Internal Pressure

Here you enter information pertaining to the factors used in the equation in NBC 2015 4.1.7.3.(3) or NBC 4.1.7.1.(3) to generate internal pressures.

Openings

You enter Building Openings category NBC 2015 Table 4.1.7.7 used to determine the internal pressure coefficient C_pi . The descriptions in table have been abbreviated to make the choices

• Uniform, small < 0.1% area,
• Non uniform, resistant, closed
• Large, often open

When using NBC 2010 Commentary I-31, these categories are phrased differently, but have the same effect.

Gust Factor C_gi

The input for gust effect factor C_gi defaults to 2.0, as per NBC 4.1.7.4. For large structures having a single unpartitioned volume without numerous overhead doors and openings, you can enter a value you have calculated from the equation in 4.1.7.4.