HIGH-TECH PROCESSES TO PRODUCE VIRTUAL MODEL OF POWERHOUSE
The first step involved in the complex task of renovating the Byllesby Dam powerhouse is determining how the building was originally constructed.
But doing that isn ' t easy when it’ s clear those who built the powerhouse more than 100 years ago did not strictly follow the original architectural drawings and failed to record their many deviations from those plans.
That’ s the challenge facing the Ayres Associates team hired by Dakota County, Minnesota, to rehabilitate the structure into a modern-day producer of electricity, while recognizing its early 20th century aesthetic glory.
Last December Jason Ingram, Ayres’ manager of land survey, sent a two-person survey crew to the Byllesby Dam site armed with the latest in high-density, or HD, laser technology. The surveyors spent two days at the site taking a set of 62 high-density laser scans of the entire complex – the dam, its adjoining floodgates, and the powerhouse.
Each of those scans creates a 3-D dataset of that part of the dam site, Ingram explained.“ The scanner measures features at a rate of up to 1 million points per second, mapping in such detail that it can look like a photograph when viewing the point cloud dataset,” he said.
Each of these 62 sets of data, called a“ point cloud,” provides precise measurements detailing key information, such as materials used, the thickness of walls, where pipes enter and exit walls, flatness of floors, and much more.
Through a process called“ registering,” surveyors will analyze each point cloud and convert the data
into one“ point cloud dataset.” This registration process“ is like putting a puzzle together, piecing each of the 62 scans together with survey-grade accuracies,” Ingram said.
Another advantage to scanning that was recognized on this project was the equipment’ s ability to pick up data on everything it can see and measure. For example, the scanning picked up the existing spillway, which is being rehabilitated, along with areas that had concrete removed along its surface. From the point cloud, cross-sections were cut and an existing surface model was generated to aid engineering staff in determining a proposed finished profile of the surface for construction. Although this was not the targeted use of the point cloud, the technology enabled all data to be collected and saved for future benefits to design staff without the need for more costly site visits.
Once that puzzle is completed, the point cloud dataset will be sent to Ayres’ BIM Specialist Bryant Christenson. BIM stands for Building Information Modeling, a process by which Christenson will use Revit computer software to convert the“ point cloud dataset” into a 3-D computer model of the entire Byllesby Dam site, including every room within the powerhouse.
“ This will give a very good representation of what’ s there,” he said.“ It will indicate all the materials that are there and their condition.”
Ingram explained that these 3-D computer models will enable Ayres architects to, in a 3-D virtual environment, remove existing equipment and add proposed new equipment to the powerhouse while identifying any potential conflicts with the building’ s existing infrastructure.
Further down the road, Christenson said, Ayres also will be able to use the 3-D computer models to create pictures of their redesign proposals that can be shown at public meetings related to the powerhouse project. When a final design decision is made, those models will be used in creating the project’ s construction documents.
– Bob Brown
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