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4D
Modeling
The Need
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Traditional design
and construction planning tools, such as 2D drawings and network diagrams, do not support
the timely and integrated decision making necessary to move projects forward quickly. They
do not provide the information |
| modeling,
visualization, and analysis environment necessary to support the rapid and integrated
design and construction of facilities. Synthesis of construction schedules from
design descriptions and integrated evaluation of design and schedule alternatives are
still mainly manual tasks. Furthermore, the underlying representations of a design and a
construction schedule are too abstract to allow the multiple stakeholders to visualize and
understand the cross-disciplinary impacts of design and construction decisions. In the
future, 4D technologies will be used for planners, designers, and engineers to analyze and
visualize many aspects of a construction project, from the 3D design of a project to the
sequence of construction to the relationships among schedule, cost and resource
availability data. These intelligent 4D models
support computer-based analysis of schedules with respect to cost, interference, safety,
etc., and improve communication of design and schedule information. |
The 4D model can visualize a lot of work that is going on in a particular area at
the same time.
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The Technology
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Extending the traditional planning tools,
visual 4D models combine 3D CAD models with construction activities to display the
progression of construction over time.However, 4D models are very time-consuming to
generate manually and cannot currently support analysis programs. The difficulty and cost
of creating and using such models is currently blocking their widespread adoption. The
construction knowledge necessary to build 4D models has been formalized and developed by a
methodology that guides project planners in generating 4D models from 3D product models.
This formalized knowledge enables project managers to create and update realistic
schedules rapidly and to integrate the temporal and spatial aspects of a schedule as
intelligent 4D models. |
The Benefits
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The 4D models have helped project stakeholders:
- Understand the relationship between construction activities
and facility operation for retrofit projects,
- Understand and improve the use of work, access, and staging
areas over time,
- Identify spatial conflicts among crews and other production
elements,
- Analyze activity sequencing,
- Improve constructability,
- Improve work flow for subcontractors, and
- Visualize the construction work to be done for a work zone,
time period, or subcontractor
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Status
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A few commercial 4D modeling tools allow a user
to link a 3D model with a construction schedule to visualize construction over time on a
computer screen. While the underlying 3D model and schedule model are based on object-oriented concepts and can be queried by the
user about their content and relationships, the resulting 4D model is purely a
visualization. 4D CAD has been used at various levels of detail from simulating and
coordinating the overall phasing of a project to coordinating the daily work of a group of
subcontractors. At the Center for Integrated Facility for Engineering, Associate Professor
Martin Fischer has lead research projects related to 4D CAD since 1994. The first project,
sponsored by Dillingham Construction and performed by Eric Collier, involved the
development of a 4D model to communicate the four-year construction project of the San
Mateo County Health Facility. Due to the success of this project, Martin Fischer continued
to pursue research related to 4D models, focusing on improving 4D tools and the value of
4D models in design and construction. |
Barriers
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- Ad-hoc modeling approach: They are built in an ad-hoc manner
without a methodology that guides their generation. This makes updating and maintaining a
4D model cumbersome by anybody else but the original creator.
- Single level of detail: They are built at a single level of
detail and do not support seamless aggregation, elaboration, and refinement of model
detail. This hinders the collaboration of general contractors and subcontractors, since
they work towards the same goal, but at different levels of detail.
- No computer-based analysis: They do not support computer-based
analyses of cost, safety, and other performance metrics. With visual 4D models, users must
carry out all of the reasoning about what they see in their heads. If properly
represented, the information necessary to build a 4D visualization could support cost
estimating and many other kinds of analyses of a design-build alternative. To support such
analyses, 4D models must represent time explicitly and cannot consist of a simple sequence
of 3D model views.
- Single user environment: They are available only for
single-user desktop environments. However, many project participants need to participate
in building and critiquing a 4D model.
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Points of Contact
- Dr. Martin Fischer, Construction Engineering and Management
Program, Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020. Tel: 650-725-4649. Fax: 650-725-6014.
E-mail: fischer@cive.Stanford.EDU
References
- Departments of Civil Engineering & Center for
Integrated Facility for Engineering, Stanford University.
<http://www.stanford.edu/group/4D/4D-home.htm>
<http://www.stanford.edu/~fischer>
- University of Strathclyde in Glasgow, Virtual Construction
Simulation Research Group <http://www.strath.ac.uk/Departments/Civeng/conman/vcsrg.html>
- Collier, Eric. Fischer, Martin. Visual-based scheduling: 4D
modeling on the San Mateo County Health Center. Computing in Civil Engineering (New York).
p 800-805
Disclaimer Statement
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Neither the Construction
Industry Institute nor Purdue University in any way endorses this
technology or represents
that the information presented can be relied upon without further investigation. |
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