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Diagonals of double angles are used for pipe bridge construction and for truss girders, among other things. They are usually subjected to tension, but it is necessary to transfer them in smaller compression forces with regard to the load application. In the case of slender diagonals in particular, you should also consider the bending due to self‑weight.
If you select the combinatorics according to EN 1990 + EN 1991‑2 and define a load case in action category gr1a, gr2, or gr5, you have to additionally define in the program which load model should be taken as a basis for the load case. This information is crucial for defining combination rules for automatic combinations according EN 1990 + EN 1991-2. In the gr1a category, you can select TS (LM1), UDL (LM1), or pedestrian and cycle track, for example. TS (LM1) is preset by default. In the gr2 category, you can select breaking and acceleration forces or centrifugal forces as a specification.
With RFEM version 5.06, member stiffnesses can be influenced by methods that are aligned with US steel construction standard ANSI/AISC 360-10. According to this standard, reduction factor τb must be considered for the determination of internal forces in all members of which the flexural resistance contributes to the model's stability. This coefficient depends on the axial force in the member: The larger the axial force, the larger τb is.
The current state of the development of finite element analysis software and computer technology allows for the calculation of more complex structure. More and more frequently, FE calculations are performed on the entire model. In this context, certain practical construction problems may appear. One of these problems is the consideration of a construction process in the model.
As mentioned in Part 1, according to the current standard DIN 18008-3, it is allowed in glass construction to represent point supports for glass components by means of FEM in order to design the adequate ultimate limit state. The rules are described in Annex B of the standard [1].
In the H - Roofs category, imposed loads have to be applied. These are usually the technician loads for construction and maintenance. Since there is no maintenance for snow, category H must not include both snow and imposed loads together. You can consider thi in the options for automatic combinations.
Building Information Modeling describes what is possibly one of the most important current topics in the entire construction software industry. However, the process is not that new, and it is a well-known fact that the total costs of a project can be positively influenced by good planning in the initial stage.
In the construction process, it is often necessary to fabricate the concrete elements in sections. A classic example of this production in sections is the use of prefabricated downstand beams, in which the slab is completed in the onsite concrete construction. By creating a new concrete area, interfaces may arise between the already hardened concrete and the fresh concrete. The transfer of the longitudinal shear forces arising between the partial cross-sections must be considered in the design.
BIM is often used when it comes to data management in civil engineering. The individual disciplines of architecture, structural design, construction, and structural monitoring are coming closer together. Building Information Modeling makes this possible.. Dlubal Software provides a wide range of formats for data exchange. The following article explains the details of the interface with Autodesk Revit and, in particular, the export settings.
A fillet weld is the most common weld type in steel building construction. According to EN 1993-1-8, 4.3.2.1 (1) [1], fillet welds may be used for connecting structural part where the fusion faces form an angle of between 60° and 120°.
In practice, an engineer often faces the task of representing the support conditions as close to the reality as possible in order to be able to analyze the deformations and internal forces of the structure subjected to their influence, and to enable construction that is as cost-effective as possible. RFEM and RSTAB provide numerous options for defining nonlinear nodal supports. The first section of my article describes the options for creating a nonlinear free support and provides a simple example. For a better understanding, the result is always compared to a linearly defined support.
In a multi-modal response spectrum analysis, it is important to determine a sufficient number of eigenvalues of the structure and to consider their dynamic responses. Regulations such as EN 1998‑1 [1] and other international standards require the activation of 90% of the structural mass. This means: to determine so many eigenvalues that the sum of the effective modal mass factors is greater than 0.9.
Lattice towers represent typical applications in steel construction. Examples of this special type of truss structure are antenna and overhead line towers, as well as columns for wind power stations, cable cars, and supporting frame constructions. The modeling can be done individually in RFEM and RSTAB by entering various tower elements. Furthermore, you can use different copy functions and parameterized input options. However, this procedure normally requires considerable effort. It is more convenient to model such structures using prefabricated catalog elements provided by the Block Manager. These elements are automatically stored in the database during program installation. Thus, you can use tower segments, platforms, antenna brackets, cable ducts, and so on as parameterized building blocks for generating diverse tower structures.
In practice, an engineer often faces the task of representing the support conditions as close to the reality as possible in order to be able to analyze the deformations and internal forces of the structure subjected to their influence and to enable construction that is as cost efficient as possible. RFEM and RSTAB provide numerous options for defining nonlinear nodal supports. This second part describes the options for creating a nonlinear support for a restraint and provides a simple example. For a better understanding, the result is always compared to a linearly defined support.
This article deals with the stiffness of standardized joints according to the DSTV (German Steel Construction Association)/DASt (German Committee for Structural Steelwork) standards, often used in steel construction, and its effects on structural analysis and design results according to DIN EN 1993-1-1.
RFEM and RSTAB are able to cover a large number of branches in the building and construction industry with their generally usable structural frame analysis and FEM programs. Designing cable structures is thus also possible in both software solutions. Some assistance tools for modeling and design will be presented in the following text.
The American Wood Council (AWC) has released the 2018 Edition of the National Design Specification (NDS) for Wood Construction. This is the second edition of the NDS to contain a chapter dedicated to cross-laminated timber (CLT) design. Therefore, a couple of revisions were included in the 2018 NDS when compared to the previous 2015 Edition.
- 001555
- Modeling | Loading
- RFEM 5
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- RSTAB 8
- RF-TIMBER AWC 5
- TIMBER AWC 8
- RF-TIMBER CSA 5
- TIMBER CSA 8
- RF-TIMBER Pro 5
- TIMBER Pro 8
- RF-JOINTS Timber | Timber to Timber 5
- JOINTS Timber | Timber to Timber 8
- RF-JOINTS Timber | Steel to Timber 5
- JOINTS Timber | Steel to Timber 8
- RF-LIMITS 5
- LIMITS 8
- RF-LAMINATE 5
- Timber Structures
- Laminate and Sandwich Structures
- Structural Analysis & Design
- Finite Element Analysis
- Steel Connections
- Eurocode 0
- Eurocode 5
- ANSI/AISC 360
- SIA 260
- SIA 265
In addition to determining loads, some particularities concerning the load combinatorics in timber design have to be considered. Contrary to steel structures, where the largest loading results from all unfavorable actions, in timber construction, the strength values depend on the load duration and timber humidity. Special characteristics have to be considered as well for the serviceability limit state design. The following article discusses the effects on the design of wooden elements and how this is possible with RSTAB and RFEM.
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.
Determining the Material Properties of Steel-Fiber-Reinforced Concrete and Their Application in RFEM
Steel-fiber-reinforced concrete is mainly used nowadays for industrial floors or hall floors, foundation plates with low loads, basement walls, and basement floors. Since the publication in 2010 of the first guideline about steel-fiber-reinforced concrete by the German Committee for Reinforced Concrete (DAfStb), a structural engineer can use standards for the design of the steel fiber-reinforced concrete composite material, which makes the use of fiber-reinforced concrete increasingly popular in construction. This article explains the individual material parameters of steel-fiber-reinforced concrete and how to deal with these material parameters in the FEM program RFEM.
In current literature, the formulas used to determine internal forces and deformations manually are usually specified without considering the shear deformation. The deformations resulting from shear force are often underestimated in timber construction in particular.
Steel-fiber-reinforced concrete is mainly used nowadays for industrial floors or hall floors, foundation plates with low loads, basement walls, and basement floors. Since the publication in 2010 of the first guideline about steel-fiber-reinforced concrete by the German Committee for Reinforced Concrete (DAfStb), a structural engineer can use standards for the design of the steel fiber-reinforced concrete composite material, which makes the use of fiber-reinforced concrete increasingly popular in construction. This article describes the nonlinear calculation of a foundation plate made of steel fiber-reinforced concrete in the ultimate limit state with the FEA software RFEM.
Slender bending beams that have a large h/w ratio and are loaded parallel to the minor axis tend to have stability issues. This is due to the deflection of the compression chord.
The building and construction industry is increasingly digitized. Structural engineers, a smaller group in the construction industry, are not always considered to be engineers who follow the latest trends immediately. There is often good reason for this. Many consider this to be the reason that topics such as utilizing the BIM method are not yet the standard in structural engineering. However, the past few years have shown that a process of rethinking has begun, and new digital trends are being picked up and applied.
The article titled Lateral-Torsional Buckling in Timber Construction | Theory explains the theoretical background for the analytical determination of the critical bending moment Mcrit or the critical bending stress σcrit for the lateral buckling of a bending beam. This article uses examples to verify the analytical solution with the result from the eigenvalue analysis.
Closed circular cross-sections are ideal for welded truss structures. The architecture of such constructions is popular when designing transparent roofs. This article shows the special features of the connection design using hollow sections.
The previous article, titled Lateral-Torsional Buckling in Timber Construction | Examples 1, explains the practical application for determining the critical bending moment Mcrit or the critical bending stress σcrit for a bending beam's lateral buckling using simple examples. In this article, the critical bending moment is determined by considering an elastic foundation resulting from a stiffening bracing.
The nested components of a telescopic boom of a construction machine, for example, transport their forces mechanically between the components.
In the world of construction engineering, the word "imperfections" has a specific meaning. In general, it describes the incompleteness of a structure or the deviation of a structural component from an ideal shape caused by the production.
The additional loads from self‑weight are usually composed of several layers; for example, classic floor and ceiling layers in buildings, or road coatings for bridge constructions. When defining load definitions in RFEM and RSTAB, you can use the multi-layer load to define the individual layers with thickness and specific weight.