Combination factors used for "Dead + Imposed + Vertical Crane + Horizontal Crane"
18
Tekla Portal Frame Designer
Environment
British Standard
The issue
Tekla Portal Frame Designer uses smaller factors then advised by the code for a combination that includes Dead + Imposed + Vertical Crane + Horizontal Crane load casesPortal Frame Desinger uses:
1.2 Dead + 1.2 Imposed + 1.2 Vertical Crane + 1.2 Horizontal Crane
But BS5950:2000 Table 2 would give
1.2 Dead + 1.4 Imposed + 1.4 Vertical Crane + 1.4 Horizontal Crane
Justification for Portal Frame approach
Portal Frame Designer follows the intention of the code but Table 2 contradicts itself for Imposed load acting with Vertical and Horizontal crane loads and is incomplete:Imposed with vertical = 1.4
Imposed with horizontal = 1.2
Imposed with vertical and horizontal = ?
Horizontal load with imposed with vertical = ?
Vertical load with imposed with horizontal = ?
The lower factors are used to take account of likelihood of the full load cases acting together. Clause 2.4.1.3 does list the 'Dead + Imposed + Horizontal Crane' combination which would give '1.2 Dead + 1.2 Imposed + 1.2 Horizontal Crane'. If you add Vertical crane load to this combination it would make no sense to increase the Imposed & Horizontal factors to 1.4. Strictly to Table 2 the factor for this additional Vertical load should be 1.4 but again this makes no sense, hence we use 1.2.