[AS/NZS 1170.2:2021] Building Wind Loads Generator

Intro

This plug-in automates the calculation of  static wind loads in accordance with the  AS/NZS 1170.2:2021 standard for enclosed building. It allows engineers to input wind design parameters and instantly visualize height-wise wind pressure and force distributions, streamlining the wind load design process.

Note: Although AS/NZS 1170.2:2021 is a joint Australian/New Zealand standard, this plug-in currently implements only the Australian provisions.

Developed with

Applicable standards

Benefits of this plugin

How to use this plugin?

1. On the left, users input the wind design parameters of the structural model.
   By default, the program is set to allow input for each of the 8 cardinal directions individually.
   Users can directly assign direction-specific values for Mz,cat, Ms, and Mt for each direction in the panel.

   

2. If you prefer to apply a single wind parameter set to all directions, go to the Wind Load Input Condition menu and select Input Only Worst-Case Value. The program will then use one governing set of values for all directions.
   

3. Once all parameters are set, click the Calculate Wind Load button at the bottom left to perform the calculation. The plugin will then instantly visualize the results—Story Force, Story Shear, and Overturning Moment—in both graph and table formats. These results can be reviewed for each of the four directions: 0°, 90°, 180°, and 270°.

   

4. Finally, click the Apply  button to assign the calculated loads to your structural model. Depending on the orientation of the structure, the loads will be applied in the +X, +Y, -X, and -Y directions. By enabling the toggle button, you can also choose to apply wind loads only in the positive directions (+X and +Y)

Note

This plugin is organized into multiple functional sections, each guiding users through the process of generating static wind loads as per AS/NZS 1170.2:2021 standards. The wind design parameters allows users to define the key design parameters required for analysis. Each parameter is based on specific clauses from the standards.

Wind Design Paramters

① VR : Regional Wind Speed

The regional wind speed (in m/s) for an average recurrence interval (R years) is provided in Section 3. For Australia, refer to Table 3.1(A) based on peak gust wind data or  [Fundamental Basic Wind Velocity Map] 

② Mc : Climate change multiplier
Given in Table 3.3, the value of Mc is typically 1.0 or 1.05, depending on the region.

③ Md : Wind Direction Multiplier
As per Section 3, the wind direction multiplier is specified in Table 3.2(A) for Australia. Values range from 0.75 to 1.00, depending on the cardinal direction.

④ Mz,cat :TTerrain/Height Multiplier
Defined in Section 4.2, Mz,cat accounts for terrain roughness and height. For varying upwind terrains, Clause 4.2.3 allows for averaging.

⑤ Ms : Shielding Multiplier
Given in Section 4.3. Use Table 4.2 for structures ≤ 25 m in height. For structures > 25 m, or when shielding is not applicable, Ms shall be taken as 1.0.

⑥ Mt : Topographic Multiplier
Defined in Section 4.4. Use:

• Equation 4.4(1) for sites in Region A4 (above 400 m elevation),

• Equation 4.4(2) for Region A0,

• Elsewhere, use the larger of the values from Clause 4.4.1(c)(i) and (ii).

Site Wind Speed

For each of the 8 cardinal directions (β), the site wind speed at reference height z is calculated using the standard equation (as per Section 4).
The orthogonal design wind speed Vdes,θ is taken as the maximum site wind speed linearly interpolated across ±45° of the orthogonal direction.

Design wind pressures
Design wind pressures, in pascals (Pa), are computed using the equation:

where :

• pair  : density of air (1.2kg/m3)
• Vdes,θ  : building design wind speeds
• Cshp : aerodynamic shape factor
• Cdyn : Dynamic response facto(see Section 6)

⑦ Cshp : Aerodynamic shape factor

For external pressures on enclosed buildings, determined using Equation 5.2(1).

In this plugin, K factors (such as Ka, Kc,e, Kl, and Kp) are assumed to be 1.0 by default and therefore not explicitly considered in the calculation.

⑧ Cpe : External pressure coefficient

Found in Table 5.2(A) for windward walls and Table 5.2(B) for leeward walls. Depends on the h/d ratio.

⑨ Ka : Area reduction factor

As per Clause 5.4.2. Use Table 5.4 for roofs and walls of enclosed buildings. Default to 1.0 for other cases.

⑩ Kc,e : Action combination factor (for external pressure)

Defined in Clause 5.4.3. Generally 1.0

⑪ Kl : Local pressure factor for cladding

From Clause 5.4.4. Genrally 1.0, unless specific local cladding pressures apply.

⑫ Kp : Porous cladding reduction factor

Defined in Clause 5.4.5. Generally 1.0, or per Table 5.8 when permeable cladding is used.

⑬ Cdyn : Dynamic response factor

As per Section 6:

• Cdyn = 1.0 if the first natural frequency > 1 Hz

• For frequencies between 0.2–1.0 Hz, use Clause 6.4 (along-wind) or 6.5 (cross-wind)

• Note: This plugin does not support flexible tall buildings. Users must manually compute Cdyn using Equations 6.2(1) or 6.3(2)

⑭ Building Plan Dimensions (b × d)
Used to determine shape factor and wind-exposed area.

Conclusion

• This plugin provides a comprehensive and user-friendly environment for generating static seismic loads in compliance with AS 1170.4:2024.
• By guiding users through standardized parameter inputs and offering dynamic visual feedback, it ensures transparency in the seismic design process. Engineers can better understand how key inputs—such as soil class, structural height, and ductility—impact the story-wise load distribution, enhancing both design quality and decision-making efficiency.
• The seamless workflow from input to visualization and export significantly reduces manual effort and promotes standardized, reproducible outcomes in structural seismic design.