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Letterman Digital Arts Center - Case Study

The BIM Process

Figure10   Demonstrates how site inspection, construction experience, an eye for detail and the use of BIM worked, preventing a serious and costly error in the construction of the central stairs in building A.  This error was discovered after the formwork was completed but the concrete was not poured.  Two days later the concrete beams were poured

Despite the efficiency of the BIM, there exists the possibility of human error as illustrated in Figure 10.  During one of the daily rounds of onsite photography, we recognized a critical error shown in the positioning of concrete formwork, an error that was quickly confirmed by referencing the BIM. This error occurred when the formwork layout person measured to the edge of concrete slab from a column that was off the standard grid.  Pouring more concrete (shown in gray in the photo on the left) in this complex post-tension slab construction would have had a serious consequence not only for the contractor but also for the entire project.  There were three more floors to be built above this floor.


Figure 10.  Illustrates the type of potential critical problems that can be created by human error. The gray transparent slab shown in the photo on the left is the graphic representation of the extra slab that would have been poured if not caught literally minutes before the pour was to occur.  Concrete Trucks were lining up to pour this level when I have discovered this problem.

Because of our familiarity with the virtual model and having experienced the building spaces before construction, we were immediately able to identify the problem and alerted the LDAC management team.  The problem was solved just as the concrete was being poured, saving what would have most definitely been a major expense to rectify later.

LDAC_P9 Pipe penetrations 01a

Figure 11.  Hand chiseled floor penetrations due to post tension cables set in the conc floor.

LDAC_P7_Conc Sleeves 02a

Figure 12.  Photo on the left demonstrates the correct installation of pipe sleeves in a shear wall.  Two 11” diamond drilling through identical 2 foot shear wall occurred.  Notice the amount of 2” rebars that were cut in the process, therefore weakening the engineered shear wall.

Through careful site coordination with the BIM, over two hundred design and construction conflicts were identified.  Most of these were corrected before construction resulting in a savings to the owner.  Unfortunately there were over 200 slab penetrations that had not been located by the general contractor and some were placed in the wrong positions. These omitted penetrations had to be chipped out with chisel and hammer due to the post tension cables and electrical conduits located inside the slabs.  In their haste to be paid at the front end the contractor tends to be pressed to pour as much concrete as possible and as quickly as possible.  Although I had pointed out to the contractor few areas where I believed that the large pipe sleeves were not installed, the response was, “we will drill later”. 


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