Albert & Mary Street - Brisbane.

This project is now complete and is a great example of my philosophy of end to end design, detailing and installation.

Contracted by Precision Steel Fabrication in Cleveland QLD I was required to produce a laser scan survey of an existing structure on the corner of Albert and Mary street in Brisbane's CBD. This intersection is incredibly busy and the tenancy being upgraded is still an active cafe so we needed a solution that caused as little disruption as possible.

Corner of Albert & Mary st

Inside the cafe

The project was to install a new staircase to provide access to the 1st floor and to install a truss frame around the corner to allow installation of electronic advertising screens. We had to fix to the existing internal steel frame in the cafe, alter its roof to install a 1st floor platform and attach the trusses to the top of the 1st floor sunshade slab. The survey had to be done in working hours and the cafe would not close or co-operate in any way with the builder.

I performed the scan survey with a Faro X130 scanner and the Trimble RTS773 to create a control network and geo-reference the scans. On this type of project the X130 scanner is brilliant as you can put it on top of ceiling tiles and awkward high ledges and capture detail you would otherwise struggle to get. I had to ensure I captured the existing roof purlins and steel work above the cafe and the X130 makes it easy.

This was a tricky structure to scan and I had to use a lot of targets to ensure a decent registration. Additionally the footpath around the site was really busy and some scans had to be attempted several times as people got in the way. I have now bought a 3.2m tripod so i can get the scanner way above the ground and pedestrians.

When it came to start working with the data I realised that due to the lighting some of the purlins and other objects were hard to see. This is where Trimble Realworks comes in. Realworks has several colouring settings for the laser scan and cycling through these makes items easy to see that would otherwise be near invisible. Below are some of the colouring options and you will see the difference.

Once you have identified the relevant parts of the structure its easy then to cut them out and export them to your CAD system. I use Tekla Structures and the system I have works well. I can import point clouds of up to 2 million points into Tekla as a colour reference object and I have not yet found the limit of how many of these I can import. Tekla does slow down a little even on my Xeon processor workstation but, the performance issues are outweighed by the benefits of being able to model to real world objects. Below are some examples of the laser scan samples being used in Tekla Structures.

Once I had got the steel work detailed and approved I added layout points and it was time to go back and set out the column base bolts and wall drillings. The site conditions were bad and it was wet so as well as marking out I actually pilot drilled the base bolt locations so we wouldn't loose the marks. The layout took half a day.

Precision Steel fabrications drilled the base and wall holes the day before installation which was to happen at night as a road closure was required. The steel work installation was largely complete in 1 night with finishing details done the next day.

This project, as I said before, is a great example of my end to end philosophy. If 1 or company individual performs the survey, produced the detail drawings and then performs the layout the chances of error are lower and the chances of a great fit to existing are increased dramatically.

Ian BrightmanComment