IStructE exam - lateral design and omit from consideration

[tcfl]

Hi,
I'm hoping to sit the next exam and starting to prep for it. One of many things I'm not sure is the level of detail for lateral design. Being on the west coast seismic mostly governs, I would assume the exam only requires wind for lateral since that's the only information given?
Also, in many cases the staircases and lift shafts are omit from consideration. When using this elements as your lateral resisting system, do you still have to design and check them or its omit from consideration totally? Would you still have to design the stair/lift shaft foundation?

Thanks in advance

 

[msquared48]

I may misunderstand your post here, but on the West Coast we DEFINITELY have to consider seismic, as well as wind.

As for the stair well system, if it is in the shear wall system, the walls will see wind and seismic loads.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

Maybe someone who has taken the IStructE exam can help. Exams in different countries are like apples and oranges.

 

[tcfl]

Thanks for the replies.
Yes, being on the west coast and practicing here seismic and wind is a must.
To clarify, the exams do not specify location for each question and only wind load information is given. The same exam is writen by everyone throughout the world every year. That's why I assumed that seismic design is omitted, except the last quesiton in recent years giving the specific for seismic design.

 

[JAE]

I think most structural exams these days include seismic questions.

 

[msquared48]

Anything to cause more stress during the exam, right JAE?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JAE]

Or strain.

 

[msquared48]

That was a stretch...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

My point was that IStructE is a UK organisation, so although the exam is the same wherever you are located, it is based on the UK way of doing things. Those of us who don't practice in the UK might not be of much assistance.

 

[ooox]

Hi tcfl,

I took this exam in Australia last year where structures need to be designed for earthquake actions. The design of my lateral system (in this case a steel braced frame)was limited to wind loading only. I did state that the lateral system would need require further checks for earthquake actions and for robustness. You will need to undertake some preliminary calcs for your lateral system, whether its a shear walls, braced frame or a moment frame and there's numerous guides out there that let you do this quickly in 15 - 30mins. You will need to check your footings as well. Make sure you clearly state how lateral loads are transferred down to foundation,e.g. vertically spanning cladding transferring to the floor plates, then diaphragm action of the floor plates to shear walls, bending and shear in the shear wall to foundations etc etc.

Be careful with bracing around lifts and stairs - I've heard bracing across a door can result in automatic failure. For example, for bracing around a stairwell indicate bracing on 3 sides AND note that you have omitted bracing on one side to allow for access etc. The question will usually give you hints where you can place bracing.

The Institution has an Exam Preparation CD which is definitely worth purchasing together with The Structural Engineers Pocket Book and Concrete Society Scheme Design Manual.

Good Luck with the exam.

nineninenine

 

[tcfl]

Thanks nineninenine, thats what I'm looking for. So the lateral system still has to be sized and designed for, even in the omitted zone of the stairs and lift shafts.

 

[ooox]

Yes, you'll need to calculate the size of these members. So- the thickness of shear walls, section size of vertical bracing or size of columns/beams in a moment frame. The omitted zones for stairs and lifts are normally where you can locate the lateral system. There may be some instances where bracing these areas is not possible e.g.the question states you can't put them there or they're positioned via a walkway to the building and will therefore contribute very little to the overall stability of the structure.

I know California has very specific rules on where seismic bracing can be located so it would be worth stating that a further check of bracing location would be necessary in your response.