CFD calculations are in general very complex. An accurate calculation of wind flow around complicated structures is very demanding on time and computational costs. In many civil engineering applications, high accuracy is not needed and our CFD program RWIND 2 enables in such cases to simplify the model of a structure and reduce the costs significantly. In this article, some questions about the simplification are answered.
When calculating regular structures, data input is often not complicated but time-consuming. Input automation can save valuable time. The task described in the present article is to consider the stories of a house as single construction stages. Data is entered using a C# program so that the user does not have to enter the elements of the individual floors manually.
With the Steel Design add-on, you can design structural steel components in the event of fire using the simple design methods according to Eurocode 3. The component temperature at the time of the design check can be determined automatically according to the temperature-time curves specified in the standard. In addition to considering a cladding for fire protection, it is also possible for you to take account of the beneficial properties of hot-dip galvanization.
A new capability within RFEM 6 when designing concrete columns is being able to generate the moment interaction diagram according to the ACI 318-19 [1]. When designing reinforced concrete members, the moment interaction diagram is an essential tool. The moment interaction diagram represents the relationship between the bending moment and axial force at any given point along a reinforced member. Valuable information is shown visually like strength and how the concrete behaves under different loading conditions.
This article shows how the “Time-Dependent Analysis” add-on is integrated in RFEM 6 and RSTAB 9. It describes how to define input data such as the time-dependent characteristics of the material, how to determine the type of analysis and how to specify loading times.
In the RFEM 6 and RSTAB 9 programs, it is possible to group objects based on different criteria. Hence, objects that meet the defined criteria can be selected and edited at the same time. This is possible with the “Object Selection” tool, which is comparable to “Special Selection” in RFEM 5. This article will show you how to group objects with “Object Selection" as a new guide object of RFEM 6 or RSTAB 9.
According to EN 1992-1-1 [1], a beam is a member of which the span is no less than 3 times the overall section depth. Otherwise, the structural element should be considered as a deep beam. The behavior of deep beams (that is, beams with a span less than 3 times the section depth) is different from the behavior of normal beams (that is, beams with a span that is 3 times greater than the section depth).
However, designing deep beams is often necessary when analyzing the structural components of reinforced concrete structures, since they are used for window and door lintels, upstand and downstand beams, the connection between split-level slabs, and frame systems.
Blast loads from high-energy explosives, either accidental or intentional, are rare but may be a structural design requirement. These dynamic loads differ from standard static loads due to their large magnitude and very short duration. A blast scenario can be carried out directly in an FEA program as a time history analysis to minimize loss of life and evaluate varying levels of structural damage.
The add-on modules for designing structural member components according to national, European, and international standards also show design results in addition to numerical output in tables graphically, as diagrams displayed on the framework.
The "4.0 Results - Summary" table displays the infinity norm at the end of the load case results. The norm is used to estimate the largest eigenvalue of a structure. The largest eigenvalue of a structure is estimated by numerical analysis, as accurate determination can be very time-consuming.
Sections are an excellent way to display and evaluate results clearly. In the RFEM and RSTAB section dialog boxes, you can display several result types at the same time.
To simulate a support clearance in a connection between members, you can use the "Diagram" function for member hinges. To use this function, first define the relevant degree of freedom as release. Then, you can select the "Diagram" function from the drop‑down list.
RFEM and RSTAB offer many display options in the Display Navigator. They can be completely different, depending on their function. You often have to click several times to make certain changes. If you want to optimize your work, you can create user‑defined views. In these views, you can save all specified settings. The following example illustrates this principle.
When designing several members in one design case, it is sometimes difficult to recognize the governing design checks. To improve the overview and to display the relevant design checks in a compact way, you can use the filter options under the result tables. These are included in all design modules of steel, aluminum, and timber structures in RFEM and RSTAB.
Instead of a quadrangular surface, you can use a B‑spline surface. The shape of this can be adjusted retrospectively, using the integrated help nodes. Depending on the necessary surface complexity, you can create a B‑spline surface with 3 × 3 or 4 × 4 help nodes.
In RF‑/STEEL EC3, you can assign the same input data to several members or sets of members at the same time. The simultaneous assignment of the input data is possible for intermediate supports, effective lengths, nodal supports, member end hinges, and shear panel and rotational restraint.
In RFEM, surfaces are automatically connected if they have common boundary lines. If the definition line of a surface is lying in another surface, the line is automatically integrated into the surface, provided that it is a planar surface. For quadrangle surfaces, however, automatic object detection would be relatively time-consuming. For this reason, the corresponding function is deactivated. The integrated objects must be specified manually.
In the calculation parameters, you can set the number of member divisions for result diagrams. The effect of this setting option is shown in the following images.
In RFEM 5 and RSTAB 8, it is possible to assign nonlinearities to member hinges. In addition to the nonlinearities "Fixed if" and "Partial activity", you can select "Diagram". If you select the "Diagram" option, you have to specify the according settings for the activity of the member hinge. For the individual definition points, it is necessary to specify the abscissa and ordinate values (deformations or rotations and the according internal forces) that define the hinge.
In RFEM, orthotropic plastic analyses using the Tsai‑Wu plasticity criterion have been possible for quite some time now. The hardening modulus Ep,x or Ep,y can be used to consider the hardening of the material during the iterative calculation.
The RF-/STEEL EC3 add‑on module allows for the fire protection design of structural steel components. The simplified analysis is performed by determining the steel temperature iteratively for a particular point of time.
Sometimes a structure needs reinforcement in cases where a new floor is being added, or when an existing member is found to be under design due to a hard-to-predict loading assumption. In many cases, the structural member may not be easily replaced, and reinforcement is implemented to meet the new loading requirement.
In RFEM and RSTAB, it is possible to define nonlinear properties of member releases. In addition to the activity diagrams and force-deformation relationship, you also have the simple option of using signs or limit values of the internal forces as criteria for the effectiveness of the release. This way, you can specify which internal forces should be transferred at the member end.
In this article, representations of a blast scenario of a remote detonation performed in RF-DYNAM Pro - Forced Vibrations are shown, and the effects are compared in the linear time history analysis.
With RF-/STEEL EC3, you can utilize nominal temperature-time curves in RFEM and RSTAB. The standard time-temperature curve (ETK), the external fire curve and the hydrocarbon fire curve are implemented. Moreover, the program provides the option to directly specify the final temperature of steel.
When evaluating line support forces, implausible diagrams sometimes arise at first glance. In particular, for variable loads at locations that also have a nodal support, at division points and edge locations of supported lines, the results sometimes show unexpected support reactions. Using the function of the linear smooth distribution in Project Navigator – Display does not always lead to the expected result diagram.