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Curved Steel Staircase Design 2

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Thulz

Civil/Environmental
May 16, 2018
5
Untitled_sbqz4d.jpg


Hi all,
Presently am working in analysis and design of curved steel staircase.
Staircase details :
Outer Curve Span - 11.4m
Inner Curve Span - 6.3m
Height of Stair - 3.3m
Rise - 150mm , Tread - 1.5m width , Varying size (approx 710mm at outer side & 330mm at inner side)
Stringer Beam - Plate of depth 350mm and 16mm thick
Tread Plate - 8mm thick Plate
Tread Plate Supports at both side - Plate 50mm wide and 8mm thick
Handrails load is taken as Nodal load of Fy= - 0.18kN (Separate analysis done)
Loading :
Live Load - 4 kN/m[sup]2[/sup]
stone Finish Load - 0.84 kN/m[sup]2[/sup] (maximum value taken)
Supports:
Both End fixed, If I go for one end fixed and other end hinged, resulting in higher reactions and even higher deflection.
So, I considered both end fixed. Knowing that I have to release moment at one end, assigned both end fixed to reduce deflection.

I have analysed in Staad pro.
Considering Stringer beam as Plate element, found with higher deflection.
If i consider Stringer beam as beam element , found with lesser deflection.
Still the deflection not in limit.

Need Clarification on Support condition and which element I have to consider for analysis? either beam element or plate element.[highlight #EF2929][/highlight]

PFA images for reference.





 
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Your support condition will depend on the fixity. So, how "fixed" is your support? Is it a tall and slender plate girder that will twist and warp? Is it a large concrete beam? Apply the reactions to the supporting members and see how much movement you get. At the end of the day, its a judgement call.
 
I probably wouldn't use bar elements for something like this, model stringers and treads with plates/shells. Fixed conditions for all shell interfaces. The mesh definition will impact the stiffness, ie the smaller the mesh the more flexibly the structure. Bar elements may overestimate the stiffness.

As a starting point I'd use pinned vertical supports top and bottom of the stair and just enough horizontal restraint to make it stable, by this I mean I'd take just the corner nodes at the top and bottom and restrain translation in the x,y,z but not rotation. If it wasn't working under these conditions then I'd look into some stronger fixity assumptions. Final pass I'd swap out the vertical pins with springs to capture the supporting structure deflection at the attachment points.



Open Source Structural Applications:
 
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