Howdy everyone?!

I’ve been digging for quite sometime now for something to share with you until I realized that I’ve been looking far beyond my nose. So here goes nothing…

Since structural engineering is but one of the team which collaborates to produce a structurally sound, functional, and elegant structure, it pays to know where we fit in the big picture. It’s like knowing the battle ground enough to know the terrain and what we’re up against. Read: they affect us and we affect them. With that said, we’re going to be more bad ass structural designers if we can have a comfortable amount of leeway and confidence to account for the yet unaccounted for including the dreaded ‘oops’ moments.

This knowing of the battle ground by the way does not imply leaving our beloved structural design discipline and majoring everything while mastering none. いいえ. We’re not going out of our comfort zone, rather, we are expanding it.

Ok, you’ve reached the end of the editorial, thank you for bearing with it.

photo from cartoonstock.com

In a project, there are stuffs that we need to ask the architects and MEP guys if they are not directly given to us. They will not tell us anything related to what they’re doing that might have an effect to us, with the exception perhaps of experienced MEP coordinators. So what are these often unaccounted for stuff that we need to consider now and how do they affect us?

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Suspended chilled water pipes in the chiller room. I would presume that the chiller room chills the water supply and then pumps it out for distribution.

snapshot form Navisworks. by yours truly

Now why does this concern us? Because the chilled water pipes are suspended from the slab above!

Normally we only provide up to 0.35 kPa for the suspended services but definitely these chilled water pipes (aside from the bulk weight of steel pipes including fittings etc, do note that these 600, 900, and 1200mm diameter pipes are full of water) are way way more than half a kilo Pascal. In one of our projects, we provided an additional 3.0 kPa to account for these water-filled, suspended chilled water pipes.

These would have been no issue if we can suspend them via a support system that’s directly connected to the columns instead of having them suspended directly in the slab above. But according to my MEP chums, you can’t usually do that given the tight space as evident in the image below.

snapshot form Navisworks. by yours truly

So this needs to be included in the slab design for both strength and deflection criteria. Period. End of argument.

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Cooling towers. Where there are chiller rooms and chiller pipes, there’s gotta be a cooling tower somewhere where, they, umm cool the water(? Better ask a mechanical guy for a more definite and correct answer).

snapshot form Navisworks. by yours truly

Per unit, these cooling towers weigh up to about 50 metric tons, so if you’ve only provided 7.5 kPa or even up to 10.0 kPa load, you’re still 3-4.0 kPa short. They’re quite massive so you wouldn’t want to miss them.

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Water tanks located in the roof. Ideally, water tanks should stay in the basement and supported on soil. But there are instances like in one of our projects where the water tanks are located on the top floor. So say you have a tank containing 2.50m high water, you should have 25 kPa of load. So regardless of what floor, if these are supported on a suspended (not on soil) medium, there will be a huge impact below.

snapshot form Navisworks. by yours truly

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Suspended busbars/busducts. Go and ask an electrical guy if you want to know more about this buswhat.

snapshot form Navisworks. by yours truly

All I know is that they’re suspended and that they weigh about 104 kgs per meter. So like the snapshot below, there are 7-5000A busducts so that means we have 728 kgs hanging load per meter or 7.14 kNs per meter. Say you have a tributary width of 9.0 meters, you’re going to have to consider 0.80 kPa of suspended services.

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Roof buildups. Typical in the buildings in the middle east where we have water proofing membrane on top of the structural slab. On top of which is insulation and on top is screed.

The combined weight of the water proofing membrane and the insulation per square area isn’t going to be much unlike the screed on top. Why the need for screed? So that rainwater will flow with gravity and the screed is your means of creating a water way with a series of high points converging to the lowest points where you usually put your rainwater pipe.

snapshot form an architectural plan. by yours truly

Now why did I put this in the list? It’s because it weighs much like concrete. Like the image below, usually the lowest point is 100mm and the highest is 200mm, maybe more depending on the slope. At this point, you should be able to determine at least the average screed thickness, or where agreed, the highest and lowest point so that you can use your engineering judgement accordingly.

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Basement levels in the transformer room. Aside from the load, which is usually assigned with 10.0 kPa live, the whole floor level if it is suspended needs to go down to a level to be coordinated with MEP for the electrical cables and pipes for power supply. These dictate the slab levels, which will trickle down to the foundation.

taken from the internet. credit goes to whoever owns this one

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The pit within the pits. For escalator and elevator pits you can be sure that there will always be sump pits below.

snapshot form Navisworks. by yours truly. can you spot the sump pit?

This is a variable to be considered when determining the required depth of excavation especially when you don’t want those pits eating a part of the foundation

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And that’s not all.

By all means, this is not the end of a definitely longer list, and the next entries may come from a different project so I may add a few stuff once in a while.