How does Tekla Portal Frame Designer determine the Combination Factors for additional crane loads?

Tekla Portal Frame Designer
18
Tekla Portal Frame Designer
crane load
combination factors
From initial inspection it would appear that Tekla Portal Frame Designer uses smaller factors than required for a combination that includes Dead + Imposed + Vertical Crane + Horizontal Crane load cases

Tekla Portal Frame Designer:
1.2 Dead + 1.2 Imposed + 1.2 Vertical Crane + 1.2 Horizontal Crane

However, BS5950:2000 Table 2 would give
1.2 Dead + 1.4 Imposed + 1.4 Vertical Crane + 1.4 Horizontal Crane

We follow 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 loadcases acting together. Clause 2.4.1.3 does list the 'Dead + Imposed + Horizontal Crane' combination (that we kind of discounted) and this 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.
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