Dlubal Info Day Online 2015 - Part 3: Earthquake Analysis in RF-DYNAM Pro (in German)
2015-11-12
Free
Duration: 34:18
Dlubal Info Day Online 2015 - Part 3: Earthquake Analysis in RF-DYNAM Pro (in German)
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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.
The story drift of a building provides valuable information about its structural behavior under seismic loads. These could cause large horizontal deformations and even instabilities. Some standards, therefore, call for a check of the story drift in its center of gravity. It indicates, for example, if a second-order analysis (P-Δ effect) is necessary.
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.
![Reduction of Building to Cantilever Structure: The individual mass points represent the floors. The deflection due to the normal compression forces shown in (a) is (b) converted into equivalent moments of displacement or shear forces [2].](/en/webimage/009762/2420261/01-en-png-12-png.png?mw=512&hash=8189361dbff525c2ff39c36a72a1ca91810208f6)
For the ultimate limit state design, EN 1998 1, Sections 2.2.2 and 4.4.2.2 [1], requires the calculation considering the second-order theory (P-Δ effect). This effect may be neglected only if the interstory drift sensitivity coefficient θ is less than 0.1. The coefficient θ is defined as follows:
$$\mathrm\theta\;=\;\frac{\displaystyle{\mathrm P}_\mathrm{tot}\;\cdot\;{\mathrm d}_\mathrm r }{{\mathrm V}_\mathrm{tot}\;\cdot\;\mathrm h}\;(1)$$
where
θ is the interstory drift sensitivity coefficient,
Ptot is the total gravity load at and above the story considered in the seismic design situation (see Expression 2),
dr is the design interstory drift, evaluated as the difference of the average lateral displacements dS at the top and bottom of the story under consideration; for this, the displacement is determined using the linear design response spectrum with q = 1.0,
Vtot is the total seismic story shear determined using the linear design response spectrum,
h is the interstory height.
$$\mathrm\theta\;=\;\frac{\displaystyle{\mathrm P}_\mathrm{tot}\;\cdot\;{\mathrm d}_\mathrm r }{{\mathrm V}_\mathrm{tot}\;\cdot\;\mathrm h}\;(1)$$
where
θ is the interstory drift sensitivity coefficient,
Ptot is the total gravity load at and above the story considered in the seismic design situation (see Expression 2),
dr is the design interstory drift, evaluated as the difference of the average lateral displacements dS at the top and bottom of the story under consideration; for this, the displacement is determined using the linear design response spectrum with q = 1.0,
Vtot is the total seismic story shear determined using the linear design response spectrum,
h is the interstory height.
![Reduction of Building to Cantilever Structure: The individual mass points represent the floors. The deflection due to the normal compression forces shown in (a) is (b) converted into equivalent moments of displacement or shear forces [2].](/en/webimage/009762/2420261/01-en-png-12-png.png?mw=350&hash=dd36dc43123116724231958668ad6cdcb13a0169)
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?
Is it possible to perform a seismic analysis with the masonry material model?
Where can I subsequently reverse the global axis system in RFEM 6 (direction of the global Z-axis)?
Where can I find the version number of RFEM 6 / RSTAB 9?
Is it possible to use the add-ons for RFEM 6 to design concrete solids?
How do I ask Mia my question so that she finds the best answer?
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