Track Design Handbook for Light Rail Transit, Second Edition (2012) / Chapter Skim
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From page 602... ...
13-i Chapter 13 -- LRT Track Construction Table of Contents 13.1 INTRODUCTION 13-1 13.2 GENERAL REQUIREMENTS -- ALL TRACKFORMS 13-1 13.2.1 Project Procurement Methods 13-1 13.2.1.1 Design/Bid/Build 13-1 13.2.1.2 Construction Management-General Constructor (CMGC) 13-2 13.2.1.3 Design/Build 13-3 13.2.1.4 Design/Build/Operate/Maintain (DBOM)
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From page 603... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-ii 13.2.4.10.2 Survey 13-16 13.2.4.10.3 Document Control 13-17 13.2.4.11 On-Track Construction Equipment 13-17 13.2.5 Relocation of Utilities 13-17 13.2.6 Activate Detours 13-17 13.2.7 Quality Process 13-17 13.2.7.1 Developing the Quality Program 13-18 13.2.7.2 Checklists 13-19 13.2.7.3 Non-Conformance Reports 13-19 13.2.8 Reinforcing Steel (Embedded and Direct Fixation Track) 13-19 13.2.8.1 Epoxy Coated Rebar 13-20 13.2.8.2 Black (Uncoated)
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From page 604... ...
LRT Track Construction 13-iii 13.3.2.1.1 Plinth 13-34 13.3.2.1.2 Inserts in Invert 13-35 13.3.2.2 Rail Cant and Superelevation 13-35 13.3.2.3 Preparatory Work 13-36 13.3.2.4 Top-Down Construction (Recommended) 13-36 13.3.2.4.1 Check Guideway 13-36 13.3.2.4.2 Rail/Plate Support System 13-36 13.3.2.4.3 Handling Material 13-37 13.3.2.4.4 CWR 13-37 13.3.2.4.5 Some Recommendations on Packaging 13-38 13.3.2.4.6 Welding Rail 13-38 13.3.2.4.7 Surface Preparation 13-38 13.3.2.4.8 Setting the Track 13-39 13.3.2.5 Drill and Epoxy Method of Direct Fixation Track Construction 13-43 13.3.2.5.1 Surface Preparation 13-43 13.3.2.5.2 Scabble Concrete 13-43 13.3.2.5.3 Survey for Grout Pads 13-43 13.3.2.5.4 Pour Grout Pads to Rail Tolerances 13-44 13.3.2.5.5 Layout Hole Pattern 13-44 13.3.2.5.6 Drill Holes into Invert 13-44 13.3.2.5.7 Repair Grout Pads 13-45 13.3.2.5.8 Clean Holes 13-45 13.3.2.5.9 Mix Epoxy and Install Anchor Inserts/Bolts 13-45 13.3.2.5.10 Attaching Fasteners to Grout Pads and Setting CWR 13-45 13.3.2.5.11 Shim Rails to Elevation or Grinding the Grout Pads 13-45 13.3.2.5.12 Line and Gauge Rails 13-46 13.3.2.5.13 Thermal Adjustment 13-46 13.3.2.6 Embedding Inserts into Precast Segments 13-46 13.3.2.7 Top-Down Methodology Advantages 13-47 13.3.2.8 Lessons Learned the Hard Way 13-48 13.3.3 Construction Issues for Embedded Track 13-49 13.3.3.1 Construction Concept 13-49 13.3.3.1.1 Top Down 13-49 13.3.3.1.2 Bottom Up 13-49 13.3.3.1.3 Drill and Epoxy 13-50 13.3.3.1.4 Slab Concept 13-50 13.3.3.1.5 Tub Concept 13-50 13.3.3.1.6 Trough Concept 13-50 13.3.3.2 Preparatory Work 13-50 13.3.3.3 General Overview of Construction 13-51 13.3.3.3.1 Excavation and Drainage 13-51 13.3.3.3.2 Compaction 13-52 13.3.3.3.3 Installing Underground Electrical Conduits 13-52 13.3.3.3.4 CWR 13-52 13.3.3.3.5 Construction in the Urban Environment 13-52 13.3.3.3.6 Safety 13-53
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From page 605... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-iv 13.3.3.3.7 Welding Rail 13-53 13.3.3.3.8 Setting the Track with Isolation 13-53 13.3.3.3.9 Thermal Adjustment of Embedded Rail -- Required? 13-53 13.3.3.3.10 Placing Initial Concrete Only up to Base of Rail -- or Not 13-54 13.3.3.4 Lessons Learned the Hard Way 13-54
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From page 606... ...
13-1 CHAPTER 13 -- LRT TRACK CONSTRUCTION 13.1 INTRODUCTION The purpose of this chapter is to offer discussion on procedures and topics that are relevant not only to the construction of all types of trackforms but the entire construction process in general. Many instances of unsatisfactory construction occurred in part because the designers had little or no field experience.
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From page 607... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-2 in accordance with the plans, specifications, and other contract documents. "As-built" drawings are produced, and final payment is made to the constructor(s)
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From page 608... ...
LRT Track Construction 13-3 preliminary pricing of the in-progress design, but also the qualifications of the candidate CMGC firms and their proposed technical approach to the construction of the project. The owner, usually aided by an engineering firm, will review all proposals submitted and select the CMGC team that they believe will provide the best value.
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From page 609... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-4 As with CMGC, the schedules can be very short since construction can begin before the entire project is designed. This is an advantage but could also be the cause for modifying the work or the design if the pace of construction exceeds the ability of the designer to fully investigate all of the interfaces between facilities and systems.
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From page 610... ...
LRT Track Construction 13-5 ramifications for the success of the project, particularly with respect to the schedule. The two major material procurement options are owner furnished and constructor furnished, and each has advantages and disadvantages.
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From page 611... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-6 management process that includes both quality controls by the vendor and monitoring by the owner and the designer must be followed, including documentation, so that the products furnished to the constructors meet both the specified requirements and the schedule. 13.2.2.1.2 Advantages and Disadvantages to the Owner Advantages of owner furnished to the owner: • On a project that is an extension of an existing LRT system with previously established standards, if the owner furnishes the material to the constructor(s)
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From page 612... ...
LRT Track Construction 13-7 The owner must have a process in place to review and approve shop drawings prior to the constructor purchasing the material. Bear in mind that if any changes are identified during those shop drawing reviews, they may result in a claim or change order that in most cases will add cost to the project.
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From page 613... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-8 construction difficulty. Some designs are easy to build, some are hard to build, and some are impossible to build.
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From page 614... ...
LRT Track Construction 13-9 Chapter 8 covers this topic more extensively, the discussion below addresses stray current from a construction perspective. In a typical electrified rail transit system, the traction power current leaves the substation using either an overhead catenary system or a power rail (also known as "contact rail" or "third rail")
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From page 615... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-10 Products that can be used for electrically isolating the track are discussed in Chapters 5 and 8, and that information will not be repeated here. Note that the electrical isolation system should not prevent the rail from deflecting under load.
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From page 616... ...
LRT Track Construction 13-11 If electrical isolation is only checked at the end of the construction, any requisite repairs will be far more expensive than if the issue was discovered earlier. 13.2.3.4 Tolerances Realistic tolerances for manufacturing and construction must be identified in the bid documents and coordinated with each other so that the track system can meet the expected performance requirements.
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From page 617... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-12 emergency field modifications that could unintentionally jeopardize both the integrity of the track and the safety of the passengers. 13.2.3.5.1 Special Trackwork Fabrication Inspection Inspecting material and processes during all phases of the project is important.
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From page 618... ...
LRT Track Construction 13-13 them at lower cost. If such matters are not discovered until the construction phase, it typically results in delays, design changes, change orders, claims, counterclaims, and possibly even litigation.
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From page 619... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-14 13.2.4.4 Vehicular Traffic Management Especially if a project is in an urban environment, vehicular traffic must be taken into consideration. Detours should be identified and permits requested well in advance of construction.
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From page 620... ...
LRT Track Construction 13-15 prepared so that there is no lost time in production and claim negotiation. These types of materials may fall into the category of "unforeseen" conditions and may stop a job in its tracks.
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From page 621... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-16 13.2.4.9.3 Dig Safe The appropriate utility companies should always be notified prior to any excavation. Generally, on any LRT project, there has been extensive coordination with the utilities during the design phase of the project; therefore, most, if not all, of the utilities will have been relocated well in advance of track construction.
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From page 622... ...
LRT Track Construction 13-17 This survey may be very elaborate if the documents are brought to the 100% stage. This survey also forms the basis for interferences with utilities or structures.
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From page 623... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-18 forever without a good quality program (QP) during construction.
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From page 624... ...
LRT Track Construction 13-19 c. Plinth concrete placement d.
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From page 625... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-20 13.2.8.1 Epoxy-Coated Rebar If the method of controlling stray current is the "isolation" method, it is necessary to coat the reinforcing steel with epoxy. This adds another level of protection from stray current.
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From page 626... ...
LRT Track Construction 13-21 collecting some of this information, but the raw output data are generally not immediately useful without some analysis. Track geometry cars are generally programmed to detect deviations from a particular FRA track class and the raw output data need to be filtered to gain an accurate understanding of the actual conditions.
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From page 627... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-22 13.2.11.2 Safety Certification Safety certification, which is now an FTA requirement, is a process that begins during final design engineering and extends through the construction process. A safety certification process, managed by safety specialists, will result in certification checklists that must be completed at milestones in the design and construction process.
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From page 628... ...
LRT Track Construction 13-23 cause for a non-conformance report (NCR)
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From page 629... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-24 schedule. What is certain is that the constructor who is doing the trackwork will have appreciably different concepts about how the project can be constructed than those of the designer.
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From page 630... ...
LRT Track Construction 13-25 13.3.1.2.2 Handling Material All track material must be handled properly and the constructor should prepare and submit a material handling plan for every component. This plan should include the equipment to be used and the method of rigging as well as the type and size of the dunnage separating the layers.
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From page 631... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-26 13.3.1.2.3 Underground Systems Construction Even once earthwork has been completed to create the trackbed, it is not yet time to begin track construction. First, prior to installing the subballast, the constructors responsible for the installation of underground electrical ductwork and manholes should be required to complete as much of their work as possible.
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From page 632... ...
LRT Track Construction 13-27 placed, it needs to be compacted to the specified density and the finish elevations verified. Compaction is usually done with a vibratory roller, the larger the better.
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From page 633... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-28 Whichever method is chosen, it is imperative that the concrete ties lay flat and do not have ballast bearing at their centers as this will cause the ties to crack later in the process. Some ballast screeding equipment compensates for this by creating a slight concave depression along the center of the track.
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From page 634... ...
LRT Track Construction 13-29 track from ever staying in proper alignment. Then, the only way to fix the problem is to cut the rail and add or subtract rail as necessary.
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From page 635... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-30 Extra care must be taken when using these machines so they do not drop the tamping tools on top of a tie, damaging it. It is also necessary to set the depth that the tamper's work heads go into the ballast.
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From page 636... ...
LRT Track Construction 13-31 Rarely will the rail naturally be at the optimal neutral temperature when it is time to anchor it in place. It is therefore necessary to adjust the rail so it will be in a zero-stress condition at the target rail temperature.
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From page 637... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-32 In this example, the rounded answer is 6 ½ inch [165 mm]
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From page 638... ...
LRT Track Construction 13-33 It is essential that the two rails of a track be anchored at very nearly the same neutral temperature. A tolerance of plus or minus 5 degrees F [3 degrees C]
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From page 639... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-34 • Not poking ballast: If the ballast is touching the underside of the rail, the electrical isolation test will fail. Failure of the test is typically cause for an NCR.
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From page 640... ...
LRT Track Construction 13-35 construction methods since it is placed after the invert is poured, and the fastening devices or inserts are surrounded by the plinth concrete. 13.3.2.1.2 Inserts in Invert When inserts are placed in the invert or slab concrete, the most direct construction method is "bottom up".
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From page 641... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-36 • "Line" and "alignment" mean the same thing. This is the physical path that the track will follow.
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From page 642... ...
LRT Track Construction 13-37 devising the support system. Including them will bring out the problems that may be encountered so that solutions can be made prior to the construction.
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From page 643... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-38 longitudinal movement of the rail requires rollers be placed under the rail. Whichever method is chosen, it must be well thought out.
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From page 644... ...
LRT Track Construction 13-39 Dowels/stirrups projecting from the invert need to be straight and clean. If epoxy coated, their coatings should be checked and touched up as necessary before subsequent construction makes them difficult to access and inspect.
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From page 645... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-40 finished plinth for the rail fastener. The steel shim also prevents concrete from entering the voids on the underside of the direct fixation rail fastener.
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From page 646... ...
LRT Track Construction 13-41 bucket can be used. If there is access alongside the track, concrete can be placed directly from the concrete truck.
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From page 647... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-42 sufficient initial cure time, assuming proper concrete placement and curing procedures were incorporated. In colder weather, this may need some adjustment.
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From page 648... ...
LRT Track Construction 13-43 shimmed to provide the correct rail profile within tolerance and all rail fastener anchor bolts have been properly torqued. Thermal Adjustment: Matching the concrete and rail stresses is an important part of this activity.
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From page 649... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-44 pitch on the grout pad is incorrect, it will affect the cant of the rail and will generate an improper wheel-to-rail interface. 13.3.2.5.4 Pour Grout Pads to Rail Tolerances The grout pads must now be poured.
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From page 650... ...
LRT Track Construction 13-45 13.3.2.5.7 Repair Grout Pads After holes are drilled into the grout pad and the invert, some pads may be damaged or broken. These must be repaired properly in order to maintain a proper bearing surface for the fastener.
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From page 651... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-46 Shimming and re-canting can change the horizontal alignment and track gauge. For this reason, it is advisable to correct the vertical parameters first.
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From page 652... ...
LRT Track Construction 13-47 a variety of lengths so as to provide a reasonably consistent amount of thread engagement. Verification that the appropriate length bolt has been used at a particular location would be very difficult and tedious.
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From page 653... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-48 • It is always more cost-effective to do it right the first time. Re-work is costly and will affect both the quality of the track structure and the money aspect to achieve the tolerances.
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From page 654... ...
LRT Track Construction 13-49 risk. Rail temperatures rise dramatically during the morning and then level off for many hours before finally decreasing after sunset.
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From page 655... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-50 13.3.3.1.3 Drill and Epoxy When drilling holes in concrete and placing inserts or threaded rods, it must also be performed within the track tolerances. In some cases, these tolerances have been set to 1/16 inch [1.5 mm]
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From page 656... ...
LRT Track Construction 13-51 • Determining accessibility, that is, for each discrete activity, how the constructors will get materials, equipment, and labor to and from the worksite. • Identifying the volume of vehicular traffic for the purpose of road closures and detours.
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From page 657... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-52 stone and wrapped in a filter fabric. Cleanouts are typically placed at strategic locations, mainly in the bottom of vertical curves.
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From page 658... ...
LRT Track Construction 13-53 13.3.3.3.6 Safety Safety is the number one concern of all parties involved including the general public. A professional, well-trained safety engineer should be employed and always invited to meetings offering a perspective from a safety point of view.
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From page 659... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-54 placed and cures. Notably, the concrete pour itself will have temperature range restrictions (typically 40° to 95° F / 4° to 35° C)
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From page 660... ...
LRT Track Construction 13-55 • Not testing the boot or isolation method: If the boot is not tested for holidays prior to placing concrete, the track-to-earth resistance test may fail. If this test fails, it is quite an ordeal to locate the problem.
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From page 661... ...
Track Design Handbook for Light Rail Transit, Second Edition 13-56 a safe and quality product for themselves and their families to use. It is the responsibility of everyone on the project to do their best to achieve this.
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