FAQ 002237 EN

Add-on Modules DYNAM Pro RF-DYNAM Pro DYNAM Pro - Equivalent Loads RF-DYNAM Pro - Equivalent Loads DYNAM Pro - Natural Vibrations RF-DYNAM Pro - Natural Vibrations

How can I consider tension members in RF-/DYNAM Pro?

Answer

To study a system with tension members in RF-/DYNAM Pro it is recommended to define several Natural Vibration Cases (NVCs) and to use the stiffness modification options. The natural vibration analysis is a linear analysis of frequencies and mode shapes, tension members are considered as trusses in RF-/DYNAM Pro and can cope with tension and compression to the same degree. To estimate how the frequencies change when the tension members fail you can import this initial state into RF-/DYNAM Pro via a Load Case where you deactivate the members manually or via a Load Case where the tension members failed due to the load state. The defined NVCs can be assigned to Dynamic Load Cases (DLCs) to perform, for example, a response spectrum anaylsis with the export of equivalent loads (add-on module RF-/DYNAM Pro Equivalent Loads).

The equivalent loads that are exported into Load Cases in the main program RFEM / RSTAB are evaluated with consideration of all nonlinearities, in some cases this can lead to conflicts. An example is illustrated in the picture. In the first case no stiffness modifications are used in RF-/DYNAM Pro and therefore all members are considered in the dynamic analysis, but in RFEM / RSTAB the tension member fail due to equivalent loads. When you want to perform a completely linear analysis you must deactivate the nonlinearities in RFEM / RSTAB. In the second and third illustrated case an initial condition is imported where the tension members are not available. The equivalent loads are therefore based on the same structure as the structure for the calculation of internal forces and deformations.


In the response spectrum analysis or the time history analysis with the add-on module RF-/DYNAM Pro Forced Vibrations the modified stiffness of the Natural Vibration Cases (NVCs) is also used for the calculation of further results. The overall linear analysis with consideration of initial conditions is performed within the module RF-/DYNAM Pro.

Keywords

Tension members, nonllinear, nonlinearities, dynamic

RSTAB Dynamic Analysis
DYNAM Pro - Forced Vibrations 8.xx

Add-on Module

Dynamic and seismic analysis including time history analysis and multi-modal response spectrum analysis

RSTAB Dynamic Analysis
DYNAM Pro - Equivalent Loads 8.xx

Add-on Module

Seismic and static load analysis using the multi-modal response spectrum analysis

RFEM Dynamic Analysis
RF-DYNAM Pro - Equivalent Loads 5.xx

Add-on Module

Seismic and static load analysis using the multi-modal response spectrum analysis

RSTAB Dynamic Analysis
DYNAM Pro - Natural Vibrations 8.xx

Add-on Module

Dynamic analysis of natural frequencies and mode shapes of member models

RFEM Dynamic Analysis
RF-DYNAM Pro - Natural Vibrations  5.xx

Add-on Module

Dynamic analysis of natural frequencies and mode shapes of member, surface, and solid models