The concept of effective length is widely used by practising engineers and represents an important step in the design process of members under compressive forces, therefore a state of art method has been established. One of these practical procedures to define the buckling length factor is the alignment chart method. Most engineers use this method in lieu of an actual stability analysis in the interest of simplification and reducing workflow.
It has been used by the CSA to include buckling, also adopted by the AISC, ACI 318-14 and AASHTO standards, among others.
Advance Design is using this method to compute the buckling length coefficient and it is called the GA-GB method:
When we look at the effective length factor equation-for members in braced frame:
We can clearly distinguish two constants GA and GB ; they represent the stiffness ratio of columns and girders at two and joint A and B respectively.
They are defined by:
For this 3D model, the beam in orange is connected at two points A and B, point A represents the base of the element, as shown in the figure a rigid support is created to model the foundation, point B defines the other end connected to the girders, in this case four beams are connected to the vertical member. Using the above method AD is computing the effective length. The first scenario is when we have unbraced frame the value is 5.69 m and 5.2 m for lfz and lfy respectively, for braced frame the values will be 3.63 m and 3.15 m
In addition to the auto calculation option, it is possible to input a user-defined value and use it for the buckling design. AD makes it easier for the engineer to design all kinds of elements by providing an easy interface and thanks to a powerful machine the results are obtained instantaneously.
For additional information, Graitec customers may contact their local support teams.
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