Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Performance specifications

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Dennis,

Jay Shilstone, and Jim Shilstone before him are highly respected in the
concrete mix design community.  

Maybe you did not pick up on it, but we were discussing CONCRETE performance
specs only.  In other words, if it is only strength that is of concern,
specify the f'c, don't specify the cement.  If you are concerned about
freeze thaw, specify the cycles, not the air entrainment.  If you are
concerned about abrasion, specify the abrasion requirements, not require
trap rock.  There are many solutions to each of these performance goals.

The vast majority of engineers do not know what goes into concrete mix
design requirements.  It varies markedly regionally, and varies from
supplier to supplier.  Most engineers do not even know how to determine the
proper standard deviation, and yet they approve concrete mix designs.

Regards,
Harold O. Sprague


> -----Original Message-----
> From:	Dennis Wish [SMTP:dennis.wish(--nospam--at)verizon.net]
> Sent:	Wednesday, June 25, 2003 7:37 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	RE: Performance specifications
> 
> Harold,
> I am vehemently against attempting to define a performance standard for
> a building in any high risk zone. The first discussion of performance
> standards that I was aware of was in the 1991 SEAOC Blue Book in which
> they discussed performance design ideas in their "Vision 2000". I don't
> believe the original concept is feasible as it suggests promises of
> performance that can easily be wiped out by some new component in
> seismic design that is not currently incorporated in our design. Come to
> think about it, wasn't the impact on the cost of damage during the
> Northridge Earthquake due to information we did not have prior to the
> event. 
> Whenever you work within methodologies based upon Empirical information,
> the resulting damage is used to tweak out the next method proposed in a
> future code or by emergency ordinances.
> 
> Now if the idea of performance is limited to materials which are
> normally designed by Working Stress Design or by Ultimate Strength
> methods, then this is different, but would eliminate wood framed
> low-rise structures. We've designed using WSD and USD for a long time
> and our codes are tweaked out for these practices
> 
> What I am so strongly against is making promises to the public as to a
> level of performance that may change with every code cycle - i.e.; "If
> your building was design between 2000 and 2003 then the level of damage
> is within performable limits, however if was designed after 2003, then
> the level of performance should be better." Boy can you imagine the
> opportunities for expert witness work and the legal profession. I think
> I should get out of this business and open my Hot Dog Stand before
> performance based design becomes a reality.
> 
> Sincerely,
> Dennis S. Wish, PE
> California Professional Engineer
> Structural Engineering Consultant
> http://www.structuralist.net
> dennis.wish(--nospam--at)verizon.net
> 
> 
> -----Original Message-----
> From: Sprague, Harold O. [mailto:SpragueHO(--nospam--at)bv.com] 
> Sent: Wednesday, June 25, 2003 9:57 AM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: RE: Performance specifications
> 
> 
> Jay,
> 
> It has been a while, but Jim Shilstone and I had many discussions on
> this topic.  Now to your specific questions:
> 
> 	1) Is there an "official" ASCE or SEA position on performance 
> 	specifications? If so, where can I find it?  
> 	I am not aware of any position.
> 
> 	2) What characteristics would engineers need to specify to be
> assured of 
> 	getting the performance they need?
> 	Some characteristics that immediately come to mind are: strength
> (compression, and modulus of rupture) at various ages (7, 14, 28, 90
> days), density at 7 days 28 days and at equilibrium, modulus of
> elasticity, durability (freeze / thaw, abrasion, etc.), shrinkage
> (plastic and drying), workability (your father's specialty), sulfate
> resistance, chloride resistance, other chemical resistance, heat / fire
> resistance, set times, set characteristics, bleed water characteristics,
> ability to consolidate for the given reinforcing and placing methods,
> pumpability, heat of hydration, finishability for flatwork (can it be
> steel troweled, magnesium troweled, or flat finished at all), can it be
> placed underwater, rebar corrosion characteristics (like for silica
> fume, or DCI), cure time and methods, acceptance criteria for all
> aspects of testing, resolution criteria for strength / cylinder tests
> (how are the cylinders stored in the field), are cubes or cylinders to
> be used for strength confirmation. 
> 
> 	3) Would you, as a professional, be willing to pass off to the
> producers 
> 	the right to set and adjust proportions as needed?  
> 	Yes, as long as there were clear ASTM definitive tests to
> corroborate performance.
> 
> 	4) What could the producers do to eliminate the need for them to
> submit 
> 	mixture proportions?
> 	Conform to the specs.  There is a very spotty regional history
> of compliance to the specifications as they currently exist.
> 
> 	5) Are design engineers (who often receive little formal
> training on
> 
> 	materials and operations) qualified to specify non-performance
> related 
> 	criteria? (Don't shoot me, I'm just asking.)
> 	Not generally.  Most engineers do not understand even the basic
> acceptance criteria for mix design confirmation cylinders vs. evaluation
> and acceptance criteria.
> 
> 	6) Do design engineers really know what characteristics they
> need in concrete?
> 	Not generally.  They just know they get chewed out when the
> wheels fall off.
> 
> 	7) Any other backlash, rant or intelligent discourse you have to
> offer.
> 	Get the Bureau of Reclamation and others to offer training to
> engineers, suppliers (ready mix, admixtures, aggregate, pumpers, and
> finishers).  
> 
> 
> Regards,
> Harold O. Sprague
> 
> 
> > -----Original Message-----
> > From:	Jay Shilstone [SMTP:j.s(--nospam--at)shilstone.com]
> > Sent:	Wednesday, June 25, 2003 10:53 AM
> > To:	seaint(--nospam--at)seaint.org
> > Subject:	Performance specifications
> > 
> > I am on a committee for the National Ready Mixed Concrete Association
> > (disclaimer - I am not employed by them and none of this reflects
> their 
> > official positions) dealing with how to get performance specifications
> for
> > 
> > ready mixed concrete into the Building Code. I know lots of people and
> > groups are exploring performance specs and I thought this group might
> > point 
> > me into the right direction for an official engineering point of view
> on 
> > performance specs for concrete.
> > 
> > In a nutshell, the intent of our subcommittee is to get designers to 
> > stop
> > specifying prescriptive characteristics of concrete, such as minimum
> > cement 
> > content, maximum water/cement ratio, maximum fly ash ratios, etc. and
> get 
> > them to specify performance criteria such as minimum strength,
> abrasion 
> > resistance, freeze-thaw cycles, maximum shrinkage, permeability, etc.
> > 
> > Members of the committee would also like to get away from having to 
> > submit
> > 
> > mixture proportions, since many of the larger companies have spent a 
> > lot of money on QC and research (especially for self-consolidating 
> > concrete) and consider their proportions to be proprietary. There is a
> 
> > precedent for this. Materials Service, during the heyday of high 
> > strength concrete in Chicago, would not provide mixture proportions 
> > with submittals.
> > 
> > Here are my questions:
> > 
> > 1) Is there an "official" ASCE or SEA position on performance
> > specifications? If so, where can I find it?
> > 
> > 2) What characteristics would engineers need to specify to be assured 
> > of
> > getting the performance they need?
> > 
> > 3) Would you, as a professional, be willing to pass off to the 
> > producers
> > the right to set and adjust proportions as needed?
> > 
> > 4) What could the producers do to eliminate the need for them to 
> > submit
> > mixture proportions?
> > 
> > 5) Are design engineers (who often receive little formal training on
> > materials and operations) qualified to specify non-performance related
> 
> > criteria? (Don't shoot me, I'm just asking.)
> > 
> > 6) Do design engineers really know what characteristics they need in 
> > concrete?
> > 
> > 7) Any other backlash, rant or intelligent discourse you have to 
> > offer.
> > 
> > I thank you for your attention.
> > 
> > Jay Shilstone
> > 
> > 
> > 
> > 
> > ******* ****** ******* ******** ******* ******* ******* ***
> > *   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(--nospam--at)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 
> > ******* ****** ****** ****** ******* ****** ****** ********
> 
> ******* ****** ******* ******** ******* ******* ******* ***
> *   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(--nospam--at)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 
> ******* ****** ****** ****** ******* ****** ****** ******** 
> 
> 
> ******* ****** ******* ******** ******* ******* ******* ***
> *   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(--nospam--at)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 
> ******* ****** ****** ****** ******* ****** ****** ******** 

******* ****** ******* ******** ******* ******* ******* ***
*   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(--nospam--at)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 
******* ****** ****** ****** ******* ****** ****** ********