Temporary Wind Loading in MasterSeries

In MasterSeries, modelling temporary wind loads - for temporary works, scaffolding, falsework, short-term erection stages, or temporary structures with reduced design lives, is handled primarily through the MasterKey Wind Analysis module by modifying site return periods and seasonal exposure factors.

1. The Core Velocity-to-Pressure Squared Relationship

A common query received on the support desk involves understanding why a modest reduction in temporary basic wind speed produces a much larger reduction in final wind pressure:

• Basic Wind Speed (vb): The Probability Factor (cprob, for reduced return periods like 1-in-5 or 1-in-10 years) and the Seasonal Factor (cseason, for short-term operational windows) apply linearly to scale the basic wind velocity (vb).
• Dynamic Wind Pressure (qp): Peak dynamic wind pressure is proportional to the square of the wind velocity (qp​ ∝vb2​.

• Numerical Example: If a 1-in-5 year return period gives cprob = 0.85 and a 4-month exposure gives cseason = 0.83), the combined velocity reduction factor is:

  • 0.85 x 0.83 = 0.7055.

• Because pressure varies with vb2, the resulting dynamic pressure scales by: 

  • 0.7055^2 ≈ 0.498
• This results in an approximate 50% reduction in applied wind pressure (rather than 30%), which accurately reflects extreme value wind statistics.

2. How to Set Up Temporary Wind in MasterSeries

1. Access Site Data: Go to Loads > Wind Panel Loading (Pro) > Site Data Wind Analysis in MasterFrame or MasterPort.
2. Adjust Return Period cprob: Override the standard 1-in-50-year permanent building return period by selecting a reduced return period (e.g. 1 in 2, 5, or 10 years, or a custom risk period).
3. Set Seasonal Months cseason: If the temporary structure is erected only during specific months (e.g. summer or a 4-month window), select those specific months rather than leaving exposure set to "All Year".
4. Automatic Recalculation: Upon exiting the wind site module, MasterSeries automatically recalculates the reduced peak dynamic pressures qp across all heights and wind directions for your panels or members.

3. Key Modelling Controls for Temporary Works & Scaffolding

• Review the CsCd Structural Factor: The default CsCd = 1.15 factor in Eurocode mode accounts for dynamic augmentation and non-simultaneous gust peaks on permanent, tall building envelopes. For short-term temporary works or light scaffolding, applying CsCd = 1.15 is often overly conservative; technical support advises reviewing this setting under Wind Directions and Settings and setting CsCd closer to 1.0 where appropriate.
• Open Scaffolding & Lattice Frames (Member Loading): Automated 2D wind panels are designed for enclosed building envelopes. For open scaffolding towers, temporary unclad steel gantries, or falsework, wind loads should be calculated manually using member force coefficients (cf from EN 1991-1-4 Cl. 7.11 for lattice structures/scaffolding) applied to the dynamic pressure qp derived from MasterKey Wind, and inputted directly as 1D Member UDLs or Nodal Loads in MasterFrame.
• Transient Erection Stages: When evaluating temporary wind during cladding installation or partial erection, ensure the unclad or partially clad stage is analysed as a transient situation (per EN 1991-1-4 Cl. 2.2) [Ticket 5443].