The seismic design result is categorized into two sections: member requirements and connection requirements.
The "Seismic Requirements" include the Required Flexural Strength and the Required Shear Strength of the beam-to-column connection for moment frames. They are listed in the ‘Moment Frame Connection by Member’ tab. For braced frames, the Required Connection Tensile Strength and the Required Connection Compressive Strength of the brace are listed in the ‘Brace Connection by Member’ tab.
The program provides the performed design checks in tables. The design check details clearly display the formulas and references to the standard.
The Modal Analysis add-on provides you with the option to automatically increase the sought eigenvalues until a defined effective modal mass factor is reached. All translational directions activated as masses for the modal analysis are taken into account.
Thus, it is possible to easily calculate the required 90% of the effective modal mass for the response spectrum method.
The Concrete Design add-on allows you to perform the seismic design of reinforced concrete members according to EC 8. This includes, among other things, the following functionalities:
Seismic design configurations
Differentiation of the ductility classes DCL, DCM, DCH
Option to transfer the behavior factor from a dynamic analysis
Check of the limit value for the behavior factor
Capacity design checks of "Strong column - weak beam"
Detailing and particular rules for curvature ductility factor
Detailing and particular rules for local ductility
In the Steel Design add-on, you can perform the stability and cross-section design checks of cold-formed sections according to EN 1993‑1‑3 in compliance with Sections 6.1.2 – 6.1.5 and 6.1.8 – 6.1.10.
The Ponding load type allows you to simulate rain actions on multi-curved surfaces, taking into account the displacements according to the large deformation analysis.
This numerical rainfall process examines the assigned surface geometry and determines which rainfall portions drain away and which rainfall portions accumulate in puddles (water pockets) on the surface. The puddle size then results in a corresponding vertical load for the structural analysis.
For example, you can use this feature in the analysis of approximately horizontal membrane roof geometries subjected to rain loading.
The design of cold-formed steel members according to the AISI S100-16 / CSA S136-16 is available in RFEM 6. Design can be accessed by selecting “AISC 360” or “CSA S16” as the standard in the Steel Design Add-on. “AISI S100” or “CSA S136” is then automatically selected for the cold-formed design.
RFEM applies the Direct Strength Method (DSM) to calculate the elastic buckling load of the member. The Direct Strength Method offers two types of solutions, numerical (Finite Strip Method) and analytical (Specification). The FSM signature curve and buckling shapes can be viewed under Sections.
The new steel sections according to the latest CISC Handbook (12th edition) are available in RFEM 6. The sections are listed in the Standardized library. In the filter, select “Canada” for the region and “CISC 12” for the standard. Alternatively, the section name can be directly entered in the search box located at the bottom of the dialog box.
Have you already discovered the tabular and graphical output of masses in mesh points? That's right, this is also part of the modal analysis results in RFEM 6. This way, you can check the imported masses that depend on various settings of the modal analysis. They can be displayed in the Masses in Mesh Points tab of the Results table. The table provides you with an overview of the following results: Mass - Translational Direction (mX, mY, mZ), Mass - Rotational Direction (mφX, mφY, mφZ), and the Sum of Masses. Would it be best for you to have a graphical evaluation as quickly as possible? Then you can also graphically display the masses in mesh points.
As you've already learned, the results of a Modal Analysis load case are displayed in the program after a successful calculation. You can thus immediately see the first mode shape graphically or as an animation. You can also easily adjust the representation of the mode shape standardization. Do this directly in the Results navigator, where you have one of four options for the visualization of the mode shapes available for the selection:
Scaling the value of the mode shape vector uj to 1 (considers the translation components only)
Selecting the maximum translational component of the eigenvector and setting it to 1
Considering the entire eigenvector (including the rotation components), selecting the maximum, and setting it to 1
Setting the modal mass mi for each mode shape to 1 kg
You can find a detailed explanation of the mode shape standardization here:
Online Manual
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When performing a design according to EN 1993‑1‑3, it is possible to graphically display a mode shape for the distortional buckling of a cross-section, and for the RSECTION cross-sections.
The mode shape can also be output in RSECTION 1 for library cross-sections.
Do you want to consider other loads as masses in addition to the static loads? The program allows that for nodal, member, line and surface loads. For this, you need to select the Mass load type when defining the load of interest. Define a mass or mass components in the X, Y, and Z directions for such loads. For nodal masses, you have an additional option to also specify moments of inertia X, Y, and Z in order to model more complex mass points.
It is often necessary to neglect masses. This is particularly the case when you want to use the output of the modal analysis for the seismic analysis. For this, 90% of the effective modal mass in each direction is required for the calculation. So you can neglect the mass in all fixed nodal and line supports. The program automatically deactivates the associated masses for you.
You can also manually select the objects whose masses are to be neglected for the modal analysis. We have shown the latter in the image for a better view. A user-defined selection is made the and the objects with their associated mass components are selected to neglect the masses.
When defining the input data for the modal analysis load case, you can consider a load case whose stiffnesses represent the initial position for the modal analysis. How do you do that? As shown in the image, select the "Consider initial state from" option. Now, open the "Initial State Settings" dialog box and define the type Stiffness as the initial state. In this load case, as of which is the initial state taken into account, you can consider the stiffness of the structural system when the tension members fail. The purpose of all of this: The stiffness from this load case is considered in the modal analysis. Thus, you obtain a clearly flexible system.
You can already see it in the image: Imperfections can also be taken into account when defining a modal analysis load case. The imperfection types that you can use in the modal analysis are notional loads from load case, initial sway via table, static deformation, buckling mode, dynamic mode shape, and group of imperfection cases.
Did you know? You can easily define structural modifications in load cases of the Modal Analysis type. This allows you, for example, to individually adjust the stiffnesses of materials, cross-sections, members, surfaces, hinges, and supports. You can also modify stiffnesses for some design add-ons. Once you select the objects, their stiffness properties are adapted to the object type. In this way, you can define them in separate tabs.
Do you want to analyze the failure of an object (for example, a column) in the modal analysis? This is also possible without any problems. Simply switch to the Structure Modification window and deactivate the relevant objects.
Is your goal to determine the number of mode shapes? The program offers you two methods for this. On the one hand, you can manually define the number of the smallest mode shapes to be calculated. In this case, the number of available mode shapes depends on the degrees of freedom (that is, the number of free mass points multiplied by the number of directions in which the masses act). However, it is limited to 9999. On the other hand, you can set the maximum natural frequency the way that the program determined the mode shapes automatically until reaching the natural frequency set.
Is the calculation finished? The results of the modal analysis are then available both graphically and in tables. Display the result tables for the load case or the load cases of the modal analysis. Thus, you can see the eigenvalues, angular frequencies, natural frequencies, and natural periods of the structure at first glance. The effective modal masses, modal mass factors, and participation factors are also clearly displayed.
You have several options available to define masses for a modal analysis. While the masses due to self-weight are considered automatically, you can consider the loads and masses directly in a load case of the modal analysis type. Do you need more options? Select whether to consider full loads as masses, load components in the global Z-direction, or only the load components in the direction of gravity.
The program offers you an additional or alternative option for importing masses: A manual definition of load combinations as of which are the masses considered in the modal analysis. Have you selected a design standard? You can then create a design situation with the Seismic Mass combination type. Thus, the program automatically calculates a mass situation for the modal analysis according to the preferred design standard. In other words: The program creates a load combination on the basis of the preset combination coefficients for the selected standard. This contains the masses used for the modal analysis.
In RFEM/RSTAB, you have the option to generate and then calculate the load or result combinations required for the serviceability limit state. You can select these design situations for the deflection analysis in the Steel Design add-on. The calculated deformation values are determined accordingly at each location of a member, depending on the specified precamber and reference system. Finaly, you can compare these deformation values with the limit values.
Did you know? You can specify the deformation limit value individually for each structural component in Serviceability Configuration. Define the maximum deformation depending on the reference length as the allowable limit value. By defining design supports, you can segment the components in order to determine the corresponding reference length automatically for each design direction.
Based on the position of the assigned design supports, the distinction between beams and cantilevers is made automatically so the limit value can be determined accordingly.
You can find the serviceability limit state design checks in the result tables of the Steel Design add-on. You can display the design results with all the details at each location of the designed members. Furthermore, graphics are available for you with the result diagrams of the design ratios. This gives you a good overview.
You can also integrate all result tables and graphics into the global printout report of RFEM/RSTAB as a part of the steel design results. Thus, you can display and document the deformations of the entire structure as a part of the RFEM/RSTAB functionality independent of the add-on.
The structural analysis programs RFEM/RSTAB offer you a wide range of automated functions that make your dayily work easier. One of them is the automatic generation of load and result combinations for the accidental design situation of fire design. The members to be designed with the corresponding internal forces are imported directly from RFEM/RSTAB. You don't need to do anything else. The program has also already stored all information about the material and cross-section for you.
By assigning a fire resistance configuration to the members to be designed, you define the parameters relevant for the fire resistance design. Here you can manually specify the critical steel temperature at the design time. Or let the program to determine the temperature determined automatically for a specified fire duration. You can select from various fire temperature curves and fire protection measures. It is also possible to make further detailed settings, such as the definition of the fire exposure on all sides or three sides
The design checks for the members you have selected are carried out taking into account the governing component temperature. You can perform the cross-section design checks and stability analyses according to EN 1993‑1‑2, Section 4.2.3, in the Steel Design add-on. All reduction factors and coefficients that are necessary are stored accordingly and are taken into account when determining the load-bearing capacity.
The effective lengths for the equivalent member design are taken directly from the strength entries. You don't need to enter them again.
In each design, perform the cross-section classification first. For the cross-sections of Class 4, the design is performed automatically according to EN 1993‑1‑2, Annex E.
After completing the design, the Dlubal Software presents the fire resistance design checks clearly and with all result details. This makes the results comprehensible in detail. Furthermore, the results also contain all the parameters required for the determination of the component temperature at the design time.
You can also specifically evaluate the temperature distribution in the structural component using the temperature-time diagram.
All result tables and graphics, including the ultimate and serviceability limit state results, can be integrated into the global printout report of RFEM/RSTAB as a part of the steel design results.
Perform the fire resistance design with a reduced load-bearing capacity according to the component temperature determined automatically right at the design time. You can determine this automatically according to various temperature curves in the program (a standard temperature-time curve, an external fire curve, a hydrocarbon curve). For other types of temperature determination, it is also possible for you to manually specify the temperature to be applied in the design. You can determine this, for example, according to the parametric temperature-time curve from DIN EN 1991‑1‑2 or from a fire protection report.
The component temperature to be applied at the design time is determined automatically. You can adjust the coefficients used to determine the temperature. In this step, it is best for you to also select the hot-dip galvanizing. According to the DASt Guideline 027 "Determination of Component Temperature of Hot-Dip Galvanized Steel Components in Case of Fire", a lower emissivity of the steel surface is applied up to a limit temperature. Overall, this gives you a lower temperature for the thus more favorable fire resistance design.