Reaction loads at the Support of an overlapping structure 12

[rifa92]

Hi,

I wanted some clarification for how would the reaction loads at end supports and joint will be calculated in the case shown in the schematic diagram. The load of right structure would be supported by roller A however that load would also be transmitted to roller B. In this for value we can just assume that the uniform distributed load of the structure is 30 kg/m2 and distance horizontal distance between rollers is 1m. Thanks in advance.

 

[iv63]

Tomfh's knife bridge is a reciprocal frame discussed here Link

 

[BAretired]

If you're really fascinated with jetways, you can buy a model:

Some of them get even fancier:

BA

 

[Tomfh]

We sometimes have to specify repairs for them. The last one was after a tug got caught on the emergency stairs and pulled the whole thing along... those tug drivers are shockers

 

[r13]

iv63,

Thanks pointing to that interesting thread.

Here is an interesting book - "RECIPROCAL FRAME ARCHITECTURE" for joy reading. The book was linked by KootK at the said thread.
[link file:///C:/Users/Kai%20PC/Documents/Engineering/reciprocal-frame-architecture.pdf]Link[/url]

 

[rifa92]

I tried to solve it considering it to be a jetway bridge.

 

[BAretired]

Good for you, adjel. That is what I call perseverance, an admirable quality.
EDIT: But wait a minute. You found R[sub]A[/sub] and R[sub]B[/sub] to be equal? That doesn't sound right. Have you checked your calcs?

BA

 

[rb1957]

@tomfh … the same way Napoleon's soldiers would sit (in a circle) on each others knees (at least that's the way I've seen it pictured).

another day in paradise, or is paradise one day closer ?

 

[r13]

Tomfh,

Are the following solution correct?

1) If place a force, F, in the center, each support has R = F/3.
2) If place F on one of the knife, then its support R = F/2, and the remaining supports have R = F/4.

 

[BAretired]

Please see below for truss reactions for dimensions proposed by adjel. Note that Ra and Rb are in opposite directions for each truss (action and reaction).

BA

 

[r13]

OP,

FYI.

 

[rb1957]

damn ! don't you hate making a mistake on line 2 (of a long calc) !

another day in paradise, or is paradise one day closer ?

 

[rifa92]

Retired,
thanks for the correction. By the way I was looking at your solution, how did you calculate the span length?

 

[r13]

rb is correct. See the correction below, if that's your question.

 

[rifa92]

Retired13 thanks, but i was referring to retired own problem solution wherespan lenght was calculated 17

 

[r13]

Seems you were asking BA, rather than R13, both are "retired"

8+2+7 = 17 between supports. Note that the over lap is 2, that should be added one time only.

 

[BAretired]

@retired13,

This is a little off topic. I mentioned recently that my LibreOffice program was having difficulties drawing polygons. The file below illustrates the difficulty. After I drew two filled polygons, as soon as I attempted to draw a rectangle, the polygons vanished from the screen. You indicated the polygon routine worked for you, so it may be some sort of corruption in my computer.

BA

 

[BAretired]

Retired,
thanks for the correction. By the way I was looking at your solution, how did you calculate the span length?

I'm not sure if you were asking retired13 or myself, but I thought the span between supports on your sketch was 17'. Was I mistaken? Please see below.

EDIT: Sorry, that was the wrong image. I'll try to find the correct one.


BA

 

[r13]

Yes. I suggest to have a clean "uninstall" using windows' utility "Add and Remove Programs" (do not use any other method, even the "uninstall" came with the software), which can be found by type the phase in the search bar at the bottom left of your screen (Type here to search), next to the window icon. It uninstall the program and re-write the registry, then the problem wouldn't be carried over to the next installation. How you attach the dynamic file to E-T? Very interesting.

 

[r13]

BA,

For got to mention, after the uninstall, before download the new version, I think you need to shut down the pc then restart to make sure the registry has been completely cleaned.

 

[BAretired]

adjel,

The dimensions below are the ones I used. Please let me know if they are incorrect.

BA