I was contracted by Hyforce Engineering in Yatala (Ph: 07 3807 9044) to perform a detailed survey of an empty Bunnings warehouse in Booval Near Ipswich here in Queensland. Hyforce wanted a full and detailed scan as there were going to be many small and medium structural improvements and architectural upgrades which would have a steel work element. My brief was to get the scan, produce the workshop drawings and return to site to layout every hole that needed to be site drilled.
This was to be the most challenging project I have worked on so far.
I went out early in the morning with my son Tate knowing we had a big day ahead. 54 scans later and with very sore feet we were heading home. The Faro X130 scanner had held up beautifully as always, and the Trimble RTS773 total station gave us the control network we needed to return later. The 54 scans took a few hours to register as I still do it the old fashioned target based way. Targets give me confidence in my registration but I know that its old hat and target-less registration works fine in most cases. Therefore I will be upgrading.
The first task was to get the scan geo-referenced so we could overlay the architect drawings to check approximate positioning. (We never rely on these alone but its a start). Straight away we found a problem. The site level datum was about 100mm different from the architects datum and the position of the walls and internal steel columns was about 85mm out in 1 direction and 50mm out in the other and everything had been set out from the walls! The issue was raised and promptly ignored. Alarm bells were ringing and we realised this was the way this project would go. However the scan survey virtually eliminated the risk that was being passed to us by the project team and its woeful documentation.
The first steel to be modeled were 203 UB mullions that support the tilt panels. These were fixed to an existing header near the panel top and had window heads between them. Each mullion was to be at a panel joint. I extracted the scans at each joint and imported them into Tekla. We found that the Tilt panels were tilting by more than expected. In fact some were leaning out by 50mm once you got to the top. So we cut all of the columns so they would lean with the panels.
Along with the mullions we had to install some bracing and strengthening steel work in the roof space. Although you might argue that the scan was not needed for the mullions it was needed for the bracing in the roof space as there was no way to access this to measure it. The scan however did identify the lean of the panels which could have caused installation issues if everything was just assumed to be plumb.
A major and most risky part of this project was the 2 entry statements. The main entry was "sort of designed" to fit under and over the existing Bunnings entrance canopy. The designers wanted to retain the roof of this existing canopy as the guy ropes for the 3 flag poles were attached to them and the ground. The design asked for the new steel to fit under the existing with new columns sitting on top of the existing 203UB edge beam to make the sign tower. Extracts of the laser scan were used to position and size the existing and new steel work. The result of which was a long RFI explaining that the current design would not work due to clashes with the existing steel that had not been taken into account by the designers. There were stubs on top of the 203 edge beam with a toes down PFC on top as a small parapet channel. This was met with silence for 2 months.
We spent the next 2 months waiting. In the end, and to cut a long story short, I ended up producing a plan showing where steel could be located so it worked with the existing. (This was way above and beyond my scope and risky). After some considerable procrastination by the designers, a shared scan extract for Revit and a shared Tekla model for Revit, we got an agreement on the steel set out based on the facts that the laser scan was able to demonstrate. Further to this the scan was invaluable in locating the guy ropes to ensure no clashes. The designers had completely forgotten that they existed and the steel frame had to be shifted from the design locations by about 500mm to miss the ropes.
If I had not clash checked with the scan and just set the steel out to the architects design drawings the steel would have been useless. The re-work would have been massive not to mention the cost.
Below is the final steel frame.
Over the whole project I used the laser scan survey data to produce drawings for the 2 entry statements, the external canopies, 5 external staircases, internal panel support steel work, replacement purlins and bridging and rafter strengthening. I also did not have to return to site to perform more survey work for parts of the project that I was not expecting to be awarded or to re-measure.
The point of this long blog post is to demonstrate that a decent laser scan survey may just save you. With the worst project documentation I have ever had to use, a design team that were not engaged and an initial survey that was just plain wrong the odds were as against us as they could be. Using the laser scan survey, The Trimbe RTS773, Tekla Structures and some tenacity BIMTek delivered a successful project on time and with no rework due to poor site information.
- The scan survey eliminated most of the risk that was passed to my client via the woeful documentation and a lack of engagement by the project designers. It gave him the information to argue his case if changes to the design were needed or additional funds were required.
- Drafting to the scan survey eliminated 90% of any rework that may have been required because site conditions were not known, assumed or guessed at.
- The scan survey gave the designers and draftsmen a certainty that their designs and details will actually fit and empowered them to ask a question if things were not going to work. They have never had this luxury until this technology made it possible.
- The scan survey virtually eliminated the need to re-visit site to re-measure when variations and additional work were awarded to the fabricator.
- The scan survey, if it was used to its full potential could have given this benefit to many other trades on the site but sharing for the common good is a huge problem in construction.