three point reaction loads 1

[Bert2]

Sorry seem to have forgot how to calculate the reaction upon a three point beam, could someone point me in the right direction please... im am on the right path of quadratic equation given you have two unkowns?

please see attached.

thanks

 

[desertfox]

Hi Bert2

Try this site:-

http://www.roymech.co.uk/Useful_Tables/Beams/Continuous_Beams.html

desertfox

 

[Bert2]

thanks ill take a look.

 

[Bert2]

desertfox ; after looking at this example which is almost perfect im not 100% on the workings ; never seen it done that way and confuses me, do you know of a more traditional method?

many thanks.

 

[rb1957]

try "three moment equation".

there are many graphical methods for solving singly redundant beams ... "moment area method"

if you're comfortable with calcs, try "unit force method" ...
(1) delete one support, solve the statically determinant beam, calculate the deflection at the deleted support,
(2) apply a unit load (opposite to the deflection) at the deleted support, solve reactions and calc the deflection at the deleted support,
(3) the true reaction at the deleted support is [the deflection from (1)]/[the deflection from (2)] * 1 lb

 

[desertfox]

Hi Bert2

Try this site:-

http://www.google.co.uk/imgres?imgu...a=X&ei=QSNkTKaNKonu0wSgy5jmDA&ved=0CCcQ9QEwBA

Any chance you can share with us a little bit more information about this problem, like application etc

Regards

desertfox

 

[desertfox]

Hi Bert2

Just looking at your diagram again and I see that there is no load on the first span, only a load on the second span.
If your beam weight is very small compared with the external load on span2 which is implied by your diagram, I believe you can calculate this as a single span beam using the load and dimensions of span2 and ignore span1 completely because the reaction at the lefthand side of span1 will be very small compared to the reactions on the middle support and far righthand side of the beam.

desertfox

 

[hokie66]

The AISC Steel Construction Manual and many structural reference books have formulas for this condition, and you just have to plug in the loads and spans.

 

[dhengr]

Bert2:
As Desertfox and I suggested six or seven months ago on your ‘maximum stability angle’ thread #404-265967, you would benefit yourself greatly by finding yourself a local mentor or advisor. This is not a difficult problem if you are an engineer, and it would help you if someone right there could draw sketches for you and direct you where to look, as Hokie has. I’m not suggesting don’t ask here and I’m not suggesting you should be embarrassed about not knowing things you haven’t seen before, but if someone who you could interact directly with would take you under his wing you might discover a rewarding and enriching relationship and experience.

 

[rb1957]

if you neglect the unloaded span and solve the simply supported beam you should get a conservative answer (well conservative for bending of the beam, unconservative to the LH reaction)

 

[msquared48]

Classic use of FEM's and Moment Distribution.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[rb1957]

IMHO, classic misuse of FEM ... unless as a test case to compare with readily hand calc'd solutions

 

[dhengr]

rb1957:
I scratched my head for five minutes too, Mike couldn’t really mean Finite Element Methods, could he? Maybe, just maybe he meant fixed end moments. But maybe he was having a moment and it got redistributed; and classics, I haven’t read the classics in years and don’t remember moment distribution being covered in any of them.

 

[msquared48]

I'm too old for Finite Elemments, or am I? Well that's another subject.

I was referring to Fixed End Moments, commonly used with Moment Distribution, but you were just yanking my chain, right?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[dhengr]

Mike:
I was yanking your chain and rb’s too, but I did scratch my head for a minute; wondering what the hell, why is Mike using Finite Element Methods and moment distribution in the same sentence here, then the light went on, you weren’t pulling our chain. You couldn’t have used two such diametrically different methods for such a simple problem. But then, only you and I and a few others on this forum even know what moment distribution is, let alone have ever used it in our daily work.

 

[msquared48]

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Bert2]

desertfox;

i cant upload at the moment ....?

ill keep trying to upload a more detailed drawing

i have a programme to for the loading etc, but just want to understand it better of my own back.


thanks

 

[Bert2]

detail drawing;

 

[hokie66]

How does the truck relate to your original problem?

 

[Bert2]

i just simplified it into a basic beam with reaction calc.

which is all im after. obviously assume the body of the trailer and chassis of the cab are static with zero deflection.