The structural analysis software RFEM 6 is the basis of a modular software system. The main program RFEM 6 is used to define structures, materials, and loads of planar and spatial structural systems consisting of plates, walls, shells, and members. The program also allows you to create combined structures as well as to model solid and contact elements.
RSTAB 9 is a powerful analysis and design software for 3D beam, frame, or truss structure calculations, reflecting the current state of the art and helping structural engineers meet requirements in modern civil engineering.
Do you often spend too long calculating cross-sections? Dlubal Software and the RSECTION stand-alone program facilitate your work by determining section properties of various cross-sections and performing a subsequent stress analysis.
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The easiest case is a door lintel modeled directly on the line of the door opening without an offset. It is then necessary to generate extensions on the wall sides. In the end, the lintel thus consists of three members, as shown in Image 01.
No, it is not absolutely necessary to calculate according to the second-order or large deformation analysis when using a nonlinear material model. The material nonlinearity is also considered in the case of the calculation according to the linear static analysis.
The calculation according to the second-order analysis or the large deformation analysis means that the equilibrium is set on a deformed structure. Thus, it is geometric nonlinearity.
The difference between the second-order and large deformation is that large rotation may occur in the case of the large deformation analysis.
Thus, if there is no stability problem or if the stability problem is further analyzed, the calculation according to the linear static analysis is sufficient.
The RF‑/DYNAM Pro - Equivalent Loads add-on module only contains a linear analysis of structures. If you now apply a nonlinear model for the calculation, RF‑/DYNAM Pro - Equivalent Loads will modify it internally and treat it as a linear model. The nonlinearity in your model is the masonry, which cannot absorb any tensile forces.
The problem is as follows: RF‑/DYNAM Pro - Equivalent Loads calculates the equivalent loads linearly and exports the load cases from them. However, the load cases are subsequently calculated nonlinearly on the basis of the material model, which is not entirely correct. Furthermore, the results are superimposed according to the SRSS or CQC method, which results in tensile and compressive forces being present in the model.
In this case, you could change the masonry to isotropic linear and work with linear properties of the material model, for example. Additionally, it is possible to insert line hinges at this location, which could be used to avoid the moment restraint, for example.
When using a diagram in the program, the first strain is always given (initial strain). It depends on the resulting modulus of elasticity and cannot be controlled directly. For this, you can use a trick in the program and adjust the first strain to a desired value anyway. To do this, you have to calculate the initial modulus of elasticity and enter it in the material parameters. In your case, it would be possible to use the following procedure.
The difference between the two material models is as follows:
For both material models, you have to define the nonlinear properties in an additional dialog box. When entering data by means of a diagram, it is possible for both models to define the distribution after the last step.
The "Isotropic Nonlinear Elastic 1D" material model allows for the anti-symmetric input of the stress-strain diagram (different for the positive and negative zones), whereas the "Isotropic Plastic 1D" model only allows for symmetric input.
This is possible with the RF‑LOAD‑HISTORY add‑on module.
It is important to use the "Plastic 2D/3D" or "Plastic 1D" material model. How it works in practice is shown in this recording of a Dlubal Info Day.
Young's modulus is calculated for each step of the defined diagram according to Hooke's law:ε = σ / E
The value of the current step is displayed beneath the diagram on the right side (see Image 01).