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Frequently Asked Questions (FAQ)
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AnswerIn the ASCE 7-16, the conservative value for the Gust-factor, G, is 0.85 for rigid buildings. The engineer can calculate an alternative and more accurate value. The Gust-effect, Gf, for flexible buildings accounts for size and gust size similar to rigid buildings but also considers dynamic amplification including wind speed, natural frequency, and damping ratio.Yes, the Gust-factor G or Gf, can be adjusted in RWIND Simulation. This value can be changed within the "Wind load" tab under "Wind velocity."
AnswerThe internal pressure coefficients do not need to be considered with in the RWIND Simulation program.RWIND Simulation always outputs the net pressure on the surfaces in RFEM. When it comes to a simulation with a building that has open windows in RWIND Simulation, there is an internal pressure acting on the inside of the building. The program uses this information to determine the resulting pressure based on the external and internal surfaces. This can be seen in Figure 1.A comparison cannot be made between this coefficient in the standard and a CFD calculation because there is no direct correlation.
The wind directionality factor (Kd) from the ASCE 7-16 Sect. 26.6 is considered in the ASCE 7-16 wind load profile or RWIND Simulation calculation and can be adjusted manually by the engineer. The wind directionality factor (Kd) can be considered in RWIND Simulation by modifying the factor under the wind veloicty profile settings before running RWIND Simulation in RFEM.
This factor for various structure types can be determined from table 26.6-1 from the ASCE 7-16 .
The modal response parameters can be set in the RF-DYNAM PRO - Equivalent Forces add-on module under the Response Spectra tab. In the Code Parameters table > Type of Spectrum > Modal Response Parameters, the default is set to "No Modification". This setting can be seen in Figure 1.
Changing this to "Force Related" in the drop-down window will divide the response spectra by Ie/R based on Sect. 22.214.171.124 . Additionally, in the Code Parameters table > Coefficients, the Seismic Importance Factor (Ie) and the Response Modification Factor (R) can further be set.
The "Individually/simultaneously acting load cases" option is not available for all standards.For example, if you select the standard "EN 1990" in General Data of the model, this option is available in the "Combination Expressions" tab.On the other hand, if you select "ASCE 7‑16", for example, this option is (currently) not available.
In RFEM/RSTAB, there are various load generators available under "Tools → Generate Loads" that you can use to generate snow and wind loads according to ASCE, EN, DIN, and CTE (see Figure).
For models that do not comply with the preset standard concept, you can create load specification by using the regular loads (for example, member loads from surface loads).
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Wind Simulation & Wind Load Generation
With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.
The generated wind loads acting on these objects can be imported to RFEM or RSTAB.
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