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March 2-4, 2016 Salt Palace Convention Center Salt Lake City, Utah
TRACK C: AIRSIDE ENGINEERING WORKSHOP: 2
Title: Technology Advancements in the Field: Stringless Paving
Speaker: Gary L. Mitchell, P.E., ACPA
Date: March 2, 2016
March 2-4, 2016 Salt Lake City, Utah
Stringless slipform paving technology
www.acpa.scholarlab.com
March 2-4, 2016 Salt Lake City, Utah
Already being done at numerous airports around the country
501-4.8 Placing concrete. -- a. Slip-form construction. The
concrete shall be distributed uniformly into final position by a self-
propelled slip-form paver without delay. The alignment and
elevation of the paver shall be regulated from outside reference
lines established for this purpose.
March 2-4, 2016 Salt Lake City, Utah
Introduction – What is Stringless Paving?
Alternative to conventional stringline paving.
Uses electronic guidance systems to replace pins, sensors, and “stringline.”
Electronic guidance system controls elevation and steering of the paving machine(s).
Sometimes referred to as 3D paving.
March 2-4, 2016 Salt Lake City, Utah
Combinations of these technologies.
Robotic Total Stations.
Laser surveying.
Global Positioning Systems.
3D models.
The concepts are similar, but there are options for the technology employed
March 2-4, 2016 Salt Lake City, Utah
Timeline of Development
1990
2000
2010
1990’s – Earthwork Controls Developed and Refined
1999 – First Paving, Curb & Gutter (Alabama)
2000 – First Street (Iowa)
2003 – First Highway (Belgium)
2001 – First Airfield Paving (Various)
2000’s – Paver Controls Refined
2013 – Use is Growing
2004 – First Published Research (Iowa)
March 2-4, 2016 Salt Lake City, Utah
• Step 1 – Create survey control network.
• Step 2 – Collect field survey data of existing surface.
• Step 3 – Design pavement/create 3D model; convert data for machine inputs.
• Step 4 – Transfer simplified model to the paving machine, set up 3D instruments, tie into controls; then pave.
STEP 1 STEP 3 STEP 4 STEP 2
March 2-4, 2016 Salt Lake City, Utah
Similarities and Differences
March 2-4, 2016 Salt Lake City, Utah
Accurate Surveying is Required!
Both stringless and stringline paving methods require establishing a control network (or reference) for accurate paving.
A string control method requires more labor intensive surveying to transfer the plan geometry to the grade.
Stringless paving requires additional equipment, training and 3D data to build the pavement to plan.
Both methods work and the accuracy of either starts with the survey controls!
March 2-4, 2016 Salt Lake City, Utah
Engineering plan and profile is transferred to grade by a survey crew for stringline-controlled paving.
Basic Differences – Use of Technology
– How design data is used. – The number of surveyed control points needed to
control the paving machine. – The opportunities for survey error. – The trueness of the line and grade that the machine
follows.
Engineering plan and profile is converted to 3-D model for stringless paving machine control.
March 2-4, 2016 Salt Lake City, Utah
Benchmark
Control Points (Paving Hubs–Pins)
Stringline survey crew must set up each paving hub individually for stringline-controlled paving. There are many chances to introduce or compound errors.
Survey Reference Point Working With Stringlines Requires Many Steps
March 2-4, 2016 Salt Lake City, Utah
March 2-4, 2016 Salt Lake City, Utah
Stringline Surveying – Setting Grade on the Stake.
March 2-4, 2016 Salt Lake City, Utah
Field Surveying and Set-up Requirements for Stringless Paving
Establish Control Network: – Control points established
from field surveying. – 2 person crew. – Control points tied to
known benchmark(s). – Should be positioned:
• Out of way of any operations.
• Where they will not be bothered by the public.
• To allow instruments for machine control to see at least three control points at all times.
March 2-4, 2016 Salt Lake City, Utah
The Typical Steps Working With Stringless Paving
1. Surveying control point locations in the field at about 250 ft intervals for total station control and even greater intervals for laser or GPS control.
2. Placing each control point.
3. Performing automated surveying of the project site to build the terrain model.
4. Developing 3D model from plans.
5. Error-checking the 3D model.
6. Setting up instruments on the grade and tying them into at least three control points for paving.
9. Moving machine into position & checking (validating) the pan elevation using the instruments before paving.
10. Checking radio and/or laser communication between instruments and paver.
11. Moving the instruments along the grade as paving progresses.
March 2-4, 2016 Salt Lake City, Utah
Benchmark
Control Points
The stringless survey crew must plan the location of control points. The number depends on terrain, urban development and instruments (total station, laser or GPS)
March 2-4, 2016 Salt Lake City, Utah
Time Efficiency Improvements with Stringless
– Reduces field surveying. – Eliminates labor intensive
stringline surveying for hubs and stakes.
– Eliminates need for string line, stakes and accessories.
– Reduces opportunities to introduce surveying errors.
– Reduces overall preparation time on the grade.
These efficiencies will save construction costs while the technology will improve paving quality!
March 2-4, 2016 Salt Lake City, Utah
Spatial Requirements Reduced with Stringless
– A string-controlled operation requires about 5 feet clearance on each side: • 3 ft. for paver track and workers.
• 1 ft. for hubs and stringline stakes.
• 1 ft. for safety devices
– A stringless operation requires 1-2 feet less clearance on each side.
– Benefits: • Increases phasing and traffic control
pattern considerations.
• Improves project feasibility.
• Provides safer access to grade for crew and trucks.
Stringless technology helps increase feasibility of concrete paving in tight areas.
5 ft.
March 2-4, 2016 Salt Lake City, Utah
Machine Control Improvements with Stringless
– Places engineer’s design directly into machine(s).
– Controls elevation, slope, and steer of machines with truer input.
– Reduces or eliminates cords created by stringline hubs/pins.
– Reduces wave patterns introduced by improperly tensioned stringline sensors.
The control points that link the 3D model to the real world are the key to paving accuracy.
March 2-4, 2016 Salt Lake City, Utah
Sensors for Controlling Machine Elevation and Position.
Stake
Stringline
Elevation Sensor Touches Top or Bottom of String
Steering Control Sensor Touches Inside of String
Grade Stake
March 2-4, 2016 Salt Lake City, Utah
Sensors for Controlling Machine Elevation and Position.
Sensors Require Hand Tuning to
Get Accurate and Smooth Paving
Results
March 2-4, 2016 Salt Lake City, Utah
Stringlines represent the pavement using a series of cords. The cords are easy to see in this curve – even with a close staking interval.
March 2-4, 2016 Salt Lake City, Utah
These cords are built into the pavement, as can be seen here with cords in a horizontal curve.
March 2-4, 2016 Salt Lake City, Utah
Stringless technology represents the pavement using mathematical equations representing tangents and curves (a “true” profile).
Smooth Curve
March 2-4, 2016 Salt Lake City, Utah
Eliminates cords in vertical curves.
Eliminates stringline factors affecting smoothness: o Sag (stringline expansion in hot weather).
o Push up (improperly tensioned sensors).
o Deviations from loss of contact.
o Bumps from knots/splices.
o Crew fidgeting with sensor controls.
Sensor Follows Sagging String
Sensor Pulls String if Not Properly Tensioned
Sensor Looses Contact
March 2-4, 2016 Salt Lake City, Utah
Quality and Process Control Benefits with Stringless
More precise machine control (digital) to much smaller increments.
Better and more consistent ride quality.
Control over material quantities and costs.
Lower yield loss.
Control of horizontal and vertical curves is significantly more accurate to the plan – arcs are paved versus a series of cords!
March 2-4, 2016 Salt Lake City, Utah
Stringless control of thick airport paving.
March 2-4, 2016 Salt Lake City, Utah
What’s Required to Transition to Stringless?
Contractor:
– Capital expenditures.
– Investment in control (control points).
– Understanding line-of-sight for instruments.
– Understanding weather and environmental considerations for total stations, lasers and GPS.
– Learning curve/training – dedication of trained personnel to run stringless operation and work with 3D model.
March 2-4, 2016 Salt Lake City, Utah
What’s Required to Transition to Stringless?
• Owner/Agency:
– Acceptance – allow its use.
– Adopt end-result mindset (specifications) for thickness, smoothness.
– Provide (or validate) control points.
– Provide plans and CAD files to contractor for use in creating 3D model.
– Learning curve/training for field inspection or construction management staff.
March 2-4, 2016 Salt Palace Convention Center Salt Lake City, Utah
Title: Technology Advancements in the Field: Stringless Paving
Speaker: Chad Ackley, P.E., CHA Consulting, Inc.
Date: March 2, 2016
March 2-4, 2016 Salt Lake City, Utah
Introduction
• Stringless technology/automatic grade control from the design engineer’s perspective
• Review of recent runway rehabilitation at Myrtle Beach International Airport using this technology
• Lessons learned
• Look ahead
March 2-4, 2016 Salt Lake City, Utah
MYR – Runway 18/36 Rehabilitation
March 2-4, 2016 Salt Lake City, Utah
MYR Project Overview
• Single runway airport
– (9,500 feet x 150 feet)
• 12 taxiway connectors
• Former USAF base
• Multiple pavement sections (asphalt and PCC); runway extended twice since original construction
• PCC ends structurally deficient for A320 and A321
• Non-standard longitudinal and transverse gradients
March 2-4, 2016 Salt Lake City, Utah
MYR Project Overview
• P-401 Asphalt Overlay
• Variable depth milling
• Two variable depth leveling courses
• Uniform 2-inch surface course
March 2-4, 2016 Salt Lake City, Utah
MYR Project Overview
• Tourism major component of the local economy
• Off-season and off-peak construction – September, 2014 to March, 2015
• Night work only – Weeknights: 10:45 PM – 6:45 AM
– Weekends: 11:45 PM – 5:30 AM
– Runway open to traffic during the day
• P-401-4.1 Weather Limitations – Surface temperature of underlying course (45 degrees F)
– Wilmington, NC terminal stopped shipping PG 76-22 binder for the surface course (too stiff to pipe in cold temps)
March 2-4, 2016 Salt Lake City, Utah
MYR Project Overview
• This job demanded speed and efficiency
• Stringless paving was key! (…else we may still be paving…)
March 2-4, 2016 Salt Lake City, Utah
Design Considerations
• Five surfaces
– Existing Surface
– Milled Surface
– 1st Lift Surface
– 2nd Lift Surface
– Finished Surface
• What’s the best way to present the information to the contractor?
– Contractors want the digital design files
– Release disclaimer
[1/19/2016 1:55 PM] Bravo, Laura:
March 2-4, 2016 Salt Lake City, Utah
Design Considerations
• Contractor imported our design elevations from MS Excel into their Carlson Takeoff Suite software
• We were able to compare each surface before construction started • Makes it easier on contractor, but ensures correct transfer of data
March 2-4, 2016 Salt Lake City, Utah
Design Considerations
As-built final surface compared very well to design surface; no payment adjustments
March 2-4, 2016 Salt Lake City, Utah
Lessons Learned
• Night construction = terrible project photos
• Temporary pavement markings
– Saved time each night by outlining using Polaris Brutus with spray can mounted to machine control equipment
March 2-4, 2016 Salt Lake City, Utah
Lessons Learned
• Expand the survey area – Automatic grade control equipment doesn’t like being near the edges
of the survey data
– Contractor recommended 300-400 feet of additional survey beyond the limits of construction
• AutoCAD drawings – presentation vs. functionality – Annotated/blocked/hatched features in AutoCAD do not show up on
machine control equipment in the field
– Redraw symbols (to scale) using polylines
March 2-4, 2016 Salt Lake City, Utah
Going Forward
Where do project digital files (*.xml, etc.) fit into the discrepancy chain?
AE firms: is our product transitioning away from paper plans to the digital design model?
March 2-4, 2016 Salt Lake City, Utah
Going Forward
• How does your QA/QC reviewer ‘check’ a digital file?
• Where to focus design efforts in plan production? – Paper
– Digital
– How will that work with FAA specs like P-152 (cross sections)?
• When do we distribute the digital files? – After contract award
– During bidding?
March 2-4, 2016 Salt Lake City, Utah
Going Forward
• Automatic grade control equipment is here to stay – As design engineers, we need to learn out to handle this
technology advance practically, professionally, legally and within our E&O guidelines
March 2-4, 2016 Salt Palace Convention Center Salt Lake City, Utah
Title: TECHNOLOGY ADVANCEMENTS IN THE FIELD STRINGLESS PAVING
Speaker: Robbie Pope, PE at GOMACO Corp
Date: March 2, 2016
March 2-4, 2016 Salt Lake City, Utah
Presentation Outline
What is 3D stringless paving?
Benefits of using 3DMC.
What technology is currently in the market?
Why are contractors moving away from traditional paving methods?
What infrastructure does a contractor need in place to implement
stringless technology?
What happens once the 3D technology is purchased and in place?
Workflow of Stringless Paving
March 2-4, 2016 Salt Lake City, Utah
What is 3D Stringless Paving?
Question:
What is Stringless Paving?
Answer:
A 3D Machine Control system that simplifies jobsite logistics, reduces costs and improves quality and safety
Question:
How does it work?
Answer:
It uses a variety of sensors and surveying instruments to monitor your machine’s real-time positions compared to a digital model to automatically control the movements of steering and elevation.
March 2-4, 2016 Salt Lake City, Utah
What is 3D Stringless Paving?
In short it removes the guidelines that traditionally run the length of the jobsite and replaces that with survey instruments and a virtual stringline.
March 2-4, 2016 Salt Lake City, Utah
What is 3D Stringless Paving?
A Brief History of Stringless Paving First machine automated tests using total stations occurred in Germany in 1997.
First construction application was high speed railway paved in Germany in 1998.
First road in USA both graded and paved without stringlines was on Sept. 14 1999 in Ida Grove Iowa.
Stringless Use on Airports Military RAF/USAF Fairford (UK); USAF Kirtland (NM, USA); USAF Lakenheath (UK); Belle Chasse Naval Reserve New Orleans, LO (USA); Homer Regional Airport, LO (USA); Travis USAF Cal USA; El Centro Cal, USA; Virgin Galactic Spaceport, New Mexico; Jacksonville USAF, Florida; Tulsa Air National Guard, Oklahoma;
Civil Zurich & Basel International (Switzerland); London Heathrow & Stansted, Edinburgh Intl., Farnborough, Luton Intl. (UK); Paris Charles de Gaulle (France); Atlanta Hartsfield Jackson Intl., Baton Rouge; St Louis, Missouri; Indianapolis, Indiana; Toulouse (France); Chicago O’Hare; Guadeloupe (Caribbean); Paris Orly (France); Charlotte, NC, USA; JFK Airport, New York, USA; Fort Lauderdale-Hollywood, Florida, Dallas Love Field; BWI, Baltimore International
March 2-4, 2016 Salt Lake City, Utah
What is 3D Stringless Paving?
Partial List of North American use of Stringless Paving Projects State Company Project NY Coldsprings, Surianello, Tutor Perini 90, JFK MI Toebe, AJAX 196, 75, 10, DTW PA Golden Triangle WV Hiway paving MD Cherry Hill Construction Andrews AFB IN Primco, Milestone, Walsh, FWI 69,31,24,IND IL Walsh, D's construction, MCI, ET Simonds 80,74,57,94,ORD KY Harper 416 WI Walsh 94 MO FWI, Millstone Bangert STL, 70, 270 AR Weaver Baily, Harper XNA Airport (NW Arkansas) TX MCM, HRT JV, Texas Sterling, Granite, Lonestar,Kiewit DAL, HRT, City streets in Lubbock, 26, 114, 635, Burleson (NTTA Chisholm Trail) GA Scruggs, MCI, APAC, Kiewit 75, ATL, 85, 92 SC Zachary, MCI, Lane 385, AFB in Charleston, 20 NC Hiway Paving, Zachary, Lane, Archer Western/Walsh Raleigh Durham toll road, CLT, Apex VA Hiway Paving FL Pepper, Kiewit, Archer Western, Head Inc Jacksonville AFB, FLL Airport, 95 LA Kiewit AFB OK Head inc. Tulsa Air National Guard KS Ideker Highway 24 NE Paulsen, Hawkins US-35, US-30, I-80, City streets IA Manatts, MCI, Flynn, Croell, MFT I-80, I-29, 680, I-35, HWY-20, 380, DSM, OMA, ALO, multiple county roads CO Kiewit NM Montoya Space port, 64 AZ Southwest, RL Wadsworth, Kiewit/Sundt 101 UT Provo River constructors JV, RL Wadsworth, Wadsworth Brothers Orem I-15, Logan US-10 ID CPC OR CPC CA Baldi Brothers, CC Meyers El Centro AFB, Travis AFB, 132, 4 NV Southwest Reno HI Baldi Brothers AFB Hawaii TN APAC Memphis Airport Alberta Flatiron Ontario Coco, O'leary 402 Quebec EBC Mexico Cemex
March 2-4, 2016 Salt Lake City, Utah
Benefits of using 3DMC
A 3DMC system simplifies jobsite logistics, reduces costs, improves quality and safety
Removes stringlines and pins from the jobsite
• Removes installation, maintenance & removal costs
• Increases work safety, especially at night
• Removes down time from stringline breaks/bumps during production
Puts the 3D job design directly onto the machine
• Eliminates survey setup errors in stringline influences
• No waiting for setting-out before production
• No dependency on setup – work wherever you have 3D data
• Increases productivity, quality and performance bonuses
Controls height, slope (and steer) of machines
• Delivers a precisely-constructed product
• Optimises amount of new material needed
• Reduces over-trimming/milling, overpouring
• Improves concrete yields and material cost savings
March 2-4, 2016 Salt Lake City, Utah
Logistical Advantages During and After Construction
Roadway is now open
Trucks no longer need to back up so far
No “Gates” in wireline needed
Better versatility moving through site
No lost time to tear down of wireline
Benefits of using 3DMC
Wireline Clearance
Track grade now only needs to be the width of the actual machine profile, allowing this technology to be used in much tighter spaces and confined areas.
March 2-4, 2016 Salt Lake City, Utah
Technology in Market Today
All 3 major developers of survey instruments have 3D Slip-Form Paving solutions.
March 2-4, 2016 Salt Lake City, Utah
Technology in Market Today
Overview of the instrument technology types
offered and their applications
Total Station
accuracy +/-0.001’
*line of sight
Slipform Pavers
Trimmers
Milling Machines
Curb & Gutter
Asphalt paving
Millimeter GPS
accuracy +/-0.01’
*with good satellite signal
Slipform Pavers
Trimmers
Milling Machines
Curb & Gutter
Asphalt paving
GPS RTK
accuracy +/-0.1’
*with good satellite signal
Slipform Paver**
Placer/Spreaders
Follow-up Machines
Curb & Gutter Steering
Asphalt Paving Steering
**used only in mixed modes with
other sensors on fill-in lanes
March 2-4, 2016 Salt Lake City, Utah
There are many different sensor choices and many different applications for each sensor
TPS
VS
GPS
Technology in Market Today
Choose your sensors wisely!
SO
March 2-4, 2016 Salt Lake City, Utah
Technology in Market Today
March 2-4, 2016 Salt Lake City, Utah
Why Contractors use it?
are expensive, time-consuming
and error-prone to install
are easily damaged before and
during paving
are easily misaligned (errors
increase costs)
are a significant site safety hazard
interfere with site logistics,
increase concrete delivery time,
haul costs, and reduce
productivity.
greatly increase pre-production
planning & surveyors workload
Because stringlines…
March 2-4, 2016 Salt Lake City, Utah
Why Contractors use it?
Good site engineers/surveyors are hard to find, and expensive
Stringlines don’t always ‘model’ the concrete design accurately
“Go in, pave & get out” ability minimizes machine standing time – ideal for
time-critical paving operations (e.g. ‘live’ airports, roads)
Estimated 50% survey cost reduction - one surveyor or engineer
manages the 3D system
Estimated 20% productivity increase (up to 50% in complex areas)
Direct construction from CAD design – no intermediate rework
One 3D model for trimming and paving = material cost savings
Advantages the paving contractors are seeing in implementing 3DMC
March 2-4, 2016 Salt Lake City, Utah
Contractor Infrastructure Required
March 2-4, 2016 Salt Lake City, Utah
3D Sensors – Total Stations
1” accuracy total station
Fully robotic operation
Automatic prism tracking
Simple setup and position fix
Can be used for any surveying tasks
10-12Hz measurement rate
Backlight & heater for night operation
Typical working Range ± 300ft
Tracking accuracy ±0.01 at 300ft
Contractor Infrastructure Required
Components Leica PaveSmart
March 2-4, 2016 Salt Lake City, Utah
Machine GPS
Supports GPS & GLONASS systems for
maximum operational time
Simple setup and position fix routine
Identical user interface to TPS – no
extra training required
Can be quickly removed from machine and used for any site surveying tasks
True 20Hz measurement rate
Typical Tracking Accuracy:
Position ±0.03FT
Height ±0.06FT
3D Sensors – GPS (for machine steer option only)
Contractor Infrastructure Required
Components Leica PaveSmart
March 2-4, 2016 Salt Lake City, Utah
Contractor Infrastructure Required
Machine
Computer
Radios
Slope Sensor
360⁰ Prism
Total Station #1
(Guidance)
Total Station #2
(Guidance) Total Station #3
(As-builts)
Survey
Control
Point
360⁰ Prism
Slope Sensor
Survey
Control
Point
March 2-4, 2016 Salt Lake City, Utah
PZL-1 (Positioning Zone Laser) Transmits Unique Laser Zone
Signal 500 Foot Diameter Auto-Leveling 4 Channel Operation Alkaline Batteries, NiMH
Rechargeable, & External Power
mmGPS Transmitter
Contractor Infrastructure Required
• PZS-MC (Positioning Zone Sensor for Machine Control)
Receives & Decodes the Laser Zone Signal
360o beam Detection Rugged, Shockproof Design IPX6 Waterproof DC8V~DC32V Power Supply
mmGPS Machine Sensor
Used in 2D & 3D applications Touch screen Windows XP Operator selectable views
GX-60
3DMC User Interface
March 2-4, 2016 Salt Lake City, Utah
Total Station Option
GX-60 Display • LCD Color Touchscreen
Machine Prism • integrated GPS+ antenna
Machine Radio Long range Bluetooth
PS-101 Total Station • 1” (arc-second) resolution • +/- 3mm at 100m • Fully Robotic
Contractor Infrastructure Required
March 2-4, 2016 Salt Lake City, Utah
Trimble PCS900
Consists of:
CB460 Display
• Color screen
SPS930 Total Stations
• 1” accuracy
• +/- 3mm at 100m
Machine Radio
MT900 Active Prism
MS992 GPS Receiver Head
Dual-Axis Angle / IMU Sensor
Contractor Infrastructure Required
March 2-4, 2016 Salt Lake City, Utah
Now what do we do with it?
We just bought all this stuff and nobody knows how to use it!!
Tips for Successful Implementation
Contractor Buy-In Training
• Provided by vendors on customer jobsites around the world
Experience • Many field procedures are new compared to using string
• It is a repetitive skill but the learning curve is not steep
Adoption • Field crews must fully adopt to be successful
Role changes • Added responsibilities for foreman/groundman
• 3DMC interface replaces wands for making real-time steering and grade changes
• Replace stringline crew with Field Tech • Crew member dedicated to setting up survey instruments and QC checks
• Data Prep - may be done in-house or contracted out
Equipment and Training up to date • Market is frequently changing/updating and releasing new products
March 2-4, 2016 Salt Lake City, Utah
Now what do we do with it?
We just bought all this stuff and nobody knows how to use it!! How can the owner/agent get involved in the construction process?
Tips for Successful Implementation
Agency Buy-In Knowledge
• A basic understanding of the process
Quality Control (includes both before and
after pave) • Check sub-grade before paving
• Verify digital model before paving
Field Verification • Obtain their own survey instruments for
QA/CQ
• Use Contractors instruments for QA/QC
Additional tools • Utilize other tools such as real-time
smoothness indicators and auto-survey &
as-built functions
March 2-4, 2016 Salt Lake City, Utah
Before you order the Concrete Trucks!
1) Establish Control FIRST! 2) Maintain control network and have quality check continuously throughout
the entire time frame of the project! 3) Know or define where the existing project (roadway) is today X,Y,Z 4) Know where the proposed project will be upon completion (model of
proposed) – Your yield is at stake! 5) Do a quality check BEFORE you pave! (i.e. dry run the machine) 6) Make corrective actions to the surface prior to paving if necessary!
Preferable Pre – project check list!
Workflow of Stringless
March 2-4, 2016 Salt Lake City, Utah
Workflow of Stringless
Stringless Paving vs Wire
Working with Stringline…
Inspect design – calculate setting-out lists for each lane
Setup a total station, survey each hub or pin position with total station (or GPS if accuracy isn’t important!)
Hammer (or drill) in each pin, minimum 1 line for each lane of concrete/asphalt
Check pin alignment & adjust if required
Survey and set stringline height on each pin (min. 2 men)
Install & tension clamps and stringlines
“Eyeball” & adjust stringlines before paving
Move machine into position, set sensors to stringline
Check machine position relative to stringlines
Start Production, monitor machine position
Ensure (or hope!) nothing disturbs or damages stringlines during paving/milling…
Reference
Point
Walk left 5ft!
Walk right 1ft!
Up a bit!
Down a bit!
STOP!
Reference
Point
March 2-4, 2016 Salt Lake City, Utah
Workflow of Stringless
Data Prep is Crucial
Don’t let it scare you – the 3D model is simply a digital representation of the stringline
The virtual stringline model now becomes one of the most important aspects of paving
The success of accurately and smoothly paving depends on the quality of the digital model
Built from Alignment Data, Profile Data, and Template Data
Built from Horizontal and Vertical Curves
Built from Station, Offset, and Elevation
Will the Owner/Agent/Designer provide this data?
How do we model the paving?
Grading model are typically for use with GPS guided machine – accuracy required ~ 0.1ft
Grading models are surface based and 2D linework is only for reference
Paving models are for Total Stations or Lasers – accuracy required ~ 0.01ft
Paving models are based on alignments (means paver steering is also automated)
Paving Models vs. Grading Models
March 2-4, 2016 Salt Lake City, Utah
Design software has different
tools for creating 3D Data
These packages are used by
designers from all aspects of
Owner/Agents
These packages below export generic formats that the manufacturer software can recognize
Linework = .DXF Surface= .XML Alignment Models= .XML
Workflow of Stringless
March 2-4, 2016 Salt Lake City, Utah
Surface Model Quality Assessment
Basic steps in prediction analysis on 3D model An example of how to preview theoretical smoothness of a 3D model
Open digital model in CAD software
Sample from 3D Polyline/Surface
Build Profile
Sample from Profile
Isolate data for ProVal
Create a Project
Add data from model
Run ride quality and/or smoothness quality
Make adjustments if necessary and run the check again
Workflow of Stringless
Quality analysis is more than just a overall number Look closer at the data to analyze for problem areas, specifically bridge ties, transitions into existing pavements and joint matching
– Overall the 3D Model looked reasonably good – IRI less than 30
– A closer look at the numbers in the continuous analysis shows problem areas where grinding may occur.
– Learn to use the different ProVal tools effectively so that we can better analyze our 3D models
Workflow of Stringless
March 2-4, 2016 Salt Lake City, Utah
Calibration Why and when to Calibrate?
Why?
• Precise paving
• Optimal machine performance
• Optimal concrete thickness & cost savings
• Prism locations, relative to Mould “Origin” , must be determined
• Slope sensors must be accurately adjusted (relative to machine & each other!)
When?
• At first installation (commissioning)
• At EVERY subsequent change of the machine (width change, disassembly/reassembly)
Risks if ignored?
Mis-matched slope sensors can cause machine “twisting”
• Poor concrete surface finish
• Risk of structural damage to machine (leg barrels, tracks are stressed) “jumpy” machine
Machine will not pave at correct elevation or position
Workflow of Stringless
March 2-4, 2016 Salt Lake City, Utah
Practical Issues… In the field!
How do we know what is going on without seeing the stringlines?
How do we know where we are in reference to the model?
What is the contractor doing to verify placement?
How does the Owner/Agent get involved in the Quality Process?
Workflow of Stringless
March 2-4, 2016 Salt Lake City, Utah
Field Adjusting the Machine on the fly
If position needs horizontal adjusting…
…just like stringline control
we can adjust position at
front and rear independently,
without stopping the paver
If the level needs vertical adjusting…
…just like stringline control
we can adjust all leg heights,
and draft independently,
without stopping paving
Digital Offsets, no hand cranking and
forgetting
Real-time steering and grade adjustments are easy
Workflow of Stringless
Practical Issues Moving the Robots (‘Leapfrogging’)
Maximum Range Robot-to-Paver is <= 300FT (*depends on conditions)
We don’t need to stop the paver – all done on the fly
Before maximum range is reached, move 3rd Robot to new position &
setup (Position & Orientation Fix).
Press ‘Swap Robot’ on computer
System switches control from #2 (or #1) to #3 Robot automatically
Move ‘old’ Robot to new position, setup and repeat procedure
Ensure enough Reference Points visible for Setup (Position & Orientation Fix)
* temperature, humidity, air quality
Workflow of Stringless
March 2-4, 2016 Salt Lake City, Utah
“Leapfrogging” Part 1 All Theodolites in “Start” Position
TS #3
TS #1
TS #2
Workflow of Stringless
“Leapfrogging” Part 2 Move Theodolite #3 ahead, Setup, Transfer Control (#2-#3)
TS #3
TS #1
TS #2
Workflow of Stringless
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“Leapfrogging” Part 3 Move Theodolite #2 ahead, Setup, Transfer Control (#1-#2)
TS #3
TS #1
TS #2
Workflow of Stringless
“Leapfrogging” Part 4 Move Theodolite #2 ahead, Setup, Transfer Control (#3-#1)
TS #3
TS #1
TS #2
Workflow of Stringless
March 2-4, 2016 Salt Palace Convention Center Salt Lake City, Utah
Please feel free to contact me at ay time by any of the listed means below:
Robbie Pope, PE
GOMACO Corporation
3D Controls Engineer
(712) 371-3991 Cell