Structural Engineering: 2008-05-18

Saturday, May 24, 2008

2007 cbc special seismic load combinations

I’ve been away from the list for quite some time, I have looked through the archives for messages on this topic and found none.

Should we be using the CBC Equations 16-22 & 16-23 or ASCE 7-05 section 12.4.3.2 Equations 6 & 8?

I do not find any reference in the CBC which requires the use of the ASCE equations. My confusion comes from the Seismic Design Manual Volume 2, Ex. 2 using the ASCE equations for the uplift of shear panel on a beam.

Thanks,

Mark D. Baker

Baker Engineering

re: fire damaged concrete

I agree with Harold but Steve made some good points too. I would do a visual review after cleaning and look for spalling and cracking, this is the main effect on concrete slabs-on-grade. But then again, concrete SOG all tend to crack some from curing, settlement, lack of expansion joints, etc. so you may have a difficult time diffentiating. I would not be too worried, but if it is a thickened/monolithic type wall footing you may want to look around bearing walls for slab cracking. But generally I think of SOG as a dirt cover.... Just seal the cracks like Harold said and be done with it (after your investgation).

However, I have done a few fire investgations of residential fires and masonry and concrete resist fire damage quite well. By that I mean no noticeable cracking or spalling is noticed. In an electrical panel explosion once on a project of mine it spalled off a chunk of the unreinforced CMU. But I would think heat would affect the slab the least as the hottest part of the fire would be in the ceiling structure not next to the slab, but this is just my opionion and I am no fire engineer.

But you did say this thing got hot enough for steel to deflect, and that can happen at around 575 deg F. That is the same approximate temp when concrete begins to lose its strength also. This is according to "Forensic Structural Engineering Handbook" by Ratay. "Guide to Deterioration and Failure of Building Materials" by Heckroodt puts it this way:

The strength of concrete is not severely affected by temps below 250 c (482F), but drops 80% at 450 C (842 F), and to 50% at 650 C (1202 F). Not sure why these numbers are so much higher than Steve's source, but I am just the messenger.

I could scan a couple pages of this book if you would like.

HTH,

Andrew

According to Composition and Properties of Concrete (MGH 1968), concrete =
samples subjected to temperature "T" and crushed after cooling had the =
following compressive strength (relatively to that at 70F): 85% at =
T=3D200F, 70% at T=3D450F, 50% at T=3D700F.

Although technically unreinforced, SOGs may be subjected to considerable =
forces under the normal use conditions. Besides, due to the concrete =
strength loss, the new post-installed anchors will not have the =
specified strength. This means that the residual loss of strength due =
to the fire strongly justifies the post-fire replacement of at least the =
portions of SOG exposed to the fire. =20

In my experience, the insurance companies did not have any problems =
covering such losses.

V. Steve Gordin, SE
Irvine CA

Andrew Kester, P.E.
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Ave., Suite 301
Orlando, FL 32803
M 407-921-1617
F 321-249-0349

Friday, May 23, 2008

RE: Special Inspections was: CBC Ch 17

Harold
For all the problems with DSA/OSHPD the inspector of record system that they have works pretty good. You might want to check it out.
Your reference to special inspections as QC is at odds with the IBC and FEMA 450. True construction quality assurance requires that the Contractor actively work to correct problems that are found by inspections. The contractual relationships in typical construction contracts do not require that the contractor work to minimize problems. When problems are found they are corrected and nobody seems to ask how to correct the root cause. All too often the approach taken is to correct the mistakes identified but do nothing about the other likely defects not found.
Mark Gilligan

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RE: Pages from AASHTO

Thanks Steve,

I believe that is what I am looking for. So don’t bother with the older pages. At the moment a Guiness, but it has been a long day. I have a proposal to do this weekend that will take a lot of prep. So, since it has been a long day, I will probably move to a cocktail next, probably a Manhattan.

By the way, how have you been? Haven’t talked to you for quite a while.

Thanks again,

Joe

From: Steve Gordin [mailto:sgordin@sgeconsulting.com]
Sent: Friday, May 23, 2008 5:38 PM
To: Seaint
Subject: Re: Pages from AASHTO

Joe,

I have an older version of AASHTO (1996) and can scan and email those pages; however, you can get all info you need on the CALTRANS site:

http://www.dot.ca.gov/hq/esc/techpubs/manual/bridgemanuals/bridge-design-specifications/page/section5.pdf

What kind of beer you got?

V. Steve Gordin, SE
Irvine CA

----- Original Message -----

From: Joseph R. Grill

To: seaint@seaint.org

Sent: Friday, May 23, 2008 17:16

Subject: Pages from AASHTO

I realize it is late on a Friday afternoon. I am cracking a beer myself. But, I was hoping one of you out there might have a few pages from the AASHTO Spec that could be emailed to me to use until I get the entire spec ordered.

It has been a while, but it is in the foundation section. There are some drawings and related text concerning retaining wall designs. What I am looking for in particular are the cantilevered sheet pile formulas, and soldier pile embedment formulas with the related text. If I can get that, I will buy you a beer the next time you are in Arizona.

Thanks,

Joe

Re: Pages from AASHTO

Joe,

I have an older version of AASHTO (1996) and can scan and email those pages; however, you can get all info you need on the CALTRANS site:

http://www.dot.ca.gov/hq/esc/techpubs/manual/bridgemanuals/bridge-design-specifications/page/section5.pdf

What kind of beer you got?

V. Steve Gordin, SE
Irvine CA

----- Original Message -----

From: Joseph R. Grill

To: seaint@seaint.org

Sent: Friday, May 23, 2008 17:16

Subject: Pages from AASHTO

I realize it is late on a Friday afternoon. I am cracking a beer myself. But, I was hoping one of you out there might have a few pages from the AASHTO Spec that could be emailed to me to use until I get the entire spec ordered.

It has been a while, but it is in the foundation section. There are some drawings and related text concerning retaining wall designs. What I am looking for in particular are the cantilevered sheet pile formulas, and soldier pile embedment formulas with the related text. If I can get that, I will buy you a beer the next time you are in Arizona.

Thanks,

Joe

Pages from AASHTO

I realize it is late on a Friday afternoon. I am cracking a beer myself. But, I was hoping one of you out there might have a few pages from the AASHTO Spec that could be emailed to me to use until I get the entire spec ordered.

It has been a while, but it is in the foundation section. There are some drawings and related text concerning retaining wall designs. What I am looking for in particular are the cantilevered sheet pile formulas, and soldier pile embedment formulas with the related text. If I can get that, I will buy you a beer the next time you are in Arizona.

Thanks,

Joe

Lags in Holdowns

I just found out that a contractor substituted lagged HD5As for the
spec'd HTT16 shearwall holdowns. Capacity works, but I'm not sure about
the lags. I never spec bolted holdowns because the deflections are so
high, but I haven't thought about lagging them. Simpson catalogue says
"Lag bolts will not develop the listed loads." They will, however, help
with the deflection issue, and after what we learned in Northridge that
seems like a good thing. How do lags really perform under cyclic
loading, particularly when put into a double 2x column? I know the NDS
values are going to be < 1/2 to begin with, and with p/8D = ~0.6 it's
going to get worse, but what about the more practical questions: does
it behave like a bolt, as far as lateral yield modes? Does it rock back
& forth and then just pull out?

These are the questions that make me think my company should have our
offices in a warehouse with a full lab w/ shake table, so that at this
time on Friday afternoons we could stop work, crack a few beers, and
answer these questions for ourselves.

Gordon Goodell

Re: Was embedded timber post (80 Tons trailer impact on Structure)

Chris:

I also love your sense of humor.
Have a great Memorial weekend and enjoy the bike riding.

Casey K. Hemmatyar, SE

-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com]
Sent: Friday, May 23, 2008 2:01 PM
To: seaint@seaint.org
Subject: Re: Was embedded timber post (80 Tons trailer impact on Structure)

On May 23, 2008, at 2:03 PM, Casey K. Hemmatyar wrote:

> I love your responc(s)es.
> You're right but the is a 1/2 factor in the basic equation.
Oh, hell--right you are. I looked at the two numbers and thought to
myself that looks like a factor of 2 somewhere. I wonder if… nahhh,
how could I make a mistake that simple.' Then I hit send and started
thinking about a bike ride this afternoon. Obviously I should have
taken the bike ride, then made a fool of myself instead of the other
way around.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/

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bullet proof concrete?

A friend of mine is asking me what kind of concrete would be equivalent to a UL 752 level 3 bullet proof rating, they are thinking of replacing a compressed ballistic grade fiberglass roving with something cheaper in a new construction project. Perhaps some kind of masonry would also be an option… I am not familiar with hardened construction standards, is there a resource out there I could look at? Any experiences to learn from?

Aaron

Re: Was embedded timber post (80 Tons trailer impact on Structure)

On May 23, 2008, at 2:03 PM, Casey K. Hemmatyar wrote:

> I love your responces.
> You're right but the is a 1/2 factor in the basic equation.
Oh, hell--right you are. I looked at the two numbers and thought to
myself that looks like a factor of 2 somewhere. I wonder if… nahhh,
how could I make a mistake that simple.' Then I hit send and started
thinking about a bike ride this afternoon. Obviously I should have
taken the bike ride, then made a fool of myself instead of the other
way around.

Post Installed Anchors in Concrete

ASCE 7-05 Section 13.4.2 item B for Rp states that Rp shall not exceed 1.5 when the post installed anchor is not prequalified for use in seismic design per ACI 355.2.

To me, this means we can use any anchor products that do not have ICC approval provided we use Rp = 1.5 in our Fp calculation and also bump up the force to 1.3 Fp since it's into concrete or masonry.

Anyone disagree with that?

-gm

Hi,

For the following book I missed Page 82 and 83.

HANDBOOK OF STRUCTURAL STEELWORK

Design Examples & Ultimate Loads to BS 5950 Part 1

& Section Properties to BS4 Part l

BS 4848 Parts 2 & 4.

by: A. D. Weller CEng, FiStructE, MBCS in association with
R H. Allen CEng, MICE, MWeldI

Can anybody having this book kindly scan and email to me?

Thanks in advance.

Best Regards,

Michael Z. Zhang P. Eng.

Aluminum Exposed To Seawater

I'm desiging a small gate (i.e., 5'x5') that will be exposed to seawater.

Is 6061-T6 a valid temper/alloy for a structure that will be subjected to this corrosive condition during it's design life? Is there another temper/alloy that's more appropriate?

TIA,
Charlie Canitz, PE
Annapolis, MD

Stay informed, get connected and more with AOL on your phone.

Re: Was embedded timber post (80 Tons trailer impact on Structure)

Casey

Don't forget the Brewski's ...you will be revised and it is Friday

Joe Venuti
Johnson & Nielsen Associates
Palm Springs, CA

Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence" on AOL Food.

Re: Was embedded timber post (80 Tons trailer impact on Structure)

"The quantity Casey is figuring is an energy not a force, because the
relationship he's using is the definition of kinetic energy."

agree

On Fri, May 23, 2008 at 2:53 PM, Christopher Wright <chrisw@skypoint.com> wrote:
>
> On May 23, 2008, at 12:41 PM, Casey K. Hemmatyar wrote:
>
>> Just to refresh your memory, it has a 28,340 k-ft of Force but not
>> Energy.
>
> Not to nag, but you're both wrong.
>
> David figured the energy correctly but misinterpreted the work as a moment.
> If you're looking at the and came up with the average force that would
> decelerate the truck in 30 inches. If you ran the truck into a post the post
> would have to deform 30 inches under the influence of that force--actually
> the total of the deformation of the post and the deformation of the truck
> would be 30 inches. What would actually happen is that the initial force
> would be much greater than the average; the post would snap off and the
> truck would be damaged but probably keep moving.
>
> Casey also calculated the energy, only in metric units and then put it equal
> to a force, which it isn't. I'm not sure how the calculation got carried
> out, but the mass in kg of an object that weighs 80 tons = (80)(2000)/2.2046
> = 72575 kg and 70 mph = (70)(88/60) = 102.667 ft/sec or (0.3048)(102.667) =
> 31.293 m/sec That makes the kinetic energy (72575)(31.293)^2 =71069 kJ, not
> 39779 kJ.
>
> The quantity Casey is figuring is an energy not a force, because the
> relationship he's using is the definition of kinetic energy.
>
>
> But the actual bottom line is that running a truck into an embedded timber
> post, will snap the post and not do much to slow the truck, except if the
> truck jackknifes and rolls after the impact. If you've ever seen a collision
> of a truck and a telephone pole, it's pretty clear.
>
> Christopher Wright P.E. |"They couldn't hit an elephant at
> chrisw@skypoint.com | this distance" (last words of Gen.
> .......................................| John Sedgwick, Spotsylvania 1864)
> http://www.skypoint.com/~chrisw/
>
>
>
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RE: Was embedded timber post (80 Tons trailer impact on Structure)

Chris:

I love your responces.

You're right but the is a 1/2 factor in the basic equation.

I need to go for my lunch!

Regards

Casey K. Hemmatyar, SE

-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com]
Sent: Friday, May 23, 2008 11:54 AM
To: seaint@seaint.org
Subject: Re: Was embedded timber post (80 Tons trailer impact on Structure)

On May 23, 2008, at 12:41 PM, Casey K. Hemmatyar wrote:

> Just to refresh your memory, it has a 28,340 k-ft of Force but not

> Energy.

Not to nag, but you're both wrong.

David figured the energy correctly but misinterpreted the work as a

moment. If you're looking at the and came up with the average force

that would decelerate the truck in 30 inches. If you ran the truck

into a post the post would have to deform 30 inches under the

influence of that force--actually the total of the deformation of the

post and the deformation of the truck would be 30 inches. What would

actually happen is that the initial force would be much greater than

the average; the post would snap off and the truck would be damaged

but probably keep moving.

Casey also calculated the energy, only in metric units and then put

it equal to a force, which it isn't. I'm not sure how the calculation

got carried out, but the mass in kg of an object that weighs 80 tons

= (80)(2000)/2.2046 = 72575 kg and 70 mph = (70)(88/60) = 102.667 ft/

sec or (0.3048)(102.667) = 31.293 m/sec That makes the kinetic energy

(72575)(31.293)^2 =71069 kJ, not 39779 kJ.

The quantity Casey is figuring is an energy not a force, because the

relationship he's using is the definition of kinetic energy.

But the actual bottom line is that running a truck into an embedded

timber post, will snap the post and not do much to slow the truck,

except if the truck jackknifes and rolls after the impact. If you've

ever seen a collision of a truck and a telephone pole, it's pretty

clear.

Christopher Wright P.E. |"They couldn't hit an elephant at

chrisw@skypoint.com | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania

1864)

http://www.skypoint.com/~chrisw/

******* ****** ******* ******** ******* ******* ******* ***

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(HSS Sections imported from China) porches in seismic areas

Talking about HSS sections, there are problems related to the HSS tube sections manufactured in China. This issue pertains to the defective HSS Seam Welds due to lack of fusion, cracks and splits.
You may look at DSA Bulletin 07-03 on and photographs on DSA web site:
http://www.documents.dgs.ca.gov/dsa/bulletins/BU_07-03_UPDATE2_3-7-08.pdf
There are also Visual Guides on http://www.dsa.dgs.ca.gov/Labs/hss_pictures.htm identifying the problems.

Regards
Casey K. Hemmatyar, SE

_________________________________________________________________________________________________________________
Chris,
May want to look at the plate forces a bit closer. I may not have looked close enough at the forces at the plates which may be larger due to the moment from the column moment. I was winging it without sketches. I'll look at it a bit more this evening also.
Joe

-----Original Message-----
From: chris.slater@gmail.com [mailto:chris.slater@gmail.com] On Behalf Of Chris Slater
Sent: Thursday, May 15, 2008 4:48 PM
To: seaint@seaint.org
Subject: Re: porches in seismic areas

That makes sense. One more option to put in the holster.

Thanks!

On Thu, May 15, 2008 at 4:35 PM, Joseph R. Grill <jrgrill@cableone.net>
wrote:
> Yes, I was thinking lighter loads. Also, only "similar" to a Simpson base.
> If the side plates are taller, say 12", then the bolts could have a 9"
> spacing. A 5/8" bolt in a 6x6 DF would give you 1420x1.6=2272 lbs per
bolt.
> At 9" couple that would give a 1704 ft-lb moment resistance. At 7'
> you could restrain a 240# lateral load. That would be for the bolts
> only. At
90
> degrees that same 240 lbs applied at the top (I'm being kind of
> general
> here) of two 3" wide plates produces a moment at the bottom of the
> plates
of
> 1440 in-lbs (if I'm correct). Looks like 2-3/8" plates might work at
> the
90
> degree situation. Depends on how big the porch and how many posts
resisting
> the seismic or wind. If deflections at the top of the post are
> agreeable,
if
> may be work.
> Joe
>
> -----Original Message-----
> From: chris.slater@gmail.com [mailto:chris.slater@gmail.com] On Behalf
> Of Chris Slater
> Sent: Thursday, May 15, 2008 4:00 PM
> To: seaint@seaint.org
> Subject: Re: porches in seismic areas
>
> I think the loads would have to be incredibly light.
>
> Given a 7' column, with only 500# of lateral load, you get 3500 #-ft.
> That's resisted by the couple in the bolts, at 3" apart. So each bolt
> winds up needing to be able to resist 14 kips. Pretty sure NDS values
> for through bolts in double shear are at the most in the 4 kip range.
> Maybe less...
>
> Am I missing something?
>
> On Thu, May 15, 2008 at 3:14 PM, Joseph R. Grill
> <jrgrill@cableone.net>
> wrote:
>> Another option? But, probably for lighter laterally loaded columns.
> Using
>> a column base, shaped similarly to a Simpson CB or LCB but heavier
>> plates and bolts. For loads in one direction the side plates resist
>> the column base moment by bending. For loads in the perpendicular
>> direction the
> bolts
>> resist the column base moment in bolt values perpendicular to grain.
>> Any thoughts?
>>
>> Joe Grill
>>
>>
>>
>> From: Jnapd@aol.com [mailto:Jnapd@aol.com]
>> Sent: Wednesday, May 14, 2008 12:43 PM
>> To: seaint@seaint.org
>> Subject: Re: porches in seismic areas
>>
>>
>>
>> Andrew
>>
>>
>>
>> You are correct steel tubes are not that expensive and I use them all
>> the time. Contractors and home owners freak out when you mention
>> steel. They don't understand where to buy, how to use and therefore
>> it must cost way
> to
>> much is the normal response.
>>
>>
>>
>> I tell clients all the time you can use the City or County spec for
>> knee braced patio supports; but if you go beyond the size they
>> recommend I
will
>> not sign or approve any knee-braced wood post..no exceptions.
>>
>>
>>
>> Dennis and I do most of our work within 0-15 km of the San Andreas Fault.
>> Our area has been expecting a 6.5 - 7.5 Quake for the last 20 years.
>> Landers and Big Bear quakes were not on the main fault branch.
>>
>>
>>
>> What I do when requested is install a 6x6 post inside a HSS6x6x.25
column.
>> The tube extends 2-3 ft above ground with the post embedded 12' into
steel
>> tube. Clients put stone or brick around the tube so you see just the
wood.
>> The height of the wood depends on how many post are available.
>>
>>
>>
>> I always consider a trellis roof as a solid roof..because within 5
>> years
> it
>> usually is.
>>
>>
>>
>> I sleep quite well at night.
>>
>>
>>
>> Joe Venuti
>> Johnson & Nielsen Associates
>> Palm Springs, CA
>>
>> ________________________________
>>
>> Wondering what's for Dinner Tonight? Get new twists on family
>> favorites
at
>> AOL Food.
>
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Re: Was embedded timber post (80 Tons trailer impact on Structure)

On May 23, 2008, at 12:41 PM, Casey K. Hemmatyar wrote:

> Just to refresh your memory, it has a 28,340 k-ft of Force but not
> Energy.
Not to nag, but you're both wrong.

David figured the energy correctly but misinterpreted the work as a
moment. If you're looking at the and came up with the average force
that would decelerate the truck in 30 inches. If you ran the truck
into a post the post would have to deform 30 inches under the
influence of that force--actually the total of the deformation of the
post and the deformation of the truck would be 30 inches. What would
actually happen is that the initial force would be much greater than
the average; the post would snap off and the truck would be damaged
but probably keep moving.

Casey also calculated the energy, only in metric units and then put
it equal to a force, which it isn't. I'm not sure how the calculation
got carried out, but the mass in kg of an object that weighs 80 tons
= (80)(2000)/2.2046 = 72575 kg and 70 mph = (70)(88/60) = 102.667 ft/
sec or (0.3048)(102.667) = 31.293 m/sec That makes the kinetic energy
(72575)(31.293)^2 =71069 kJ, not 39779 kJ.

The quantity Casey is figuring is an energy not a force, because the
relationship he's using is the definition of kinetic energy.

But the actual bottom line is that running a truck into an embedded
timber post, will snap the post and not do much to slow the truck,
except if the truck jackknifes and rolls after the impact. If you've
ever seen a collision of a truck and a telephone pole, it's pretty
clear.

******* ****** ****** ****** ******* ****** ****** ********

RE: Was embedded timber post (80 Tons trailer impact on Structure)

If both the missile and the target behave in a linear fashion, the problem is relatively easy. But when it comes to vehicular impact barriers, the math is incredibly complex. The forcing function creating the demand is nonlinear because the vehicle is a deformable body and the the barrier itself and in the soil create a nonlinear response. The Department of State has performed a lot of studies and has developed a rating system predicated on testing. Barriers are rated with a ranking predicated by K. They vary the velocity at impact.

The old 10k at 18" came from the old BOCA code for parking garage barriers. It was adopted in the UBC after a tragic accident in a California parking garage in the early 1990's. It is not a definitive requirement regarding vehicular impact, and it does not accurately capture the real response. It is better than nothing.

Regards,
Harold Sprague

Date: Fri, 23 May 2008 11:12:36 -0700
From: d.topete73@gmail.com
To: seaint@seaint.org
Subject: Re: Was embedded timber post (80 Tons trailer impact on Structure)

Oh yeah, I forgot the other 3 zeros... i had seen Joe's post about the embedded posts at K-rails to resist the 10kip force at 30" above road surface. Thank you for checking my "fuzzy math."

On Fri, May 23, 2008 at 10:41 AM, Casey K. Hemmatyar <khemmatyar@gmail.com> wrote:

Great David;

Just to refresh your memory, it has a 28,340 k-ft of Force but not Energy.
Applying Work-Kinetic Energy Theorem:
W_net = K_f – K_i= ½*mv^2
W [Work]= ½*mv^2
m=mass; kg
v= Speed; meter/sec
W=(½) (80*1016)*(70*1.609*1000/3600)^2=39,779,275 Joules (This is "Work")

1 Joule≈0.73756 ft-lb
F [Force]=39,779,275*0.73756/1000=29,340 ft-k

Regards
Casey K. Hemmatyar, SE
___________________________________________________________
From: David Topete [mailto:d.topete73@gmail.com]
Sent: Friday, May 23, 2008 8:59 AM
To: SEAINT
Subject: Was embedded timber post

http://news.enquirer.com/apps/pbcs.dll/article?AID=/20080521/NEWS01/805210387

If my calcs are correct, an 80-ton trailer at 70 mph creates 26,200 ft-kips of energy. (F = 1/2 mv^2 if my math serves me correctly... ) That is about 10k at 30". Or am i way off?

--
David Topete, SE

--
David Topete, SE

Give to a good cause with every e-mail. Join the i'm Initiative from Microsoft.

RE: Was embedded timber post (80 Tons trailer impact on Structure)

This sounds like designing fenders for ships. The ship has velocity energy which is converted into elastic energy in the fender.

Bob Garner

From: Casey K. Hemmatyar [mailto:khemmatyar@gmail.com]
Sent: Friday, May 23, 2008 11:27 AM
To: seaint@seaint.org
Subject: RE: Was embedded timber post (80 Tons trailer impact on Structure)

Bill:

You're right the ft*kips is an Energy unit. However the unit I've indicated is ft-kips (not ft*kips) and it is Force unit.

Regards
Casey K. Hemmatyar, SE

-----Original Message-----
From: William Haynes [mailto:gtg740p@gmail.com]
Sent: Friday, May 23, 2008 11:07 AM
To: seaint@seaint.org
Subject: Re: Was embedded timber post (80 Tons trailer impact on Structure)

Energy or work has units of ft*kips, not force. The force required to
stop a vehicle also depends on the internal response of the vehicle
during the impact.

On Fri, May 23, 2008 at 1:41 PM, Casey K. Hemmatyar
<khemmatyar@gmail.com> wrote:
> Great David;
>
> Just to refresh your memory, it has a 28,340 k-ft of Force but not Energy.
>
> Applying Work-Kinetic Energy Theorem:
>
> Wnet = Kf – Ki= ½*mv^2
>
> W [Work]= ½*mv^2
>
> m=mass; kg
>
> v= Speed; meter/sec
>
> W=(½) (80*1016)*(70*1.609*1000/3600)^2=39,779,275 Joules (This is "Work")
>
>
>
> 1 Joule≈0.73756 ft-lb
>
> F [Force]=39,779,275*0.73756/1000=29,340 ft-k
>
>
>
> Regards
>
> Casey K. Hemmatyar, SE
>
> ___________________________________________________________
>
> From: David Topete [mailto:d.topete73@gmail.com]
> Sent: Friday, May 23, 2008 8:59 AM
> To: SEAINT
> Subject: Was embedded timber post
>
>
>
> http://news.enquirer.com/apps/pbcs.dll/article?AID=/20080521/NEWS01/805210387
>
>
>
> If my calcs are correct, an 80-ton trailer at 70 mph creates 26,200 ft-kips
> of energy. (F = 1/2 mv^2 if my math serves me correctly... ) That is about
> 10k at 30". Or am i way off?
>
> --
> David Topete, SE

Re: Concrete Assessment after Fire

Chris,

According to Composition and Properties of Concrete (MGH 1968), concrete samples subjected to temperature "T" and crushed after cooling had the following compressive strength (relatively to that at 70F): 85% at T=200F, 70% at T=450F, 50% at T=700F.

Although technically unreinforced, SOGs may be subjected to considerable forces under the normal use conditions. Besides, due to the concrete strength loss, the new post-installed anchors will not have the specified strength. This means that the residual loss of strength due to the fire strongly justifies the post-fire replacement of at least the portions of SOG exposed to the fire.

In my experience, the insurance companies did not have any problems covering such losses.

V. Steve Gordin, SE
Irvine CA

----- Original Message -----

From: Chris Slater

To: seaint@seaint.org

Sent: Friday, May 23, 2008 09:58

Subject: Concrete Assessment after Fire

I'm working with a client whose home recently caught fire. A good
part of the structure is still intact, though badly burned. There's a
stairway in the home that is built of tube steel with concrete treads.
The fire got so hot that the weight of the treads caused the tube
steel to bend down significantly.

The client is discussing the way forward with his insurance company
and one question he has is about the integrity of the existing slab
foundation. The house was built in the 60's, so it's unclear what
sort of reinforcement is in the slab. From the top, there's no visual
clues as to the condition. It's black in places, but seems intact.

So here's my questions:

- Are there some good resources out there where I can learn about
concrete performance after a fire?
- Does anyone know of a company in Northern California (the home is in
Davis) that can do post-fire concrete assessment?

Thanks in advance,

Chris

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
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*   Questions to seaint-ad@seaint.org. Remember, any email you
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*   without your permission. Make sure you visit our web
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RE: Was embedded timber post (80 Tons trailer impact on Structure)

Bill:

You're right the ft*kips is an Energy unit. However the unit I've indicated is ft-kips (not ft*kips) and it is Force unit.

Regards
Casey K. Hemmatyar, SE

Energy or work has units of ft*kips, not force. The force required to
stop a vehicle also depends on the internal response of the vehicle
during the impact.

RE: Hold downs with "Perforated Shear Wall Method" and "Force Transfer Method"

That 10 psf minimum pressure for MWFRS would NOT apply to uplift as that
section is written. As that section is written the 10 psf is a pure
horizontal force put on the vertical projection/outline of the structure.

If you want to talk the specific wind pressures, then we can open up that
can of worms again. I would argue that in the case that I described (check
of overtuning and net uplift of a shearwall) the MWFRS pressures would be
used to get the overturning force, but C&C pressures would be used for the
net uplift. This is because the overturning portion is being used to
overall lateral support the entire structure and the entire structure gets
MWFRS, but the net uplift is purely due to a tributary uplift area of the
shearwall, which is NOT wind on the whole structure.

As to number of holddowns, you SHOULD in general get more holddowns in a
traditional segmented or discrete shearwall system than if you do a
perferated shearwall. The idea behind a perferated shear wall is that the
WHOLE wall length is the shearwall and thus only needs holddowns at the
ends...and there is enough "stuff" above and below any opennings to
sufficiently engage the whole wall as one large shearwall, even if it does
have holes. OTOH, a segmented/discrete will have several shearwalls along
the length of the overall wall section...and each shearwall will have to
have holddowns to resist overturning. And if those discrete/segmented
shearwalls are tall, skinny walls, then they will likely have beefier
holddowns than if you have some nice short, squat walls (moment
arms...moment arms).

Regards,

Scott
Adrian, MI

-----Original Message-----
From: Joseph R. Grill [mailto:jrgrill@cableone.net]
Sent: Friday, May 23, 2008 10:55 AM
To: seaint@seaint.org
Subject: RE: Hold downs with "Perforated Shear Wall Method" and "Force
Transfer Method"

I'm going to confuse the issue some more. O.K. in using the net uplift in
overturning calculations that means the roof uplift forces are loading the
MWFRS. ASCE 7-05 (6.1.4.1) uses a 10psf minimum on the vertical plane. What
about the horizontal plane for uplift? I don't see a minimum required for
that. For the uplift can you just use the vertical component of the outward
forces on the roof from 7-05. Or is there a minimum that I am not seeing?

I guess the reasons for these questions is I have a small box addition. I am
getting a lot of hold downs using the traditional segmented design. I am
going to get some real comments from the number of hold downs for this small
structure. Therefore, I started looking at the other two methods to cut
down on the number of hold downs. But as things go sometimes, there are
more questions that come up.

Joe

-----Original Message-----
From: Scott Maxwell [mailto:smaxwell@umich.edu]
Sent: Friday, May 23, 2008 7:01 AM
To: seaint@seaint.org
Subject: RE: Hold downs with "Perforated Shear Wall Method" and "Force
Transfer Method"

I think I understand the intent of what you are saying, but wording does
bother me.

With wind or seismic in one direction so that the shearwall is not loaded,
but there is overall uplift on that wall, there would be no possible
"double-dipping" as the wall would not be subjected to overturning (assuming
a simple diaphragm, thus no torsional effects).

With the wind or seismic in the other direction, the wall (if a shearwall)
should be exposed to both overturning and potentially net uplift (due to
wind uplift or the vertical component of a seismic force...overall, more
logical to think about it in terms of net wind uplift) AT THE SAME TIME.
Thus, the same dead load should be resisting both the uplift AND the
overturning. In other words, your FBD of the shearwall will have the wind
overturning force, the net uplift, and the 60% of the dead load that would
work to resist both...all as loads applied to the shearwall. I don't
consider that "double-dipping". I agree that if, for some reason, you check
the wall seperately for uplift and for overturning, then the same dead load
should not be used in both check...but I would think you should be checking
both uplift and overturning in the same check.

Am I missing something?

Regards,

Scott
Adrian, MI

-----Original Message-----
From: Showalter, Buddy [mailto:Buddy_Showalter@afandpa.org] On Behalf Of AWC
Info
Sent: Friday, May 23, 2008 9:47 AM
To: seaint@seaint.org
Subject: Re: Hold downs with "Perforated Shear Wall Method" and "Force
Transfer Method"

One caveat however, the WFCM does not use dead load to offset uplift and use
the same dead load again to offset overturning (double-dipping). So in the
WFCM tables, we only show dead load offsetting uplift loads.

******* ****** ****** ****** ******* ****** ****** ********

RE: Concrete Assessment after Fire

There are resources for fire damaged concrete, but I can't recall any on a slab on grade foundation. A slab on grade foundation is generally considered as unreinforced concrete.

I would power wash the concrete. Do a chain drag to detect delaminations and spalling. Look at the color. The first color change that indicates a measure of degradation is pink. You can do local spot repairs for small delaminations and spalling. You can epoxy inject any cracking.

You might also want to check for flatness using a straight edge and the ACI 117 as a bench mark for acceptance.

Regards,
Harold Sprague

> Date: Fri, 23 May 2008 09:58:05 -0700
> From: chris@jdwylieengineering.com
> To: seaint@seaint.org
> Subject: Concrete Assessment after Fire
>
> I'm working with a client whose home recently caught fire. A good
> part of the structure is still intact, though badly burned. There's a
> stairway in the home that is built of tube steel with concrete treads.
> The fire got so hot that the weight of the treads caused the tube
> steel to bend down significantly.
>
> The client is discussing the way forward with his insurance company
> and one question he has is about the integrity of the existing slab
> foundation. The house was built in the 60's, so it's unclear what
> sort of reinforcement is in the slab. From the top, there's no visual
> clues as to the condition. It's black in places, but seems intact.
>
> So here's my questions:
>
> - Are there some good resources out there where I can learn about
> concrete performance after a fire?
> - Does anyone know of a company in Northern California (the home is in
> Davis) that can do post-fire concrete assessment?
>
> Thanks in advance,
>
> Chris
>
> ******* ****** ******* ******** ******* ******* ******* ***
> * Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> * This email was sent to you via Structural Engineers
> * Association of Southern California (SEAOSC) server. To
> * subscribe (no fee) or UnSubscribe, please go to:
> *
> * http://www.seaint.org/sealist1.asp
> *
> * Questions to seaint-ad@seaint.org. Remember, any email you
> * send to the list is public domain and may be re-posted
> * without your permission. Make sure you visit our web
> * site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********

E-mail for the greater good. Join the i'm Initiative from Microsoft.

Re: Was embedded timber post (80 Tons trailer impact on Structure)

Oh yeah, I forgot the other 3 zeros... i had seen Joe's post about the embedded posts at K-rails to resist the 10kip force at 30" above road surface. Thank you for checking my "fuzzy math."

On Fri, May 23, 2008 at 10:41 AM, Casey K. Hemmatyar <khemmatyar@gmail.com> wrote:

Great David;

Just to refresh your memory, it has a 28,340 k-ft of Force but not Energy.

Applying Work-Kinetic Energy Theorem:

W_net = K_f – K_i= ½*mv^2

W [Work]= ½*mv^2

m=mass; kg

v= Speed; meter/sec

W=(½) (80*1016)*(70*1.609*1000/3600)^2=39,779,275 Joules (This is "Work")

1 Joule≈0.73756 ft-lb

F [Force]=39,779,275*0.73756/1000=29,340 ft-k

Regards

Casey K. Hemmatyar, SE

___________________________________________________________

From: David Topete [mailto:d.topete73@gmail.com]
Sent: Friday, May 23, 2008 8:59 AM
To: SEAINT
Subject: Was embedded timber post

http://news.enquirer.com/apps/pbcs.dll/article?AID=/20080521/NEWS01/805210387

If my calcs are correct, an 80-ton trailer at 70 mph creates 26,200 ft-kips of energy. (F = 1/2 mv^2 if my math serves me correctly... ) That is about 10k at 30". Or am i way off?

--
David Topete, SE

--
David Topete, SE

RE: Was embedded timber post (80 Tons trailer impact on Structure)

Great David;

Just to refresh your memory, it has a 28,340 k-ft of Force but not Energy.

Applying Work-Kinetic Energy Theorem:

W_net = K_f – K_i= ½*mv^2

W [Work]= ½*mv^2

m=mass; kg

v= Speed; meter/sec

W=(½) (80*1016)*(70*1.609*1000/3600)^2=39,779,275 Joules (This is "Work")

1 Joule≈0.73756 ft-lb

F [Force]=39,779,275*0.73756/1000=29,340 ft-k

Regards

Casey K. Hemmatyar, SE

___________________________________________________________

From: David Topete [mailto:d.topete73@gmail.com]
Sent: Friday, May 23, 2008 8:59 AM
To: SEAINT
Subject: Was embedded timber post

http://news.enquirer.com/apps/pbcs.dll/article?AID=/20080521/NEWS01/805210387

If my calcs are correct, an 80-ton trailer at 70 mph creates 26,200 ft-kips of energy. (F = 1/2 mv^2 if my math serves me correctly... ) That is about 10k at 30". Or am i way off?

--
David Topete, SE

Concrete Assessment after Fire

I'm working with a client whose home recently caught fire. A good
part of the structure is still intact, though badly burned. There's a
stairway in the home that is built of tube steel with concrete treads.
The fire got so hot that the weight of the treads caused the tube
steel to bend down significantly.

The client is discussing the way forward with his insurance company
and one question he has is about the integrity of the existing slab
foundation. The house was built in the 60's, so it's unclear what
sort of reinforcement is in the slab. From the top, there's no visual
clues as to the condition. It's black in places, but seems intact.

So here's my questions:

- Are there some good resources out there where I can learn about
concrete performance after a fire?
- Does anyone know of a company in Northern California (the home is in
Davis) that can do post-fire concrete assessment?

Thanks in advance,

Chris

******* ****** ****** ****** ******* ****** ****** ********

RE: Hold downs with "Perforated Shear Wall Method" and "Force Transfer Method"

Joe Grill wrote:

"I am getting a lot of hold downs using the traditional segmented
design. I am
going to get some real comments from the number of hold downs for this
small
structure. Therefore, I started looking at the other two methods to cut
down on the number of hold downs."

I use the force transfer method most of the time, and detail openings
that do not have enough plywood around the opening to transfer the load
with CS16 strapping over the plywood at header and sill, 3' onto the
hdr/sill & 3' blocked back into the diaphragm. Once you know that the
header won't pop off the trimmers you can expect the wall to behave as a
longer unit including the opening. But...you have to know that the load
can really be transferred at the boundary of each pier. If there's too
much, you need to anchor it.

Look at the uplift or OT at the end of the pier (including -60% of the
DL (max)), and subtract your plywood capacity from Table 2306.1 (180plf
if unblocked, run vertically--you can increase this based on your
specified blocking/nailing/ply direction, but I always use Case 2, 8d
@6,12, 7/16" ply, 2x framing members for this analysis b/c it's the
worst case, and quite often what I end up seeing in the field) x length
of shearwall above & below the opening. What's left is what you have to
hold down, but quite often this quick analysis will obviate the need for
holdowns at many piers.

regards,
Gordon