 Soffit width = 10-6

31 Web Slant Ratio (V/H) AASHTO Standard 2.5V/1.0H Light rail girder 1.4V/1.0H Adjacent segment 3.0V/1.0H Light rail girder 1.1V/1.0H

32 Web Slant Ratio (V/H) TOWARDS VERTICAL MORE SLOPE Web appears shallower Soffit is narrower

33 Web Slant Ratio (V/H) 3.0V/1.0H 2.5V/1.0H 1.4V/1.0H 1.1V/1.0H Selected Web Slant: 2.5V/1.0H

34 Super-Elevation Adjust plinth heights instead of rotate the boxes Reduce vertical ups and downs of the tracks Reduce the length of vertical curves of the tracks

35 RECTANGULAR PIER SECTION Typical Pier Shape & Size

36 RECTANGULAR PIER SECTION Typical Pier Shape & Size

37 CIRCULAR (OCTAGON) PIER SECTION Typical Pier Shape & Size

38 CIRCULAR (OCTAGON) PIER SECTION Typical Pier Shape & Size

39 Pier Shapes and Sizes Column vs. Shaft Constructability

40 Pier Column Constructability WSDOT BDM Section WSDOT Standard Specifications, Section 6-19 Column Nominal Dia Max. Dia. Cover Max. Cage Dia Nominal Shaft Dia Metric Casing Dia Shaft Max (Outside) Reinf Dia Tolera nce Rebar ft. ft. in. in. ft. ft. in. in. in Note (1) Note (2) Note (1) Note (2) Assume up to three #11 mian reinforcing bar each bundle Assume up to three #14 mian reinforcing bar each bundle

41 Thank you! Questions? APTA RAIL CONFERENCE JUNE 2016