Holdfast Training Services Trial Blog

Whilst I’m pleased to see the Phase 2s on here so the Phase 3s can now wind down the blog contributions, I think RF is under the impression I may be hiding under a rock again, so below is a brief summary of some of the work i’ve done recently using a calculator and felt tip pens.  They’re all work in progress so feel free to comment with any suggestions, advice or queries.

Selfridges Drainage Management Plan

Below is the latest of 4 technical notes i’ve produced as part of the Selfridges Drainage Management Plan.  They’ve let their drainage get in a bit of a mess and there are literally places where shit has hit various fans (or more importantly some expensive handbags).  Expedition were initially engaged to summarise the issues.  They reviewed the drainage systems and produced 20 recommendations thinking that Selfridges would say thanks but no thanks.  Un/Fortunately depending on your perspective they turned around and tasked Expedition to enact every one of them.  There started 2 years of work for the civils team charged out at 15k per month.  What a terrible example of poor asset maintenance I hear you cry!  But is it really? £15k is probably two of their mid range handbags….retail space is worth a hell of a lot more to them when it’s operating than when a contractor has some hoarding up so they can do maintenance.  In retail, as in construction, decisions are made on a commercial basis, and sometimes this trumps engineering factors. If you can’t understand a seemingly ludicrous engineering decision, make sure you’re considering all the wider factors.

That said their latest idea to put a new toilet block on a part of the system that’s potentially already overworked (the exact drainage routes still aren’t known) seems truly crazy, and the work below (still in progress) is me trying to work out exactly how crazy it might be, and how to politely tell them.

EXP 326-4 Outfall 2 Assessment[2015]

Taipei Airport Drainage

Expedition are completing the concept design for the drainage masterplan for a new terminal at Taipei airport.  The detailed design is being done by Arup.

I was looking at the structural support for the downpipes.  There were a number of constraints.  The design requires twin stainless steel downpipes (circa 500mm diameter) to be supported from the roof truss and at berm level, but unsupported between so they resemble steel columns.    Large thrust forces will be developed at the pipe bends, high wind loads are expected, differential movement is expected between the roof and the ground (+/-45mm horiz. and 15mm vert.), seismic effects must be considered.

I initially looked at cantilevering the pipe 8m from the ground to alleviate the differential movement issue, which required me to assess the dynamic response of the pipe to the expected wind load, and the thrust of the water hitting the top of the hopper.  However the lead engineer wasn’t entirely uncomfortable with this, with too many variables for us to mitigate the risk without unwarranted analysis at concept level, so I then had to look at options for supporting at truss and berm level.

The latest (although potentially not final concept) using WGS 77 Victaulic couplings as a “flexible” (the meaning of the word here is relative as their flexibility is limited 9mm per m length) is shown below.  Although we calculated the forces and specified the couplings we omitted this from the concept document. We’re not paid to develop detail so why take on the liability.  I also got slapped on the wrist for writing “WGS77 or similar”. Despite seeing this approach numerous times on site it’s avoided in the design office as it opens up all kinds of legal issues if a “similar” product fails.