-
Structural Timber and Concrete Level Of Development (LOD): When
to Draw the Line and Where to Model It! IKERD Consulting: Will F.
Ikerd, PE, CWI, LEED AP, Principal, President ITW Building
Components Group: Steve Bumbalough, Product Manager, Global
Software Development IKERD Consulting: Brenda Herrera Ikerd, CFO,
(English & Spanish Version, AU Online)
Code SE4912 (Las Vegas, Live) Companion Virtual Personations:
SE5475 (Virtual English) | SE5118 (Virtual Spanish) Printed
2011-11-13
Description: This class will provide an in-depth discussion of
the level of development (LOD) of structural timber and concrete
models at the different stages in a building lifecycle: design,
construction and ownership. We will consider the new AIA BIM
Protocol Exhibit E202 that defines models on a scale of 100 to 500.
The class will cover how structural timber and concrete models are
used by architects, mechanical engineers, construction managers,
sub-contractors, and fabricators. Most importantly, the class will
discuss how each of these stakeholders uses timber and concrete
structural models differently and need different content. We will
demonstrate how the newly issued Structural Engineering Institute
LOD BIM (authored by speaker Will Ikerd) can be used to define team
expectation of what should be modeled. Practical examples of model
development issues will be shown, along with effective approaches
to resolve the challenges of using the SEI LOD model as an early
BIM planning tool.
Learning Objectives At the end of this class, you will be able
to:
Describe what LOD is. Identify who LOD should be used on your
project. Describe good practices for BIM models when working with
teams on collaborative projects.
Speakers: Will Ikerd, PE, LEED AP [email protected] Principal,
President IKERD consulting
Steve Bumbalough [email protected] ITW Building Components Group
Product Manager, Global Software Development
Brenda Herrera Ikerd [email protected] Principal, CFO IKERD
consulting
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Structural Timber and Concrete Level Of Development (LOD): When
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About the Speakers: Will Ikerd, P.E., CWI, LEED AP e:
[email protected] Will Ikerd is a nationally recognized consultant in
structural engineering and building enclosures utilizing Building
Information Modeling in both design and construction. Will also
specializes in implementing BIM strategies for construction
management firms interested in expanding their work in Virtual
Design and Construction (VDC). He co-chairs the national American
Society of Civil Engineers (ASCE) Structural Engineering Institute
- Council of American Structural Engineering (SEI-CASE) committee
on BIM, is co-chair of the BIM Forum's Designer's Sub-forum, and
chairs the Structural Engineers Association of Texas Committee on
BIM. Will is also a member of American Institute of Steel
Construction (AISC) Technology Integration (TI) committee for the
steel industry use of BIM and a member of American Concrete
Institute (ACI) 131 Committee on BIM for concrete. He is a
practicing professional engineer who frequently speaks and writes
about BIM, civil, and structural engineering, and building
enclosure design. He is Principal at IKERD Consulting LLC and can
be reached at [email protected].
Steve Bumbalough e: [email protected] Steve Bumbalough is
Product Manager for Global Software Development within the ITW
Building Components Group. ITW is a global diversified manufacturer
of products that cross over several major market segments such as
Industrial packaging, Food Equipment, Polymers, Transportation, and
Construction Products. Founded nearly 100 years ago in 1912, ITW
started off as a small company manufacturing hand tools and
components for the transportation and communications industries
prior to WW1.
Today, ITW has a market cap of roughly $24B with over 5000
product lines and 60,000 employees. We are structured of over 825
different business units in 52 different countries. ITW likes to
foster growth thru product innovations, extending current products
to new industries and acquiring businesses that improve offerings
to their current customer base.
One of ITWs guiding principles is the 80/20 principle which, in
a nutshell, simply acknowledges that 80% of a companys sales are
driven by 20 % of its products sold to key customers. In the truss
and wall panel industry the 80 is represented by the light frame
wood industry. Between builders and the supply chain, residential
and light commercial markets remain one of the most highly
fragmented in the construction industry as a whole. So providing
solutions to connect these dots and define levels of development
for the digital models based on corresponding deliverables is what
ITW does. Drawing a home and framing it, optimizing it, and
manufacturing it from a single model is revolutionizing BIM for the
timber marketplace.
Brenda Herrera Ikerd e: [email protected] Brenda Herrera Ikerd is a
founding partner and majority owner of Ikerd Consulting LLC and its
subsidiary i2concepts.com, a building information modeling and
technology integration consultancy that focuses on the use of
Virtual Design and Construction (VDC). She has worked in design and
construction in the United States and Mexico since the mid-1990s
before starting her BIM and VDC consulting firm in 2003 that
specializes in the areas of structure and building envelope. She is
currently co-authoring a book on VDC with Autodesk Navisworks
software in both English and Spanish. She can be contacted at
[email protected].
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Contents Description:
.........................................................................................................................................
1Learning Objectives
............................................................................................................................
1Speakers:
............................................................................................................................................
1About This Session & Paper
...............................................................................................................
4Definitions
...........................................................................................................................................
4Ikerd's Rules Of Thumb for Design Level Structural Modeling
(100-350 LOD) .................................. 71. Avoid
Re-modeling, Strive for Collaboration (IFC & CIS/2):
................................................. 72. Clearly
Define the Local X,Y,Z Origin
...................................................................................
73. Model Typical 1/8" Plan Content for Design (LOD ~300)
..................................................... 84. Model
Structure as it will be Constructed:
............................................................................
85. Do Not Duplicate Model Content Across Disciplines (A, S, &
MEP) ..................................... 86. Use Shared Model
When Two Disciplines Need to Control the Content:
............................. 87. Don't Assume Construction Ways
& Means During Design
................................................. 88. Match BIM
Material with Project Specifications (LOD 300)
.................................................. 99. Have Senior
Engineers in Responsible Charge Open & Review their Models
..................... 910. Not All Steel, Concrete, Masonry and
Wood Content is Structural ....................................
1011. Train the team Inside & Out
................................................................................................
10About the E202 OBJECT CLASSIFICATION UniFormat & MasterFormat
....................................... 11Hierarchical Structural
LOD Model, version 2010.11
........................................................................
13Model Management
..........................................................................................................................
15Initial Responsibilities of the Structural Model
..................................................................................
15File Formats
......................................................................................................................................
15LOD 100
............................................................................................................................................
17LOD 200
............................................................................................................................................
18LOD 300
............................................................................................................................................
19LOD 350
............................................................................................................................................
20LOD 400
............................................................................................................................................
21LOD 450
............................................................................................................................................
22LOD 500
............................................................................................................................................
23Example, Tilt-Up Panel Concrete (CSI MF# 03 47 13) & Shared
Models ........................................ 24Resources &
Bibliography
.................................................................................................................
29
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About This Session & Paper This paper suggests protocols,
expected levels of development, and authorized uses of Building
Information Models in the structural aspects of a project. It also
recommends specific responsibility for the development of
structural model content to a defined Level of Development at key
project milestones that are to be developed by the project teams.
This paper is only meant as a guide to aid project teams in
discussing the structural level of development on their projects
and should not be used without a thorough consideration of the
contents application and consequences. This paper references the
AIA E202 (American Institute of Architects [AIA], 2008) which is a
document that provides a framework for defining model definition.
In addition to the E202, the session will present information from
the authors work as well as content that they have adapted from the
Consensus Doc 301 BIM Addendum (ConsensusDOCS, 2008) , the AISC
Steel Detailing manual (American Institute of Steel Construction
[AISC], 2009) and ACI's concrete reinforcing detailing manual
(American Concrete Institute [ACI], 2008). Finally, examples are
shown on the structural LOD that could be applied to most typical
projects. The paper also includes sample general notes related to
BIM in structural construction documents, and an excel spread sheet
tool to aid in defining a projects structural LOD. Project contract
forms such as design-bid-build, design-build, design-assist and IPD
will be mentioned but are beyond the focus of this session. It is
assumed that regardless of the project form, all members of the
design team can work together and collaborate with the construction
managers team.
Definitions The following are common definitions used in this
paper that have been adapted from the AIA E202 and the 301 BIM
Addenda.
Building Information Model (BIM) is defined as a relational
database of building objects that stores information such as
geometry, material, schedule, cost and many other aspects of the
objects. A Building Information Model(s) is a digital
representation of the physical and functional characteristics of
the Project it is created for. Building Information Modeling means
the process and technology used to create the models.
Federated Model is defined as a relational database of building
objects that store information such as geometry, material,
schedule, and cost that is created from two or more separate
models. An example of a federated model would be the combination of
an architectural BIM, a structural BIM and a MEP BIM. The 301 BIM
Addendum defines a Federated Model as "a Model consisting of linked
but distinct component Models, drawings derived from the Models,
texts, and other data sources that do not lose their identity or
integrity by being so linked, so that a change to one component
Model in a Federated Model does not create a change in another
component Model in that Federated Model."
Level of Development (LOD) in the AIA E202 describes the level
of completeness to which a Model Element is developed (Architects,
American Institute of, 2008). LOD should only be used to describe
individual model objects. It is an incorrect application of LOD to
refer to an overall model as a particular LOD, rather a model is a
collection of objects that are varying LODs.
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Level of Detail (LOD) is a deprecated term that should no longer
be used in describing BIM content. The level of detail of model
object geometry is often very misleading as a measure of the
quality of the information that objects represents. As an example,
a steel open web joist in Revit Structure looks highly detailed at
the fine level of display. However, the web geometry is only
suggestive and not developed. The geometry detail is very precise
but the information the object conveys is in-accurate and not
developed. For this reason, the AIA and the AGC BIM Forum use the
term Level Of Development to describe a model object.
Model Element is defined by the AIA E202 as a portion of the
Building Information Model representing a component, system or
assembly within a building or building site. For the purposes of
this paper focused on structural content, Model Elements are
represented by the Construction Specifications Institute (CSI)
MasterFormat classification system with cross referencing to the
Omniclass system.
Model Element Author is defined by the AIA E202 as the party
responsible for developing the content of a specific Model Element
to the LOD required for a particular phase of the Project. Model
Element Authors should be identified at the beginning of a project
in the LOD table that accompanies this document.
Model User is defined by the AIA E202 as any individual or
entity authorized to use the Model on the Project, such as for
analysis, estimating or scheduling.
Construction BIM is defined by the 301 BIM Addendum as "a Model
that (a) consists of those aspects of the Project that are to be
modeled as specified in the BIM Execution Plan prepared pursuant to
this Addendum; (b) utilizes data imported from a Design Model or,
if none, from a designer's Construction Documents; and (c) contains
the equivalent of shop drawings and other information useful for
construction." As a reference, the authors consider this a BIM with
a LOD greater than 300 as described in this paper.
Contribution is defined by the 301 BIM Addendum as " the
expression, design, data or information that a Project Participant
(a) creates or prepares, and (b) incorporates, distributes,
transmits, communicates or otherwise shares with other Project
Participant(s) for use in or in connection with a Model for the
Project." This is typically adding or modifying a BIM to change its
LOD.
Contributor is defined by the 301 BIM Addenda as "a Project
Participant who makes a Contribution." In the structural domain
these would include Owners, Architects, Construction Managers,
Steel Fabricators, and Erectors.
Design Model is defined by the 301 BIM Addendum as "a Model of
those aspects of the Project that (a) are to be modeled as
specified in the BIM Execution Plan prepared pursuant to this
Addendum and (b) have reached the stage of completion that would
customarily be expressed by an Architect/Engineer in
two-dimensional Construction Documents. This shall not include
Models such as analytical evaluations, preliminary designs,
studies, or renderings. A Model prepared by an Architect/Engineer
that has not reached the stage of completion specified in this
definition is referred to as a Model." This is typically a BIM with
a LOD less than or equal to 300.
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Drawings are defined by the 301 BIM Addendum as "(a) those
two-dimensional plans, sketches or other drawings that are Contract
Documents under the Governing Contract and are created separately
from, and are not derived from, a Model and (b) those
two-dimensional projections derived from a Model supplemented with
independent graphics and annotations specified by the Parties to be
Contract Documents."
Full Design Model is defined by the 301 BIM Addenda as a Model
consisting of coordinated structural, architectural, MEP and other
Design Models designated in the BIM Execution Plan to be produced
by the design team." This is typically comprised of BIMs with LODs
of 300 but may require greater LOD than 300.
Level of Development 350, Pre-construction Coordination Model
Elements is defined by the author as that content that goes beyond
what designers have information to show but is less than a
manufacturing level of development. This could include construction
engineered items such as light gage kicker locations, open web
joist web member configuration, miscellaneous steel braces, and
curtain wall systems. This content is not always available from
designers due to the information being contingent on which
manufactures are selected by the contractor. However, content such
as these can effect 3D spatial trade coordination and is typically
needed before full fabrication level of development model elements
(LOD 400) can be made. Models with LOD of 350 can be a hybrid of
manufacturing level information that is known along with 3D massing
based on rational assumptions for that content that falls short of
a LOD 400.
Level Of Development 450, Site Construction \ Erection Content
Model is defined by the author as that content that goes beyond
what is needed in the LOD 400 fabrication model to include
temporary building content that is used during onsite construction.
This could include construction items such as erecting braces, form
work bracing, shores, back shores, scaffolding, and cranes. This
content can be beneficial when conducting site planning and 4D
scheduling of the construction.
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Structural Timber and Concrete Level Of Development (LOD): When
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Ikerd's Rules Of Thumb for Design Level Structural Modeling
(100-350 LOD) The following are my opinions on eleven topics I
believe are fundamental to workable model element development in
the design and construction of structures. Some of them relate more
to sociology than technology (9, 10, and 11). As you review them,
please send your comments and feedback to me ([email protected]). Below
is a summary of my eleven rules of thumb followed by a more
detailed definition of each:
1. Avoid Re-modeling, Strive for Collaboration (IFC & CIS/2)
2. Clearly Define the Local X,Y,Z Origin During Design 3. Model
Typical 1/8" Plan Content for Design 4. Model Structure as it will
be Constructed 5. Do Not Duplicate Model Content Between A, S &
MEP 6. Use Shared Model When Two Disciplines Need to Control A
Given Content 7. Don't Assume Construction Ways & Means During
Design (Ask!) 8. Match BIM Material with Project Specifications 9.
Have Engineers in Responsible Charge Open & Review Their Models
10. Not All Steel, Concrete and Wood Content is Structural 11.
Train the Team Inside & Out on Structural BIM LOD
1. Avoid Re-modeling, Strive for Collaboration (IFC &
CIS/2):
Where possible, avoid modeling content that will have little
downstream value. Most 3D structural detailing applications used do
not readily import Revit content beyond the basic standard member
information. As an example, approximately 90% of the North American
steel detailers working in 3D are using one of two non-Autodesk
applications for steel detailing. To date, these common steel
detailing applications do not readily read in any custom families
such as connections, gusset plates, and built-up members. Strive
for modeling content that will export to IFC and CIS/2 formats when
possible. Critically review the value of modeling content if it
cannot be used downstream in construction via model hand-off or
export.
2. Clearly Define the Local X,Y,Z Origin The project general
notes and specification should clearly define the local relative X,
Y, Z coordinates that other trades will use in construction that
are coordinated with the structural model. I typically prefer
defining the X,Y coordinates of the origin (0,0) at the southwest
most column grid intersection with a south and west offset of 10,
100 or 1000 feet depending on the project size. The southwest
column intersection is chosen so that the structure is in a
positive X-Y coordinate system. The offsets of 10, 100 or 1000 feet
south and west of the origin are so that any portions of the
building that extend south or west of the project origin grid
intersections will also be within a positive X-Y coordinate system.
The Z elevation should be defined as 0, 100' or absolute elevation
depending on firm preference. I typically use a relative 100
elevation. We also establish plan north as being in the positive Y
direction.
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Structural Timber and Concrete Level Of Development (LOD): When
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These rules above form the basis of the projects local relative
building coordinate system. This process aids linking the
structural model to 3rd party applications that are based on
traditional CAD coordinate systems. A benefit of defining the local
relative origin early and stating it in the projects general notes
is so other models that are developed for shop drawings from the
construction documents have a point of reference to follow when
they are submitted for review. This local relative building
coordinate system is also tied back to the civil engineers state
plane coordinate system. The civil state plane absolute coordinate
system will then have a set relationship with the structural local
relative coordinate system of an X, Y, and Z offset and a Z-axis
rotation. Using this set relationship between the civil absolute
and structural relative coordinate system, all federated project
models can be easily converted to absolute or relative systems
depending on the owners preference in their facility management
models (LOD 500).
3. Model Typical 1/8" Plan Content for Design (LOD ~300) For
design documents (LOD ~300) model those elements that would
traditionally appear on a 1/8" scale structural plan.
4. Model Structure as it will be Constructed: Model as it is
built at LOD 300 and higher. Material strengths and other similar
items should be modeled as they are specified in the construction
documents.
5. Do Not Duplicate Model Content Across Disciplines (A, S,
& MEP) Do not duplicate model content in different design team
models. Rather create a shared model with that shared content that
is linked into the structural and architectural model for
example.
6. Use Shared Model When Two Disciplines Need to Control the
Content: Use a shared model when two or more designers need to
control model elements. Structural content that is a candidate for
a shared model would be structural slabs with architectural
recesses, load bearing tilt-panels with architectural reveals,
miscellaneous support steel and lentil shelf angles, and interior
masonry walls.
7. Don't Assume Construction Ways & Means During Design
Structural design (LOD
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Structural Timber and Concrete Level Of Development (LOD): When
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9
a. Concrete pour breaks and construction joints in continuous
concrete sections.
b. Tilt-wall panel numbers for erecting sequences.
8. Match BIM Material with Project Specifications (LOD 300) The
material names, strengths and other properties used in the
structural BIM shall be correlated with the project specifications
and general notes. Structural model materials should match those
that will be used in the design. My preference is for firms to
develop a consistent color template for their structural materials
that will aid in checking model content. Projects with existing
structures for example that have A36 steel wide flange members with
new construction with A992 steel should be modeled with the proper
materials for each. Concrete should similarly have a separate BIM
concrete material property for each distinct concrete mix design
shown in the projects general notes and specifications. This may
mean there will be a 3000 psi mix with air-entrainment for exposed
concrete members and a second 3000 psi mix without air-entrainment
for interior conditions. Steels should have separate material and
color at a minimum for the following types :
a. A500 (HSS sections) b. A36 (angle and plate material) c. A992
(wide flange members) d. F1557 (anchor rod material) e. A53 (pipe
material)
9. Have Senior Engineers in Responsible Charge Open & Review
their Models Many states that I am aware of have some requirements
to the effect of having the structural engineer who will be sealing
the design of a building to have continuous and direct supervision
and oversight of the work product used to create the design. This
is often part of a states definition of Responsible Charge. As
such, it seems reasonable that the structural engineer of record
should be opening the models and reviewing the work done in them by
their EIT's, junior engineers and technicians. Engineers who have
not learned the BIM tools in their office enough to open the models
and walk through them cannot make informed decisions about BIM LOD.
It is hard to understand how senior engineers who cannot open and
review models can manage BIM projects to a LOD and write proposals
that define that LOD using a process that they cannot access. I am
not suggesting that firm owners and senior engineers model their
own projects. However, they should consider having a very basic day
to day level of knowledge that will allow them to open the models,
walk through them and review the content without having to ask a
junior engineer to come help them spin the model around. The level
of competency to be able to navigate a model typically only takes
one or two hours of effort to learn and allows the engineer in
responsible charge to be an active part of their design in BIM.
More importantly, it gives them a powerful way to mentor and train
the next generation of engineers by
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Structural Timber and Concrete Level Of Development (LOD): When
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10
having them review their junior engineers work in a graphically
rich 3D environment.
10. Not All Steel, Concrete, Masonry and Wood Content is
Structural Not all model content that is steel, concrete, masonry
and wood is structural nor should it be in the structural engineers
model beyond typical 2D details. Examples of such content would be
steel lintels supporting brick over architectural openings,
non-load bearing masonry and wood framing architectural partition
walls, concrete site paving, concrete recesses in floors and
concrete mechanical equipment pads. All such content should be
modeled by the discipline that has the greatest control over the
design and /or coordination of the element.
11. Train the team Inside & Out All of the discussion of
structural BIM LOD is academic unless everyone who works on the
project understands what the goal for the project LOD are. This
means that PM and engineers in the firm need to learn how to master
the BIM tools. These engineers must then work with their architects
and mechanical engineers to form a rational approach to the LOD
across the project.
-
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Structural Timber and Concrete Level Of Development (LOD): When
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is demonstrated in a structural engineers ability to provide
project specification in MasterFormat before the structural design
is complete. Early in the project, they know what the foundation
system will be. For example, the engineer knows if the structure
will have concrete (Division 03), masonry (Division 04), steel
(Division 05) or timber (Division 06). Furthermore, they know if
there design will have open web joists (CSI MF 05 21 19.00), tilt
wall (CSI MF 03 47 13.00) and steel roof decking (CSI MF 05 31
23.00) for example. In addition to the six base numbers in
MasterFormat, the user can add a two digit decimal suffix to the
numbers to further refine the organization of structural content.
Thus, I will use MasterFormat in this presentation to aid in
defining structural content that compliments the UniFormat used in
the AIA E202.
The first 2 numbers in MasterFormat define the traditional
divisions and I suggest using these as the fundamental frame work
to organize a discussion around the level of structural model
element development. 03-XX-YY.zz: Concrete 04-XX-YY.zz: Masonry
05-XX-YY.zz: Metals (Steel, Ext.) 06-XX-YY.zz: Wood, Plastic, Ext.
10-XX-YY.zz: Finishes 31-XX-YY.zz: Fnd., Earthwork 32-XX-YY.zz:
Exterior, Site 36-XX-YY.zz: Misc.
Sample of authors structural LOD table for structural concrete
content.
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Structural Timber and Concrete Level Of Development (LOD): When
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13
Hierarchical Structural LOD Model, version 2010.11 The following
Hierarchical Structural LOD model, developed by the author, is a
tool that is being developed to aid in graphically defining
structural model content for project teams. The descriptions are
only our opinions and the definitions will need to be adjusted
depending on the project that they are applied to. My intent in
creating this content and the sample models provided is to identify
the specific content requirements and associated authorized uses
for each Model Element at seven different levels of completeness
that are typically at progressively higher-levels of model element
development. The general concept is that each subsequent LOD
typically builds on the previous level and includes all the
characteristics of previous levels. However, in structures and
building enclosures this is not always the case. Current practice
for many engineered items such as structural steel connections,
unitized curtain wall systems, or steel open webbed joists is for
the model content to be remodeled in the construction model. The
design models (LOD 300 or less) of these elements are rarely being
used to electronically automate the creation of the construction
models (350+) due to lack of software interoperability.
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Structural Timber and Concrete Level Of Development (LOD): When
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The summary below outlines a sample of a possible seven level
system for the structural level of model element development. These
levels are namely:
Ikerd's Structural LOD Adapted From AIA E202-08 LOD LOD
CONCEPT
PHASE TRADITIONAL PHASE (TYP.)
EXAMPLE
100 Conceptualization Schematic Design Little model content with
some massing, 2D lines and a structural narrative.
200 Criteria design Design Development General structural
objects are modeled to reserve space.
300 Detailed Design Construction Documentation
Create 2D construction documents, general estimating and 3D
spatial validation
350 Beyond Detail Design
Pre-Construction Detailed estimating and 3D Spatial Validation
content that is not in the designers models.
400 Fabrication Detail Construction Administration
Shop Drawing level information.
450 Erection & Site Installation
Construction Administration
Daily field erection reports added to the structural model.
Temporary site items such are cranes, etc.
500 Facility Management
Hand Over Maintenance & Renovation
Sample of authors structural model element LOD for the
foundation edge condition of a slab-on-grade system.
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Structural Timber and Concrete Level Of Development (LOD): When
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Model Management The level of model element development is not
complete if it does not define who is responsible for managing
model content for each defined phase of the project. This paper
suggests that the structural model information at LOD of 100 is
typically addressed with the aid of structural design narratives as
this is all that is typically required early on in a project. When
a structural LOD of 200 is required, the structural consultant
should be responsible for the content until it is handed off to the
preconstruction phase which in the US is typically at a LOD of 300
to 350 on most commercial building projects.
Initial Responsibilities of the Structural Model The party
responsible for managing the structural model shall facilitate the
establishment of protocols for the following:
1. Model origin, coordinate system, and units 2. File storage
location(s) 3. Processes for transferring and accessing files with
other team members 4. Uploading models to the Spatial Validation
manager. 5. Access rights
File Formats
The level of model element development is not complete if it
does not include a definition of the applications that are used. As
an example, the teams BIM Execution plan should state "Models shall
be delivered in the following format(s) as appropriate to their use
for example: The following examples would be for the level of model
element development for design intent which is typically shown as
300 to 350 as suggested in this paper.
Use of Model Application Required File Format(s) Architectural
Design Intent
Revit Architecture 2011 Source *.RVT Exported *.NWC (Navisworks)
Exported *.DWG (for non-Revit team members) Exported *.IFC (for
non-Revit team members)
Mechanical Design Intent
Revit MEP 2011 Source *.RVT Exported *.NWC (Navisworks) Exported
*.DWG (for non-Revit team members) Exported *.IFC (for non-Revit
team members)
Structural Design Intent
Revit Structure 2011 Source *.RVT Exported *.NWC (Navisworks)
Exported *.DWG (for non-Revit team members) Exported *.IFC (for
non-Revit team members)
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The following examples are LOD summary sheets that teams should
develop at the beginning of a project. They are:
LOD 100 LOD 200 LOD 300 LOD 350 LOD 400* LOD 450* LOD 500*
*For the structural design aspects of the LOD topic of this
session, we will mainly focus on LOD 100 through 350. Few owners
are currently requiring content that would be defined at LOD 500.
Future updates to the structural LOD model will include level 500
topics.
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LOD 100
Typical Model Element Content:
The majority of structural content is actually not modeled at
this level. Structural definition is typically accomplished by
providing a structural narrative to accompany the architects
massing model. This provides ample information for contractors to
conceptually price early designs. When structural modeling is
created it is only overall structural massing indicative of area,
height, volume, location, and orientation in 3D.
Authorized Uses
General coordination of space. Reserving required spaces for the
building exterior system. Early conceptual estimating.
Estimating. Conceptual estimating if a structural narrative is
provided along with the architectural LOD 100 model. These may be
used to develop some estimate based on general area, volume or
similar conceptual estimating techniques (e.g., square feet of
floor area, pound of steel per square foot, etc.).
Schedule. The Model may be used for very general project phasing
such as 'existing structure' vs. 'new structure'.
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LOD 200
Typical Model Content. Overall structural massing indicative of
area, height, volume, location, and orientation may be modeled in
three dimensions or represented by other data. Main structural
members and systems are modeled with generic standard modeling
tools for the creation of 2D construction documents.
Authorized Uses: Design Development Document level information.
The model will be accompanied by general notes, connections, and
typical details to define higher level information that is not
typically shown in 1/8" scale plans.
Estimating. DD level estimating along with the DDs and
specifications. Conceptual estimating at best if a structural
narrative is provided along with the structural BIM.
Schedule. The Model may be used for very general project phasing
such as 'existing structure' vs. 'new structure'.
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LOD 300
Typical Model Content. Main structural members and systems are
modeled with standard modeling tools for the creation of 2D
construction documents. Examples of these structural members that
are modeled with standard tools in the BIM application (like Revit)
are gridlines, levels, columns, beams, slabs, walls, main gravity
systems and main lateral systems.
Authorized Uses: Create Construction Document (CD) level
information that is shown in plans. The model will be accompanied
by general notes, connections, and typical details to define higher
level information that is not typically shown in 1/8" scale
plans.
Estimating. CD level estimating along with the CDs and
specifications.
Schedule. The Model may be used for very general project phasing
at the construction document level.
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LOD 350
Typical Model Content. Modeling beyond main structural members
and systems with standard BIM application tool for the creation of
2D construction documents but at lower level of detail than would
be required for fabrication. In Revit, this level of model
typically requires modifying existing families or using frequent in
place families to model content that is not traditionally shown on
a 1/8" set of drawings. An example of such content would be in a
design model where the gusset plates modeled on the braces of steel
frames by a custom brace family or via in place families. Another
example of LOD 350 level content would be miscellaneous steel and
brick shelf angles. Modeling of structural loads would be other
examples of content in this LOD that is beyond the content used to
create construction plan documents.
Authorized Uses: Detailed 3D spatial validation.
Estimating. Construction Document level estimating.
Schedule. The Model may be used for very general project phasing
of main structural systems and some detailing scheduling.
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LOD 400
Typical Model Content. Fabrication level information.
Authorized Uses: Creating shop and fabrication level
information.
Estimating. Detail estimating with fabrication level
information.
Schedule. Detail scheduling with fabrication level
information.
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LOD 450
Level of Detail 450, Site Construction \ Erection Content is
defined by the author as that content that goes beyond what is
needed in the LOD 400 fabrication model to include temporary
building content that is used during onsite construction. This
content can be beneficial when conducting site planning and 4D
scheduling of the construction.
Typical Model Content. This could include construction items
such as erecting braces, whalers, scaffolding, and cranes.
Authorized Uses: Detailed construction coordination of the
site.
Estimating: Detailed construction estimating that includes job
site level information.
Schedule. Detailed construction scheduling for 4D
scheduling.
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LOD 500
Typical Model Content. Content at this level must be determined
on a case by case basis with the owners and facility managers.
Authorized Uses: Uses at this level must be determined on a case
by case basis with the owners and facility managers.
Estimating. Estimating of items such as service life and
operating cost at this level must be determined on a case by case
basis with the owners and facility managers.
Schedule. Scheduling building usage of items such as room use at
this level must be determined on a case by case basis with the
owners and facility managers.
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Example, Tilt-Up Panel Concrete (CSI MF# 03 47 13) & Shared
Models The images below show common typical details for tilt-up
concrete panel construction that is classified with CSI MF # 03 47
13. A LOD of 300 would be the detail required to create
construction document plans at a 1/8" scale. Historically,
architects have shown the panel elevations of the buildings and as
such, many structural engineers have not provided full building and
panel elevations. It is traditionally the architects role to define
window, door and other wall openings. The architect would normally
be the one to define panel reveals, recesses and joint locations
with feedback from the structural engineer.
This would be an example of model elements that would be a
candidate for a shared model. The architect would have their model
with all architectural content such as interior walls and plans
except for the tilt-walls. The structural engineer would have their
model with all structural content
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and plans except for the tilt-walls. The structural model would
have items such as the foundation and interior steel structure and
the typical tilt wall details that have been previously shown. The
team would then have a third separate "Tilt-Wall Only Model"
without any plans. The team would schedule which firm has the
'rights' to modify the 3rd shared model at a give time of the week.
We would recommend something like a weekly schedule where the
architectural team has model editing 3 days and the structural team
has it 2 days. At all-times, each team would have the previous
week's 'published' shared model linked into each of their models.
When the structural team has the model for editing, they would be
reviewing the architectural design for structural considerations.
This would eliminate any duplicate modeling for the tilt-walls on
the design side and would also allow all team members to take the
models to an appropriate level of detail for construction
documents. As the design passes into preconstruction, the tilt-wall
model could be easily federated in Navisworks and coordinated with
the steel detailers LOD 350 and 400 level models for pre-shop
drawing review. The most important aspect of the shared model is
that it allows each discipline to control the model content that
they are responsible for without having duplicated content in
multiple models. The table below shows how the LOD table could be
used to define this workflow. Note the thirteen line items that
were noted for the tilt-up concrete panels to CSI MF # 03 47 13 in
the image below. Pay attention to line items that change Model
Element Author from one LOD to a higher LOD when defining
structural elements LOD with the table provided in this paper.
Consider a shared design team model for such objects where multiple
parties must control the object during the design phase of the
project (typically LOD 300 or less).
Sample of LOD of Tilt-Wall using authors spreadsheet developed
with the CSI MasterFormat 2010 titles and numbers and the custom
added categories. STRL = Structural Engineer Designer, ARCH =
Architectural Designer, STLD = Steel Detailer, CONC Concrete
Contractor, TBD = To Be Determined on a case by case basis. Example
of shared model for the tilt up panel walls on a building. The
image on the left shows the structural model. The image on the
right Is the architectural model with interior walls, windows,
dry-wall, ceilings and lights. The model in the middle is the
Shared Design Model that both teams work in and use to create their
construction document plans.
STRUCTURAL
SHARED BIM
ARCHITECTURAL
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Example, Wood Joist Framing
Wood Joist systems are a class of structural content that are
made of engineered products and vary by manufacturer. As such, the
generic joist content in Revit looks highly detailed but is not
necessarily accurate as it relates to the chord sizes and web
configurations. The joist depths and weight are correct. However,
there are many different manufactures who make joists and they have
considerable freedom to design the web configurations, joist seats
and chords. No two manufactures will be the same. There is little
value in designers creating custom joists to approximate these
manufactures unknowns. It is typically better to specify that the
joist manufacture will provide a 3D model of their content as part
of the shop drawings. This is particularly important if MEP or
other trades need to run building systems through the webs of the
joists.
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SAMPLE GENERAL NOTES FOR CONSTRUCTION DOCUMENTS The following
sample general notes provide ideas for construction documents to
provide guidelines to the construction team to develop models
beyond LOD 300. They also provide a framework for the structural
design team to utilize higher level fabrication models as part of
their shop drawing review. BUILDING INFORMATION MODELING
A STRUCTURAL BUILDING INFORMATION MODEL (BIM) HAS BEEN PREPARED
FOR THIS PROJECT. A READ ONLY NAVISWORKS (NWD) FILE IS AVAILABLE
THAT SHOWS THE PROJECT SCOPE AND INCLUDES PHOTOGRAPHIC MARKERS OF
EXISTING COMPONENTS OF THE BUILDING. THIS FILE IS AVAILABLE FOR
DOWNLOAD WITH THE FOLLOWING WEBSITE INFORMATION PURSUANT TO
ACCEPTANCE OF OUR ONLINE ELECTRONIC FILE TRANSFER AGREEMENT. THIS
MODEL WILL BE AVAILABLE FOR SIXTY (60) DAYS FROM THE DATE THAT
THESE DRAWINGS ARE ISSUED FOR CONSTRUCTION. WEBSITE ADDRESS:
http://www.xxxx USER NAME (CASE SENSITIVE): xxxx PASSWORD (CASE
SENSITIVE): xxxx THE FOLLOWING BIM REQUIREMENTS ARE PART OF THE
CONTRACT DOCUMENTS:
i. THE GENERAL CONTRACTOR SHALL PROVIDE A BIM SPECIFICATION TO
INSURE THAT ALL SUB CONTRACTOR MODELS CAN BE FEDERATED.
ii. THE GENERAL CONTRACTOR SHALL FACILITATE THE BIM VIRTUAL
DESIGN AND CONSTRUCTION (VDC) COORDINATION PROCESS.
iii. THE GENERAL CONTRACTOR SHALL CONDUCT CONSTRUCTION
COORDINATION
MEETINGS TO COORDINATE SUB CONTRACTOR MODELS, TO ESTABLISH
PRIORITIES OF SYSTEMS, AND TO FACILITATE SCHEDULING PRIOR TO
SUBMITTING SHOP DRAWINGS FOR A GIVEN ZONE OF THE PROJECT. THE
DESIGN TEAM SHALL BE INVITED TO THESE MEETINGS AND NOTIFIED OF THEM
TWO WEEKS IN ADVANCE OF THE MEETINGS.
iv. EACH OF THE FOLLOWING TRADES SHALL PROVIDE DIMENSIONALLY
ACCURATE 3D MODELS OF WHAT THEY WILL INSTALL THAT ARE COORDINATED
WITH THEIR SHOP DRAWINGS FOR 3D SPATIAL VALIDATION WITH THE
STRUCTURE AND EACH TRADE: MECHANICAL, ELECTRICAL, FIRE PROTECTION,
DRYWALL, CEILINGS, CIVIL SITE WORK, PLUMBING, CAST-IN-PLACE
CONCRETE, CONCRETE EMBEDS, STRUCTURAL STEEL, MISCELLANEOUS STEEL,
BUILDING ENVELOPE, LIGHT GAGE COLD FORMED STEEL AND ANY OTHER
TRADES THAT COULD AFFECT THE STRUCTURE.
v. ALL 3D TRADE MODELS USED FOR SHOP DRAWINGS SHALL BE MADE
AVAILABLE IN AN EXPORTED AUTOCAD 2007 DWG FORMAT AND NAVISWORKS NWC
FILE TO THE DESIGN TEAM TEN BUSINESS DAYS PRIOR TO SHOP DRAWINGS
BEING SUBMITTED FOR REVIEW.
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vi. SUB-CONTRACTORS SHALL USE THE STRUCTURAL CONCRETE AND
STRUCTURAL
STEEL CONTRACTORS MODELS TO COORDINATE THE SCOPE OF THEIR WORK
AND CLEARANCES WITH THE BUILDING STRUCTURE AND ALL OTHER
DISCIPLINES.
vii. 3D SPATIAL VALIDATION SHALL BE CONDUCTED SUCH THAT THE
MODELS ARE BROKEN UP AND SUBMITTED BY ZONES. EACH ZONE IS DEFINED
FROM FINISH FLOOR ELEVATION OF ONE FLOOR TO THE NEXT FLOOR.
viii. THE ORIGIN COORDINATES FOR ALL 3D TRADE MODELS SHALL BE
SET AS FOLLOWS:
a. LEVEL ONE FINISH FLOOR = 100'-0" b. THE GRID LINE
INTERSECTION OF GRIDS "A" AND "11" SHALL BE SET AT X= 1000'-0
AND Y= 1000'-0".
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Structural Timber and Concrete Level Of Development (LOD): When
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Resources & Bibliography
www.IKERD.com
Author, Will Ikerd, email: [email protected] If interested in
discussing this topic with the author or receiving updates of the
LOD model, please send an email to schedule a phone call, or online
GoToMeeting (or Skype for international calls).
Autodesk Documentation & Online Help
http://usa.autodesk.com/adsk/servlet/pc/index?siteID=123112&id=15115212
SEIbim.org
AECOknowledge.com
Bibliography
American Concrete Institute [ACI]. (2008). ACI Detailing Manual
- 2004, Pub. SP-66 (04). Farmington Hills: ACI.
American Institute of Steel Construction [AISC]. (2009).
Detailing for Steel Constrution, 3rd Edition. Chicago: AISC.
American Institute of Architects [AIA]. (2008). AIA Document
E202 2008. Washington, DC: AIA.
ConsensusDOCS. (2008). ConsensusDOCS 301: Building Information
Modeling (BIM) Addendum. Arlington: ConsensusDOCS.