This article presents the basic concepts in structural dynamics and their role in the seismic design of structures. Great emphasis is given to explaining the technical aspects in an understandable way, so that readers without deep technical knowledge can gain an insight into the subject.
Surfaces in building models can be of many different sizes and shapes. All surfaces can be considered in RFEM 6 because the program allows to define different materials and thicknesses as well as surfaces with different stiffness and geometry types. This article focuses on four of these surface types: rotated, trimmed, without thickness, and load transfer.
This article deals with the determination of the concrete reinforcement for a beam stressed by tension only according to EN 1992-1-1. The aim is to show the tensile load of a member-type element (without imposed deformations) and to define the concrete reinforcement in accordance with the standard's construction rules and provisions using the RFEM structural analysis software.
For the design of concrete surfaces, the rib component of the internal forces can be neglected for the ULS calculation and for the analytical method of the SLS calculation, because this component is already considered in the member design. To do this, select the check box in the "Details" dialog box. If no rib was defined, this function is not available.
In RF-/FOUNDATION Pro, you can also calculate unreinforced foundation plates according to Section 12.9.3 of EN 1992-1-1 [1]. To do this, select the "Without bending reinforcement according to 12.9.3" check box in the "Foundation Plate" section of the "Details" dialog box.
The shear force resistance VRd,c without computational shear force reinforcement according to 6.2.2 of EN 1992-1-1 [1] or 10.3.3 of DIN 1045-1 [2] is calculated depending on the longitudinal reinforcement ratio. If the required longitudinal reinforcement from the bending design is used for the calculation of VRd,c, this leads to an underestimation of the shear force resistance without shear reinforcement in the vicinity of the hinged end supports. In contrast to the shear force, the required bending reinforcement decreases in the direction of the support. Furthermore, the actually inserted longitudinal reinforcement usually deviates significantly from the required bending reinforcement in the end support area (for example, in the case of non-staggered beam reinforcement).
For cross‑laminated structures with large spans, downstand beams or hybrid structures are often used. They can be modeled in RFEM 5 by using surfaces and member cross‑sections. In both structural systems, curved downstand beams are also possible without any problems. In the case of the curved surface, the member is always appropriately generated by means of the automatic member eccentricity with the thickness distance of the surface and the member. The downstand beam can also be connected flexibly by means of a line release.
Friction plays an important role in practice. Without friction, the brakes of cars would be useless, objects on inclined planes would just slide away, and prestressed bolt connections would be impossible.
To determine the distance between two nodes or the angle between two objects without using the dimensioning function, you can simply use the "Measure" option on the "Tools" menu. Here, you can also choose between various measure functions.
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.
Structures are naturally three-dimensional. However, because it was impossible to perform calculations on three-dimensional models easily in the past, the structures were simplified and broken down into planar subsystems. With the increasing performance of computers and related software, it is often possible to do without these simplifications. Digital trends such as Building Information Modeling (BIM) and new options for creating realistic visualized models reinforce this trend. But do 3D models really offer an advantage, or are we just following a trend? The following text presents some arguments for working in 3D models.
This technical article deals with the stability analysis of a roof purlin, which is connected without stiffeners by means of a bolt connection on the lower flange to have a minimum manufacturing effort.
Eurocode 2 provides two ways to perform a crack width design. On one hand, the crack width design according to 7.3.3 can be performed without direct calculation by means of tables for the limitation of the member spacing and diameter. On the other hand, the crack width wk can be determined directly according to 7.3.4 and compared to a limit value.
Pay particular attention to the connection points of members and surfaces when you deal with mixed systems, because not all internal forces can always be transferred without difficulty at the coupling location.
When you perform the subsequent modeling of a beam under an existing floor, the first issues that arise are which forces should be transferred between the downstand beam and the floor, and whether a composite effect is the goal. In this case, the floor should rest on the downstand beam without a composite.
When modeling a reinforced concrete rib with a masonry wall above, there is the risk that the rib is underdesigned if the structural behavior of the masonry is not correctly considered and the connection between the masonry wall and downstand beam is not modeled sufficiently accurately. This article deals with this issue and shows the possible modeling options of such a structure. In this example, the reinforcement is determined only from the internal forces and without secondary minimum reinforcement.
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.
Modeling planar structural components such as glass panes is generally possible only in RFEM. If it is necessary to define the stiffening effect of a pane in a particular case, it can also be simulated in RSTAB.
When performing control calculations and comparing the internal forces and the resulting required reinforcement of downstand beams, large differences can occur. Although the same load assumptions and spans are applied, some programs or the manual calculation display very different internal forces compared to the FEA model. The differences already occur in the case of the centric member and without considering the internal forces' components from the possible effective slab widths.
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.
When designing steel columns or steel beams, it is usually necessary to carry out cross-section design and stability analysis. While the cross-section design can usually be performed without giving further details, the stability analysis requires further user-defined entries. To a certain extent, the member is cut out of the structure; therefore, the support conditions have to be specified. This is particularly important when determining the ideal elastic critical moment Mcr. Furthermore, it is necessary to define the correct effective lengths Lcr. These are required for the internal calculation of slenderness ratios.
The secondary reinforcement according to DIN EN 1992-1-1 9.2.1 is used to ensure the desired structural behavior. It should avoid failure without prior notification. The minimum reinforcement has to be arranged independently of the size of the actual loading.
In theory, an ideal gas consists of freely moving mass particles without extension in a volume space. In this space, each particle moves at a speed in one direction. The collision of one particle with another particle or the volume limitations leads to a deflection and a change in the speed of the particles.
SHAPE-THIN allows you to calculate section properties and stresses of any cross-sections. If a flange or a web is weakened by bolt holes, you can consider this by using null elements. The stresses are subsequently recalculated with the reduced cross-section values. In this case, it is necessary to pay a special attention to shear stresses. By default, these are set to zero in the area of the null elements. When recalculating shear stresses with the reduced cross-section values and without further adaptation, it turns out that the integral of the shear stresses is no longer equal to the applied shear force. The following example shows in detail how to calculate the shear stress.
The RF-PIPING and RF-PIPING Design add-on modules allow you to design piping systems according to EN 13480-3 [1], ASME B31.1 and B31.3. In the case of the European standard, the determination of pipe stresses is based on the formulas of Section 12.3 Flexibility Analysis. Depending on the stress type, one or more resulting moments is applied without regard to each other. This differentiation occurs when determining the stresses due to occasional loads, for example.
Heat loss due to external components without thermal decoupling of the internal components is enormous. For this reason, external structural components are thermally separated from the building envelope using a special built-in component. For the connection of a balcony slab with a reinforced concrete floor, Schöck Isokorb® or HALFEN HIT Insulated Connection can be used, for example. For the design of such built-in components, the respective technical approval must be taken into account. The following article shows an example of considering Schöck Isokorb® in the FEM calculation.
Buildings must be designed and dimensioned in the way that both vertical and horizontal loads are conducted safely and without large deformations in the building. Examples of horizontal loads are wind, unintentional inclination, earthquake, and a blast.