Ballast deck bridges

[NW Mailing List]

The reverse trend on NS is to convert curved bridges, especially on the
Pokey, to ballast deck because of alignment problems at the abutments and
the non-standard bridge ties.  Bridge ties are pre-cut or "dapped" to help
superelevate the curve, but must allow for girder horizontal (chord)
alignment and vertical alignment for increasing flange thickness towards
the span center, even for any rivets under each tie.  So each tie must be
individually cut and tagged with a serial number and are ordered from an
outside supplier with a lead time of 6-8 months.  In comparison, ballast
decks start looking cheap and easy.

Grant Carpenter


> Date: Mon, 19 Mar 2012 09:37:00 -0400 (EDT)

> From: NW Mailing List <nw-mailing-list at nwhs.org>

> Subject: Re: Clinch Valley Division CV 464.01 over Clear Creek, Norton

> 	vicinity,	Wise County, VA

>

> Is it possible the superstructure was rebuilt in 1939 and yet this

information may not have been included within the archived records. However
I also wonder why an existing bridge would need replacement after only 20
years of service?

>  

> Any advice, thought or suggestion would be appreciated.  Thank you for

your time.

> Joe-

>  

> Ballasted deck trestles were a rarity on the N&W .  This type of span had

an advantage--

> it used common, everyday cross ties. Steel spans required cut to order

bridge ties. The

> ballasted deck trestle had a huge disadvantage -- failure to drain

properly.  Although

> Atlantic Coast Line (for one) had many ballasted deck trestles, N&W

preferred steel spans.

> After all, N&W could produce its own ties at the Radford plant.  After 20

years of service,

> the bridge at Clear Creek may have begun to show the results of poor

drainage--

> accumulating weight on the concrete slabs,  piers settling, etc.        

Harry Bundy