you may have been specifying 1.5" of precamber on beam forms "for years" BUT
i doubt that the formwork contractor or GC has been doing it. do you check
forms prior to concrete placement?
my experience of similar spans with similar formwork systems has been that
no precamber (or a nominal only, like 0.5") is used UNLESS the spans are RC.
for 60' beams spans i presume they are PT and with "normal" levels of PT in
the beams the deflections should be "under control".
Mark Geoghegan BE (Hons.-Structural)
S T R U C T U R A L T E C H
AUSTRALIA - GUAM - HAWAII
>From: Nicholas Blackburn <nblackburn(--nospam--at)fdgoak.com>
>To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
>Subject: Beam Camber
>We frequently design long-span, one-way slab parking structures and
>a minimum camber of 1.5" for the beam formwork. The beams are typically on
>the order of 60' long. We have a current project where the formwork
>supplier is objecting to the camber, noting that 1/2" or so is common and
>can be achieved by simply jacking the forms. We have been using 1.5" for
>years and this is the first comment of this nature. Does anyone have other
>experiences/insight as to reasonable camber. The forms are standard steel
>cunningham-type beam forms, 14" wide at the bottom w/ 1:30 side draft and a
>total depth from bottom of beam to top of slab of 35".
>Nicholas Blackburn, PE
* This email was sent to you via Structural Engineers
* Association of Southern California (SEAOSC) server. To
* subscribe (no fee) or UnSubscribe, please go to:
* 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