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Frequently Asked Questions (FAQ)
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You can find this setting in "Details," under the "Fire Resistance" tab.You can also control the time of fire resistance individually for each member or set of members.Then, it is possible to find the input in Table 1.10 for members, or Table 1.11 for sets of members.
Yes, it is possible.When applying a new surface load, it is possible to set "Temperature" as a load type. Instead of applying the uniform load distribution, it is possible to apply the variable load distribution (for example, linear in Z).For the load values, you can specify whether the constant temperature or the delta temperature should be applied.This results in the following load specification:And the following results (deformation in this case):
To apply this in the program, it is necessary to copy the "Temperature" load case (see Figure 01). All loads contained in the load case will be copied as well. One of the load cases is used for the ultimate limit state (ULS) load combinations, the other one for the serviceability limit state (SLS). The loading in the load case for ULS is now multiplied by 1.0/1.5 = 0.667 (see Figure 02).
In order to ensure that both load cases do not occur simultaneously, but only for the specific design situation, the exceptions are determined in the respective combination expressions. For ULS, it is quite simple to define the dead load case in the way that it is not combined with the temperature load case for SLS (see Figure 03). SLS applies exactly the other way around, that is, the load case of dead load is not combined with the temperature for ULS (see Figure 04). In this case, the "Differently for each combination expression" option must be activated.
The desired load combinatorics is then obtained (see Figure 05).
This is possible: For this, select the "Temperature" load distribution for the member load and then specify trapezoidal variable distribution over the length and height of the cross-section.
AnswerTo create a temperature load on a bar with the COM interface, simply use a bar load with the following parameters:Dim memload As RSTAB8.MemberLoadmemload.Direction = LocalZTypememload.Distribution = UniformTypememload.Magnitude1 = T_cmemload.Magnitude2 = dTmemload.ObjectList = "1"memload.Type = TemperatureTypeT_c corresponds to the constant temperature component and dT to the top and bottom different.
AnswerThis can not be implemented in RFEM on the load side. It could be possible to display this behavior on the Structure page by means of orthotropic surfaces.
The thermal expansion coefficient for the material is probably zero. As soon as you change it back to a realistic value, the note should no longer appear.
AnswerThe method according to EC 3 can only be used for the temperature curves from EN 1990-1-2. In addition, with the simplified calculation of the steel temperature in the EC 3-1-2, it is only possible to take into account increasing temperature profiles; a drop in the temperature is not available in this simplified calculation. However, it is also possible to use direct steel temperatures in the program (see Figure 1).
AnswerIn the program, you can enter a final temperature of the steel. This function has been implemented to use e.g. results from real fire events or fire test locations and carry out the analyzes with a more accurate temperature, since the temperature rise is usually divided into several phases in real firing and thus is more favorable for the design.When carrying out design on the level of temperature, it turns out that the highest temperature that occurs in the structural component is less than the critical steel temperature. The critical steel temperature is the temperature at which the component resistance is just as high as the loading due to mechanical loads.This is not a design according to ULS, since no stability analyzes are usually carried out in this case. Therefore, it is possible to use this method for the preliminary design of a structural component by calculating e.g. the critical temperature using the factor of utilization for the moment loading. We do not offer this method directly, but you have the possibility to determine a critical temperature of the structural component iteratively by specifying the temperature, but I would recommend to consider the stability analyzes. The determined critical temperature may be smaller than the one of the formulas in the Eurocode, because as usual, no stability analysis is considered.
Why do I get no stresses on the top or bottom side of a member loaded with temperature (heating on the top side) if the member has no elastic foundation? Or more specifically, why does the upward curved member (due to heating on the top side) have tension stress on the bottom side if the member has elastic foundation? There must be compression stress on the bottom side.
The topic can be easily illustrated on a single-span beam. For this, three structural systems are described below. These models are documented in the attached file.
Statically determined system (no foundation), dT = 80 ° on the top side
The member is curved upwards, but is free of stress in itself.
Like System 1, but with an additional member elastic foundation. The member elastic foundation is entered without a possible failure (nonlinearity).
If you would display the stresses sigma_x of the member for System 2a, you obtain compression on the top side of the member and tension on the bottom side of the member (see Figure 01).
Due to the curvature of the member and the existing member elastic foundation, the contact force p-z occurs, which should prevent the member curvature upwards (see Figure 02).
These contact forces p-z (Figure 02) are caused by the member curvature due to the temperature and the applied member elastic foundation. The illustrated contact forces can be replaced by the member load opposed to the curvature. This is shown in System 2b in the example file.
The member elastic foundation is removed and a variable member load is entered in the Z-direction.
When comparing the results (for example, deformations u-z) on both System 2a and System 2b, you obtain the results with the same value (see Figure 03).
Moreover, you can also display the stresses sigma_x for both System 2a and System 2b. These have also the same value (see Figure 04).
System 3 should only document the stresses due to the temperature difference on a statically determined system (without foundation).
The results documented in the "single-span beam" example can also be transferred to the surfaces with elastic foundations.
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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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