unusual structural design + dome kinda roof structure

[Groszni]

Hello eng tips user
Im designing this structural steel mosque(the link contains the top view of the structure), its has 2 stories and 28m x 28m area, the seismic design category is D and im using a steel moment frame. the problem is im not allowed to put the column but just on the side of the building that are already show on the shop drawing. i tried run an analysis and the deflection of the plate+beam is EXTREMELY high! its like 2ft wow. so i would really aprreciate if you would help me out with some advice ! how do i model the dome in the structural program like ETABS and SAP? can i just make the dome as a load like when you model a structure without the roof truss? and oh when you designing steel moment frame with reinforced concrete slab what kinda slab you model in program such an etabs is it shell? membrane? or what? and may i know why?

regards

 

[daranguiz]

Hi, can you explain a little more? Can you attach an elevation?

 

[Groszni]

@daranguiz hey thanks for the response! each story has the same height its 4.25m and the dome radius is 3 m

 

[jayrod12]

How deep are your beams? Based on some rules of thumb I would expect them to be close to 2m deep. You can't realistically think you can span 28m with anything normal do you? I don't think the 3m dome is really the issue. The span of the main structure is.

 

[BAretired]

My advice to you is to put ETABS and SAP aside until you get an idea how you wish to frame the structure using pencil and paper.

You say the deflection of the plate plus beam is about two feet? What size of beam? What plate?

For a 28m span, you will probably require substantial steel trusses, perhaps in the order of two meters deep for both floor and roof.

BA

 

[Groszni]

@jayrod12 yeah never face this kind of problem in college before im a fresh graduated. And oh because the seismic category design is D, i have to use a SMF too! the column would be extremely big too right?

@BAretired i use the WF 18*192 i know ive should use the W40, and the plate is made from rc with 12cm thick of the floor and 10cm thick of the roof deck

 

[Ingenuity]

i use the WF 18*192 i know ive should use the W40

and the plate is made from rc with 12cm thick of the floor and 10cm thick of the roof deck

Do you have a mentor or experienced/senior engineer that you can consult with for this project?

Listen to jayrod12 and BAretired - you need to conceptually frame this building "on paper" before you dive into black-box computer analysis.

If you don't have personal access to a senior advisor then grab a text/reference on large span steel framing and use L/D ratios to obtain trial member sizes. Check with local construction/fabrication companies (or your countries institute of steel construction) to see what are economic methods to your locale.