Contract drawings — long the backbone of every dam rehabilitation and construction project — are often limited because they only present two-dimensional (2D) information. Designers can counteract the limitations presented by contract drawings by incorporating three-dimensional (3D) modeling earlier into the design phase. Understanding and utilizing these emerging technologies plays a vital role in helping reduce misunderstandings between the design engineers and the contractor.
Throughout the life cycle of a project — from the initial design to construction — converting contract drawings into 3D models — both as renderings and scaled physical models created with 3D printers — has proven invaluable for improved visualization, design development and refinement, and constructability reviews and sequencing, among other processes.
Enhancing visualization during the design phase
Design engineers can use 3D modeling to refine complex design details that are often required in dam construction or rehabilitation. In the design phase of a project, this proves especially beneficial for visualization and refinement of details, verification of the design, and quantity and cost estimation.
Specifically, 3D models are being used to develop and refine design details for a number of dam construction project elements, including:
- structural components with joints and keys, including spillway walls and spillway slabs;
- complex concrete jointing and structures, including labyrinth spillways;
- components within concrete, including reinforcement, anchors and dowels, waterstops, pipes and outlets, formwork ties and rods, and drains;
- interfaces between components, including intersection of earth embankments and concrete walls; and
- additions to existing structures, including anchors, sheet pile, bridges, railings, and possible conflicts with existing components.
In practice, Michael Baker International engineers relied on 3D modeling during the design of a new control tower to be constructed on a new spillway slab. The design of this structure required detailing of the control tower exterior walls and interior bulkhead and the interface between the spillway slab and control tower walls. The design included the sizing of reinforcement, openings in the walls, and waterstop connections.
The initial design drawings for this portion of the project were used to build a 3D model for the area. As the design phase progressed, the model was refined to show waterstops and their tie-ins to the control tower wall, as well as to create additional cross sections, details, and an isometric view for the contract drawings for the project.
The 3D modeling detailed in this project translates across multiple facets of a project, proving valuable for checking designs developed and represented in 2D on the contract drawings by “constructing” the model from the developing contract documents. While the level of detail inputted in the 3D models is at the discretion of the developer, the more detailed the model, the more useful it is for checking the design for a dam rehabilitation or construction project.
Since 3D models can be broken out for specific complex areas of a project, they prove particularly useful in evaluating reinforcement configurations, waterstop locations and clearances, and other conditions at joints in complex structures. When reviewing individual elements, the design can be easily modified to address potential conflicts in a cost-effective manner prior to construction.
Additionally, another design process benefitting from 3D modeling is quantity takeoffs for use in preparation of cost estimates. Elements included in the model are counted or measured, such as the length of waterstops, number of prefabricated waterstop unions, the volume of individual concrete pours, or the number of dowels and reinforcing members. The use of 3D models has proven particularly beneficial in cases where quantity takeoffs based on 2D drawings would be time consuming or likely to introduce error.
Developing an understanding of the construction sequence during the design phase of a dam project can be challenging, and a thorough constructability review during the design phase is critical for the success of a project. Developing a 3D model at different phases of the project encourages the designer to consider the construction sequence in detail and identify possible improvements or conflicts.
Achieving stakeholder buy-in
With the scope and visibility of dam projects, and the impact a dam plays on an entire region, receiving support from owners, public stakeholders, and regulatory agencies is paramount for a project’s success. As an effective tool to visually create a realistic representation of a dam construction project prior to construction, 3D modeling is used to produce 2D renderings that incorporate images of portions of the project, such as a lake, shoreline, and surrounding area.
Renderings showing the completed dam rehabilitation or construction project are particularly useful for presentations to key stakeholders. They quickly and effectively convey the final appearance of the project after construction, reduce the time required for stakeholders to understand the project, and eliminate the need for detailed 2D drawings and other concepts that can be difficult to understand. These renderings are created without the need for a separate model, which can be costly and time consuming. Scaled physical models of the entire project or individual project components can also be produced from the 3D modeling to provide a tangible demonstration.
As a dam project moves from the design and presentation phases to the construction phase, the developed models are carried through with minimal additional effort and provide a valuable tool for personnel in the field. With available mobile applications to display 3D models directly on a mobile device or tablet, construction personnel can rapidly and efficiently access supplemental information and accurately record construction information.
A 3D model can help with review of submittals, proposed construction sequences, and development of or changes to designs based on field conditions encountered. Design changes are often required in a short timeframe during construction, and 3D models can help to expedite the process.
During construction planning, models can include concrete formwork, equipment positions at various stages of construction, phasing for water control and diversion, and other features and can incorporate construction sequencing. This allows engineers to more effectively evaluate work plans, schedules, and other submittals.
Three-dimensional models are also helpful tools when performing construction inspections. The model is used by field personnel as a supplement to the contract documents to develop an understanding of what to expect in the field prior to construction. With the help of the 3D model, the inspector can identify potential errors or conflicts, alert the contractor, and if necessary, develop a solution before the issue significantly impacts construction.
One such example is the detailing of reinforcement around construction joints and waterstops. The 3D model is used by field personnel during construction to verify the waterstop orientation, location, prefabricated unions, reinforcement locations, formwork locations, and overall layout.
These models are carried through construction to track progress as it occurs in the field. The model is updated and modified as construction occurs, and quantities can be tracked or checked using the model. This allows construction personnel to rapidly and accurately review installed quantities, pay applications, and other progress submittals. Volumes, surface areas, lengths, and other quantities are available at the click of a button if a 3D model is properly updated as construction occurs. Updating the model during construction also allows rapid and accurate preparation or checking of as-built drawings, and provides for additional detail to be incorporated into as-built drawings.
Life cycle benefits
Three-dimensional modeling provides benefits for dam design and construction through enhanced visualization of the project during design, refinement of complex details within the contract drawings, modeling the anticipated construction sequence, and project visualization for the owner, public, and other stakeholders. This technology is particularly beneficial for complex components of dam projects such as control tower structures, spillways and training walls, or interfaces between components of structures.
Ultimately, as designers, engineers, and construction personnel continue to embrace the use of 3D modeling in the dam construction process, the resulting projects will be completed more effectively and efficiently.
Chad Davis, P.E., vice president, Infrastructure Practice executive; Joseph Kudritz, P.E., civil engineer; Jared Deible, P.E., technical manager; and Jacob Bench, E.I., civil associate, are all with Michael Baker International (www.mbakerintl.com).