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RF-/DYNAM Pro - Equivalent Loads allows you to determine the loads due to equivalent seismic loads according to the multi‑modal response spectrum method. In the example shown here, this was done for a multi‑mass oscillator.
- 000487
- Modeling | Structure
- RFEM 5
-
- RF-STEEL 5
- RF-STEEL AISC 5
- RF-STEEL AS 5
- RF-STEEL BS 5
- RF-STEEL CSA 5
- RF-STEEL EC3 5
- RF-STEEL GB 5
- RF-STEEL HK 5
- RF-STEEL IS 5
- RF-STEEL NBR 5
- RF-STEEL NTC-DF 5
- RF-STEEL SANS 5
- RF-STEEL SIA 5
- RF-STEEL SP 5
- RF-ALUMINUM 5
- RF-ALUMINUM ADM 5
- RSTAB 8
- STEEL 8
- STEEL AISC 8
- STEEL AS 8
- STEEL BS 8
- STEEL CSA 8
- STEEL EC3 8
- STEEL GB 8
- STEEL HK 8
- STEEL IS 8
- STEEL NBR 8
- STEEL NTC-DF 8
- STEEL SANS 8
- STEEL SIA 8
- STEEL SP 8
- ALUMINUM 8
- ALUMINUM ADM 8
- Steel Structures
- Process Manufacturing Plants
- Stairway Structures
- Structural Analysis & Design
- Eurocode 3
- ANSI/AISC 360
- SIA 263
- IS 800
- BS 5950-1
- GB 50017
- CSA S16
- AS 4100
- SP 16.13330
- SANS 10162-1
- ABNT NBR 800
- ADM
The support conditions of a beam subjected to bending are essential for its resistance to lateral-torsional buckling. If, for example, a single-span beam is held laterally in the middle of the span, the deflection of the compressed flange can be prevented, and a two-wave eigenmode can be enforced. The critical lateral-torsional buckling moment is increased significantly by this additional measure. In the add-on modules for member design, different types of lateral supports on a member can be defined using the "Intermediate supports" input window.
In the case of open cross-sections, the torsional load is removed mainly via secondary torsion, since the St. Venant torsional stiffness is low compared to the warping stiffness. Therefore, warping stiffeners in the cross-section are particularly interesting for the lateral-torsional buckling analysis, as they can significantly reduce the rotation. For this, end plates or welded stiffeners and sections are suitable.
The Eurocode for DIN EN 1991‑1‑4:2010‑12 describes wind loads acting on structural systems.
For automatic load case combination in RFEM and RSTAB, you have to enter the possible interaction of load cases. In addition to the simultaneous or alternative occurrence of all load cases of an action, an option for different combination conditions is possible.
In RFEM and RSTAB, snow drift is considered according to 5.3.4(3) of DIN EN 1991‑1‑3 for saw-tooth roofs.
For a timber connection as shown in Figure 01, you can take into account the torsional spring rigidity (spring stiffness for rotation) of the connections. You can determine it by means of the slip modulus of the fastener and the polar moment of inertia of the connection.
In the RF-/TIMBER Pro, RF-/TIMBER AWC, and RF-/TIMBER CSA add-on modules, you can consider the resulting deformation of a member or set of members. In addition to the local directions y and z, you have the option "R." This allows you to compare the total deflection of a girder to the limit values given in the standards.
The automatic creation of combinations in RFEM and RSTAB with the "EN 1990 + EN 1991‑3; Cranes" option allows you to design crane runway beams as well as support loads on the rest of the structure.
Besides the standardized gamma method, you can display the semi-rigid composite beams also as a framework model.
In addition to the geometry and shape of a flat roof, you can also take into account the formation of an eaves area when generating the loading.
The new RF‑/DYNAM Pro - Natural Vibrations module has been available since RFEM version 5.04.xx and RSTAB version 8.04.xx were released. Masses can now be imported directly from load cases and load combinations.
Eurocode 1, Parts 1 to 3, and American standard ASCE/SEI 7-16 describe the general effects due to snow loads. The load applications for duopitch, monopitch, and flat roofs required by the standards are stored in a tool in RFEM and RSTAB so that these effects can be generated easily.
In RF‑/TIMBER Pro, it is also possible to define the effective length for lateral-torsional buckling. The effective length for lateral-torsional buckling is then calculated according to EN 1995‑1‑1, Table 6.1. This option is useful especially for non-uniform load introduction.
In the H - Roofs category, imposed loads have to be applied. These are usually the technician loads for construction and maintenance. Since there is no maintenance for snow, category H must not include both snow and imposed loads together. You can consider thi in the options for automatic combinations.
At first glance, the material list for masonry seems empty. The reason for this is that bricks and mortar can be used in many combinations, which would lead to a very long and unclear list. Therefore, it is necessary first to create a new material for masonry in order to consider these possible combinations in the calculation.
According to DIN EN 1990/NA:2010‑12 – NDP to A.1.2.1(1) Comment 2, it is necessary to apply only one of the two climatic actions in the combination expressions for actions according to 6.4.3 and 6.5.3 in the case of places located up to +1,000 m above mean sea level if snow and wind are available as collateral actions, in addition to non‑climatic leading action.
According to DIN EN 1990/NA:2010‑12 - NDP to A.1.2.1(1) Comment 2, it is possible to neglect the combination of snow as a collateral action in cases of wind/snow combination with wind as the leading action in wind zones III and IV.
Due to the structural efficiency and economic benefits, dome-shaped roofs are frequently used for storehouses or stadiums. Even if the dome has the corresponding geometrical shape, it is not easy to estimate wind loads due to the Reynolds number effect. The external pressure coefficients (cpe) depend on the Reynolds numbers and on the slenderness of the structure. EN 1991‑1‑4 [1] can help you to estimate the wind loads on a dome. Based on this, the following article explains how to define a wind load in RFEM. Wind loads of the structure shown in Image 01 can be divided as follows: Wind Load on Wall, Wind Load on Dome.
For the ultimate limit state design, EN 1998-1 Section 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.
Silos are used as large containers for storage of bulk materials such as agricultural products or source materials as well as intermediates of industrial production. The structural engineering of such structures requires a precise knowledge of the stresses due to particulate solids in the building structure. The standard EN 1991‑4 "Actions on Silos and Tanks" [1] provides the general principles and requirements for determining these actions.
RFEM and RSTAB provides two different methods for the superposition of load cases. Using load combinations, the loads of individual load cases are superimposed and calculated in a "big load case". On the other hand, result combinations only combine the results of the individual load cases. This article describes the with the basis of defining result combinations and explain it in detail on two examples.
My previous article Result Combinations 1 explained the basic principles of result combinations on simple examples. This article describes a further application case that combines the definition options of Examples 1 and 2. Likewise, the effort should be compared to a combination by means of load combinations.
The previous article described the actions on silos according to DIN EN 1991-4. On an example of a free standing cylindrical silo for cement with a conical hopper, filling loads of the silo hopper were calculated.
This article describes the determination of force coefficients using a wind load and the calculation of a stability factor due to lateral-torsional buckling.
Wind is the only climatic load acting on every type of structure in every country in the world, unlike snow. The wind speed depends on the geographic location of the building. Currently, this is one of the main reasons for the necessity of regional division (wind zone) and consideration of the altitude stipulated within the official standards; the variation of the dynamic pressures according to the height above the ground for a "normal" site deprived of masking effect should be taken into account as well.
If an aluminum member section is comprised of slender elements, failure can occur due to the local buckling of the flanges or webs before the member can reach full strength. In the add-on module RF-/ALUMINUM ADM, there are now three options for determining the nominal flexural strength for the limit state of local buckling, Mnlb, from Section F.3 in the 2015 Aluminum Design Manual. The three options include sections F.3.1 Weighted Average Method, F.3.2 Direct Strength Method, and F.3.3 Limiting Element Method.
This article presents a simple example of a lattice structure to explain how to determine wind loading as a function of the lattice solidity.
In a multi-modal response spectrum analysis, it is important to determine a sufficient number of eigenvalues of the structure and to consider their dynamic responses. Regulations such as EN 1998‑1 [1] and other international standards require the activation of 90% of the structural mass. This means: to determine so many eigenvalues that the sum of the effective modal mass factors is greater than 0.9.
If the wind load for buildings or structures is to be determined by the simultaneous assumption of aerodynamic pressure and suction coefficients on the windward and leeward sides of the building, the correlation of the wind pressure on zones D and E of the wall surfaces may be taken into account.