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RE: ASCE 07

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Richard,
 
I presume that the inquiry is more or less rhetorical.  But to address the concerns:
 
1. How many of the changes are due to actual failures in the field of structures properly designed by previous editions?
Code changes are predicated on the evolution of the engineering practice and lessons learned.  The lessons can be theoretical in that we develop loads with a probability of incipient failure of the structure or structural element for a given loading and expected performance.  As professionals, we would be extremely remiss and criminal to wait for a failure if we know that there is a problem with the methodology however that knowledge is acquired. 
 
We can and do extrapolate from failures.  The soft story provisions were derived from structures like Olive View Hospital.  Engineers noted cracking with the steel moment connections following the Northridge earthquake.  The connections were studied and determined to be a systematic problem.  The code was changed accordingly.  There are many examples. 
 
2. How many of the changes are due to mistakes in previous editions?
Some code changes are corrections of mistakes in the code, mistakes in interpretation, and mistakes in implementation. 
 
3. How many of the changes are based on the results of computer generated model failures that have never been experienced in actuality?
As with the "How many of the changes..."; it is impossible to quantify.  But if we can predict failures, we should do so.  I am not sure if you are questioning the fidelity of computer modeling in this inquiry.  But that is why we have large capacity shake tables, wind tunnels, static testing, etc.  We use testing to assure the fidelity of computer models.  When doing any computer modeling, fidelity using testing is key. 
 

Regards, Harold Sprague
 
> From: RLHess(--nospam--at)HessEng.com
> To: seaint(--nospam--at)seaint.org
> Subject: RE: ASCE 07
> Date: Thu, 7 Jul 2011 11:26:16 -0700
>
> Questions:
>
> 1. How many of the changes are due to actual failures in the field of
> structures properly designed by previous editions?
>
> 2. How many of the changes are due to mistakes in previous editions?
>
> 3. How many of the changes are based on the results of computer generated
> model failures that have never been experienced in actuality?
>
> Richard Hess, S.E.
> Member, SEAOC Code Committee
>
> -----Original Message-----
> From: Bill Polhemus [mailto:bill(--nospam--at)polhemus.cc]
> Sent: Thursday, July 07, 2011 7:42 AM
> To: <seaint(--nospam--at)seaint.org>
> Subject: Re: ASCE 07
>
> ASCE 7-10 is the very, very most recent edition. Be aware it is chock-full
> of major changes. (Also be aware that it will not be referenced until IBC
> 2012. IBC 2009 references ASCE 7-05).
>
> William L. Polhemus, Jr. P.E.
> Via iPhone 4
>
> On Jul 7, 2011, at 9:25 AM, "Gary L. Hodgson and Assoc."
> <design(--nospam--at)hodgsoneng.ca> wrote:
>
> > Folks,
> >
> > Is ASCE 07 the latest standard for "Design Loads for Buildings and Other
> Structures"?
> >
> > Gary
> >
> >
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