Extended Three-dimensional Analysis of Building Systems (ETABS) is a popular tool for structural engineers to utilize when designing and analyzing buildings. In ETABS, members’ stiffness can be modified by stiffness modifiers, which helps get the right structural response. Learn about stiffness modifiers and how to use them in ETABS in this post.
What are these Stiffness Modifiers?
Modifiers of stiffness are used to modify the stiffness of a structural system’s members. A member’s stiffness is established by the qualities of its material, the geometry of its cross-section, and the length of the member.
The structural response can be drastically altered by modifying the total stiffness of the system, which can be done by modifying the stiffness of the individual elements.
Adjusting EtaB’s Rigidity
Members’ stiffness can be modified in ETABS to achieve the desired result. Individual members or sets of members can have their stiffness modified. How to adjust stiffness in ETABS is as follows:
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Define the members
First, the model’s members must be defined before applying any stiffness modifiers. A CAD program can be imported, or the members can be drawn directly in the ETABS interface.
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Designate the Part’s Features
After the members have been defined, they must be given the attributes of the corresponding sections. The stiffness of a member is defined by its section qualities, which include its cross-sectional area, moment of inertia, and other geometric properties.
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Use the stiffness modifiers.
When the members’ sections have been defined, stiffness modifiers can be applied. To do so, right-click on a member and pick “Frame Properties” from the resulting menu.
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Enter the desired value for the stiffness modifier.
The stiffness modifier value for each member can be set in the “Frame Properties” dialogue box. The value of the stiffness modifier may be larger than 1, or it may be less than 1. The stiffness of the part is decreased for values below one and increased for values above 1.
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Examine the model’s results.
The structural reaction can be predicted by analyzing the model after applying stiffness modifiers. If a certain reaction is desired, the stiffness modifiers can be tweaked accordingly.
Organizational Members
Stiffness modifiers may need to be applied to a set of members rather than to each member individually in some circumstances. In ETABS, this is accomplished by forming a “frame section” consisting of all the group members and then applying the stiffness modifier to the formed frame section.
Altering Rigidity Inconsistently
It may be required to modify the stiffness of a member at several locations, depending on the circumstances. For a member with a tapered cross-section, the thicker end may require a greater stiffness modifier. ETABS allows this by segmenting the member and adding separate stiffness modifiers to each fragment.
Conclusion
The stiffness modifier in ETABS is a potent tool for changing the stiffness of structural parts. Stiffness modifiers allow for global changes in system stiffness, which can have far-reaching effects on how a structure responds. This article explains how to utilize stiffness modifiers in ETABS so that users may get the required response from their structural models.
