In many frame and truss structures, it is no longer sufficient to use a simple member. You often have to consider cross-section weakenings or openings in solid beams. In such cases, you can use the "Surface Model" member type. It can be integrated into the model like any other member and offers all the options of a surface model. The present technical article shows the application of such a member in an existing structural system and describes the integration of member openings.
The recently introduced Webservices gives users the ability to communicate with RFEM 6 using their programming language of choice. This feature is enhanced with our High Level Functions (HLF) Library. The libraries are available for Python, JavaScript, and C#. This article looks at a practical use case of programming a 2D Truss Generator with Python. "Learning by doing," as the saying goes.
For a frame trussed from below, compression members are to be modelled perpendicular to the inclined beam. The member length and the intersection with the horizontal beam are defined.
This technical article deals with the design of structural components and cross-sections of a welded truss girder in the ultimate limit state. Furthermore, the deformation analysis in the serviceability limit state is described.
When modeling frame structures, RFEM and RSTAB provide various options for controlling the transfer of internal forces and moments at the connection points of members. You can use the member types to determine whether only forces act on the connected members, or whether moments act on them as well. In addition, you can use hinges to exclude specific internal forces from the transfer. One special form is scissor hinges, which allow for realistic modeling of roof structures, for example.
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.
A site joint consisting of hollow sections with end plates will be designed. It is the bottom chord of a truss that has to be divided for transport reasons.
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.
During the form-finding process, the slip modulus of a substructure is also taken into account when searching for the equilibrium state. You can also consider large deflections of supporting trusses or pure bending deformation of the edge beams when determining the membrane shape.
The previous post on this topic describes instabilities that may occur when using tension members. The example shown refers primarily to wall stiffening. Now, instability error messages can also refer to nodes within the range of supports. Truss girders and support trusses are especially susceptible to this. What causes the instability here?
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.