Hi,

I had created this spreadsheet a few years back for analyzing continuous beams with any number of supports and loads. Thought I would share this and others can use it/modify it as per your requirement. Should be fairly easy to modify the code as I have written sufficient comments to understand it.

Force method is used, Euler-bernoulli equations are used to calculate deflections.

It support any number of supports,point moments , loads , uniform distributed loads. Will output shear , moment diagrams, reaction forces.

Doesn't support axial loads atm.

I haven't looked at it yet - does it do alternating live loads easily?  This is the one aspect of many ...MANY... software programs that is left out of their codes yet is mandated by many building codes.
 

@JAE

I am an aerospace guy and I am not really sure what alternating live loads are. If you can explain how they act I can check if it can be added to the spreadsheet.

 

missil3,
In building design (and in a different way in bridge design) the building codes require that any type of continuous framing be analyzed with due regard for possible combinations of loaded spans.

For instance, if you have a six span beam system, it is possible in a floor area to have some of the beams loaded and some not.  This creates situations where higher moments and shears occur over that found by loading all the spans together.

The combinations required are comprised of six arrangements:

Odd spans loaded
Even spans loaded
All spans loaded
Adjacent span arrangement 1 (load spans 1, 2, 4, 5)-skip 3 and 6
Adjacent span arrangement 2 (load spans 2, 3, 5, 6)-skip 1 and 4
Adjacent span arrangement 3 (load spans 1, 3, 4, 6)-skip 2 and 5

There are no other combinations possible.

For the odd/even spans you will find maximum positive moments.
For the adjacent spans you will find maximum negative moments.
For some of the adjacent and, I think, the total load you will get maximum shears.

The codes don't directly state whether 100% of the live loads must be alternated like this, presuming the engineer will use judgement as to how much of the live load will be semi-permanent so sometimes engineers will skip 75% of the live load and leave the other 25% in place as a  total load (all span) condition.

 

Thanks for the detailed explanation.

I think this can be coded as a separate macro to run different load combination as per the requirement. Have a look at what the spreadsheet does, I think this will easier if you just do a small macro to do the live loads instead of altering the base macros.  

do you only hav a metric versiop?

Yes the only units used are SI units in the spreadsheet. However you can test by using same consistent units everywhere and it should work with English units too.

missil3,

was there any attachement to the thread? or is the spreadsheet removed?

Ya there was supposed to be an attachment , not sure what happened. Here is the link for the attachment:

http://files.engineering.com/download.aspx?folder=...

• http://files.engineering.com/download.aspx?folder=bf9e2cf9-559b-4bf5-8a88-0

it would be nice to calc displacements (or EI*displacement) as a preparatary step from redundant beam analysis (unit force method).

heyy,, plz can u give me examples for continuous beam .. i dun understand it well..

Here are few examples: http://www.elpla.com/elpla_en/images/continuousbea...

Its just a beam that has intermediate supports. Usually such beams are statically indeterminate.

@rb1957 : Ya, adding beam deflections as an output should be useful but I don't know if I will get around to doing that. If you know your way around VBA should be an easy thing to do.

The most generic case would be using the stiffness matrices of each beam and simply inverse the total matrix to get the nodal displacements. In case of beams, only 2 degrees of freedom will be active (shear force and bending moment), so this task won't be much difficult to program.
Regards.

Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis
http://www.engissol.com/cross-section-analysis-des...