In addition to our technical support (e.g. via chat), you’ll find resources on our website that may help you with your design using Dlubal Software.
Frequently Asked Questions (FAQ)
Search FAQ
Further Information
Customer Support 24/7

Answer
Fire resistance design is not implemented in the RF‑LAMINATE addon module by default.However, you can calculate the charring rates yourself and consider them accordingly in the module. In the following example, this is explained on a simple plate.Structural system (Figure 01): Span 5 m
 Plate width 2 m
 LC1 (permanent) 1 kN/m² plus dead load
 LC2 (medium) 2.5 kN/m²
 3 layers
 S1 35 mm C24
 S2 20 mm C24
 S3 35 mm C24
Factors for fire resistance: Charring rate ß0 = 0.65 mm/min
 Pyrolysis zone k0d0 = 7 mm
 Charring time t = 30 min
 Effective thickness def=t ß_{0}+k_{0}d_{0}=30 min × 0.65 mm/min+7 mm = 26.5 mm
Remaining thickness of Layer 3 = 35 − 26.5 = 8.5 mm > 3 mm → thickness may be applied. (Figure 02)Because of the modified layer thicknesses, a new stiffness matrix results, which is applied in RFEM for accidental combinations with the characteristic stiffness values. For the ultimate limit state, the design values are calculated here (Figure 03). 
Answer
In principle, it is also possible to perform detailed analysis in RF‑LAMINATE. In the case of a very high shear distortion, for example, it can be reasonable to use orthotropic solids for modeling. The video shows a simple modeling and result evaluation of a layer structure by using solids.
A criterion, as of when is the modeling using solids useful, is the shear correction factor. Further information and other criteria can be found in the following FAQ:

Answer
The easiest way to consider this is to use the RF/JOINTS Timber Steel to Timber module. For this purpose, the module decomposes the original connection, and creates a new structural system that considers the flexibility accordingly. This is taken into account separately for loadbearing capacity, suitability for use, and exceptional. 
Answer
In RFEM and RSTAB, the simplified design from [1], Chapter 2.2.3, have been implemented for the automatic load combinations. This means that strictly speaking, only structures concerning the final deformation may be analyzed, in which materials with identical creep behavior occur since the creep deformations are considered in a simplified way on the load side. If the structure is a mixed structure made of wood with different creep properties or in combination with steel, the final deformations must be determined according to [2] Amendment to 2.2.3 as follows:
'(4) If a structure consists of structural components or components with different creep properties, the longterm deformations should be calculated according to 2.3.2.2 (1) due to the quasipermanent combination of actions with the final values of the mean values of the corresponding elasticity, shear, and displacement modules. The final deformation u_{fin} is then calculated by superposition of the initial deformation due to the difference of the characteristic and quasipermanent combinations of actions with the longterm deformation.'
However, this requires a superposition of results from different load combinations, which cannot be implemented automatically in RFEM and RSTAB.
If the different creep properties are to be taken into account, the load combinations must be created manually, and the stiffness must be reduced according to the creep coefficient.The procedure is described using the example of a timberconcrete composite floor presented on the Info Day 2017. Below this FAQ, you can find the link for this. 
Answer
The increase of the crack factor k_{cr} still has to be done manually because the program does not know where the end of the grain is defined. To do this, divide the member by 1.5 m from the end of the grain so that the affected areas can be designed as a separate member (see Figure 01).Two design cases are now required (File → New Case ...). In case 1, members within the 1.5 m are selected for the design. In case 2, it is necessary to select the members where the 30% needs to be considered. Then, in case 2, the k_{cr} value is adjusted manually in the settings for the National Annex. Thus, a k_{cr} of 0.65 results for C24, which is entered as shown in Figure 02. The design is carried out this way with an increased k_{cr} value. 
Does the RF‑LAMINATE program consider the shear correction factor for crosslaminated timber plates?
Answer
The shear correction factor is considered in the RF‑LAMINATE addon module by using the following equation.
$k_{z}=\frac{{\displaystyle\sum_i}G_{xz,i}A_i}{\left(\int_{h/2}^{h/2}E_x(z)z^2\operatorname dz\right)^2}\int_{h/2}^{h/2}\frac{\left(\int_z^{h/2}E_x(z)zd\overline z\right)^2}{G_{xz}(z)}\operatorname dz$with $\int_{h/2}^{h/2}E_x(z)z^2\operatorname dz=EI_{,net}$The calculation of shear stiffness can be found in the English version of the RFLAMINATE manual, page 15 ff.For a plate with the thickness of 10 cm in Figure 01, the calculation of the shear correction factor is shown. The equations used here are only valid for simplified symmetrical plate structures!Layer z_min z_max E_x(z)(N/mm²) G_xz(z)(N/mm²) 1 50 30 11,000 690 2 30 10 300 50 3 10 10 11,000 690 4 10 30 300 50 5 30 50 11,000 690 $\sum_iG_{xz,i}A_i=3\times0.02\times690+2\times0.02\times50=43.4N$$EI_{,net}=\sum_{i=1}^nE_{i;x}\frac{\mbox{$z$}_{i,max}^3\mbox{$z$}_{i,min}^3}3$$=11,000\left(\frac{30^3}3+\frac{50^3}3\right)+300\left(\frac{10^3}3+\frac{30^3}3\right)$$+11,000\left(\frac{10^3}3+\frac{10^3}3\right)+300\left(\frac{30^3}3\frac{10^3}3\right)+11,000\left(\frac{50^3}3\frac{30^3}3\right)$$=731.2\times10^6 Nmm$$\int_{h/2}^{h/2}\frac{\left(\int_z^{h/2}E_x(z)zd\overline z\right)^2}{G_{xz}(z)}\operatorname dz=\sum_{i=1}^n\frac1{G_{i;xz}}\left(χ_i^2(z_{i,max}z_{i,min})\;χ_iE_{i,x}\frac{z_{i,max}^3z_{i,min}^3}3+E_{i,x}^2\frac{z_{i,max}^5z_{i,min}^5}{20}\right)$$χ_i=E_{i;x}\frac{z_{i,max}^2}2+\sum_{k=i+1}^nE_{k;x}\frac{z_{k,max}^2z_{k,min}^2}2$χ_{1} 13.75 10^{6} χ_{2} 8.935 10^{6} χ_{3} 9.47 10^{6} χ_{4} 8.935 10^{6} χ_{5} 13.75 10^{6} $\sum_{i=1}^n\frac1{G_{i;yz}}\left(χ_i^2(z_{i,max}z_{i,min})χ_iE_{i,y}\frac{z_{i,max}^3z_{i,min}^3}3+{E^2}_{i,y}\frac{z_{i,max}^5z_{i,min}^5}{20}\right)=$
8.4642 10^{11} 3.147 10^{13} 2.5 10^{12} 3.147 10^{13} 8.4642 10^{11} Total 6.7133 x 10^{13}$k_z=\frac{43.4}{{(731.2e^6)}^2}6.713284\;e^{13}=5.449\;e^{3}$$D_{44}=\frac{{\displaystyle\sum_i}G_{xz,i}A_i}{k_z}=\frac{43.4}{5.449\;e^{3}}=7,964.7 N/mm$This corresponds to the resulting value in RF‑LAMINATE (Figure 02). 
Answer
To consider average regions when designing in RFLAMINATE, they must always be activated in the detail settings of the addon module. See Figure 01 with the detailed settings in RFLAMINATE for this. 
Answer
Basically, all crosssections of the solid and hybrid crosssection groups can be designed in the RF/TIMBER Pro program. In Figure 01, they are displayed on the right.
For more complex asymmetrical crosssection shapes, it may be necessary to adjust the allowable inclination of principal axis on a userdefined basis in the addon module (see Figure 02).

Answer
In the case of cross laminated timber panels not glued to the narrow sides and a walllike structural behaviour, the torsion stress in the glued joints is often decisive. This design is performed according to the explanations in the literature reference below according to the following equation.$\eta_x=\frac{\tau_{tor,x}}{f_{v,tor}}+\frac{\tau_x+\tau_{xz}}{f_R}=\frac{\displaystyle\frac{3\ast n_{xy}}{b(n1)}}{f_{v,tor}}+\frac{{\displaystyle\frac{\frac{\partial n_x}{\partial x}}{n1}}+\tau_{xz}}{f_R}\leq1$Values: b board width
 n number of board layers
 n_{xy} shear in pane plane
 $\frac{\partial n_x}{\partial x}$ shear of board layers
 $\tau_{xz}$ shear in thickness direction
 f_{R} rolling shear strength
 f_{v,tor} torsional shear strength
For the ydirection, the design is analogous but with the values for the ydirection. 
Answer
These factors reduce the torsional stiffness D_{33} as well as the shear stiffness D_{88} of the corresponding stiffness matrix elements of a surface. Since crosslaminated timber is generally not glued at the narrow side, it is also not possible to transfer shear stresses to the timber narrow sides. Thus, the stiffness would be overestimated in this case. For this reason, the stiffness must be reduced accordingly.Some manufacturers have already provided us these values when delivering the layer structures. They result from the internal analysis. The explanation for determining the correction factors is covered in [1]. The analysis of this work has also been included in the Austrian Annex to EN 1995‑1‑1 [2]. The result is shown in Figure 02. The ratio of the timber width (a) to the timber thickness (t_{i}) can be taken from the respective approval.
Contact us
Did you find your question?
If not, contact us via our free email, 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 standalone 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.
Your support is by far the best
“Thank you for the valuable information.
I would like to pay a compliment to your support team. I am always impressed how quickly and professionally the questions are answered. I have used a lot of software with a support contract in the field of structural analysis, but your support is by far the best. ”