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Re: Post Tension (SAP Question)

[Subject Prev][Subject Next][Thread Prev][Thread Next] Wael,

This all depends on whether or not there is an overturning problem with your foundation. If there is one, then the vertical cables could be extended as permanent rock anchors to resist the overturning. The use of these will depend on the local authorities acceptance of rock anchors to provide stability (some designers, including myself,do not like using them for this) or just to provide a factor of safety and also the availability of a company that can provide high quality permanent rock anchors. The anchors used for temporary works are not adequate and even many of the so called permanent anchors provided by many prestressing companies are not of sufficient quality for this type of anchor..


At 11:43  2/02/01 +0200, you wrote:
Gil Brock:
 
I agree with you that Strut/Tie Model is more appropriate in this case. I am using "Prestressed Concrete Structures, by Micheal Collins) as reference on this point.
 
I am holding down the wall at the other end using PT tendons starting from wall top down to foundation mat. (although in fact the center wall has two cantilevers at each end however there is in each wall a cantilever whose span is much longer than the other).
 
Let me know how do you think about this way to overcome the uplift problem.
 
Wael
----- Original Message -----
From: Gil Brock
To: seaint(--nospam--at)seaint.org
Sent: Thursday, February 01, 2001 4:06 AM
Subject: Re: Post Tension (SAP Question)

Wael,

This cantilever wall would appear to be a deep beam, not a flexural member. In this case a conventional PT analysis using equivalent loads would not be the correct approach though the should also be checked as a flexural member to determine if deep beam or flexural action controls. You need to do a strut/tie analysis of the cantilever to determine the tension strut force required to balance the compression strut (like a corbel design) and provide the PT to carry this tension strut force using straight tendons, anchored back to the very far end of the wall away from the cantilever, in the top of the section.

Also, how are you holding down the wall at the other end away from the cantilever. It looks as if you may have an uplift problem.


At 09:07  30/01/01 +0200, you wrote:
I am designing a structure whose system includes Walls which act as part of the gravity system and shear wall as well. The walls act like cantilever (cantilever span is 43' , worst span). I modeled the walls as shells on the SAP 2000 however I want to locate PT cables in those cantilevered parts of the wall. My question, is there a way to introduce the PT forces to the shells in the SAP or it is only available for Frames. If so, how do I model this wall as a frame? The wall height is 55' and rests on a fdn mat on a length of only 42'. The walls total length is 104'
 
Thanks in advance.
 
Wael Shabana, P.E.

Regards  Gil Brock
Prestressed Concrete Design Consultants Pty. Ltd.
5 Cameron Street Beenleigh Qld 4207 Australia
Ph +61 7 3807 8022              Fax +61 7 3807 8422
email:  gil(--nospam--at)rapt.pcdc.com.au
webpage:        http://www.home.aone.net.au/rapt.pcdc/

Regards  Gil Brock
Prestressed Concrete Design Consultants Pty. Ltd.
5 Cameron Street Beenleigh Qld 4207 Australia
Ph +61 7 3807 8022              Fax +61 7 3807 8422
email:          gil(--nospam--at)raptsoftware.com
email:          sales(--nospam--at)raptsoftware.com
email:          support(--nospam--at)raptsoftware.com
webpage:        http://www.raptsoftware.com