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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.
The RX‑TIMBER stand-alone program offers you the option to optimize the lateral-torsional bracing. With this selection, the program iteratively determines the required minimum length of the lateral-torsional bracing.
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.
In timber design, beams are often built from several timber elements. The individual elements can be connected with glue, nails, bolts, or dowels. A glued connection is to be assumed as rigid. In the case of dowel‑type fasteners, the joint is compliant (slip joint), and the cross‑section properties of the connected elements cannot be fully applied.
The same structures are often needed in several projects, such as the purlin with columns and braces in this example. The dimensions can be changed directly in RFEM or RSTAB by shifting the nodes.
For relatively large or relatively small surfaces, it can happen that the automatically created result values do not fit the model: In the case of large surfaces, there can be too many result values; in the case of small surfaces, too few.
With the RF-/TIMBER Pro add-on module, you can perform the vibration design known from DIN 1052 for the design according to EN 1995-1-1. In this design, the deflection under permanent and quasi-permanent action at the ideal one‑span beam may not exceed the limit value (6 mm according to DIN 1052). If you consider the relation between the natural frequency and the deflection for a hinged single-span beam subjected to a constant distributed load, the 6 mm limit value results in a minimum natural frequency of about 7.2 Hz.
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.
The RF-/LIMITS add-on module allows you to compare the ultimate limit state of members, member ends, nodes, nodal supports, and surfaces (RFEM only) by means of a defined ultimate load capacity. Furthermore, you can check nodal displacements and cross-section dimensions. In this example, the column bases of a carport are to be compared with the maximum allowable forces specified by the manufacturer.
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.
Besides the standardized gamma method, you can display the semi-rigid composite beams also as a framework model.
You can make various settings in order to achieve a clearly‑arranged display of the result values. For example, some users may not want the white background in text bubbles. You can adjust the background in "Display Properties" using the Transparent and Background color option.
- 000945
- Add-on Modules
- RF-FRAME-JOINT Pro 5
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- JOINTS Steel | Column Base 8
- JOINTS Steel | DSTV 8
- JOINTS Steel | Pinned 8
- JOINTS Steel | Rigid 8
- JOINTS Steel | SIKLA 8
- JOINTS Steel | Tower 8
- JOINTS Timber | Steel to Timber 8
- JOINTS Timber | Timber to Timber 8
- RF-JOINTS Steel | SIKLA 5
- RF-JOINTS Steel | Column Base 5
- RF-JOINTS Steel | DSTV 5
- RF-JOINTS Steel | Pinned 5
- RF-JOINTS Steel | Rigid 5
- RF-JOINTS Steel | Tower 5
- RF-JOINTS Timber | Steel to Timber 5
- RF-JOINTS Timber | Timber to Timber 5
- FRAME-JOINT Pro 8
- Steel Structures
- Timber Structures
- Steel Connections
- Eurocode 3
- Eurocode 5
In addition to the result tables, you can create three-dimensional graphics in RF‑/FRAME‑JOINT Pro and RF‑/JOINTS. This is a realistic representation of a connection to scale.
The joint type "Main member only" in RF‑/JOINTS Timber - Steel to Timber can also be applied for more than one connected member.
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.
Not only do RF-/STEEL EC3 and RF-/TIMBER Pro perform cross-section designs and stability analyses, they allow you to perform serviceability limit state designs. For this, it is possible to relate the deformation to the undeformed initial system or to shifted members ends.
In order to represent the stiffness of the entire structure correctly, you can consider shear coupling between the ceiling and the downstand beam using the line release. This way, you can define a spring constant, thus avoiding the replacement system by using coupling members. The spring constant results from the shift modulus of the fastener, which can be determined according to EN 1995-1-1 or ANSI/AWC NDS, for example.
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.
As of the program version X.06 of the RF‑/TIMBER Pro, RF‑/TIMBER AWC, and RF‑/TIMBER CSA add‑on modules, notches and cross‑section reductions can be considered in the design. The procedure is as follows:
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.
In the case of tension connections with cleats subjected to unilateral loading, the external members (side timber) are loaded by an additional bending moment due to the eccentric load distribution. However, this fact is not mentioned in EN 1995‑1‑1 and is considered in the National Annex to DIN EN 1995‑1‑1 by the reduction of the tensile strength. This reduction depends on the pull-off strength of the fasteners.
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.
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.
Long-span glued-laminated beams are usually supported by a reinforced concrete column with torsional restraints.
Basically, you can design the structural components made of cross-laminated timber in the RF-LAMINATE add-on module. Since the design is a pure elastic stress analysis, it is necessary to additionally consider the stability issues (flexural buckling and lateral-torsional buckling).
The following article describes a design using the equivalent member method according to [1] Section 6.3.2, performed on an example of a cross-laminated timber wall susceptible to buckling described in Part 1 of this article series. The buckling analysis will be performed as a compressive stress analysis with reduced compressive strength. For this, the instability factor kc is determined, which depends primarily on the component slenderness and the support type.