High Tension Wire Tower Foundation

[m_naeem_b]

I want to design a foundation for high tension cable tower for seismic. Can any one have experience about it and have any related material? kindly share with me. Towers are 150 ft in hight. Also design both towers which are 400ft apart.

[UmarMakhzumi]

I want to design a foundation for high tension cable tower for seismic. Can any one have experience about it and have any related material? kindly share with me. Towers are 150 ft in hight. Also design both towers which are 400ft apart.

Can you please share the drawings?

Thanks

[m_naeem_b]

I dont have any drawing yet. 

 

Two towers supporting chair lift like in murree.

 

two towers are 2280 ft part , below river is flowing.

 

I have to design towers as well as the foundation of towers. 

[UmarMakhzumi]

I haven't done something ditto to what you are explaining, but I would like future information on this being shared, so that, may be, we can develop something ?

 

Thanks.

[Waqar Saleem]

software RISAtower may be helpful in the design ...

[asadishaq]

This is the schematic sketch of what  I and M.Naeem  want to design.

DRAWING.zip

[UmarMakhzumi]

This is the schematic sketch of what  I and M.Naeem  want to design.

Cant open the archive. Can you please upload drawings as pdf?

 

Thanks.

[m_naeem_b]

see attached file...

chair lift.pdf 111111.pdf

[UmarMakhzumi]

Thanks for sharing the drawing in pdf format. I am writing down a design approach, and would request everyone to throw their comments and questions. Lets start by:

 

1) Design Criteria

2) Expected loads on structure

3) Possible limit states

 

1) Design Criteria

I believe that you have been working on this for some time and will be having a design criteria outlining what code do you want to design this structure on, and what material strengths do you intend to use. Please post the design criteria document here.

 

2) Expected loads on structure

• The structure is a pair of columns, with motors installed at the top of the that push/ move the chair lift. I would recommend that each column pair would be joined and braced at different levels to provide a stiff support (how far are they ? ; present framing doesn't look to work, I would suggest a truss tower). Possible loads are:
• Weight of motors.
• Possible thrusts at starting and stopping of chair lifts or when faced with load shedding.
• Weight of chair lifts and passengers (considering number of persons and chair lifts at a given time).
• Wind load on columns.
• Weight of cable and its reaction on columns. (Cable are eccentric from column center)

3) Possible limit states

• Apparently, columns need to be laterally stiff enough to maintain tension in the chair lift cables. 
• Uneven support settlement. Utilization of piles to be kept to 60% and under to avoid that. It also depends upon various factors, but I am just throwing in a bullet.
• Maximum unsupported length of cable. You many wanna do a check on that to make sure things outside your scope don't fail. I remember, we did a problem in Theory of structures for a suspension bridge. Similar concept.
• Overturning Check.
• Shear failure of piles. (throwing in a bullet)
• Anchor Bolt Failure. (from sketch it looks like anchor bolt shown are typical and not designed)
• Frost Jacking.
• You can use a higher importance factor as failure can be catastrophic.

Some other questions.

• How good is the geo-technical data ?
• Please share: what you have done till now. Also list things that you haven't designed and are using typical details.
• Are anchor bolts designed ?
• Are piles designed properly ? 
• How are you calculating wind load ? what code ? are you doing any manual checks on that or just software ?
• What is the seismic class of the site ?
• Are there any structures near by ?
• How high is the water table ?
• What is the confidence level on structural steel available ? Local from a mill or properly tested sections.
• Is the soil subjected to frost heave ? Are piles and pile cap designed for that ? Are piles concrete or steel ?
• Do you have more drawings to share ?
• You foundation looks inadequate ?
• Free standing columns(present framing) would be out of proportion. I would Suggest having a Truss Tower; load path would be robust and your site construction would be easy and cheap too.

I would welcome comments and more questions. Naeem, I am looking forward to your reply.

 

Cheers.

[Syed]

Dear Engineers,

 

Without going into any in-depth design I have just checked roughly the steel column size required for the stability concern, i-e, the size required to keep the slenderness ratio (k l/r) within 200, it comes out to be around 36 X 36 inches X 1/2 inch thickness, which gives the slenderness ratio of 187. I am not sure about the thickness requirement at this stage because it will also be governed by the fulfillment of strength requirements, i-e, the design load-moment interaction. I believe that every code has the stability requirements (The slenderness limitation), depending upon the importance of the compression member itself, it may sometimes be less than 100 in some codes, better to check with the code upon which the design is being carried out. I took the height of column as 150 feet and assume "k" as 1.5, which may increase depends upon the boundary conditions at column top. I suggest that a truss type of column be selected and also to keep in mind the workability / Installation process while designing these columns.

 

Wish you good luck

[m_naeem_b]

1)Design Criteria:

I am using following code

a.      ACI

b.    LRFD

c.       ANSI

 

2)Expected Load on Structure:

·         Structure comprises of two truss tower with 2250ft apart. And 204ft level difernece. ( as shown in PDF drawing that I sent to u before.)

·         Two truss tower are connected with cable.

·         Weight of chair lift is 2000KG

·         Total number of passenger are 12.

·         Cable is eccentric. But I model cable on RISA-3D software kindly check( see attached file)

3)Possible limit states:

·         I didn’t design upper structure yet, how can answer your question about piling or foundation.

·         Seismic Zone-2B (SPC-C).

·         Site class= C

·         Wind is 120mph.

·         No any structure is near by.

·         Water table is 10ft below NGL.

·         Soil is not subjected to forest heave.

·         1^st upper structure will clear , then I will design pile foundation for that tower with Machine room.

·         I just did all in software.

[m_naeem_b]

My models are attached.

tower.SDB

wire.r3d

Edited August 24, 2013 by Umar Makhzumi
I have attached models here. Now you can upload SAP and RISA 3D Files here.

[m_naeem_b]

Recommendation

Following are the outputs of the preliminary design of Chair Lift project.

 

Type

3S

Drive L ocat ion

Top

Tension L ocat ion

Bot t om

Slope ( ft)

1:10.75

Horizontal al ( ft)

2250

Vert ical ( ft)

204

Speed ( m/s)

7.0

Trip Time ( minutes)

6.0

Initial Capacity y ( ppl)

12

Initial Carriers

2

Design Capacity ( ppl)

15

Design Carriers

2

Downhill L oad ( %)

100

Continuous  kW

350

Main Drive(Diesel Engine)

550 hp

Extra Drive (Diesel Engine) (For light and others)

50 KW ( 70 hp)

Auxiliary Drive

N/A

Track Rope ( mm)

56 (2.2 in)

Haul Rope ( mm)

41 (1.6 in)

Type of Carrier

12 passengers

[Syed]

Can you please make me understand the process of movement of the chair lifts. How it is controlled? Is there a single cable that starts from one tower and takes a round over the rest of towers with pulley action, i-e, the single cable becomes the part of both Up-Way movement and the Down-Way movements?  Or there are two independent movements going on, i-e, the Up-Way and the Down-Way separately? If two separate movements going on (involving the two opposie set of towers) then within each system where are those pulleys located that turn the motion of cable by 180 degrees? OR Will those pulleys be apart from both the towers? I just want to think about the transfer of lateral load of the chair lifts to the towers during motion as well as at static conditions. Of course slope is one of the factor that will generate a component of lateral load but apart from it, is there any pulley reaction transferring to the columns?

 

Regards

[UmarMakhzumi]

 

My models are attached.

 

I will check your RISA Model and get back to you on this. Do you have any further details about the working of chair lift system as Syed asked ?

 

Thanks

[m_naeem_b]

Only two towers with three cables. But middle cable is main cable, and chair lift moves to and fro with this cable. Other two cables are supporting cables. (Like tricable gondola). Chair lift will not moves 180deg when it reaches to tower. Clint want to construct , just one plate form near towers, and chair lift will moves up again.

[m_naeem_b]

Is there any suggestion or recommendation? 

[UmarMakhzumi]

Is there any suggestion or recommendation? 

I have started looking at it. Hopefully will be done by this weekend. 

[m_naeem_b]

Thanks ....for your cooperation

[UmarMakhzumi]

 

My models are attached.

 

Naeem, your model is incomplete. There are no load cases defined other than dead. Wind will govern the design for the structure. You members are almost all overstressed in basic gravity load combinations. Your should provide complete braces to the foundation so that for all lateral loads (esp wind) load path is complete and there is no bending in the framing members. I should have seen this way before but I am sorry due some unexpected work I couldnt check it. Anyhow, revise your framing. Put cross-braces or chevron bracing on all faces instead of knee braces; that will make your forces from top to bottom through tension and compression and you dont need any moment joints. Apply wind load (v.v. imp) . if you dont know how to do it let me know. I can help you for auto loading in SAP. Your model needs a lot of rework.

[Ayesha]

Thanks ....for your cooperation

 

What are the updates ? What did you do ?