Moment Area Theorems!!

Can the moment area theorems and Macaulay's(double integration) methods be used to calculate deflections in indeterminate structures?

Does anyone use this methods in practise i.e. in practical design?

 

[dlew]

gen doubt!!! ,

Most of the practicing engineers will use a computer program to obtain the deflections of indeterminate structures. Unless you use formulas to determine the deflections (Roark's "Formulas for Stress and Strain" contains deflections for members subject to several types of loading, and also for members subject to end moments), the hand calculation of deflections is a tedious and laborious work.

Can the moment areas method be used to calculate deflections of individual members with end moments? Yes, it can.

Can it be used to calculate lateral deflections of rigid frames? Possibly, but I am not sure.

 

[JAE]

One of my oral exam questions for my MS degree asked what I would do if I had performed a computer analysis on a 10 story frame building but failed to ask the computer for deflections and I only had moments in the beams and columns. (this was before computers were friendly, of course)...what would I do if I needed the lateral deflection at the top?

The answer was to lay out your column moments from bottom to top, and use Moment Area to get the deflection at the top. I won't reveal whether I answered correctly or not...but obviously, I know now that Moment Area can get deflections for you.

 

Thanks very much dlew,JAE for your interest.If possible could you make a mention of Macaulay's (double integration) method too, i.e. if it could be used to find deflections in inderminate structures??

 

[austim]

gendoubt,

In my experience, Macaulay's method is only suited to very simple structures. In practice, I never used it for anthing more than single span beams, with/without end restraint, and with simple loadings. I could still do that without having to refer to textbooks , but would not normally consider it (unless I was stuck somewhere without access to my computers).

My venerable University notes (which would be about 50 years old today ;-)) include examples of a three span beam with elastic suports and a single bay portal. But don't forget, that was before any general use of computers, Fortran or whatever, and general structural frame analysis packages were unheard of.