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RE: wood deck/pedestrian bridge

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Andrew,

I am not familiar with the FBC but the 1997 Edition of the Uniform Building
Code lists pedestrian bridges in Table 16-A, Item 20, as 100 psf.

A structure as defined in the UBC can be almost anything.  It doesn't
necessarily have to be a building.

Jim Persing

> -----Original Message-----
> From: Andrew D. Kester [mailto:andrew(--nospam--at)baeonline.com]
> Sent: Wednesday, March 26, 2003 5:12 AM
> To: seaint(--nospam--at)seaint.org
> Subject: wood deck/pedestrian bridge
>
>
>
> We are designing three small pedestrian bridges/ boardwalk
> structures for a
> local park, going over small canals. In the past I have used the local
> building code provisions for the uniform live load for
> smaller boardwalk
> structures, as well as some engineering judgement for point loads and
> deflections. Local building code rules regarding handrail
> design were also
> used. The designs came out fine and no construction or user
> complaints from
> a serviceability standpoint (deflection/vibration/ bounciness).
>
> However, on this project, I am rethinking my design loads
> after rereading
> the local building code, as well as the larger scale of these
> bridges. From
> the FBC, Chpt 16, the actual occupancy for use:
>
> Balcony and decks (exterior) same as occupancy, but not less
> then 60 psf
> On one and two family dwellings 40psf
>
> Well, boardwalks and pedestrian bridges, etc., in a park are
> not attached to
> a structure, these are nowhere near another structure. It seems like a
> pedestrian bridge is outside of the intent of the building
> code load, given
> for decks attached to structures or next to buildings. I
> suppose using 60
> psf would be ok and reasonable, as the decks are 6ft wide.
> This means a 2ft
> strip would accomodate about 4 people weighing 180lbs (not
> that likely). But
> it could accomodate a class field trip, a party, who knows,
> so I feel better
> using AASHTO guidelines for pedestrian bridges, for uniform
> live load=85psf,
> and also for deflection > l/500. Since the local building
> code does not
> really address this stuff, I think it it logical to cross compare with
> another source. I doubt I will have to justify my design to a
> permitting
> agency in detail, but I would like to use some nationally recongized
> criteria.  Also, I was going to use handrail design, as well
> as sway/lateral
> loading of the bridge, from the building code because they
> seem applicable
> to this type of structure. This will govern over wind design
> because there
> is not much for a lateral surface for wind.
>
> Is their a problem mixing the two codes, using the building code for
> handrail design, and sway design, and AASHTO for uniform live load and
> deflection AASHTO? If anyone has the AASHTO handrail, and
> sway/lateral loads
> handy for pedestrian bridges, or where I can download that
> info, that would
> be appreciated.
>
>
> TIA
>
> Andrew D. Kester, EI
> Structural Engineer
> Bentley Architects & Engineers
> 665 W. Warren Ave.
> Longwood, FL 32750
> 1-407-331-6116
> andrew(--nospam--at)baeonline.com
> www.baeonline.com
>
>
>
>
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