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Load tables and charts - The interaction between vertical and horizontal loading is shown to allow the most efficient selection when using wind loading to BS6399 part 2. The values shown are ultimate values in kN and are based on the Eaves Beam being connected to the first purlin by the eaves strut(s) which restrains the eaves beam and transmits part of the horizontal wind loads through the diaphragm action of the roof.
Restraint struts are required on all spans.
Design criteria are valid when the eaves beams are fitted exactly as shown in the Multibeam literature.
Spans up to 12m are possible, subject to minimum volumes - for further details contact our Technical Department.
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Deflection values -
Vertical deflection capacities are shown for a deflection limit of L/180. Where the deflection capacity shown exceeds the Ultimate (and SLS) it is only shown to allow the deflection at a lower load to be prorated. Where the dead load is a higher proportion of the total load than for normal roofing (tiled roof etc) then the allowable deflection limit should be reviewed. |
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Example
Span 6.0m, distance to first purlin 1.8m, distance to top side rail 1.8m,
Ultimate down (((dead+services) x 1.4) + (super x 1.6)) x 6.0 x 1.8/2 = +6.847 kN
Ultimate uplift ((dead x 1.0) - (wind uplift x 1.4)) x 6.0 x 1.8/2 = -6.156 kN
Ultimate uplift (((dead + super) x 1.2) - (wind uplift x 1.2)) x 6.0 x 1.8/2= -1.166 kN
Pressure on side = wind pressure x 1.4 x 6.0 x 1.8/2 = +6.048 kN
Suction on side = wind suction x 1.4 x 6.0 x 1.8/2 = -9.072 kN
Consider if side load pressure or suction is critical.
Suction value is 9.072 x 0.67% = 6.078 this value is just critical use this value.
The dead + services + super is not critical as it does not act in combination with any of the other loads. In this case the critical case is Ultimate uplift 6.156kN in combination with 9.072 x 0.67 suction (see use of chart above).
E185140 provides a horizontal pressure capacity of 5.6kN with a vertical uplift of 6.156
E215170 provides a horizontal pressure capacity of 7.2kN with a vertical uplift of 6.156
Thus the section that should be adopted is the E215170 with struts at mid span. |
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