D3.B.13 Design of Tapered Beams
Sections will be checked as tapered members provided that are defined either as a Tapered I section or from a USER table.
Example using a Tapered I section:
UNIT CM MEMBER PROPERTY 1 TO 5 TAPERED 100 2.5 75 25 4 25 4
Example using a USER table:
START USER TABLE TABLE 1 UNIT CM ISECTION 1000mm_TAPER 100 2.5 75 25 4 25 4 0 0 0 750mm_TAPER 75 2.5 50 25 4 25 4 0 0 0 END
You must specify the effective length of unrestrained compression flange using the parameter UNL.
The program compares the resistance of members with the applied load effects, in accordance with BS 5950-1:2000. Code checking is carried out for locations specified by the user via the SECTION command or the BEAM parameter. The results are presented in a form of a PASS/FAIL identifier and a RATIO of load effect to resistance for each member checked. The user may choose the degree of detail in the output data by setting the TRACK parameter.
The beam is designed as other wide flange beams apart from the Lateral Torsional Buckling check which is replaced by the Annex G.2.2. check.
D3.B.13.1 Design Equations
A beam defined with tapered properties as defined above will be checked as a regular wide flange (e.g., UB or UC), except that the following is used in place of clause 4.3.6, the lateral torsional buckling check.
D3.B.13.2 Check Moment for Taper Members as per clause G.2.2
The following criterion is checked at each defined check position in the length of the member defined by the BEAM parameter.
Mxi ≤ Mbi (1 - Fc/Pc) |
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D3.B.13.2 G.2.3 Slenderness lTC
λTC = yλ |
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D3.B.13.4 G.2.4.2 Equivalent slenderness ITB for tapered members
λTB = cntνtλ
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D3.B.13.5 G.2.5 Taper factor
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Otherwise, c is taken as 1.0 (unity).