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sarif.muhammed General Sponsor
Joined: 20 Jul 2009 Posts: 7
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Posted: Sun Jul 21, 2019 4:31 am Post subject: Single stair steel stringer beam at centre |
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Dear All,
What are the precautions or checks we need to do in order to design a steel stair case with steel stringer beam at center as shown in images,
Does I section is a viable solution for this?
Thanks
Sarif
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sakumar79 ...
Joined: 18 Apr 2008 Posts: 713
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Posted: Tue Jul 23, 2019 10:57 am Post subject: |
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Dear Er Sarif,
In addition to typical design for DL+LL, the stringer beam has to be designed for DL+Half LL assuming the half LL is fully on one side of the beam. This will result in UDT on the girder and hence ISMB sections may not be most suitable. Rectangular Tubes, Double ISMC as Box sections or a tube built up with plates may be more economical.
Hope that helps
S Arunkumar
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dgupta General Sponsor
Joined: 07 Sep 2009 Posts: 32
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Posted: Fri Jul 26, 2019 10:11 am Post subject: |
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You may want to check for vibration as well.
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abhio ...
Joined: 08 Mar 2010 Posts: 548
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Posted: Fri Sep 06, 2019 1:41 pm Post subject: |
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Please also consider lateral load on the handrail as per IS: 875 (Part - II).
The toughened glass/ acrylic balustrade is interesting. I suppose it requires very strict deflection control to prevent cracking.
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logeshcivil SEFI Regulars
Joined: 07 Aug 2017 Posts: 35
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Posted: Mon Aug 29, 2022 5:41 am Post subject: |
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Dear sefians
If i were to design Staircase as shown in the figure.How should i go about it.What would be the ideal thickness of the plate?
What are the points should i consider for the design?
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vikram.jeet General Sponsor
Joined: 26 Jan 2003 Posts: 3839
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Posted: Mon Aug 29, 2022 10:27 am Post subject: |
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sakumar79 wrote: | Dear Er Sarif,
In addition to typical design for DL+LL, the stringer beam has to be designed for DL+Half LL assuming the half LL is fully on one side of the beam. This will result in UDT on the girder and hence ISMB sections may not be most suitable. Rectangular Tubes, Double ISMC as Box sections or a tube built up with plates may be more economical.
Hope that helps
S Arunkumar |
Yes , very nicely enlightened . Stair one one side loaded will give torsional moment at supports .and Box pipe / double channels welded together in box shape are more suitable.
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sakumar79 ...
Joined: 18 Apr 2008 Posts: 713
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Posted: Wed Aug 31, 2022 3:33 am Post subject: |
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logeshcivil wrote: | Dear sefians
If i were to design Staircase as shown in the figure.How should i go about it.What would be the ideal thickness of the plate?
What are the points should i consider for the design? |
Dear Er Logesh,
If you look carefully, you can see a central tapered plate below the tread. Hence,
1. Design the tread as a double cantilever for foot fall load. Normal Live Load as UDL should not be considered and instead point loads close to edge will be more critical. Deflection check may also be critical in this case
2. Design the vertical tapered plate as a cantilever from the wall
3. Design the weld connection for transfer of bending stresses from the vertical plate to the plate along wall edge
4. Design the stringer plate and bolts to transfer the bending stress from the plate to the wall
Other sefians may point out any step/check I missed
Hope that helps
Arunkumar
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vikram.jeet General Sponsor
Joined: 26 Jan 2003 Posts: 3839
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Posted: Wed Aug 31, 2022 7:43 am Post subject: |
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sakumar79 wrote: | logeshcivil wrote: | Dear sefians
If i were to design Staircase as shown in the figure.How should i go about it.What would be the ideal thickness of the plate?
What are the points should i consider for the design? |
Dear Er Logesh,
If you look carefully, you can see a central tapered plate below the tread. Hence,
1. Design the tread as a double cantilever for foot fall load. Normal Live Load as UDL should not be considered and instead point loads close to edge will be more critical. Deflection check may also be critical in this case
2. Design the vertical tapered plate as a cantilever from the wall
3. Design the weld connection for transfer of bending stresses from the vertical plate to the plate along wall edge
4. Design the stringer plate and bolts to transfer the bending stress from the plate to the wall
Other sefians may point out any step/check I missed
Hope that helps
Arunkumar |
Nice response fm Er Arun.
Only reg supporting wall -
In case wall is rcc , it seems OK as it can take bending moments .
In case of bk wall ( without stringer rcc beam sandwiched in masonry )
Regarding check of stresses in wall ,if stair loaded fully , moment from stringer plate , transfered to wall and causing bending Tensile stresses in masonry be checked .
Just to illustrate : stair width = 1.0m
Point load of 130 kg at tip of cantilever may cause Mo in wall along vertical direction
= 130x1.0= 130 kgm / tread width of say 30cm
( this 130 kg pt load was as per earlier IS 875 , but if revised same value may be taken as per rev)
Taking tread width as 30cm, bk wall 23 cm th
BM =130x100= 13000 kgcm per 30 cm , thisBM is caused in vertical direction of wall
If all steps are loaded , the bending Tensile stress in bk masonry
= 130x100 x6 / (30x23^2)
= 4.91 kg/cm2
Direct comp stress due to masonry wt
And considering wall section at lowermost step level
This section is subjected to uniform BM of 130 kgm/ 30cm , the vertical BM from upper steps get transfered at base section
Taking F/F ht
Direct comp stress = 3.0m
Masonry wt = 500x3.0 = 1500 kg / m run
Comp stress at wall bottom = 1500 /(23x100) = 0.65 kg/cm2
Hence n
Tensile stress ,net = 4.91 -0.65 = 4.26 Tensile Not OK * cf 0.7 kg/cm2 for 1:6 bkwork
( * relaxations due bk masonry sandwiched between rcc slab at floor level can be taken to some extent but bk masonry stress is far off from permitted )
Rcc wall would suit otherwise 345 th wall can be tried
Just a rough illustration but engineers can further refine.
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