A double‑mass system consists of two shafts and two masses represented by the corresponding moments of inertia, concentrated in a given distance as nodal masses. The left shaft is fixed, and the right mass is free. Neglecting the self‑weight of the shafts, determine the torsional natural frequencies of the system.
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As gravity loads act on a structure, lateral displacement occurs. In turn, a secondary overturning moment is generated as the gravity load continues to act on the elements in the laterally displaced position. This effect is also known as "P-Delta (Δ)". Sec. 12.9.1.6 of the ASCE 7-16 Standard and the NBC 2015 Commentary specify when P-Delta effects should be considered during a modal response spectrum analysis.
RFEM offers the option to perform a response spectrum analysis according to ASCE 7-16. This standard describes the determination of seismic loads for the American market. It might happen that the P-Delta effect has to be considered due to the stiffness of the entire structure in order to calculate the internal forces and carry out the design.
The ASCE 7-22 Standard [1], Sect. 12.9.1.6 specifies when P-delta effects should be considered when running a modal response spectrum analysis for seismic design. In the NBC 2020 [2], Sent. 4.1.8.3.8.c gives only a short requirement that sway effects due to the interaction of gravity loads with the deformed structure should be considered. Therefore, there may be situations where second-order effects, also known as P-delta, must be considered when carrying out a seismic analysis.
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.
Use the "Independent mesh preferred" option in the FE mesh settings to create an independent FE mesh for the integrated objects. This allows you to generate a significantly more detailed and precise FE mesh for individual objects that are integrated into one another.
In the "Edit Section" dialog box, you can display the buckling shapes of the Finite Strip Method (FSM) as a 3D graphic.
In RFEM 6 and RSTAB 9, you have the option to enter "Visual Objects" as guide objects. You can import the file formats 3ds, stl, and obj.
These objects allow you to create a better reference to the dimensions.
Do you have individual column sections and angled wall geometries, and need punching shear design for them?
No problem. In RFEM 6, you can perform punching shear design not only for rectangular and circular sections, but for any cross-section shape.
In RF‑/DYNAM Pro, the "From self-weight of structure" option is available in a mass case. Is it always necessary to activate this option in order to consider the dead load of the structure?
The performance when starting the programs or working in the program has become noticeably worse. What could be the cause of this?
Is it possible to influence the transverse distribution of a load in the case of the Isotropic | Masonry | Plastic material model?
What is the effect of the "Independent FE Mesh Ppreferred" option in the mesh settings?
How do I define a plastic hinge in RFEM 6?
How do I set a uniaxial load transfer for a plate?
