New Suggested 2/18/2021 by Suraphong Powanusorn



Moment Magnification due to P=Delta for Braced and Sway Frame in MidasCivi las per AASHTO LRFD b)

I have a question on the moment magnification as per AASHTO LRFD b)


One way to find a solution to this problem is to perform a geometrically non linear analysis to obtain magnified moment, considering the time effect using age adjusted modulus of crack concrete. 


Another is to calculate the moment magnification assuming the code equation above.   But, the Elastic Euler buckling will need to be defined.  I am not sure of Midas has any option to automatically calculate the moment magnification by defining the Effective Length Factor and Ratio of sustained DL/Total Factored Load to evaluate the time effect in evaluating the effective section properties for calculating Euler Buckling load.


The other method is to manually calculate the moment magnification externally and apply the factor to the end force/moment and input in Midas GSD to check if it remain within the interaction diagram.


I think the  most logical way is the third choice as it is a tangible way to know that the moment is magnified.   But it is very time consuming.  If the second option is available to obtain the result automatically, then it will be handy.


The first method can be a good solution but I am afraid the independent checking engineer  may have a doubt in the results unless we can have it compared and show that they provide similar results, within the same order of magnitude of accuracy.


Please let me know if the second option is available in the current release MidasCivil.

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