Post Tensioned Floors-Technical Report 43 -URGENT

Post by r***@rediffmail.com
As per the Technical Report 43 on Post Tensioned Floors published by
the Concrete Society, the tendon profile is so obtained such that the
dead load is balanced.The slab depth is decided based on the imposed
load criteria.
1) Now I want to know that if there is any better way to obtain the
tendon profile?

If you look into text books regarding prestressing and post tensioning you
will see there are a few types of profiles that can be used. If you have
ADAPT and their manual you will see the profiles available. The common
profile is a parabolic curve that simulates the uniform load bending moment
curve. The intent is to balance the dead load. If you have a large
concentrated live load you can use a harped profile which is nothing more
than straight lines from the tendon pull location to the bottom of the
member at the point load location.

Post by r***@rediffmail.com
2)Am I right if I say that if the tendon profile is decided so as to
balance the dead load as well as live load then the check for strsses
at "Transfer Stage" may create a problem such that the tensile
stresses at an extreme fibre may exceed the tensile strength of
concrete.

The intent is to balance dead load. Sometimes you can balance more dead
that exists which will, of course, take some of the live load on the way.
Precedents say that you shouldn't go more than 200%. If you feel that some
of the live load needs to be balanced, maybe due to deflection, it might be
a good thing. This needs some engineering judgment and experience. You
always have to check what the tensile stresses at each stage are so that
they don't exceed code allowances. Commonly 6*fc'^.5. This is final tensile
stress limit with all loads applied. Initial stresses for tension prior to
applied live load (at transfer) at stressing is 3*fc'^.5 at the top of the
element which will be come the compression area when live load is applied.

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and live load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the profiles
that can be used with their program and what type of loading to use them
with. RAM concept (not familiar with) will also do this but I think it is
not just a slab system or a beam-slab system but an entire floor/beam, flat
plate, or two way system which will take some time to model. ADAPT also has
one that does the same.

Hope all this helps.

Chuck...

______________________________________________________________
Charles I. Dinsmore, PE SE RA, M.ASCE ~ ***@comcast.net
***@hotmail.com

r***@rediffmail.com

2007-02-08 17:43:39 UTC

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and live load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the profiles
that can be used with their program and what type of loading to use them
with. RAM concept (not familiar with) will also do this but I think it is
not just a slab system or a beam-slab system but an entire floor/beam, flat
plate, or two way system which will take some time to model. ADAPT also has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Thanks for the response.Can you send me ADAPT's manual?

r***@rediffmail.com

2007-02-08 17:47:19 UTC

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and live load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the profiles
that can be used with their program and what type of loading to use them
with. RAM concept (not familiar with) will also do this but I think it is
not just a slab system or a beam-slab system but an entire floor/beam, flat
plate, or two way system which will take some time to model. ADAPT also has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Suppose, we have a two way slab system having stiif supports all round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?

Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

Chuck

2007-02-09 08:09:56 UTC

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and live load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the profiles
that can be used with their program and what type of loading to use them
with. RAM concept (not familiar with) will also do this but I think it is
not just a slab system or a beam-slab system but an entire floor/beam, flat
plate, or two way system which will take some time to model. ADAPT also has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Suppose, we have a two way slab system having stiif supports all round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not be stiff
supports depends on the way they are connected to the slab ) usually the
longer spans will get more prestressed force than the short span depends on
the tributary area. Loads are usually set up the same way that a two way
system is with no prestressing. The support areas are usually defined with
column strips and middle strips where the column strips are the supporting
elements of the slab in both directions. If post tensioned the balancing is
still a percentage of the dead load to the tributary strip elements. Again
you have to get a text somewhere with all the secrets for post tensioning
structures. Some of the conditions that are not initially apparent are
explained in those texts.

CID...
______________________________________________________________
Charles I. Dinsmore, PE SE RA, M.ASCE ~ ***@comcast.net
***@hotmail.com

r***@rediffmail.com

2007-02-10 11:10:42 UTC

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and live load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the profiles
that can be used with their program and what type of loading to use them
with. RAM concept (not familiar with) will also do this but I think it is
not just a slab system or a beam-slab system but an entire floor/beam, flat
plate, or two way system which will take some time to model. ADAPT also has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Suppose, we have a two way slab system having stiif supports all round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not be stiff
supports depends on the way they are connected to the slab ) usually the
longer spans will get more prestressed force than the short span depends on
the tributary area. Loads are usually set up the same way that a two way
system is with no prestressing. The support areas are usually defined with
column strips and middle strips where the column strips are the supporting
elements of the slab in both directions. If post tensioned the balancing is
still a percentage of the dead load to the tributary strip elements. Again
you have to get a text somewhere with all the secrets for post tensioning
structures. Some of the conditions that are not initially apparent are
explained in those texts.
CID...
______________________________________________________________
- Show quoted text -

1)In the manual for ADAPT I've read that,ADAPT reports alao the
"Secondary Moments" in the output report.What is the significance of
the user knowing the magnitude of secondary moments?I know what are
"secondary moments" and why they occur, bur I wanna know that what
when using a software what is the significance of knowing the
secondary moments for the user?

2) In the design process for ADAPT , they have the final effective
design approach and system bound approach.In the final effective
design approach prestress losses are not calculated and hence
parameters regarding those are not given in the input.In system bound
approach all losses are calculated.
But, in software if the anchorage set, friction coefficient are set as
0 then the losses will be 0.What is so special about these approaches
in ADAPT?

Chuck

2007-02-11 07:23:58 UTC

The intent is to balance dead load. Sometimes you can balance more dead
that exists which will, of course, take some of the live load on the way.
Precedents say that you shouldn't go more than 200%. If you feel that some
of the live load needs to be balanced, maybe due to deflection, it
might
be
a good thing. This needs some engineering judgment and experience.
You
always have to check what the tensile stresses at each stage are so that
they don't exceed code allowances. Commonly 6*fc'^.5. This is final tensile
stress limit with all loads applied. Initial stresses for tension
prior
to
applied live load (at transfer) at stressing is 3*fc'^.5 at the top of the
element which will be come the compression area when live load is applied.

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and live load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the profiles
that can be used with their program and what type of loading to use them
with. RAM concept (not familiar with) will also do this but I think
it
is
not just a slab system or a beam-slab system but an entire floor/beam, flat
plate, or two way system which will take some time to model. ADAPT
also
has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Suppose, we have a two way slab system having stiif supports all round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not be stiff
supports depends on the way they are connected to the slab ) usually the
longer spans will get more prestressed force than the short span depends on
the tributary area. Loads are usually set up the same way that a two way
system is with no prestressing. The support areas are usually defined with
column strips and middle strips where the column strips are the supporting
elements of the slab in both directions. If post tensioned the balancing is
still a percentage of the dead load to the tributary strip elements.
Again
you have to get a text somewhere with all the secrets for post tensioning
structures. Some of the conditions that are not initially apparent are
explained in those texts.
CID...
______________________________________________________________
- Show quoted text -

All moments are shown that influence the design. The secondary moments add
to the service moments. If they don't show them in the output and you try
and check the stresses which don't meet the final output based on the
service load moments you will think something is not correct. I think that
it is a good thing. It is also shown how calculated and added to service
moments in any text books for post tensioned concrete.

Post by r***@rediffmail.com
2) In the design process for ADAPT , they have the final effective
design approach and system bound approach.In the final effective
design approach prestress losses are not calculated and hence
parameters regarding those are not given in the input.In system bound
approach all losses are calculated.
But, in software if the anchorage set, friction coefficient are set as
0 then the losses will be 0.What is so special about these approaches
in ADAPT?

Look closer at the input selections. You have the option to input of losses
to be considered which have been shown on typical structures in PTI
calculation examples for slabs and beams in their manuals. The second
method is not to input your own losses you think that will be developed (
from PTI and the ACI codes ) and let ADAPT calculate the losses for you.

CID...

r***@rediffmail.com

2007-02-11 09:33:46 UTC

The intent is to balance dead load. Sometimes you can balance more dead
that exists which will, of course, take some of the live load on the way.
Precedents say that you shouldn't go more than 200%. If you feel that some
of the live load needs to be balanced, maybe due to deflection, it
might
be
a good thing. This needs some engineering judgment and experience.
You
always have to check what the tensile stresses at each stage are so that
they don't exceed code allowances. Commonly 6*fc'^.5. This is final tensile
stress limit with all loads applied. Initial stresses for tension
prior
to
applied live load (at transfer) at stressing is 3*fc'^.5 at the top of the
element which will be come the compression area when live load is applied.

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and live load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the profiles
that can be used with their program and what type of loading to use them
with. RAM concept (not familiar with) will also do this but I think
it
is
not just a slab system or a beam-slab system but an entire floor/beam, flat
plate, or two way system which will take some time to model. ADAPT
also
has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Suppose, we have a two way slab system having stiif supports all round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not be stiff
supports depends on the way they are connected to the slab ) usually the
longer spans will get more prestressed force than the short span depends on
the tributary area. Loads are usually set up the same way that a two way
system is with no prestressing. The support areas are usually defined with
column strips and middle strips where the column strips are the supporting
elements of the slab in both directions. If post tensioned the balancing is
still a percentage of the dead load to the tributary strip elements.
Again
you have to get a text somewhere with all the secrets for post tensioning
structures. Some of the conditions that are not initially apparent are
explained in those texts.
CID...
______________________________________________________________
- Show quoted text -

Thanks a million for the response.
I did not get you regarding my second question on losses.Any software
on Post Tensioned Slab design will have the inputs required for
frictional coefficient,anchorage set.If we enter these values as "0"
then automatically the losses are not calculated.
Then, these losses can be calculated when the manufacturer gives the
values for the parameters concerned.Then , what is so special about
ADAPT "Effective Design Approach" and "System Bound Approach".Next, I
am sory, but what is the full form "PTI"?

r***@rediffmail.com

2007-02-11 19:37:11 UTC

The intent is to balance dead load. Sometimes you can balance more dead
that exists which will, of course, take some of the live load on the way.
Precedents say that you shouldn't go more than 200%. If you feel that some
of the live load needs to be balanced, maybe due to deflection, it
might
be
a good thing. This needs some engineering judgment and experience.
You
always have to check what the tensile stresses at each stage are so that
they don't exceed code allowances. Commonly 6*fc'^.5. This is final
tensile
stress limit with all loads applied. Initial stresses for tension
prior
to
applied live load (at transfer) at stressing is 3*fc'^.5 at the top of the
element which will be come the compression area when live load is applied.

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and live load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the
profiles
that can be used with their program and what type of loading to use them
with. RAM concept (not familiar with) will also do this but I think
it
is
not just a slab system or a beam-slab system but an entire floor/beam, flat
plate, or two way system which will take some time to model. ADAPT
also
has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Suppose, we have a two way slab system having stiif supports all round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not be stiff
supports depends on the way they are connected to the slab ) usually the
longer spans will get more prestressed force than the short span depends on
the tributary area. Loads are usually set up the same way that a two way
system is with no prestressing. The support areas are usually defined with
column strips and middle strips where the column strips are the supporting
elements of the slab in both directions. If post tensioned the balancing is
still a percentage of the dead load to the tributary strip elements.
Again
you have to get a text somewhere with all the secrets for post tensioning
structures. Some of the conditions that are not initially apparent are
explained in those texts.
CID...
______________________________________________________________
- Show quoted text -

Eagerly awaiting your response!!!

Chuck

2007-02-12 09:38:17 UTC

Post by r***@rediffmail.com
As per the Technical Report 43 on Post Tensioned Floors published by
the Concrete Society, the tendon profile is so obtained such
that
the
dead load is balanced.The slab depth is decided based on the imposed
load criteria.
1) Now I want to know that if there is any better way to obtain the
tendon profile?

If you look into text books regarding prestressing and post
tensioning
you
will see there are a few types of profiles that can be used. If
you
have
ADAPT and their manual you will see the profiles available. The common
profile is a parabolic curve that simulates the uniform load
bending
moment
curve. The intent is to balance the dead load. If you have a large
concentrated live load you can use a harped profile which is
nothing
more
than straight lines from the tendon pull location to the bottom of the
member at the point load location.

The intent is to balance dead load. Sometimes you can balance
more
dead
that exists which will, of course, take some of the live load on
the
way.
Precedents say that you shouldn't go more than 200%. If you feel
that
some
of the live load needs to be balanced, maybe due to deflection, it
might
be
a good thing. This needs some engineering judgment and experience.
You
always have to check what the tensile stresses at each stage are
so
that
they don't exceed code allowances. Commonly 6*fc'^.5. This is final
tensile
stress limit with all loads applied. Initial stresses for tension
prior
to
applied live load (at transfer) at stressing is 3*fc'^.5 at the
top of
the
element which will be come the compression area when live load is
applied.

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and
live
load
condition. You might have uniform loading where you use the parabolic
profile. You might have two big concentrated loads you might use harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the
profiles
that can be used with their program and what type of loading to
use
them
with. RAM concept (not familiar with) will also do this but I think
it
is
not just a slab system or a beam-slab system but an entire
floor/beam,
flat
plate, or two way system which will take some time to model.
ADAPT
also
has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Suppose, we have a two way slab system having stiif supports all round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not
be
stiff
supports depends on the way they are connected to the slab )
usually the
longer spans will get more prestressed force than the short span
depends
on
the tributary area. Loads are usually set up the same way that a two way
system is with no prestressing. The support areas are usually
defined
with
column strips and middle strips where the column strips are the supporting
elements of the slab in both directions. If post tensioned the
balancing
is
still a percentage of the dead load to the tributary strip elements.
Again
you have to get a text somewhere with all the secrets for post tensioning
structures. Some of the conditions that are not initially apparent are
explained in those texts.
CID...
______________________________________________________________
- Show quoted text -

Eagerly awaiting your response!!!

PTI Is the American 'Post Tension Institute'. Try PTI.com If that
doesn't work just go to Google and search for Post Tension Institute.
CID...

r***@rediffmail.com

2007-02-12 16:50:45 UTC

Post by r***@rediffmail.com
As per the Technical Report 43 on Post Tensioned Floors
published by
the Concrete Society, the tendon profile is so obtained such
that
the
dead load is balanced.The slab depth is decided based on the
imposed
load criteria.
1) Now I want to know that if there is any better way to obtain
the
tendon profile?

If you look into text books regarding prestressing and post
tensioning
you
will see there are a few types of profiles that can be used. If
you
have
ADAPT and their manual you will see the profiles available. The
common
profile is a parabolic curve that simulates the uniform load
bending
moment
curve. The intent is to balance the dead load. If you have a large
concentrated live load you can use a harped profile which is
nothing
more
than straight lines from the tendon pull location to the bottom
of the
member at the point load location.

Post by r***@rediffmail.com
2)Am I right if I say that if the tendon profile is decided so
as to
balance the dead load as well as live load then the check for
strsses
at "Transfer Stage" may create a problem such that the tensile
stresses at an extreme fibre may exceed the tensile strength of
concrete.

The intent is to balance dead load. Sometimes you can balance
more
dead
that exists which will, of course, take some of the live load on
the
way.
Precedents say that you shouldn't go more than 200%. If you feel
that
some
of the live load needs to be balanced, maybe due to deflection, it
might
be
a good thing. This needs some engineering judgment and experience.
You
always have to check what the tensile stresses at each stage are
so
that
they don't exceed code allowances. Commonly 6*fc'^.5. This is final
tensile
stress limit with all loads applied. Initial stresses for tension
prior
to
applied live load (at transfer) at stressing is 3*fc'^.5 at the
top of
the
element which will be come the compression area when live load is
applied.

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is
to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and
live
load
condition. You might have uniform loading where you use the
parabolic
profile. You might have two big concentrated loads you might use
harped
profile. But for many spans and with uniform loading you would use a
continuous parabolic profile. Again ADAPT manual will show all the
profiles
that can be used with their program and what type of loading to
use
them
with. RAM concept (not familiar with) will also do this but I think
it
is
not just a slab system or a beam-slab system but an entire
floor/beam,
flat
plate, or two way system which will take some time to model.
ADAPT
also
has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________

Suppose, we have a two way slab system having stiif supports all round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not
be
stiff
supports depends on the way they are connected to the slab )
usually the
longer spans will get more prestressed force than the short span
depends
on
the tributary area. Loads are usually set up the same way that a two way
system is with no prestressing. The support areas are usually
defined
with
column strips and middle strips where the column strips are the supporting
elements of the slab in both directions. If post tensioned the
balancing
is
still a percentage of the dead load to the tributary strip elements.
Again
you have to get a text somewhere with all the secrets for post tensioning
structures. Some of the conditions that are not initially apparent are
explained in those texts.
CID...
______________________________________________________________
- Show quoted text -

Eagerly awaiting your response!!!

PTI Is the American 'Post Tension Institute'. Try PTI.com If that
doesn't work just go to Google and search for Post Tension Institute.
CID...- Hide quoted text -
- Show quoted text -

Can I interpret like this:

ADAPT follows the design approaches for Post Tensioning as the
"Effective Force Approach" and "System Bound Approach".In the
effective force approach the parameters for post-tensioning losses are
not entered in the Inputs in the pre-processor.Right?

These parameters can be entered in the Post-processor.Right?Does it
imply when enetering the values in the pre-processor the user has no
idea of the material details regarding the post-tensioning?And hence
only calculates the post-tensioning force and not the tendon spacing
and tendon numbers?

But, when the user is in the post-processor stage he has the idea of
the material details from the manufacturer and hence can go ahead with
entering the parameters pertaining to losses.Right?

Chuck

2007-02-13 07:18:13 UTC

Post by r***@rediffmail.com
As per the Technical Report 43 on Post Tensioned Floors
published by
the Concrete Society, the tendon profile is so obtained such
that
the
dead load is balanced.The slab depth is decided based on the
imposed
load criteria.
1) Now I want to know that if there is any better way to obtain
the
tendon profile?

If you look into text books regarding prestressing and post
tensioning
you
will see there are a few types of profiles that can be used.
If
you
have
ADAPT and their manual you will see the profiles available.
The
common
profile is a parabolic curve that simulates the uniform load
bending
moment
curve. The intent is to balance the dead load. If you have a
large
concentrated live load you can use a harped profile which is
nothing
more
than straight lines from the tendon pull location to the bottom
of the
member at the point load location.

Post by r***@rediffmail.com
2)Am I right if I say that if the tendon profile is decided so
as to
balance the dead load as well as live load then the check for
strsses
at "Transfer Stage" may create a problem such that the tensile
stresses at an extreme fibre may exceed the tensile strength of
concrete.

The intent is to balance dead load. Sometimes you can balance
more
dead
that exists which will, of course, take some of the live load on
the
way.
Precedents say that you shouldn't go more than 200%. If you feel
that
some
of the live load needs to be balanced, maybe due to
deflection,
it
might
be
a good thing. This needs some engineering judgment and experience.
You
always have to check what the tensile stresses at each stage are
so
that
they don't exceed code allowances. Commonly 6*fc'^.5. This is
final
tensile
stress limit with all loads applied. Initial stresses for tension
prior
to
applied live load (at transfer) at stressing is 3*fc'^.5 at the
top of
the
element which will be come the compression area when live load is
applied.

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile is
to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead and
live
load
condition. You might have uniform loading where you use the
parabolic
profile. You might have two big concentrated loads you might use
harped
profile. But for many spans and with uniform loading you
would
use a
continuous parabolic profile. Again ADAPT manual will show
all
the
profiles
that can be used with their program and what type of loading to
use
them
with. RAM concept (not familiar with) will also do this but I
think
it
is
not just a slab system or a beam-slab system but an entire
floor/beam,
flat
plate, or two way system which will take some time to model.
ADAPT
also
has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________
Charles I. Dinsmore, PE SE RA, M.ASCE ~

Suppose, we have a two way slab system having stiif supports
all
round
like a masonry wall.Now, the load transferred in shorter direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not
be
stiff
supports depends on the way they are connected to the slab )
usually the
longer spans will get more prestressed force than the short span
depends
on
the tributary area. Loads are usually set up the same way that a two way
system is with no prestressing. The support areas are usually
defined
with
column strips and middle strips where the column strips are the
supporting
elements of the slab in both directions. If post tensioned the
balancing
is
still a percentage of the dead load to the tributary strip elements.
Again
you have to get a text somewhere with all the secrets for post tensioning
structures. Some of the conditions that are not initially
apparent
are
explained in those texts.
CID...
______________________________________________________________
- Show quoted text -

All moments are shown that influence the design. The secondary
moments
add
to the service moments. If they don't show them in the output and
you
try
and check the stresses which don't meet the final output based on the
service load moments you will think something is not correct. I
think
that
it is a good thing. It is also shown how calculated and added to service
moments in any text books for post tensioned concrete.

Post by r***@rediffmail.com
2) In the design process for ADAPT , they have the final effective
design approach and system bound approach.In the final effective
design approach prestress losses are not calculated and hence
parameters regarding those are not given in the input.In system bound
approach all losses are calculated.
But, in software if the anchorage set, friction coefficient are
set
as
0 then the losses will be 0.What is so special about these approaches
in ADAPT?

Look closer at the input selections. You have the option to input
of
losses
to be considered which have been shown on typical structures in PTI
calculation examples for slabs and beams in their manuals. The second
method is not to input your own losses you think that will be
developed
(
from PTI and the ACI codes ) and let ADAPT calculate the losses for you.
CID...- Hide quoted text -
- Show quoted text -

Eagerly awaiting your response!!!

PTI Is the American 'Post Tension Institute'. Try PTI.com If that
doesn't work just go to Google and search for Post Tension Institute.
CID...- Hide quoted text -
- Show quoted text -

ADAPT follows the design approaches for Post Tensioning as the
"Effective Force Approach" and "System Bound Approach".In the
effective force approach the parameters for post-tensioning losses are
not entered in the Inputs in the pre-processor.Right?
These parameters can be entered in the Post-processor.Right?Does it
imply when enetering the values in the pre-processor the user has no
idea of the material details regarding the post-tensioning?And hence
only calculates the post-tensioning force and not the tendon spacing
and tendon numbers?
But, when the user is in the post-processor stage he has the idea of
the material details from the manufacturer and hence can go ahead with
entering the parameters pertaining to losses.Right?

Please Raj

Why do you keep putting yourself in this situation. Everything is described
in the ADAPT manual for everything that you have asked for in this thread.
You are close with the above but I still don't think you understand. You
can find all the answers in the PTI post tensioning book, in ADAPT manual
where they go through examples for the design and analysis for different PT
examples. You also have to be aware and STUDY the ACI ( American Concrete
Institute ) and the latest codes in your area.

r***@rediffmail.com

2007-02-13 14:22:01 UTC

Post by r***@rediffmail.com
As per the Technical Report 43 on Post Tensioned Floors
published by
the Concrete Society, the tendon profile is so obtained such
that
the
dead load is balanced.The slab depth is decided based on the
imposed
load criteria.
1) Now I want to know that if there is any better way to
obtain
the
tendon profile?

If you look into text books regarding prestressing and post
tensioning
you
will see there are a few types of profiles that can be used.
If
you
have
ADAPT and their manual you will see the profiles available.
The
common
profile is a parabolic curve that simulates the uniform load
bending
moment
curve. The intent is to balance the dead load. If you have a
large
concentrated live load you can use a harped profile which is
nothing
more
than straight lines from the tendon pull location to the bottom
of the
member at the point load location.

Post by r***@rediffmail.com
2)Am I right if I say that if the tendon profile is decided
so
as to
balance the dead load as well as live load then the check
for
strsses
at "Transfer Stage" may create a problem such that the
tensile
stresses at an extreme fibre may exceed the tensile strength
of
concrete.

The intent is to balance dead load. Sometimes you can balance
more
dead
that exists which will, of course, take some of the live load
on
the
way.
Precedents say that you shouldn't go more than 200%. If you
feel
that
some
of the live load needs to be balanced, maybe due to
deflection,
it
might
be
a good thing. This needs some engineering judgment and
experience.
You
always have to check what the tensile stresses at each stage
are
so
that
they don't exceed code allowances. Commonly 6*fc'^.5. This is
final
tensile
stress limit with all loads applied. Initial stresses for
tension
prior
to
applied live load (at transfer) at stressing is 3*fc'^.5 at the
top of
the
element which will be come the compression area when live load
is
applied.

Post by r***@rediffmail.com
3)In softwares lke RAM Concept, ADAPT if the tendon profile
is
to be
optimised what procedure they adopt?

In ADAPT you select the profile to be used based on your dead
and
live
load
condition. You might have uniform loading where you use the
parabolic
profile. You might have two big concentrated loads you might
use
harped
profile. But for many spans and with uniform loading you
would
use a
continuous parabolic profile. Again ADAPT manual will show
all
the
profiles
that can be used with their program and what type of loading to
use
them
with. RAM concept (not familiar with) will also do this but I
think
it
is
not just a slab system or a beam-slab system but an entire
floor/beam,
flat
plate, or two way system which will take some time to model.
ADAPT
also
has
one that does the same.
Hope all this helps.
Chuck...
______________________________________________________________
Charles I. Dinsmore, PE SE RA, M.ASCE ~

Suppose, we have a two way slab system having stiif supports
all
round
like a masonry wall.Now, the load transferred in shorter
direction
will be more than the laod in longer direction.Right?
Now, how to decide how much load should be balanced in shorter
direction and how much in the longer direction?

A two way system with masonry walls ( although those walls may not
be
stiff
supports depends on the way they are connected to the slab )
usually the
longer spans will get more prestressed force than the short span
depends
on
the tributary area. Loads are usually set up the same way that a
two way
system is with no prestressing. The support areas are usually
defined
with
column strips and middle strips where the column strips are the
supporting
elements of the slab in both directions. If post tensioned the
balancing
is
still a percentage of the dead load to the tributary strip elements.
Again
you have to get a text somewhere with all the secrets for post
tensioning
structures. Some of the conditions that are not initially
apparent
are
explained in those texts.
CID...
______________________________________________________________
- Show quoted text -

All moments are shown that influence the design. The secondary
moments
add
to the service moments. If they don't show them in the output and
you
try
and check the stresses which don't meet the final output based on the
service load moments you will think something is not correct. I
think
that
it is a good thing. It is also shown how calculated and added to service
moments in any text books for post tensioned concrete.

Post by r***@rediffmail.com
2) In the design process for ADAPT , they have the final effective
design approach and system bound approach.In the final effective
design approach prestress losses are not calculated and hence
parameters regarding those are not given in the input.In system bound
approach all losses are calculated.
But, in software if the anchorage set, friction coefficient are
set
as
0 then the losses will be 0.What is so special about these approaches
in ADAPT?

Look closer at the input selections. You have the option to input
of
losses
to be considered which have been shown on typical structures in PTI
calculation examples for slabs and beams in their manuals. The second
method is not to input your own losses you think that will be
developed
(
from PTI and the ACI codes ) and let ADAPT calculate the losses for you.
CID...- Hide quoted text -
- Show quoted text -

Eagerly awaiting your response!!!

PTI Is the American 'Post Tension Institute'. Try PTI.com If that
doesn't work just go to Google and search for Post Tension Institute.
CID...- Hide quoted text -
- Show quoted text -

Please Raj
Why do you keep putting yourself in this situation. Everything is described
in the ADAPT manual for everything that you have asked for in this thread.
You are close with the above but I still don't think you understand. You
can find all the answers in the PTI post tensioning book, in ADAPT manual
where they go through examples for the design and analysis for different PT
examples. You also have to be aware and STUDY the ACI ( American Concrete
Institute ) and the latest codes in your area.

Yes, I have been going throught he ADAPT manual.I just want to know if
am right here:
That, the effective force method is used when the the structural
designer is different from the post tensioning supplier and the design
is done before the supplier is selected.But , in the ADAPT post-
processor we have the "Friction and long term loss post-processor"
wherein when the design is carried out using effective force approach
the designer in this post-processor can enter the parameters
pertaining to the losses and the program now computes the losses.Right?
Does that mean when in the post-processor the user has has the
required information regarding the losses parameters?

In a design practice if the the structural designer is different from
the post tensioning supplier the information regarding losses is
computed by the post-tensioning supplier and it is the post-tensioning
supplier who decides the number of strands,etc.Right?Then, why does
ADAPT include the Friction and long term loss post-processor for the
Efective Force approach?

Chuck

2007-02-14 09:41:17 UTC