UKH

Hello,

I'm not sure if this entry is right here. However, I think that your experience in the area of rope attachment could be very helpful for an upcoming project, which will be taking place in a disused cooling tower (89 m diameter). In the broadest sense, the planned installation is similar to a slackline / highline setup.

First of all a few basic info about the structure: The intended use involves the use of the inner cooling tower concrete cladding (concrete grade not known, probably > B35)  for the purpose of restraining an approximately 2m icosahedron structure installed at 3 suspension points in 17 meters height through three slackline-bungee cord-icosahedron joints. The icosahedron construction will be located in about 5 m height in the cooling tower center.

For the basic clarification of the installationI have attached a link to different pictures https://imgur.com/a/sUR7wjI

The first purpose of the setup is to climb inside the icosahedron structure and create a vertical bouncing of the system in the amount of several meters by body centering displacements.  You could use a harness in combination with a slackline leash and climb or maybe walk on the line to reach the icosahedron structure from one of the three suspension points. Because of the cooling tower structure, it is difficult to reach the suspension point, therefore a slackline leash makes no sense. So for the cooling tower I will use a rope ladder to climb inside. For the next year I plan to install the structure in a cliffy environment, thus a slackline leash could become very effective.

My actual question relates to the planned attachment to the cooling tower concrete wall and whether it is reasonable or stable enough.

The icosahedron construction (40kg empty weight) weighs about 150 kg with me and additional equipment and should form an angle of about 15 degrees to the suspension points. The tensile forces should be more or less 2 KN for each of the 3 suspension points. As a result of the dynamics generated, the tensile forces could increase up to 4 KN.

In the upper area (17 m height), four Fischer FAZ II M12 / 30 anchor bolts should be placed at each of the three suspension points (the boreholes are approx 25 cm apart) in combination with bolt tabs and M8 quick links connections. Due to the four quick links connections, a 10.5 mm static rope should be guided through two M12 delta quick links (50KN) and be freely movable. Each strand is then about 80 cm long. As a connection node a triple or fourfold fishermens knot is considered. In addition, each rope strand is to be secured by means of a 16 mm sling loop via a figure 8 follow through knot. By the two delta quicklinks two slacklines (the second slackline serves as a backup) are deflected, starting from the icosahedron  to a steel plate near the ground  (25 cm x 30 cm x 0.8 cm, fixed with 4 Fischer FAZ II 12/30 anchor bolt on the Cooling tower wall) by means of  two Gibbon shackles (50 KN). As Weblocker I will be using lashing buckles (breaking load 50 KN). Because of the slackline deflection, the upper fixed points in 17 m height are more loaded. The advantage however results from the better handling during clamping. For an assessment, I would be very grateful.

many Greetings

Frank

How much will you pay for the engineering consultancy you seek?

Ok, maybe I have given too much information. I schould focus on the upper suspension point with the chosen knot system.  I dont know, if these knots (a fourfold fishermens knot with a static rope  in combination with a sling loop) could handle 4 kN dynamic forces. https://imgur.com/1hAhIu9

thanks for your reply

Can't help but agree with Deadeye on this one! Don't think your insurance company will be swayed by advise on here!

However in respect to your anchor set up: A double fisherman's knot is one of the strongest knots going when combined with New low stretch rope of EN1891 Type A it has been tested to over 20KN. However in your photograph the rope is serving know purpose whatsoever, as it is not independent for each anchor, failure of a tape or an anchor will loosen your rope sling and simply transfer the load onto the next anchor and so on and so on!! Get rid of all that tape crap, make your LONG rope sling, clip each anchor, 3 is enough, bring all strands to a central point and tie a big figure of 9 on the bight(loop). connect your shackles to this power point. I'd be more worried about your anchor points in the concrete and if your working out your vector angles and loads correctly 

I can assume the cheque's in the post then!!!!

Thanks for your reply. Yes, I am using a static EN1891 Type A rope. I have thought before about to tie all the rope strands like they often do in highline systems. The problem for me could be, that if the big power point  is moving in different direction, because of the dynamic movement of the icosahedron structure in my case, there could be a different weight distribution on each anchor point.  So because I am not using an independent system, the rope can transfer more or less uniform forces to each anchor while the system is moving. The tapes (each one is independent, not as tight as the rope and used as a backup) is preserving the system from a schock load if an anchor or the rope fails. Anyway, like you said, I could use one long tape and bring all tape strands to a central point and tie a big figure of 9 on the bight(loop) as a backup system because it will have more regular strands.  And  yes, I am also a little bit worried about the concrete anchor points, but each Fischer FAZ II bolt has a working load of 9 kN, so it should be ok if I controll the system with a tensile force meter.  

many Greetings

The quality of unknown concrete exposed to decades of hot water and steam would be my concern. Personally I'd simplify the anchor design massively then consult an engineer and a rope access technician or perhaps a circus rigger.

Jk

Er...this "disused" cooling tower...would this be a climate protest at a coal fired station?

If it isn't...be damn sure you are not likely to disturb roosting bats or, depending on timing, nesting raptors. These are well protected by law and are known denizens os such structures.

I just like the question (:

Judging from the picture I'd be fairly confident that if the concrete for the anchors survived the drilling then your icosahedron will very likely fail a long time before the anchors fail.

Remember "Static" rope isn't actually static, its low stretch, (not to be confused with dynamic) It can stretch up to a maximum of 5% with a 150kg static load! On the initial tensioning of the anchors the rope will stretch somewhat and the knot will settle, all allowing some degree of equalization of the anchor points, (assuming the angles aren't way out!)

BTW your not a cage dancer are you?

I think when engineers are planning a cooling tower, they consider the impingement of hot water and steam for the use of a few decades under static requirements. Actually, the cooling tower was used 24 years. But who knows it exactly, an engineer or specialist can do a cylinder pressure test or use a schmidtscher hammer, I schould give it a try. 

You can use an anchor tester to make sure the anchors are safe. Hilti makes one. 

https://www.hilti.co.uk/anchor-fixings/dispensers,-accessories,-testers/tes...

Hm, they have filled the inside of the tower with  a 10 meter thick white sand layer. The cooling tower is not used for cooling anymore but it is used for motor sport. This is not a quiet place, it is a fun park, so no bats, no nesting raptors. https://imgur.com/a/NG53L5S

In general, because of the triangle structure, the icosahedron is very stabil. In each of the 30 bamboo  pole (3-4 cm diameter) a non stop M 8 threaded bar is integrated.  Each of the M 8 threaded bar has a min 14,6 kN breaking load and each bungee rope joint is connected to five M8 threaded bars with five singing Rock eye slings. 

Thanks for your Feedback. May be cage dancing will be an option in the future.

many Greetings 

Frank

And each bar opposite the anchor point is in compression, not tension and has additional failure modes such as bending and buckling - don't bank on 14kN as being relevant - you may not rupture the bars but that doesn't mean the structure is stable in use.

The bolts are torque controlled anchors so don´t need testing.

Personally I´d forget all the tape, maillons, knots etc and just get a fixing plate welded up to take 4 or 6 bolts. But then what do I know?

Thanks for your reply. Never heard about an anchor tester before, this would be a good idea.

many Greetings

Frank

Thanks for your reply. I have called the Fischer support this morning. They say, the torque controlled anchors don`t need tested in steel construction, but you have to control it in combination with concrete if you don`t know the concrete class.

That´s confusing!

Indeed but just the same they don't always get it right or we wouldn't have cooling towers that fall down in a storm or concrete spalling off motorway bridges. The ropes and couplings bit is all easily calculable, it's the concrete that needs to be inspected and probably tested to ensure your design is safe.

Jk

Thanks for your reply. Yes there will bending and buckling, but bamboo is really good in keeping pressure but bad for tension. So the threaded bars are used for the 2-4 kN tension and the bamboo keeps the pressure. Each of the three icosahedron joint has a breaking load of 5*14,6 kN=73 kN for the tension. Sure it will be less because of different fixing angle. In consideration of a 1:10 secuity factor, you schould not go over 700-800 kg.  I am using 15 - 20 bungee ropes (depends on the person inside the icosahedron) on each of the three joint. Each one can stretch 200% at  0,21 kN , 20 *0,21kN= 4,2 kN in total for each joint.  If I reach this tension, the stretching will stop. So this will limit the whole system to a more or less maximum of 4 kN. 

Yes, I was also wondering, but that is what they said to me. 

Hmmm, all this KN and testing but the bit that probably matters most and you're happy with "really good bamboo"?

I know it's widely used in scaffolding and the like but before I trusted my life to balancing 400Kg on top of a bit of "really good bamboo" (albeit cored with 8mm threaded bar) I think I'd probably examine it further.

Still your project, what could possibly go wrong?

All this strikes me as a very elaborate attempt at getting a Darwin award...

somewhere in the peak, stanage maybe?

then you'll have the top answer if anyone asks what you've ever done on that geological subcategory

Yes, the anchor tester will test the anchor as well as the matrix in which it is embedded. 

The icasohedron exist out of 30 bamboo poles. The max 4 kN will be distributed on all 30 poles. There will be no more than 15 poles who absorbs the pressure. That means, there are 4kN/15=0,26 kN pressure for one pole in longitudinal direction. I have tested each bamboo pole in the past. I placed each pole on two trestles and stood in the middle of the pole with a weight of nearly 100 kg, without the threaded bar inside and had no breaks. In longitudinal direction there would be more load possible but i have not tested. The max 4 KN are only produced at the maximum amplitude, so if one pole break, the system could stop within seconds to the starting point where i have no more then 2 KN forces. Nevertheless, I have planned to consult a structural engineer in the future to calculate the breaking load of the icosahedron.