2010 Rail Conference

Vancouver, BC

APTA/AREMA

Joint Recommended Practices:

Embedded Track Design

Hugh J. Fuller, PE

AREMA / APTA JOINT

EFFORT• Goal: develop up-to-date recommended track &

infrastructure practices for urban rail transit

• How: combine the membership resources of APTA and AREMA

• Method: creating up-to-date recommended practices for rail transit design, construction and maintenance using known best practices and research findings

APTA/AREMA Joint Recommended Practices for the Design of Rail Transit Track

The Situation

in 2005

• The need for up-to-date design and construction standards for street-running, embedded track and non-ballasted tracks of various types was becoming critical

• Very few individuals with actual streetcar design and/or operating experience are left, and practically none on the rosters of the consulting firms responsible for designing these new systems.

The Situation

in 2005

• The demise of the supply infrastructure, both in-house at the Agencies and the supply firms, such as Bethlehem Steel, a major supplier of trackwork materials

• The considerable difference in organizational structure and membership support between AREMA and APTA is a complicating influence

The Situation

in 2005

• No real “standard,” proven designs

• Increased the costs of construction because some were over-designed

• Or under-designed because of lack of experience

• No single reference that dealt with the multiple complex issues

• Time to get a grip!

The Solution

Begins

• AREMA and APTA agreed to a working relationship to solve this problem

• Jointly approved Memorandum of Understanding

• AREMA will develop, codify and publish the up-to-date recommended best practices

• APTA will assist AREMA by providing volunteers from the membership of several APTA Technical Forums

The Recommended Practices Team• Co-Chairman – Craig Goodall – AREMA

• Co-Chairman – Hugh Fuller – APTA

• AREMA Committee 12 Chairman – Keith Powley

• APTA Track/ N&V Forum Chairman – Rick Brown

• APTA Chief Engineer – Martin Schroeder

• Other AREMA committees will be involved for some topics

The Joint Practices

Leadership

The Recommended Practices Team

• Non-Ballasted Track – Joe Shaffer, GCRTA

• Corrosion Control – Ed Wetzel, UTRS

• Sharp Curves – Dave Boate, VHB

• Special Trackwork – Transit – Tom Lee, Nortrak

• Clearances – Tom Irion, Metro King County

• Wheel/Rail Interface – Brian Whitten, ENSCO

• Embedded Track – Bill Moorhead, Trammco

The Working Group

Leaders

Embedded Track

Working Group

Embedded Track Issues

• Track geometry and alignment parameters; ride comfort, safety (may need adjustment regarding lateral acceleration rates and spirals lengths)

• Vehicle to track interaction; wheel to rail interaction, both vehicle and track maintenance implications, lubrication and friction control, critical wear criteria

• Design track modulus, vertical and horizontal (this might prove troublesome, as opinions vary considerably)

• Infill concrete; flangeways; allowance for wheel overhang, track drains, junction boxes, etc.

• Welded rail: welding, handling, placement, closure welds, de-stressing where possible

9

Embedded Track

Working Group

Embedded Track Issues to be Resolved by Research

• Wheel/Rail Interface - Can we standardize and reduce the unexplained proliferation of wheel profiles and canted vs. uncanted rail?

• Rail Welding – Can we reduce dipped welds by matching weld hardness to rail hardness?

• Track Slab Design – Do we need reinforcing steel in the track slab?

• Track Alignment Design – Can we increase the speed of light rail vehicles through curves?

10

Wheel/Rail Interface

A Few of the Many Wheel Profiles in Use Today

11

Rail Welding

• AREMA Manual of Railway Engineering dealing with rail welding qualification and quality control procedures uses the “Slow Bend Test”

• The Slow Bend Tests (SBT) requirements specified for Thermite Welding (TW) may require the manufacturers of welding kits to furnish portions that are softer than the joined rails in order to meet the specified minimum deflections for standard and high strength rails

• APTA/AREMA Embedded Track Working Group is now drafting RP language for publication in Chapter 12 dealing with welding qualification and QC procedures for rail intended for embedment in pavement.

12

Rail Welding

• The majority of the plastic yielding required to meet the SBT may take place in the TW and HAZ’s, not the parent rail

• The current SBT requirements do not have any provision for taking the IX of the rails/TW’s being tested into account

• Almost all European grooved rails have a cross section requiring the TW’s to have very high ductility so as to survive the SBD deflection requirements; high ductility often means “soft welds” – soft welds often result in dipped welds

• When rails are embedded in concrete pavement, the possibility of repair welding dipped welds/HAZ’s is almost non-existent

13

Rail Welding

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Rail Welding

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Embedded Track Slab

16

• There is no design standard for transit embedded track specifying the dynamic impact factor to be used in designing the track slab.

• A wide variety of dynamic factors are chosen, resulting in widely varying slab designs for essentially identical support conditions and operating parameters.

• The designs vary from the heavily reinforced through totally unreinforced.

• The ETWG is working on rationalizing the dynamic impact factors by obtaining measured vibration testing data and a compendium of factors currently used by designers, and will try to develop a recommended practice by melding those sources into a reasonable and safe set of standards, based on operating conditions.

Embedded Track Slab

17

Curve Unbalance

18

• A test program to evaluate ride quality for higher unbalance speeds on curves was organized

• To determine if a proposed higher unbalance (equivalent to 0.15g) than current AREMA standards (0.10g) is comfortable enough for short ride LRT service

• A standard LRV, equipped with an accelerometer with recorder, and car speedometer with recorder, operated multiple times over several curves

• 0.15g lateral acceleration (equal to 9 inches of unbalanced superelevation) vs. 0.10g (comparable to 6 inches unbalance)

Curve Unbalance

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The Recommended Practices Team

APTA/AREMA Joint Recommended Practices for the Design of Rail Transit

Track

• Non-Ballasted Track – Joe Shaffer, GCRTA

• Corrosion Control – Ed Wetzel, UTRS

• Sharp Curves – Dave Boate, VHB

• Special Trackwork – Transit – Tom Lee, Nortrak

• Clearances – Tom Irion, Metro King County

• Wheel/Rail Interface – Brian Whitten, ENSCO

• Embedded Track – Bill Moorhead, Trammco

The Working Group

Leaders

2010 Rail Conference

Vancouver, BC

APTA/AREMA

Joint Recommended Practices:

Embedded Track Design

Hugh J. Fuller, PE