RF-/TIMBER NBR | Design

The calculation of timber panels is carried out on simplified member or surface structures. This article describes how to determine the required stiffness.

The stiffening of timber structures is usually carried out by means of timber panels. For this purpose, structural components consisting of slabs (chipboard, OSB) are connected with members. Several articles will describe the basics of this construction method and the calculation in the RFEM program. This first article describes the basic determination of the stiffnesses as well as the calculation.

Using the Timber Design add-on, timber column design is possible according to the 2018 NDS standard ASD method. Accurately calculating timber member compressive capacity and adjustment factors is important for safety considerations and design. The following article will verify the maximum critical buckling strength calculated by the Timber Design add-on using step-by-step analytical equations as per the NDS 2018 standard including the compressive adjustment factors, adjusted compressive design value, and final design ratio.

After opening the add-on module, it is necessary to select the members/sets of members, load cases, load or result combinations for the ultimate and the serviceability limit state design. The materials from RFEM/RSTAB are preset and can be adjusted in RF‑/TIMBER NBR. The material properties listed in the respective standard are included in the material library.

When checking the cross-sections, you can specify whether to consider a cross-section selected in RFEM/RSTAB, or a modified cross-section. Then, you can define the load duration classes, moisture service conditions, and timber treatment.

The deformation analysis requires the reference lengths of the relevant members and sets of members. Furthermore, you can define a specific direction of deflection, precamber and the beam type.

After the calculation, the module displays results in clearly arranged result tables. All intermediate values (for example, governing internal forces, adjustment factors, and so on) can be included in order to make the design more transparent. The results are sorted by load case, cross-section, set of members, and members.

If the analysis fails, the affected cross-sections can be modified in an optimization process. It is also possible to transfer the optimized cross-sections to RFEM/RSTAB for a new calculation.

The design ratio is represented with different colors in the RFEM/RSTAB model. This way, you can quickly recognize critical or oversized areas of the cross-section. Furthermore, result diagrams displayed on the member or set of members ensure targeted evaluation.

In addition to the input and result data, including design details displayed in tables, you can add all graphics into the printout report. This way, comprehensible and clearly arranged documentation is guaranteed. You can select the report contents and extent specifically for the individual designs.

• Full integration in RFEM/RSTAB including import of all relevant information and internal forces
• Design of members and continuous members for tension, compression, bending, shear, and combined internal forces
• Stability analysis for lateral-torsional buckling and buckling according to the equivalent member method or the second order analysis
• Serviceability limit state design by limitation of deflections
• Brazilian material library and cross-section library
• User-defined entry of rectangular and circular cross-sections
• Cross-section optimization with optional transfer to RFEM/RSTAB
• Optional import of effective lengths from the RSBUCK or RF‑STABILITY add‑on module
• Detailed result documentation including references to design equations of the used standard
• Various filter and sorting options of results including result lists by member, cross-sections, x-location, or by load case, load and result combination
• Consideration of moisture service conditions
• Visualization of the design criterion on the RFEM/RSTAB model
• Data export to MS Excel