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Frequently Asked Questions (FAQ)
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AnswerNo, this is unfortunately not possible.If the option 'Tension Stiffening' is not applied for the calculation, the distribution coefficient ζ is either '0' for 'uncracked' or '1' for 'cracked'. See also the technical article for the distribution of the distribution coefficient ζ linked below.But the manual specification of e.g. ζ = 0.5 is not possible.
AnswerFor the calculation of deformations in cracked sections (state II), the RF‑CONCRETE Deflect extension is available in the RF‑CONCRETE Surfaces add-on module.RF‑CONCRETE Deflect requires an explicit load situation for the analytical calculation of deformations in cracked sections (state II), which is only given by using the load combinations (CO). Result combinations do not provide an explicit load situation, no matter if an additive or an enveloped OR combination. Therefore, when applying an RC for the calculation of deformations in RF‑CONCRETE Surfaces by using RF‑CONCRETE Deflect, you receive the mentioned error message. See Figure 01.To avoid this problem, you can simply generate load combinations (CO) instead of result combinations (RC). If you still want to perform the ultimate limit state design with RCs, you can manually create a LC in addition to the existing RCs, for which you want to calculate the deformations by means of RF‑CONCRETE Deflect. See Figure 02.It is important that for the calculation of the deformations, RF‑CONCRETE Surfaces applies the loads from a quasi-permanent design situation by default. See Figure 03. This means that the LC, for which the deformations are to be calculated, must be defined as "quasi-permanent." As an alternative, it is also possible to user-define the check boxes for the settings of design situations (see Figure 03).
AnswerThe RX‑TIMBER Brace program is generally used for the calculation of the stiffening of double-tapered beams with variable cross-section height. They can be designed in the RX‑TIMBER Glued‑Laminated Beam program.From the RX‑TIMBER Glued-Laminated Beam program, you receive the equivalent loads by beam listed for each load case. The calculation is performed according to Section 220.127.116.11 of EC5. This equivalent load must be transferred to the RX‑TIMBER Brace program for the identical load cases (Figure 01).The axial forces calculated in RX‑TIMBER Brace must be again defined as additional forces in RX‑TIMBER Glued-Laminated Beam. In this case, it is necessary to make a distinction between the compression force in the upper chord of the brace and the tension force in the bottom chord of the brace. Both axial forces must be applied separately. From the tension forces of the bottom chord results a deflection force in the spatial system, which can be applied as an additional moment (Figure 02).
AnswerIt is possible that the module determines a high required reinforcement for SLS if it is not possible to fit the provided reinforcement in the cross-section or rather in the reinforcement layer. It is also possible that the deflection analysis leads to high required reinforcement.SolutionIt could be a solution to increase the maximal number of reinforcement layers. With a higher number of reinforcement layers it is possible to provide a higher reinforcement (picture 1).For deflection analysis it could be a solution to disable the automatically increasing of the longitudinal reinforcement for serviceability limit state design and define a minimal reinforcement (picture 2). In combination with other SLS checks it could be useful to calculate the deflection analysis in a separate case.
AnswerThe deduction of the precamber in the serviceability limit state design is actually not regulated in steel structures. However, in response to customer requests, we have adopted the corresponding add-on module according to the timber or concrete add-on module. However, according to the standard specification, this value should only be considered in the quasi-permanent design combination.This does not apply to the characteristic and frequent design situation. Thus, as soon as the design situation in the add-on module is adjusted accordingly (see figure), the applied precamber is also subtracted from the resulting deformation.
AnswerThe Young's modulus in the state II is not directly output in the deflect calculation.But you can switch to the result window "3.3 Point-by-Scavity Serviceability Design" and filter an FE mesh or grid point for which you want to see the design details. See Figure 01.In the table, select the result row for the "u z, local " deformation.Then, click the [i] button to display the design details for the selected point.In the design details, you can find the intermediate values for the deformation analysis, such as the moment of inertia of the cross-section in state I and state II, the distribution coefficient zeta, and the final cross-section values. See Figure 02.Since these intermediate values are always determined when you open the design details table and are always displayed and temporarily saved for that point, the intermediate values can not be displayed graphically for the designed surface.
AnswerIt is often the case that the selection of out-of-date materials may have an impact on the deformation of the beam. Please note that the material properties should always be taken from the respective standard. The material properties of the same material may differ depending on the standard and its National Annex.For example, the same concrete was selected in this example, but the concrete has C35 / 45 | DIN 1045-1 compared with concrete C35 / 45 | DIN EN 1992-1-1 concerning a smaller modulus of elasticity (see Figure 1). Consequently, a larger deflection is created in the mid-span of the reinforced concrete beam, which is only loaded by its self-weight (see Figure 2).
In RFEM, you can simulate a pulley by using the 'Cable on Pulleys' member type. In this way, it is possible to calculate pulley systems, for example.
It is necessary to ensure that the member including all buckling points only consists of one polyline (see the figure). Otherwise, the model would be suspended on nodal supports and no force deflection would occur at these points.
In order to calculate the deformations in cracked state in RF‑CONCRETE Surfaces, it is necessary to select at least one load case or combination in the 'Serviceability Limit State' tab in Window '1.1 General Data' (see Figure 01).
In the lower part of the window, specify whether the method of check should be 'Analytical' or 'Nonlinear'.
- If 'Analytical...' is selected, it is necessary to activate the 'Deflection with RF‑CONCRETE Deflect' option in the detailed settings (see Figure 02).
- If 'Nonlinear...' is selected, the design of deformations can also be found under the detailed settings. The 'deformation' is activated here by default (see Figure 03).
In concrete design, the design situations can be defined as characteristic with direct load, characteristic with forced deformation, frequently and quasi-constantly.
You can view the verifications required according to the standard for the respective dimensioning initiatives in the detail settings of the add-on module (see Figure 1).
If proofs are now activated in tab sheet 1.6 under suitability for use that do not correspond to the design situation, a hint will appear after the calculation.
In this case it is recommended to define the necessary design situations or to remove the proofs to be calculated in register 1.6.
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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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