DRAFT B-301-1.0 base LOD sill abutment model example

Model feature example download package (.ZIP)

The DRAFT version 1.0 of the Base Level of Detail (LOD) sill abutment model feature example is available for review. This DRAFT example release is part of Wisconsin DOT's effort to update our design model standards by utilizing 3D design objects to communicate level of detail expectations and other geometric requirements of design models.

Additional information about the purpose of design model feature examples can be found at Design model standards update

The geometric elements of a Base LOD example will establish a feature-oriented standard for the minimum required level of detail for design model deliveries. These examples will define a standard that produces design models that are an accurate representation of design intent, and are consistent with plan sheets.

Design model features developed to a Base LOD will contain accurate geometric information, but less design geometry information than Advanced LOD features. Base LOD features are accurate, but may not be fully representative of proposed work.

Base LOD should focus designers' efforts on elements of design geometry that are most beneficial to construction project needs and representation of design intent. The Base LOD standard will minimize design efforts on elements that provide lesser construction project benefits.

Model feature examples define geometric requirements of design models including level of detail expectations and key elements of feature representation. This example represents the design of the earthwork embankment cone that supports a sill abutment for a typical overpass structure. It consists of a TOP and DATUM (finished earthwork) surface model of the roadway underneath the bridge, roadway approach to the bridge, and the earthwork cone including slope paving area.

As a Base LOD example, it must accurately represent elements of design geometry traditionally communicated on WisDOT plans. It should include all critical elements of design geometry for sill abutment earthwork in regard to representation of design intent. It should also include all critical elements of design geometry needed for construction operations. It will not be a complete representation of design geometry. Construction project users of the design model may need to interpret design intentions from the information provided to develop supplemental detail for a construction model to meet the needs of construction operations.

A Base level feature should contain sufficient detail to ensure the design concept is geometrically consistent with itself and with surrounding terrain. In other words, the Base design model ensures the feature is constructable.

1. Highly resolved and accurate design detail in critical areas
   1. 1 foot corridor frequency spacing in areas of
      1. Clear zone transition
      2. Slope paving
      3. Wing wall earthwork and slopes
   2. Standard detail in other areas (corridor frequency spacings from FDM 15-5-7.2.2.1)
2. Important breaklines
   1. Completed design should have highly detailed breaklines and design data representing
      1. Clear zone transitional elements
      2. Slope paving
      3. Earthwork grade at abutment

Design model files in Construction Data Packet required formats

These files are representations of the design model deliverables which would be included in contractor data packets (see FDM 19-10-43.10 for design delivery requirements and CMM 7-10.3 for construction responsibilities)

1. BaseLOD-SillAbut-dft1.xml
   1. TOP and DATUM (finished earthwork) DTM surfaces in LandXML v1.2 format, this file meets surface model delivery requirements for WisDOT contractor data packets.
2. ACAD-BaseLOD-SillAbut-CrdrBreaklines-dft1.dwg
   1. TOP and DATUM breakline file in AutoCAD format, this file meets breakline delivery requirements for WisDOT contractor data packets.
   2. All Civil 3D corridor graphical elements are also included in AutoCAD format, layer name conventions are used to identify elements used in the design surface model definition.
   3. Elements used in the design TOP surface model definition are identified by layers named specific to TOP elements.
   4. Elements used in the design DATUM surface model definition are identified by layers named specific to DATUM elements.
   5. Elements used in both the design TOP and DATUM surface model definition are identified by layers named specific to TOP/DATUM elements.
   6. Corridor elements not used to define surface model geometry are on generic corridor layers.
3. ACAD-BaseLOD-SillAbut-Datum3DFace-dft1.dwg
   1. DATUM (finished earthwork) surface model triangle file in AutoCAD format, this file meets TIN triangle delivery requirements for WisDOT contractor data packets.
4. ACAD-BaseLOD-SillAbut-Top3DFace-dft1.dwg
   1. TOP surface model triangle file in AutoCAD format, this file meets TIN triangle delivery requirements for WisDOT contractor data packets.

Non-Construction Data Packet files

These files are not Construction Data Packet deliverables:

1. C3D-BaseLOD-SillAbut-dft1.dwg
   1. Civil 3D design data that produced the model feature example. This file is provided for informational purposes only, it is not intended to convey Civil 3D Project delivery requirements or design model delivery requirements.
   2. Workflow used in development of the Civil 3D design data for this model feature example may not be consistent with best MDU workflow recommendations. It is one way to produce design content.
   3. Content of file and data structure is not consistent with Civil 3D project delivery requirements, all data is in a single dwg. Data was structured in this manner for convenience of sharing model feature example source data.
2. ACAD-BaseLOD-SillAbut-DatumContour-dft1.dwg
   1. DATUM (finished earthwork) surface model contours (0.2' major, 0.05' minor) and surface model boundary in AutoCAD format. Contour files are not required in WisDOT contractor data packets, but contours could be added as a required design deliverable if the contracting industry indicates they are useful. Contour files are produced from Civil 3D design data with little effort and are an effective visual representation of surface models.
3. ACAD-BaseLOD-SillAbut-TopContour-dft1.dwg
   1. TOP surface model contours (0.2' major, 0.05' minor) and surface model boundary in AutoCAD format. Contour files are not required in WisDOT contactor data packets, but contours could be added as a required design deliverable if the contracting industry indicates they are useful. Contour files are produced from Civil 3D design data with little effort and are an effective visual representation of surface models.
4. BaseLOD-SillAbut-CrdrBreaklines-dft1.pdf
   1. PDF provided for non-C3D users who would like to review model examples. 3D PDF file with graphical representation of model breaklines and additional corridor elements.
5. BaseLOD-SillAbut-Datum3DFace-dft1.pdf
   1. PDF provided for non-C3D users who would like to review model examples. 3D PDF file with graphical representation of DATUM TIN triangles.
6. BaseLOD-SillAbut-Top3DFace-dft1.pdf
   1. PDF provided for non-C3D users who would like to review model examples. 3D PDF file with graphical representation of TOP TIN triangles.
7. BaseLOD-SillAbut-DatumContour-dft1.pdf
   1. PDF provided for non-C3D users who would like to review model examples. 3D PDF file with graphical representation of DATUM (finished earthwork) contours.
8. BaseLOD-SillAbut-TopContour-dft1.dwg
   1. PDF provided for non-C3D users who would like to review model examples. 3D PDF file with graphical representation of TOP contours.

Slope paving

The slope paving area is the portion of the earthwork cone that falls underneath the bridge. See the outlined area in Diagram 1 #dia1 below.

The slope paving area of the sill abutment earthwork is a critical feature that is designed to a high level of detail in the example. This is a risk reduction measure that will help prevent issues on construction projects. Bridges are sometimes built early in construction project phasing, before the earthwork operation for the associated roadways is substantially started. When this happens, the abutment earthwork cone is constructed to support construction of the abutment, but earthwork of surrounding features may not be developed until later in the project. Contractors need to complete construction of the slope paving before the bridge girders are placed, while heavy equipment can still access the slope paving area. Sometimes the earthwork operations to construct the underneath roadway have not commenced, and the slope paving area must be shaped without the benefit of the entire area being constructed to grade. If the design geometry between the earthwork cone and the roadway features beneath the bridge has inconsistencies and those problems aren't discovered until after girders are set, reshaping the slope paving area without the benefit of heavy equipment access will require significant effort, and additional construction project costs may be incurred. Developing highly detailed design model geometry in this area will help prevent that type of construction project issue from occurring.

Diagram 1 #dia1

Underneath roadway clear zone

In this example, the roadway passing underneath the bridge transitions from a ditch section as it approaches the earthwork cone to a slope paving section at the earthwork cone. The design should define geometry with sufficient detail to ensure this transition area meets roadway design standards for safety and traversability. This example assumes a longitudinal transition slope should not exceed 10:1 within the clear zone, and TOP surface model ditch sections should be traversable throughout the transition area as defined in FDM 11-15-1.

Diagram 2

Diagram 3

Diagram 4

Diagrams 5 - 8 show the transition of 3 cross sectional features within the clear zone:

1. The drainage swale flowline from just off the shoulder under the bridge to the ditch flowline in the normal section.
2. The clear zone limits point from an elevated location in the slope paving area to the ditch backslope location in the normal section.
3. The subgrade shoulder point transition from a buried condition in the slope paving area to incorporation into the TOP surface model in the normal section.

Diagram 5

Diagram 6

Diagram 7

Diagram 8

Things to consider during your review of the model:

Level of Detail

1. Is there sufficient design detail for less complex project situations?
2. Are all critical geometric elements of the roadway project captured in this Base LOD example?
3. Does this level of detail support production of plan cross sections at traditional cross section locations and frequencies for this type of work?
4. What types of risks are introduced to our projects with the lesser amount of design detail compared to an advanced level of detail representation of the feature?
5. Earthwork cone transition from slope paving to wing wall slopes was purposely omitted because of the design effort needed to develop an accurate representation of how the different elements meet together. For less complex project situations, this detail element is considered to not be a necessity. Sufficient design information is provided to support construction model development, but some design intent interpretation and supplemental detail development will be necessary to complete construction models to the extent necessary to support construction operations. Does this approach make sense? What is your perspective on this approach?

Feature representation

1. Datum/Top configuration through slope paving area. Is this suitable?

   

2. Clear zone transition strategy and transitional elements. Is this appropriate design strategy?

File content and format

1. Questions for users of contractor data packets. Breakline file is a graphic representation of Civil 3D corridors with surface model definition elements identified by Layer naming. There are extra graphical elements in the file such as corridor links (cross section elements) at each corridor frequency location (including plan cross section locations, plus additional locations not in plan cross sections).
   1. Do users of contractor data packets see value or benefit in the provision of the extra content?
   2. Would identifying the transverse corridor links which are coincident with TOP or DATUM bring additional value to design models?
2. Question for users of contractor data packets. Is the contour file a useful deliverable as a representation of surface models?

Earthwork quantification

The Base LOD for sill abutments model example does not support surface-to-surface earthwork quantification, but average end area methodology solutions are possible. Future development of advanced LOD examples will help us assess the degrees of inaccuracy in earthwork quantities. A design workflow problem to consider, what earthwork estimating workflows would work best with this Base LOD model?

Info: Additional design elements could be developed in Civil 3D to approximate slope geometry for earthwork quantification, but those elements should not be included in the model unless the slope geometry is resolved accurately. (No information is better than bad information)

Geometric constructability verification

The Base LOD model doesn't contain information about the earthwork cone transition from slope paving back to the slopes projecting from the wingwalls. These areas can be modeled to a high degree of accuracy using Civil 3D design workflows, however the extra design effort to develop that additional detail may not be justified considering the project benefit. Design intent is adequately communicated without that extra information. Construction model development workflows could use this Base LOD design model as a foundation, and add supplemental detail as needed to support contractor operations.

Designers can spot check approximate slopes in the earthwork cone transition area by measuring between Base LOD model elements in Civil 3D. This example demonstrates why slope checking is necessary. The design goal is to not exceed 2:1 slope rates throughout the embankment. In this example, the slope measured from the corner of the earthwork ledge at the abutment down to the roadway clear zone is a 1.9:1, even though the slope paving itself does not exceed a 2:1. If this example were an actual design project, the designer could move the underneath roadway's clear zone transition further south to flatten out the earthwork cone transition area.

The Base LOD should provide enough information to ensure the embankment's geometric constructability and adherence to design standards, even if the details of the slope transitions are not fully represented in the model.