Use of Automated Machine Guidance within the Transportation Industry (2018) / Chapter Skim
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Pages 67-80
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From page 67... ...
NCHRP Project 10-77 67 CHAPTER 7: BEST PRACTICES FOR AMG DESIGN MODEL DEVELOPMENT THE IMPORTANCE OF 3D MODELING When a project is constructed using AMG, construction machines compare the position of ground engaging tools against an electronic three-dimensional (3D) model that resides in a computer on the machine.
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From page 68... ...
NCHRP Project 10-77 68 The model can then be turned over to the facilities operation group, which can use the model for asset management purposes, such as recording maintenance activities, facility conditions, and performance information. The model can also be used for recording accident events and as a basis for the next capital improvement in the future life cycle.
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From page 69... ...
NCHRP Project 10-77 69 adjusts for changes in gravity on a global basis. However, modelers assume that their project is on a Cartesian coordinate system, where there is an x and y axis (eastings and northings)
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From page 70... ...
NCHRP Project 10-77 70 Agency Prepares 2D Plan Drawings Agency Completes 3D Electronic Design Pavement Design Structural Design Site Conditions Surveying DOT/Government Contractor Agency Prepares 2D Plan Drawings 3D Model Provided 2D Drawings 2D Drawings Contractor Creates 3D Model for AMG Contractor Uses 3D Model for AMG Design Completed and Contracting Mechanism 3D M od el Road Requirements (size, location, ESALs, etc.) & Prioritization Figure 7-1.
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From page 71... ...
NCHRP Project 10-77 71 buildings are to be included in a 3D model to provide context for conceptual design reviews and public presentations. The 2010 survey results for this project indicated that the photogrammetric topographical collection method was the most prevalent for transportation agencies, followed by RTK GPS and total station surveying; as of the completion of this writing (2017)
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From page 72... ...
NCHRP Project 10-77 72 GENERAL PROCEDURE FOR DEVELOPING MODELS The actual development of a 3D design model is a multi-step process and the process is summarized Figure 6-2, based on information from Taylor (2010)
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From page 73... ...
NCHRP Project 10-77 73 Reference CAD Standards At the beginning of the modeling process, reference should be made to the computer aided design standards for the agency. Layering protocols are usually included in such design standards.
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From page 74... ...
NCHRP Project 10-77 74 parametric approach which is open to changes for the future AASHTO recommended values of "maximum allowable side friction factor, driver reaction time, braking deceleration, driver eye height, object height, headlight height, and inclination angle of top of headlight beam" (Vonderohe and Hollister 2013)
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From page 75... ...
NCHRP Project 10-77 75 Generate Final Files After the constructability review is complete and adjustments have been made, a process will have to be executed so that the model is designated as the final design model. In some cases, this may require the application of the digital signature of the designer of record.
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From page 76... ...
NCHRP Project 10-77 76 drawings. The shop drawings are examined by the agency or the designer and returned, noting any exceptions taken by the reviewer.
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From page 77... ...
NCHRP Project 10-77 77 perform data preparation tasks and to create machine guidance files from the model will vary greatly depending on what data is provided and the contractor's resources. In general, most contractors start the process by reviewing the 3D model and finding out which layers are relevant to their needs.
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From page 78... ...
NCHRP Project 10-77 78 Within construction contracting organizations, the creation, development, and maintenance of the models are tasked equally between estimator functional roles, dedicated modeling specialists, and outsourced consultants. After contractor personnel have developed a 3D model, they can use it for their own purposes.
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From page 79... ...
NCHRP Project 10-77 79 different view of data transfer according to the survey results for this project. About half of them responded that their products were capable of data exchange via LandXML and they ranked that methodology as the most important.
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From page 80... ...
NCHRP Project 10-77 80 • Overall site control - Geodetic - State plane coordinate referencing - Local control • Separate standards for various surfaces and elements that require various levels of accuracy (such as earthwork finishing versus paving versus storm sewer construction) • Horizontal and vertical accuracy • Measurement and calculation densities - Data collection gird sizes - Use of break lines - Pattern line densities • Completeness of design modeling effort - Definition of designing versus detailing - Methods for delineating parts of the model that the contractor will complete • When reviews are required - During design - During machine control model preparation - Protocol for executing reviews • QA/QC - Timing, type, and density of measurement - Protocol for review and documentation • Design changes and corrections during construction - Designer versus contractor responsibility - Review process • Construction closeout - Accuracy and density of as-built measurements - Modeling standards for documenting as-built locations - Inclusion of QA/QC data • Turnover of model for archiving and use for maintenance and operation
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