#### Further Information

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• ### What is the formula used to calculate the ASCE 7 wind velocity profile?

The wind velocity profile in RWIND Simulation according to the ASCE 7-16 standard [1] is calculated based on Eq. 26.10-1. The coefficients and basic wind speed in this equation below are incorporated in the wind pressure equation.

Velocity wind pressure (imperial): qz = 0.00256 Kz Kzt Kd Ke V2

We must reference this equation to calculate the inlet velocity relative to elevation for the RWIND Simulation CFD wind tunnel. To consider only velocity rather than pressure from this equation, the basic wind speed is multiplied by the square-root of each coefficient. Notice the velocity variable in Eq. 26.10-1 is squared which requires the square root of the coefficients to be considered.

$Inlet\;velocity\;=\;V\sqrt{K_e\;\cdot\;K_{d\;}\cdot\;K_z\;\cdot\;K_{zt}}$

Because the ASCE 7-16 standard does not address wind CFD analysis and magnitude of the required inlet velocity, it is difficult to draw comparisons. Therefore, this is the closest estimate for calculating the RWIND Simulation inlet wind velocity per the code.

• ### Is it possible to perform automatic live load reduction in RFEM or RSTAB per the ASCE, IBC, or NBCC?

Live load reduction is not considered automatically in RFEM. RFEM and RSTAB are general FEA and framework programs. The program does not understand what is a floor element vs wall element. Only a general plate element is defined. It is not possible for the program to determine the area of a floor for live load reduction.

A user must manually consider the reduction by modifying the live load magnitude directly in the load application.

• ### Is it possible to use the RF/STEEL AISC module as it is and to specify the internal forces, for example, from another calculation or program?

Unfortunately, this is not possible. The design module can only be used together with the internal forces from RSTAB or RFEM.
• ### Is the Gust-effect (G or Gf) from the ASCE 7-16 Sect. 26.11 considered in RWIND Simulation?

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."

In 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.

• ### Will other standards be added to the wind profile generation options in RWIND Simulation?

Additional standards and codes to generate the wind profile automatically in RWIND Simulation will be added in the future. We are always considering feedback from our current customers on which standards will be beneficial.

• ### Does software RWIND Simulation account for the internal pressure coefficient (GCpi) from the ASCE 7-16?

The 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.

• ### Does the software RWIND Simulation consider the wind directionality factor (Kd) from the ASCE 7-16?

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 [1].

• ### When designing seismic equivalent loads with a Response Spectra Analysis (RSA) in RFEM, how can I apply the modal response parameters Ie/R according to Sect. 12.9.1.2 in the ASCE 7-16 to my results?

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. 12.9.1.2 [1]. Additionally, in the Code Parameters table > Coefficients, the Seismic Importance Factor (Ie) and the Response Modification Factor (R) can further be set.

• ### How would you best model hold down elements within panels?

In a short overview, creating hold down elements involves modeling rigid links and adding in nodal supports with non-linearity settings that allows the supports to take only tension forces. A line support is added at the bottom of the wall that only takes compression forces. The individual nodal supports connected with rigid members only take tension forces.

A more detailed look on how these elements can be model can be seen in the video below.
• ### Why is it not possible to select the individually or simultaneously acting load cases in the "Combination Expressions" tab?

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.

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If not, contact us via our free e-mail, chat, or forum support, or send us your question via the online form.

#### First Steps

We provide hints and tips to help you get started with the main programs RFEM and RSTAB.

#### 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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