The following is a list of assumptions made in the current version of the portal frame builder.

AS/NZS1170.2 Assumptions

Wind loads are assumed to be uniform over the height of the building (ie. z=h throughout).

Torsion due to eccentricities on tall buildings with h > 70m (AS/NZS 1170.2 section 2.5.4) is not considered.

Fatigue (AS/NZS 1170.2 sections 2.5.5 and 2.5.6) is not considered.

The dynamic response factor Cdyn (AS/NZS 1170.2 section 2.5.7) is taken as 1.0.

No allowance is made for impact loading due to windborne debris (AS/NZS 1170.2 section 2.5.8).

The building is assumed to be not elevated (AS/NZS 1170.2 section 5.4.1).

The permeable cladding reduction factor Kp (AS/NZS 1170.2 section 5.4.5) is taken as 1.0.

The distributed live load is applied to the entire area of the roof, even if the roof area is greater than 200m2.

The 1.4kN concentrated live load specified in AS/NZS 1170.1 (but not in conjunction with the distributed live load - AS/NZS 1170.1 section 3.1) is not applied.

IS:875 Assumptions

Wind loads are assumed to be uniform over the height of the building (ie. z=h throughout).

In IS875 (Part 3) table 6 for a longitudinal wind direction (ie. q=90deg), areas E and G are assumed to extend a distance of W/2 from the windward edge of the roof, with areas F and H extending for a further distance of W/2.

In IS875 (Part 3) table 7 for a longitudinal wind direction (ie. q=90deg), areas H and L are assumed to extend for half of the roof length from the windward edge of the roof.

IS875 (Part 3) table 7 is used for all monoslope roofs, even if h/w >= 2.

The Kc factor from clause 7.3.3.13 is assumed to be 1.0 in all cases due to the problem of complying with pd >= 0.70pz in clause 7.2. The problem occurs because pd must be calculated for the primary load cases and Kc is unknown at that stage.

Interference effects from upwind obstructions are not considered (IS875 (Part 3) section 8).

Dynamic effects due to wind are not considered (IS875 (Part 3) sections 9 and 10).

Live loads are calculated in accordance with IS875 (Part 2) table 2 and do not include any extra allowance for rain, dust or the 0.90kN incidental concentrated load specified in IS875 (Part 2) section 4.5.