Structural Engineering: 2008-07-20

Saturday, July 26, 2008

Guard Rail

The new code requires a bollard to be designed for 6000lb, 18" above
ground. The load is required to be increased to an unknown amount for
trucks and buses.

What testing is this based on? car weight? speed? Car model crushing
energy absorption?

I found where a tested medium sized truck at 120 mph is stopped with
about a 17000 lb rigid capacity.

So the code vehicle load must be for something traveling at least 60mph.

Bollards, in a parking lot to prevent parking on a sidewalk, is an
example where a lower speed impact might be more reasonable.

I know that there is a liability to have rigid barriers along a highway
due to the potential injuries to the vehicle occupants and so yielding
barriers are part of highway designs. Looking at their post embeddments,
the capacity is no where near to the 6000 lb as specified in the
building code and using the code capacity for poles cantilevered into soil.

Does one need to design for more than the legal speed limit?

Does the impact reduce by the velocity squared?

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Re: Free LRFD Pier Design Program

TJ Fu

Please, could you send me a copy.

Thanks

Ali Yehia

--- On Fri, 7/25/08, TJ Fu <tzujfu@yahoo.com> wrote:

From: TJ Fu <tzujfu@yahoo.com>
Subject: Free LRFD Pier Design Program
To: seaint@seaint.org
Date: Friday, July 25, 2008, 8:45 AM

I have developed Windows version AASHTO LRFD pier design program. It has the following features:

Stand alone – with .EXE extension, you can run this program anywhere

No input sheet – all the data required is shown on monitor screen

Retrieve old data file – save typing. You can modify the data. The data will be saved automatically.

Frame analysis for each basic loading – DL, LL, Shrinkage & Temperature, 10 kips horizontal load

Loading combinations - per AASHTO LRFD specification

Summary – maximum M, V & reactions, and the controlling load cases

Pier cap design – rebars and stirrups

Drop me a line if you are interested.

T.J. Fu, P.E.

Louisville, Ky

Tzujfu@yahoo.com

Re: Free LRFD Pier Design Program

Mr Fu,
Although we are working with different codes up here, I would be very
interested in seeing what you programmed. Can you pls send me a copy.
Gary

TJ Fu wrote:
>
> I have developed Windows version AASHTO LRFD pier design program. It
> has the following features:
>
>
>
> * Stand alone – with .EXE extension, you can run this program anywhere
> * No input sheet – all the data required is shown on monitor screen
> * Retrieve old data file – save typing. You can modify the data.
> The data will be saved automatically.
>
> * Frame analysis for each basic loading – DL, LL, Shrinkage &
> Temperature, 10 kips horizontal load
> * Loading combinations - per AASHTO LRFD specification
> * Summary – maximum M, V & reactions, and the controlling load cases
> * Pier cap design – rebars and stirrups
>
>
>
> Drop me a line if you are interested.
>
>
>
> T.J. Fu, P.E.
>
> Louisville, Ky
>
> Tzujfu@yahoo.com <mailto:Tzujfu@yahoo.com>
>
>

Friday, July 25, 2008

Re: Free LRFD Pier Design Program

Mr Fu,

Iam very interested in a copy of your program. I hope you can help me by sending a copy. Thanks in advance.

On Fri, Jul 25, 2008 at 7:45 AM, TJ Fu <tzujfu@yahoo.com> wrote:

I have developed Windows version AASHTO LRFD pier design program. It has the following features:

Stand alone – with .EXE extension, you can run this program anywhere

No input sheet – all the data required is shown on monitor screen

Retrieve old data file – save typing. You can modify the data. The data will be saved automatically.

Frame analysis for each basic loading – DL, LL, Shrinkage & Temperature, 10 kips horizontal load

Loading combinations - per AASHTO LRFD specification

Summary – maximum M, V & reactions, and the controlling load cases

Pier cap design – rebars and stirrups

Drop me a line if you are interested.

T.J. Fu, P.E.

Louisville, Ky

Tzujfu@yahoo.com

--
Atentamente,
Ing. Benjamín Arcos Reyes.
Ingeniero estructural
Ingeniería Rioboo, Proyectos Industriales
México DF 52 5559 2284
Visita: http://www.senderodelpeje.blogspot.com/

Re: Threaded ASTM A706 Rebars for Anchor Bolts

Yes, bashfully, the main motivation for doing this way is the
difficulties on applying ACI 318 Appendix D.

The task of calculating 1-1/4" diameter headed bolts to work with the
edge distance in a ring wall with so many reductions for blowout,
sidewalls blowout, .... and 0.75 cut on the seismic. Deformed rebars
provide a much cleaner solution.

Your suggestion of using template for laying out the anchor bolts was
just what I have in mind. It needs to be done one-way-or-another
1-1/4" dia. bolts or rebars.

The free software by Simpson Strong-ties is very good. However, it has
limited sizes (no 1-1/4). On some occasions where high reductions due
to the spacing are required, Simpson will reject the spacings instead
of making an effort to squeeze in some tight spaces with high
penalties that, on theory, still can be calculated according to
Appendix D.

I like what Simpson Strong-tie has offered to us. It is very nice. I
print it out their results on paper and included it on my
calculations. Their format is the most readable among all the others I
have seen.

Thanks

Szuchuan Chang, SE

RE: Free LRFD Pier Design Program

Please Mr Fu, I will be very grateful if you can send me a copy.

Alberto Guida

De: TJ Fu [mailto:tzujfu@yahoo.com]
Enviado el: Friday, July 25, 2008 8:45 AM
Para: seaint@seaint.org
Asunto: Free LRFD Pier Design Program

I have developed Windows version AASHTO LRFD pier design program. It has the following features:

Stand alone – with .EXE extension, you can run this program anywhere
No input sheet – all the data required is shown on monitor screen
Retrieve old data file – save typing. You can modify the data. The data will be saved automatically.

Frame analysis for each basic loading – DL, LL, Shrinkage & Temperature, 10 kips horizontal load
Loading combinations - per AASHTO LRFD specification
Summary – maximum M, V & reactions, and the controlling load cases
Pier cap design – rebars and stirrups

Drop me a line if you are interested.

T.J. Fu, P.E.

Louisville, Ky

Tzujfu@yahoo.com

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RE: cable guardrails

You might look here.

http://www.jakob-usa.com/

Christopher Banbury, PE

President

Ark Engineering, Inc.

PO Box 10129, Brooksville, FL 34603

22 North Broad ST, Brooksville, FL 34601

Phone: (352) 754-2424

Fax: (352) 754-2412

www.arkengineering.net

RE: cable guardrails

The latest PTI handbook (6^th edition) has a whole chapter on this. There is also an article in Concrete International by Presswalla (May of ’89) that discusses this issue.

Eric R. Ober, PE, SE

Associate

Holbert Apple Associates

3423 Olney-Laytonsville Rd., Ste. 6

Olney, Maryland 20832

(301)570-1460 (Phone)

(301)570-1462 (Fax)

-----Original Message-----
From: Jeff Smith [mailto:jeffsmith7@comcast.net]
Sent: Friday, July 25, 2008 2:55 PM
To: seaint@seaint.org
Subject: RE: cable guardrails

In the bay area I have

http://www.feeneyarchitectural.com/cablerail.php

but this is not for parking garages, you might try and call them to see if they deal with this are maybe get a referral

I googled this, don't know anything about them

http://www.secosouth.com/

From: Andrew Kester, P.E. [mailto:akester@cfl.rr.com]
Sent: Friday, July 25, 2008 11:35 AM
To: seaint
Subject: cable guardrails

Can anyone get me started with a link or PDF regarding cable guard rails?

The Arch details show cables vertically at 4" o.c. and these go through steel posts. There is a requirement on the drawing for a cable at 18" above the deck to withstand 6000lb lateral force. The spec says the top cable must support a lateral load of 200lb, standard code stuff.

We have done all types of misc handrails and guardrails, never anything for vehicles or with cables. I had always assumed this to be a bit of a specialty item, our client though is a general steel/alum fabricator not a specialty guardrail comany. They will not be able to provide any technical assistance. I know engineers who do parking garages also sometimes design the cable systems. Is this something I should pass onto a specialty engineer? This is a good ongoing client, and the relationship is important to me. If this stuff is relatively normal engineering with good tech info out there, I don't mind teaching this old dog new tricks...

Please CC me directly also, thanks in advance.

Andrew Kester, P.E.
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Drive, Suite 301
Orlando, FL 32803

re: threaded rebars

Szuchuan,

You could weld the bars to the bottom of a base plate and cast that into the footing. We use all-thread rods with a small steel square plate (PL1/4x2x2) on the end of each rod and use bar development values, though I don't know if this is in ACI or not, always assumed an all thread rod with threads through the length would have as much surface bond strength as a deformed bar. The oversized washers are there for insurance.

Or with really big uplifts we have used an embed plate the same size as the base plate, then can design the plate for upward punching shear rather than pull-out of each rod. For additional cheap safety detail a couple of bars laying on top of the plate for additional shear resistance. Like a big upside down truncated pyramid, basically similar to the failure mode of a group of 4 bolts that are not spaced very far apart.

Finally, you can often get higher values from various epoxy and expansion bolt mfr tables then you would from ACI App D, as they base their values on repetitive testing rather than formulas that cannot account for everything.

Also, I have found Simpson's ACI APP D program pretty useful for (4) bolt connections, which covers most base plates...

HTH,

Andrew

Andrew Kester, P.E.
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Drive, Suite 301
Orlando, FL 32803

RE: cable guardrails

In the bay area I have

http://www.feeneyarchitectural.com/cablerail.php

but this is not for parking garages, you might try and call them to see if they deal with this are maybe get a referral

I googled this, don't know anything about them

http://www.secosouth.com/

From: Andrew Kester, P.E. [mailto:akester@cfl.rr.com]
Sent: Friday, July 25, 2008 11:35 AM
To: seaint
Subject: cable guardrails

Can anyone get me started with a link or PDF regarding cable guard rails?

Please CC me directly also, thanks in advance.

Andrew Kester, P.E.
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Drive, Suite 301
Orlando, FL 32803

cable guardrails

Can anyone get me started with a link or PDF regarding cable guard rails?

Please CC me directly also, thanks in advance.

Andrew Kester, P.E.
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Drive, Suite 301
Orlando, FL 32803

RE: Threaded ASTM A706 Rebars for Anchor Bolts

The electric utility industry uses Dywidag or Williams anchors for transmission line tower anchorage. I worked in that industry for a while also. You need to specify your tolerance and send gage metal templates.

Regards,
Harold Sprague

> Subject: RE: Threaded ASTM A706 Rebars for Anchor Bolts
> Date: Fri, 25 Jul 2008 07:32:29 -0700
> From: rgarner@moffattnichol.com
> To: seaint@seaint.org
>
> The electric utility industry typically uses partially threaded rebar
> for anchoring their columns. Find out who fabricates for this industry
> and there's your answer.
>
> Bob Garner, S.E.
>
> -----Original Message-----
> From: Szuchuan Chang [mailto:szuchuan@gmail.com]
> Sent: Thursday, July 24, 2008 1:50 PM
> To: SEAOC
> Subject: Threaded ASTM A706 Rebars for Anchor Bolts
>
> List,
>
> Need to develop 1.25" diameter anchors for the base of an antenna dish
> to the concrete pedestal.
>
> If I leave the #10 (ASTM A706) out of concrete as dowels, will the
> contractor have problem to thread the rebar for bolting it to the
> base?
>
> It is much easier to develop the embedment strength on rebars with
> deformation than the ACI Appendix D with anchor bolts.
>
> Thanks
>
> Szuchuan Chang
>
> ******* ****** ******* ******** ******* ******* ******* ***
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RE: Threaded ASTM A706 Rebars for Anchor Bolts

Suresh,
Dayton has a good product line, but requires a bit of caution. If you are using a threaded bar, and you need a given size bar for strength, you need to select the next larger bar because of the reduction in the threaded area. The only threaded coupler that can give full strength is the tapered coupler that is used by Lenton.

Szuchuan,
When you say "easier" to develop the embedment strength, I am curious about easier for whom. It is probably easier for the designer, but not for the field.

Rebar is generally installed by a different iron worker crew as opposed to the antenna. No matter what you show on drawings, rebar is installed to a much more generous tolerance (ACI 117 Section 2.3). Anchorages and anchor bolts should be installed to the tolerance indicated in AISC 303, Section 7.5. Further, if the placement is critical, a gage metal template should be required. The difference in tolerance is huge when you compare ACI and AISC. A gage metal template will be fabricated within 1/16" tolerance.

I would then suggest that an ASTM F 1554 anchor rod be used with locked nut forming the head. You can specify a 105 ksi material. When or if you have to calculate (and prove) the deflection of the antenna, the rebar anchorage will not perform as a rigid anchor. The strain varies as you develop the rebar with depth and there will be local slippage which will effect the elongation of the anchorage and thus effect the deflection. If you use a headed anchor, you can preload the anchor and achieve a reliable and consist ant strain and a reliable deflection calculation.

You can lap rebar into the development cone of the anchor rod to assure that you can transfer the applied stresses into the concrete.

Regards,
Harold Sprague

> From: Suresh.Acharya@ci.concord.ca.us
> To: seaint@seaint.org
> Subject: RE: Threaded ASTM A706 Rebars for Anchor Bolts
> Date: Thu, 24 Jul 2008 14:46:15 -0700
>
> See
> http://www.daytonsuperior.com for rated splicing
> system/couplers/pre-threaded bars.
>
>
> -----Original Message-----
> From: Szuchuan Chang [mailto:szuchuan@gmail.com]
> Sent: Thursday, July 24, 2008 1:50 PM
> To: SEAOC
> Subject: Threaded ASTM A706 Rebars for Anchor Bolts
>
> List,
>
> Need to develop 1.25" diameter anchors for the base of an antenna dish to
> the concrete pedestal.
>
> If I leave the #10 (ASTM A706) out of concrete as dowels, will the
> contractor have problem to thread the rebar for bolting it to the base?
>
> It is much easier to develop the embedment strength on rebars with
> deformation than the ACI Appendix D with anchor bolts.
>
> Thanks
>
> Szuchuan Chang
>
> ******* ****** ******* ******** ******* ******* ******* ***
> * Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> * This email was sent to you via Structural Engineers
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> * subscribe (no fee) or UnSubscribe, please go to:
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> * without your permission. Make sure you visit our web
> * site at: http://www.seaint.org
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>
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RE: Threaded ASTM A706 Rebars for Anchor Bolts

The electric utility industry typically uses partially threaded rebar
for anchoring their columns. Find out who fabricates for this industry
and there's your answer.

Bob Garner, S.E.

-----Original Message-----
From: Szuchuan Chang [mailto:szuchuan@gmail.com]
Sent: Thursday, July 24, 2008 1:50 PM
To: SEAOC
Subject: Threaded ASTM A706 Rebars for Anchor Bolts

List,

Need to develop 1.25" diameter anchors for the base of an antenna dish
to the concrete pedestal.

If I leave the #10 (ASTM A706) out of concrete as dowels, will the
contractor have problem to thread the rebar for bolting it to the
base?

It is much easier to develop the embedment strength on rebars with
deformation than the ACI Appendix D with anchor bolts.

Thanks

Szuchuan Chang

RE: Free LRFD Pier Design Program

Please send me a copy.

David Maynard

Gillette, WY

crazyd_7@yahoo.com

From: TJ Fu [mailto:tzujfu@yahoo.com]
Sent: Friday, July 25, 2008 5:45 AM
To: seaint@seaint.org
Subject: Free LRFD Pier Design Program

I have developed Windows version AASHTO LRFD pier design program. It has the following features:

Stand alone – with .EXE extension, you can run this program anywhere
No input sheet – all the data required is shown on monitor screen
Retrieve old data file – save typing. You can modify the data. The data will be saved automatically.

Frame analysis for each basic loading – DL, LL, Shrinkage & Temperature, 10 kips horizontal load
Loading combinations - per AASHTO LRFD specification
Summary – maximum M, V & reactions, and the controlling load cases
Pier cap design – rebars and stirrups

Drop me a line if you are interested.

T.J. Fu, P.E.

Louisville, Ky

Tzujfu@yahoo.com

RE: Free LRFD Pier Design Program

I am very interested in this program. What format is it? I would appreciate receiving a copy of this.

Thanks in advance.

Bob Garner, S.E.

From: TJ Fu [mailto:tzujfu@yahoo.com]
Sent: Friday, July 25, 2008 5:45 AM
To: seaint@seaint.org
Subject: Free LRFD Pier Design Program

I have developed Windows version AASHTO LRFD pier design program. It has the following features:

Stand alone – with .EXE extension, you can run this program anywhere
No input sheet – all the data required is shown on monitor screen
Retrieve old data file – save typing. You can modify the data. The data will be saved automatically.

Frame analysis for each basic loading – DL, LL, Shrinkage & Temperature, 10 kips horizontal load
Loading combinations - per AASHTO LRFD specification
Summary – maximum M, V & reactions, and the controlling load cases
Pier cap design – rebars and stirrups

Drop me a line if you are interested.

T.J. Fu, P.E.

Louisville, Ky

Tzujfu@yahoo.com

Re: Free LRFD Pier Design Program

Dear TJ:

Please send me a copy.
Thanks.

Virendra

Virendra K. Varma, Ph.D., P.E., F. ASCE
Professor and Chairman
Department of Engineering Technology
Missouri Western State University
4525 Downs Dr, St Joseph, MO 64507
Phone: 816-271-4562
>>> TJ Fu <tzujfu@yahoo.com> 07/25/08 7:45 AM >>>
I have developed Windows version AASHTO LRFD pier design program. It has
the following features:

Stand alone – with .EXE extension, you can run this program anywhere
No input sheet – all the data required is shown on monitor screen
Retrieve old data file – save typing. You can modify the data. The data
will be saved automatically.

Frame analysis for each basic loading – DL, LL, Shrinkage & Temperature,
10 kips horizontal load
Loading combinations - per AASHTO LRFD specification
Summary – maximum M, V & reactions, and the controlling load cases
Pier cap design – rebars and stirrups

Drop me a line if you are interested.

T.J. Fu, P.E.
Louisville, Ky
Tzujfu@yahoo.com

Free LRFD Pier Design Program

I have developed Windows version AASHTO LRFD pier design program. It has the following features:

Stand alone – with .EXE extension, you can run this program anywhere
No input sheet – all the data required is shown on monitor screen
Retrieve old data file – save typing. You can modify the data. The data will be saved automatically.

Frame analysis for each basic loading – DL, LL, Shrinkage & Temperature, 10 kips horizontal load
Loading combinations - per AASHTO LRFD specification
Summary – maximum M, V & reactions, and the controlling load cases
Pier cap design – rebars and stirrups

Drop me a line if you are interested.

T.J. Fu, P.E.

Louisville, Ky

Tzujfu@yahoo.com

Re: Prestressed Double T Camber

Thank you for your responses!

I did not know that late stripping of prestressed members from the mold would cause severe camber difference.

Though, this deviation is within product tolerance (0.25"/10ft , max 0.75"/10ft) according to PCI Design Handbook;

I got 2" while 0.75x60'/10'=.45", which is very big number!

I understand camber is related with E and E is eventually affected by f'c.

In my case, when I ran a program to compare how f'c affects camber using 3500psi (@stripping)/5000psi(@28-day)

and 6000psi(@stripping)/8000psi(@28-day), cambers were only 0.5" difference.

I am still puzzled at what caused 2" camber difference.

In most precast plants, steam curing is popular and I think concrete strength does not change much between 12 hours

and 36 hours after concrete placement

because like my company weekend concrete mix may be used and steam is not provided during weekend.

Here is my conclusion:

we have to cut strands if prestressed members stay in the mold for extended hours in order to prevent strand failure and/or concrete spalling

and excessive camber variance.

I did not know second part was so important.

Thanks!

PS: Jim G., I appreciate your remedial advice!

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Thursday, July 24, 2008

RE: Residential alterations, is upgrade for wind required?

Jeff,

For the most part the loading codes are based more on economics and risk
rather than life safety issues. So depending on how pedantic the building
officials are, you can try using the extra detail in the commentary to ASCE7
to gain reduction in wind loading. For example terrain exposure averaging,
if exposure is varying on approach to building. Also consider variation of
wind speed with direction.

Then there is risk and life expectancy. The 50 year mean return period wind
speed is some what meaningless relative to the performance of the building,
it is otherwise factored. Whilst the ultimate strength limit state wind
speed with mean return period of 500 years, is the speed at which expect the
building materials to yield and permanently deform, such that after the
design event the building is no longer serviceable. It is based on a 5%
probability of exceedence in 25 years, or roughly 10% in 50 years. (for 5%
in 50 years need a 1000 year mean return period. Which we had here from 1989
to 2002, but housing industry complained.)

An existing building has a lower remaining life expectancy than a new
building. Therefore maintain the risk at say 5% and reduce the life
expectancy to suit some estimate of the desired life of the building after
the renovation.

Alternatively try working backwards, you know the resistance of the existing
structure, calculate the wind pressure required to fail it, then convert to
wind speed and then convert into mean return period, then from mean return
period and risk of 5% calculate the life expectancy. When the answer comes
out at say 2 years, see if owner wants to avoid upgrading resistance for
wind loading. One problem is convincing the owners the mathematics is valid,
when building has been there for far longer in the first place.

Another problem: unlike AS1170.2 I don't believe ASCE7 provides the wind
data or mathematical models for varying return periods.

In any case the approach is useful for assessing existing structures.

Also if the building lacks resistance I don't understand the need to remove
plywood sheathing and replace. There should be some way to add some extra
resistance: steel strap cross-bracing on inside face, or timber diagonal
struts between walls studs, and then there are various proprietary steel
bracing systems (eg. Mitek: Posi-Brace). These may not be ideal, but I
assume the existing structure has most of the resistance required. But then
I don't design diaphragm boxes so I may be on the wrong track: I'm assuming
the plywood sheathing only goes on the external face of the timber frame and
that discrete braces could be added from the interior. Also steel strap and
brackets are typically accommodated on surface behind plasterboard.

MiTek:gangnail
http://www.mii.com/australia/

Regards
Conrad Harrison
B.Tech (mfg & mech), MIIE, gradTIEAust
mailto:sch.tectonic@bigpond.com
Adelaide
South Australia

RE: Threaded ASTM A706 Rebars for Anchor Bolts

See
http://www.daytonsuperior.com for rated splicing
system/couplers/pre-threaded bars.

-----Original Message-----
From: Szuchuan Chang [mailto:szuchuan@gmail.com]
Sent: Thursday, July 24, 2008 1:50 PM
To: SEAOC
Subject: Threaded ASTM A706 Rebars for Anchor Bolts

List,

Need to develop 1.25" diameter anchors for the base of an antenna dish to
the concrete pedestal.

If I leave the #10 (ASTM A706) out of concrete as dowels, will the
contractor have problem to thread the rebar for bolting it to the base?

It is much easier to develop the embedment strength on rebars with
deformation than the ACI Appendix D with anchor bolts.

Thanks

Szuchuan Chang

RE: Storage Containers

I agree, I would think it depends on what it is being used for. What if it
was on a trailer with wheels?. People do all sorts of things with
contailers:
http://www.youtube.com/watch?v=65C9OLvmjpI
http://www.youtube.com/watch?v=D6FRLdjQqmw

-----Original Message-----
From: Gary L. Hodgson and Assoc. [mailto:ghodgson@bellnet.ca]
Sent: Thursday, July 24, 2008 4:39 AM
To: seaint@seaint.org
Subject: Re: Storage Containers

Why do they have to have footings? I see shipping container sitting on
concrete, asphalt and earth without any concern. It really depends on what
they are being used for. If for storage, then it seems they go through a
lot of movement when being shipped and now should they be on footings and be
level.
Gary

Drew Morris wrote:
> Tom Monti wrote:
>> I have a client that has been red tagged by the county for their use
>> of storage containers on their property with out a building permit.
>> These are the 40 foot containers that are used to ship products
>> overseas. Does anyone know what would be required for a foundation
>> for one of these containers? Are they designed to transmit their
>> load via the corners only? I am thinking of concrete footings on each
>> of the four corners might be sufficient.
>>
>> Thank You,
>>
> **I got involved with these a few years back, the city caught the
> owner with using some of these as storage. The end walls are some
> sort of moment frame. There should be a label/placard on the
> container that gives the allowable racking loads. I ended up using
> helical screw anchors at the corners and welding the end of the
> exposed anchor rod to a bracket welded to the container corners.**
>
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Threaded ASTM A706 Rebars for Anchor Bolts

List,

Need to develop 1.25" diameter anchors for the base of an antenna dish
to the concrete pedestal.

If I leave the #10 (ASTM A706) out of concrete as dowels, will the
contractor have problem to thread the rebar for bolting it to the
base?

It is much easier to develop the embedment strength on rebars with
deformation than the ACI Appendix D with anchor bolts.

Thanks

Szuchuan Chang

RE: Residential alterations, is upgrade for wind required?

Jeff,

If my understanding of IBC Chapter 34 and/or the IEBC is correct, if you haven't added load or decreased strength, then from a wind standpoint you get to check the shear walls using the governing provisions at the original time of construction of the house.

Gary

Gary J. Ehrlich, PE
Program Manager, Structural Codes & Standards
National Association of Home Builders (NAHB)
1201 15th Street, NW, Washington, DC 20005
ph: 202-266-8545 or 800-368-5242 x8545
fax: 202-266-8369
gehrlich@nahb.com

-----Original Message-----
From: Jeff Smith [mailto:jeffsmith7@comcast.net]
Sent: Monday, July 21, 2008 4:09 PM
To: seaint@seaint.org
Subject: Residential alterations, is upgrade for wind required?

I am working on a one story steep hill side residence, substantial
alterations, however no change to building envelope. Existing building is
one floor over partial lower level at down hill side. The new work is to
excavate out the lower level on the uphill side. Upper floor is almost at
grade on up hill side. I am seismically upgrading the building however it
appears that wind load will actually govern in the transverse direction
orthogonal to the site slope. From a wind standpoint we are not increasing
demand or decreasing existing capacity. The existing shear ply may not work
for wind load. Can I upgrade the building for only seismic loads? I have
never done this before.

Thanks, Jeff

scanner for masonry wall reinforcement

Can anyone recommend a handheld scanner for locating rebar in 8” masonry walls? I use a Zircon MT6 for preliminary steel location but it is acting up and I might consider an upgrade.

TIA

Christopher Banbury, PE

President

Ark Engineering, Inc.

PO Box 10129, Brooksville, FL 34603

22 North Broad ST, Brooksville, FL 34601

Phone: (352) 754-2424

Fax: (352) 754-2412

www.arkengineering.net

RE: Prestressed Double T Camber

A contractor once told us that he saw this in prestressed bridge beams. His crew would grumble when they got “Saturday beams” – beams that were cast on Saturday, and hence left in the forms an extra day when the plant was shut down over Sunday. They would have noticeably different camber than the other (“weekday”) beams, and they’d have to accommodate for it when they set their precast deck panels.

-- Joel

SHW Group, Inc.

Plano, TX

From: Wontae Kim [mailto:kimwontae@email.com]
Sent: Wednesday, July 23, 2008 10:41 PM
To: seaint@seaint.org
Subject: Prestressed Double T Camber

Hi!

Recntly we measured cambers of 10' wide, 60' long precast prestressed double tees for parking garage.

Generally, camber is about 3" to 4" for this kind of DTs.

But, this time all DT cambers are about 1".

Only difference in production condition is they stayed in mold more than three days because of holiday;

typically we strip precast members within 8 hours of steam curing after pouring concrete.

I heard that detensioning is required immediately when concrete drying shrinkage or temperature shrinkage may cause

severe damage to long members like bridge girders.

But, I have never heard delayed detensioning could cause 'significantly' less camber.

Will these DTs have eventually the similar camber of DTs which were stripped 8 hours later?

If you have any experience or info, please let me know.

Thanks!

wontae

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Re: Prestressed Double T Camber

Kim,
If they are "pre-topped" they will have considerably less camber than untopped.

>>> "Wontae Kim" <kimwontae@email.com> 7/23/2008 10:40 PM >>>

Hi!

Recntly we measured cambers of 10' wide, 60' long precast prestressed double tees for parking garage.

Generally, camber is about 3" to 4" for this kind of DTs.

But, this time all DT cambers are about 1".

Only difference in production condition is they stayed in mold more than three days because of holiday;

typically we strip precast members within 8 hours of steam curing after pouring concrete.

I heard that detensioning is required immediately when concrete drying shrinkage or temperature shrinkage may cause

severe damage to long members like bridge girders.

But, I have never heard delayed detensioning could cause 'significantly' less camber.

Will these DTs have eventually the similar camber of DTs which were stripped 8 hours later?

If you have any experience or info, please let me know.

Thanks!

wontae

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Re: Prestressed Double T Camber

Wontae,

Predicting camber is a black art. There are too many variables. My guess is that the 1” camber tees will not match the 3” – 4” camber tees unless they are stored for a long time or stored with dunnage further from the end (maybe 3’- 4’ instead of right at the end) for a shorter (but still long) time.

HTH,

Jim Getaz

Precast Concrete Engineer

Re: Storage Containers

Why do they have to have footings? I see shipping container sitting on
concrete, asphalt and earth without any concern. It really depends on
what they are being used for. If for storage, then it seems they go
through a lot of movement when being shipped and now should they be on
footings and be level.
Gary