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Frequently Asked Questions (FAQ)
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AnswerIn the Settings for standard (DIN 18008), you can define the design coefficient kc as user-defined.It is indicated with 1.0 in chapter 8.3.6 (DIN18008-1: 2010-12), provided that no other parts of the standard are observed.For particularly for line-supported glazings, the coefficient with 1.8 for normal glasses and 1.0 for prestressed glasses is given in chapter 7.2 (DIN18008-2: 2010-12).
AnswerFor duopitch roofs with a roof iclination of > 5 °, the roof areas F, G, H, I and J have to be separately classified according to the windward and leeward side. For the wind direction of 0 ° (wind in longitudinal direction), positive as well as negative aerodynamic coefficients have to be taken into account for roof inclinations of up to 45 °.For these cases, this results in a total of 4 possible wind combinations, depending on the building side (see Figure 1).For the wind direction of 90 ° (wind on gable side), however, there are no positive external pressure coefficients for a roof inclination of > 15 °. For a building with a roof inclination of 45 ° you would receive 10 possible wind load cases (0 ° = 4 * 2, 90 ° = 1 * 2).LC w+:Only positive (pressure) aerodynamic coefficients per roof area are used.LC w-:Only negative (suction) aerodynamic coefficients per roof area are used.LC w-/+:Negative (suction) aerodynamic coefficients for the windward side and positive (pressure) coefficients for the leeward side of the roof are used.LC w+/-:Positive (pressure) aerodynamic coefficients for the windward side and negative (suction) coefficients for the leeward side of the roof are used.If there are, for example, only negative coefficients for a load position, then only negative loads are applied to the roof surface. Consequently, there is no pressure -> therefore these values are set to 0. A load case, which thus contains only values with the size 0, could also be deselected during the generation.For example, this is always possible, as already described, for the LC w + with a wind direction of 90 ° (gable-sided wind) and a roof inclination of > 15 °.
AnswerFor example, the standard EN 1990 + EN1991-2; Use road bridges (see picture 1). Alternatively, one could of course also determine the combinations by hand. Further information can be found in our manual.
AnswerThe thermal expansion coefficient for the material is probably zero. As soon as you change it back to a realistic value, the hint should no longer appear.
AnswerSince RSTAB8 / RFEM5, the buckling length coefficients can be specified as soon as they are entered, which are then adopted when the additional modules are started.If the above message appears, the entry of the coefficients in an old version has been set to 0 and due to this incomplete bar definition, a calculation in the main program is not possible.To fix this, a value> 0 must be entered.If the buckling length coefficients still do not play a role, the entire structure should be selected, the "Edit Bar" dialog box should be opened and the coefficients should be reset to the default value of 1.0 in the "Buckling Lengths" tab.
You can adjust all partial safety factors and combination coefficients. To do this, open the 'Coefficients' dialog box in the general data of the model and then click the [New] button to create a user-defined standard (see the figure).
The concept of action categories of the new user-defined standard corresponds to the basic standard, which is preset when opening the 'General Data' dialog box.
NCI to DIN EN 1993-6, Chap. 2.3.1, permits reduction of dynamic coefficients for the value >=1,1. Therefore, you can use the reduces support forces for the design of supporting or hanger structures. As long as the "DIN" National Annex is selected in CRANEWAY and the dynamic coefficients are >=1.1, this reduction is taken into account automatically.
The message means that your system is numerically unstable. Such an instability can be often explained by inaccurate support conditions or release definitions in FE-LTB.
When selecting imperfections and also in the calculation, the critical load factor will be specified. Based on this, the critical load of the system is determined.
In the numerical calculation, this stability load is characterised by the fact that either the determinant of the stiffness matrix becomes zero, or that very high deformations occur for very small load increments in the calculation.
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