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If a canopy roof (for example, a filling station roof) should be designed, a load determination with regard to Section 7.3 of EN 1991-1-4 is required. This article shows the design of a slightly inclined troughed roof, with an example.
Using RF-CONCRETE Members, concrete column design is possible according to ACI 318-14. Accurately designing concrete column shear and longitudinal reinforcement is important for safety considerations. The following article will confirm the reinforcement design in RF-CONCRETE Members using step-by-step analytical equations as per the ACI 318-14 standard, including required longitudinal steel reinforcement, gross cross-sectional area, and tie size/spacing.
In Germany, DIN EN 1991-1-4 with the National Annex DIN EN 1991-1-4/NA regulates the wind loads. The standard applies to civil engineering works up to an altitude of 300 m.
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.
- 001530
- Modeling | Loading
- RFEM 5
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- RSTAB 8
- RX-TIMBER Glued-Laminated Beam 2
- RX-TIMBER Roof 2
- RX-TIMBER Continuous Beam 2
- RX-TIMBER Purlin 2
- RX-TIMBER Frame 2
- RX-TIMBER Column 2
- RX-TIMBER Brace 2
- Buildings
- Concrete Structures
- Steel Structures
- Timber Structures
- Process Manufacturing Plants
- Temporary Structures
- Structural Analysis & Design
- Eurocode 1
- Eurocode 0
In Germany, DIN EN 1991-1-3 with National Annex DIN EN 1991-1-3/NA regulates snow loads. The standard applies to civil engineering works at altitudes of up to 1,500 m above sea level.
The fundamental requirements of a structural system are (according to the basis of structural design) sufficient ultimate limit state, serviceability, and resistance. Structures must be designed in such a way that no damage occurs due to events such as the impact of a vehicle.
Buildings often have extensions. If the roof levels are not at the same height, this height difference (if more than 0.5 m) must additionally be considered for the snow load assumption.
DIN EN 1998-1 with the National Annex DIN EN 1998-1/NA specifies how to determine seismic loads. The standard applies to structural engineering in seismic areas.
The stiffening of timber structures is usually carried out by means of timber panels. For this purpose, structural components consisting of slabs (chipboard, OSB) are connected with members. Several articles will describe the basics of this construction method and the calculation in the RFEM program. This first article describes the basic determination of the stiffnesses as well as the calculation.
This article describes the determination of force coefficients using a wind load and the calculation of a stability factor due to lateral-torsional buckling.
When it comes to wind loads on building type structures as per ASCE 7, numerous resources can be found to supplement design standards and aid engineers with this lateral load application. However, engineers may find it more difficult to find similar resources for wind loading on non-building type structures. This article will examine the steps to calculate and apply wind loads as per ASCE 7-16 on a circular reinforced concrete tank with a dome roof.
For crane runways with large spans, the horizontal load from skewing is often relevant for the design. This article describes the origin of these forces and the correct input in CRANEWAY. The practical implementation and the theoretical background are discussed.
Slender bending beams that have a large h/w ratio and are loaded parallel to the minor axis tend to have stability issues. This is due to the deflection of the compression chord.
Long-span glued-laminated beams are usually supported by a reinforced concrete column with torsional restraints.
In current literature, the formulas used to determine internal forces and deformations manually are usually specified without considering the shear deformation. The deformations resulting from shear force are often underestimated in timber construction in particular.
In accordance with Sec. 6.6.3.1.1 and Sec. 10.14.1.2 of ACI 318-14 and CSA A23.3-14, respectively, RFEM effectively takes into consideration concrete member and surface stiffness reduction for various element types. Available selection types include cracked and uncracked walls, flat plates and slabs, beams, and columns. The multiplier factors available within the program are taken directly from Table 6.6.3.1.1(a) and Table 10.14.1.2.
In addition to the basic combination rules of EN 1990, there are other combination conditions for actions on road bridges specified in EN 1991‑2 that must be taken into account. RFEM and RSTAB provide automatic combinatorics that can be activated in the General Data when selecting the standard EN 1990 + EN 1991‑2. The partial safety factors and combination coefficients depending on the action category are preset when selecting the respective National Annex.
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.
The calculation of timber panels is carried out on simplified member or surface structures. This article describes how to determine the required stiffness.
- 001541
- Results
- RFEM 5
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- RF-DYNAM Pro | Natural Vibrations 5
- RF-DYNAM Pro | Equivalent Loads 5
- RF-DYNAM Pro | Forced Vibrations 5
- RSTAB 8
- DYNAM Pro | Natural Vibrations 8
- DYNAM Pro | Equivalent Loads 8
- Concrete Structures
- Steel Structures
- Timber Structures
- Process Manufacturing Plants
- Power Plants
- Buildings
- Dynamic and Seismic Analysis
- ASCE 7
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.
Wind blowing parallel to the surfaces of a structure can generate friction forces on these surfaces. This effect is important mainly for very large structures.
In the existing standard, there were no regulations for the distribution of snow loads for elevated solar thermal and photovoltaic systems on roofs. Only distribution of the loads was advised. It was only with the National Annex DIN EN 1991-1-3/NA: 2019-04 that specific regulations were made for this.
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.
- 001555
- Modeling | Loading
- RFEM 5
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- RSTAB 8
- RF-TIMBER AWC 5
- TIMBER AWC 8
- RF-TIMBER CSA 5
- TIMBER CSA 8
- RF-TIMBER Pro 5
- TIMBER Pro 8
- RF-JOINTS Timber | Timber to Timber 5
- JOINTS Timber | Timber to Timber 8
- RF-JOINTS Timber | Steel to Timber 5
- JOINTS Timber | Steel to Timber 8
- RF-LIMITS 5
- LIMITS 8
- RF-LAMINATE 5
- Timber Structures
- Laminate and Sandwich Structures
- Structural Analysis & Design
- Finite Element Analysis
- Steel Connections
- Eurocode 0
- Eurocode 5
- ANSI/AISC 360
- SIA 260
- SIA 265
In addition to determining loads, some particularities concerning the load combinatorics in timber design have to be considered. Contrary to steel structures, where the largest loading results from all unfavorable actions, in timber construction, the strength values depend on the load duration and timber humidity. Special characteristics have to be considered as well for the serviceability limit state design. The following article discusses the effects on the design of wooden elements and how this is possible with RSTAB and RFEM.
The elastic deformations of a structural component due to a load are based on Hooke's law, which describes a linear stress-strain relation. They are reversible: After the relief, the component returns to its original shape. However, plastic deformations lead to irreversible deformations. The plastic strains are usually considerably larger than the elastic deformations. For plastic stresses of ductile materials such as steel, yielding effects occur where the increase in deformation is accompanied by hardening. They lead to permanent deformations - and in extreme cases to the destruction of the structural component.
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.
The wind loads are regulated according to Eurocode 1 - Actions on Structures - Part 1-4: General actions - Wind loads. The nationally determined parameters of a respective country can be found in the National Annexes.
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.
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.
The article titled Lateral-Torsional Buckling in Timber Construction | Theory explains the theoretical background for the analytical determination of the critical bending moment Mcrit or the critical bending stress σcrit for the lateral buckling of a bending beam. This article uses examples to verify the analytical solution with the result from the eigenvalue analysis.