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• ### What is the meaning of "shear failure of the glued-in contact surface" in the details of the RF-LAMINATE add-on module?

New FAQ 004206 EN

In the case of CLT panels with non- cross-laminated side and a wall-like structural behavior, the torsional stress in the glued joints is often governing. This design is performed according to the explanations in the literature reference below according to the following equation.

$\eta_x=\frac{\tau_{tor,x}}{f_{v,tor}}+\frac{\tau_x+\tau_{xz}}{f_R}=\frac{\displaystyle\frac{3\ast n_{xy}}{b(n-1)}}{f_{v,tor}}+\frac{{\displaystyle\frac{\frac{\partial n_x}{\partial x}}{n-1}}+\tau_{xz}}{f_R}\leq1$

Values:
• b Board width
• n Number of board layers
• n xy shear in pane plane
• $\ frac {\ partial n_x} {\ partial x}$ Shear the board layers
• $\ tau_ {xz}$ Thrust in thickness direction
• for shear resistance
• f v, gate Torsionsschubfestigkeit
The analysis is analogous for the y-direction, but with the values for y-direction.
• ### What does note 40162 show regarding the shear strengths of Binderholz?

New FAQ 004191 EN

For the structures of the manufacturer Binderholz, the shear strengths are calculated according to the following equation as soon as the plates without thin-edge gluing have been defined and are calculated with a design of the shear failure in the plane of the pane.

$f_{v,k}=\left\{\begin{array}{l}\begin{array}{c}3,5\\8,0\frac{D_{net}}D\\\end{array}\\2,5\frac{(n-1)(a²+b²)}{6Db}\end{array}\right.$

Values:
D Element thickness
D net Sum of longitudinal and transverse layer thicknesses in the element
n Number of board layers
a = b Width of the boards in the longitudinal or transverse layers

All values in N/mm². For more detailed information, check the manufacturer's approval.
• ### What does the stiffness reduction factors k33 and k88 used in RF-LAMINATE refer to?

New FAQ 004119 EN

These factors reduce the torsional stiffness D33 as well as the shear stiffness D88 of the corresponding stiffness matrix elements of a surface. Since cross-laminated timber is generally not laminated at the narrow side, it is also not possible to transfer shear stresses to narrow sides of a timber. Thus, the stiffness would be overvalued in this case. For this reason, the stiffness must be reduced accordingly.

Some manufacturers have already informed us about these values when transmitting the layer structures. These result from internal analysis. An explanation for determining the correction factors is presented in [1]. The analysis of this work has also been involved in the Austrian Annex to EN 1995-1-1 [2] . The result is shown in Figure 02. The ratio of board width (a) to board thickness (ti) can be taken from the corresponding authorization.
• ### Is it possible to create a second design case in RF-LAMINATE?

New FAQ 004110 EN

No, this is unfortunately not possible.

The layer structure is assigned to certain surfaces in RF-LAMINATE.

The respective surface is then given the stiffness defined by this layer structure for the determination of internal forces in RFEM.

If you want to perform a calculation with different layer structures, you have to do it in a copy of the file (another model with different layer structure).

• ### How to display the primary load-bearing direction graphically in RF-LAMINATE?

New FAQ 003592 EN

While entering data in the RF-LAMINATE add-on module, there is an option to control the orthotropic direction of each individual layer graphically. To do this, simply place the cursor in the desired row of the corresponding position. Then, a coordinate system is displayed in the surface in the RFEM model (see Figure 01). This is to be interpreted as follows:

red axis = x-axis = β-value of the corresponding layer

Generally, the outer layers specify the main load-bearing direction, which is why it is sufficient to consider only the first layer. The red axis specifies the primary load-bearing direction (see Figure 01).

###### Displaying the primary load-bearing direction in RFEM
However, the primary load-bearing direction can also be interpreted directly in RFEM. The local axis systems of the surfaces can be displayed in detail (see Figure 02). The orthotropic direction β refers to the local x-axis of the surface. For the example shown in Figure 03, it has a consequence that the primary load-bearing direction for the left surface runs from one support to another and the secondary surface direction to the right surface. If you want to change the supporting direction for the right surface, it is possible to either rotate the local surface axis system (see Figure 04) or create a new structure and rotate the orthotropic direction β by 90° (see Figure 05).

If the primary load-bearing direction is not clearly evident, it is worth taking a look at the stiffness matrix of the surface (see Figure 06). There, it is possible to find the 'decisive' load-bearing direction, e.g. by means of the bending stiffness. The element D11 refers to the local x-axis of the surface and the element D22 refers to the local axis y of the surface.

• ### Is it possible to save the structures of manufacturer-specific cross-laminated timber slabs in the RF-LAMINATE add-on module?

New FAQ 003590 EN

The manufacturer-specific structures of cross-laminated timber products are saved in the central database of RF-LAMINATE.

This database is a subject of continuous extension and maintenance from our side.

If a manufacturer is supposed to be added in the database, a sample file can be requested from us to save its structures. Furthermore, it is helpful if the manufacturer provides us with information on the reduction factors of torsional and shear stiffness, the bonding of narrow sides, etc.
• ### How to calculate a timber-concrete composite floor with CLT?

New FAQ 003553 EN

Two planar structural components can be defined in the RF-LAMINATE add-on module via the Hybrid material model (Figure 1).

In this case, the automatic input of a cross-laminated timber plate would according to the manufacturer's specifications also be possible (see Figure 2).

However, the disadvantage of the input in the RF-LAMINATE add-on module consists in the requirement for a rigid connection. This is not the case for a timber-concrete composite construction. Thus, the calculation is only an approximation.

Another possibility is to couple two surfaces via a surface release or a contact solid. The advantage is that you can define almost any shear transfer this way (Figure 3). In the RFEM model file attached here, this has been defined in the middle second model.

The third option would be to define a hybrid member as specified in the third model of the attached file. In this case, however, the biaxial load transfer of the structure will not be considered. However, this method has the advantage of highly automated design. This is also explained in this FAQ .
• ### Why is the shear stiffness reduced to 10% in the RF-LAMINATE add-on module as well as for the material module orthotropic in RFEM for the shear modulus Gyz? In my opinion, the shear stiffness in slice plane Gxy would have to be reduced here?

FAQ 003351 EN

The reduction of the shear stiffness results from the fact that the fibers have a very small stiffness and a low strength perpendicular to each other. For this reason, the rolling shear strength of CLT panels is also very small.

For cross-laminated timber panels, glued sidewalls on boards are assumed. The boards are applied in the longitudinal direction along the x-axis of the coordinate system (Figure 2). For the shear stresses in Figure 2, the shear stress τyz is thus juxtaposed to the rolling shear strength.

The same applies to the shear stiffnesses. In the direction of the minor axis (yz plane), the stiffness of the individual boards is considerably smaller than in the direction of the principal axis (xz plane) and also larger than in the xy plane. The coordinate system shown in Figure 2 should be placed on the board in Figure 3.

• ### Where are saved the structures made by manufacturers of cross-laminated timber slabs in the RF-LAMINATE add-on module?

FAQ 003289 EN

In a standard installation, the structures of the manufacturers are saved as C:\ProgramData\Dlubal\RFEM 5.21\General Data.

• ### Is it possible to save the structures in a file in the RF-LAMINATE add-on module and distribute it to other computers?

FAQ 003288 EN

The user-defined assemblies from the RF-LAMINATE add-on module can be saved in any *.lyr file.

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#### 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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