of potentially non conservative items in cellbeam software -...
TRANSCRIPT
04/08/16
Overview of potentially non‐conservative items in Cellbeam software The Cellbeam software package is written by the Steel Construction Institute (SCI) on behalf of ASD Westok Ltd, trading as Kloeckner Metals UK | Westok. The package analyses and designs Westok Cellbeams ® formed from rolled sections. This document has been prepared, as certain items have been identified in the Cellbeam software package which may lead to potentially non‐conservative results. These items are tabulated below, and further information is contained in the following pages. Cellbeam users are encouraged to carefully review these items to see if further action is needed. Please contact Westok’s Technical Advisory Service on +44 (0) 113 205 5270 or [email protected] if further information is needed.
ITEM DESCRIPTION ACTION
001 Direct Load – roof beams Fix applied in V10.2
002 Direct Load – floor beams Fix applied in V10.2
003 Loads to cantilever tip Fix applied in V10.2
004 Exceptional Snow Load Partial load factor of 1.0 adopted in v10.2
005 Edge beams with Precast units For completeness, a further note has been added to v10.2
006 Primary beam with non‐sequential secondary beams
Fix applied in V10.0
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ITEM 001: Result not updating after change of direct loads – roof beams
ACTION: Fix applied in v10.2
Example: 1. Start new project
2. Add a standard rafter
3. For clarity, remove all (kN/m2) loads.
4. Add dead = 100 kN point load at 15m
5. Note summary results:
6. Max UF =0.62 (vierendeel bending)
7. Change value of point load to 200kN. Note, when load value is changed, summary
pane is not cleared as it should be.
8. Click ‘analyse’
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9. Note summary results:
10. Max UF =0.62 (vierendeel bending)
11. Adjust span by 0.5m, then back to 30m (reset result)
12. Note summary results:
13. Max UF = 1.14. This is the correct value.
14. If the above steps are repeated but the STARTING VALUE is 200kN (i.e. FAIL UF), then
changing to 100kN will result in an adjustment of the summary results on analyse.
Note that summary pane is still not cleared after change of value.
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ITEM 002: Result not updating after change of direct loads –floor beams
ACTION: Fix applied in v10.2
Example:
1. Start a new project
2. Open a composite floor beam
3. Set slab type to ‘no slab’
4. Remove all (kN/m2) loading (for clarity)
5. Add dead = 25 kN point load at 8m
6. Copy the floor beam
7. Run analysis on copied beam and note UFs:
8. Vibration is critical = 4.28 Hz
9. Change dead load to 50kN and run analysis
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10. Note – no change in summary results
11. Change span to 17.1m to reset the summary and run analyse
12. Summary results e.g. Vibration now correctly displayed.
13. Note the bug is not exhibited by the original beam, only the copied version.
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ITEM 003: No analysis of loads applied to cantilever tip
ACTION: Fix applied in v10.2
Example:
1. Tapered beam has been set up with loads only applied to the tip of the cantilever
(span = 10.1, loads applied at 10.1m ‐ see screen grab below).
2. Note very low UFs (0.03 max)
3. Change load position to 10m. Note this action replicates the direct load bug, so reset
the project analysis by, for example adjusting the span slightly then back to the
original 10.1m
4. Run analyse and note UFs – see below – max UF is now 0.99.
5. Load is ‘missing’ the end of the beam because the ‘length’ of the beam is shorter
than the ‘span’ of the beam.
6. Note this bug only applies to certain shapes of taper, e.g. flat bottom flange,
negative slope on top flange, where ‘length’ is less than ‘span’.
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ITEM 004: Partial load factor for exceptional snow load combination
ACTION: Partial load factor of 1.0 adopted in v10.2
Example:
1. Start a new project and set up a prismatic rafter with an exceptional snow load
2. Go to load combinations area and select ‘Auto‐generate’.
3. See load combination 7:
4. Exceptional snow partial load factor (ESF) = 0.2. As the notional ‘accidental load’ the
exceptional snow should have a load factor of 1.
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ITEM 005: No lateral torsional buckling check for non‐composite precast edge
beams
ACTION: For completeness, a further note has been added to v10.2
Example:
1. Start a new project and set up an edge beam, using either solid precast or hollow
core slab.
2. Run analysis; see analysis results
3. Normal stage LTB check displayed as ‘N/A’ as slab is assumed to restrain the top
flange as per the detail shown
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ITEM 006: Error in beam arrangement when secondary beams are added out of
sequence
ACTION: Fixed in v10.0
Example:
1. Start a new project, set up a composite floor beam
2. Add two secondary beams at 5.67m and 11.33m
3. Add a third secondary beam at 7m – note dimensions incorrectly displayed and shear
studs go off the end of the beam.
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4. When this error occurs there may be an unconservative effect on both the number
of studs on the beam and the reported end reactions.