Barrier Cables in the Parking Structure

[JohnRwals]

Hello!

I have a question related with barrier cable installation along the perimeter of parking structures.
These barrier cables are required for vehicle and pedestrian fall protection.
(My sketch does not show intermediate columns for the convenience.)

In my opinion, one continuous stand can be used with round plastic sleeves instead of four separate strands.
As I can use one strand, I can save many installation parts required wherever strands are cut off.
When I proposed this idea to some installation vendors, they did never install strands this way.
Can you think of any problem with this idea?

Thanks in advance!

JRW

 

[Ingenuity]

Bad idea.

Bend radius of tendons at columns will be severe.

Bursting forces due to preload on tendons at columns will be significant.

To stress the continuous tendons you will have to use center-stressing anchors (dog bones) and then corrosion protect them.

Friction losses will be significant.

You are going to need intermediate supports points too!

 

[jayrod12]

Not to mention the elongation of the cable is a function of the length of it. The longer the cable, the more potential elongation, therefore the more pre-stressing required to keep deflection in check, therefore more tension in the cable, rinse and repeat.

 

[JohnRwals]

I think some accessories can be used to prevent elongation spread.
Though very long single strand is used, that does not necessary to consider entire overall length
to control/calculate elongation or strand stress.

 

[cliff234]

I agree that this is not a good idea.

Add to the reasons already mentioned, there will be significant friction losses in the corners. I’ve never seen cables installed with such a tight bend radius (90 degree bends) inside the corner columns. Draw a plan view of a corner column to scale and draw the reinforcing steel and the cables. I’m not sure if it would even be possible to thread the cables through the corner columns.

 

[HTURKAK]

@ JohnRwals (Structural),

Just curious, what will be your approach for calculating the deflection, span and tension force due to applied load
and pre-tensioned force?

...

He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[human909]

I think some accessories can be used to prevent elongation spread.
Though very long single strand is used, that does not necessary to consider entire overall length
to control/calculate elongation or strand stress.

JohnRwals, what is your role on this job and what experience do you have on tensioned cable barriers?

-Have you actually done the calculations required to achieve the suitable tensions for them to act as a barrier?
-Have you actually looked at the free body diagram for what you propose?
-Have you considered the immense forces that could act on the columns in the event of these cables stopping a car?

Many people have told you how much of a bad idea it is. I suggest you listen to them. Or do your calculations and present it in this thread why it can work as an idea.

 

[JohnRwals]

I have summarized my idea.
I believe Method 1 is the most economical and safest method.
Bending strand is not difficult with large bending radius and surface damage/scratch can be minimized with optimal installation process.
(There is no reason to insert long cables starting and ending with the same column.)
Deflection and jacking force can be controlled as strand clamps can be adopted to adjust L and l in the formula in addition to intermediate posts.
Also, installation process can be adjusted with strand clamps; entire long strand cannot necessarily be pulled at once.
Method 2 will raise production cost and jobsite patching or pockets will be exposed, not good aesthetically.
It's dangerous to pull strands from the outside, or work at the exterior work space.
Method 3 requires many expensive parts like special anchors and inserts.

I did Method 1 about 10 years ago, but it's hard to find contractors to do this way after I moved to the South.

Thanks for your interest!

_JRW

 

[dik]

Method 1 could result in a breakdown of the cable, over a period of time Method 2 would be my preference, with a 'turnbuckle' somewhere in line.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dold]

+1 for bad idea.

In addition to everyone else's concerns you'd also be computing the deflection 'a' based on a cable length of 1200' as opposed to 200' or 400' which will make it much more difficult to keep deflections in check.

Not to mention procuring, handling, and installing a 1200' long cable. I think you're creating more problems than you're solving. And I don't think the problem you're trying to solve is a problem in the first place.

 

[hokie66]

Is reliance on cables even allowed where you are? Don't you have a requirement for maximum dimension an object can pass through openings?

 

[IRstuff]

A single point of failure over 400 ft? Is that what you are proposing? That sounds horrible to me; if the cable breaks, then a 400 ft length of cable potentially comes crashing down on kid's head?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[JohnRwals]

Of course, intermediate posts should be added as required.
(That topic is beyond this discussion.)
Generally, vehicle impact and pedestrian fall protection should be considered simultaneously.