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Re: Runway beam

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Thanks for your reply. I was however referring to underslung trolleys
carrying a hoist. The trolley is running suspended off the bottom flange and
has to run over a 1.25 ins expansion joint. The crawl beam in question is
spanning between Boiler Units in a power station. The units are totally
independent and have expansion gaps between the units.

I don't think that there is a connection devised for expansion joints in
crawl beams ? The bottom flange is subjected to cross bending and the
trolley wheel needs to be continuously supported.  The small wheels (~5 to 6
ins diameter) also cannot move over gaps larger than about 1/8 ins otherwise
the gap interferes with the with the movement. The flanges also need to be
perfectly level at joints. Mitring the flange tends to weaken the flange in
cross bending because the wheels are close to the edges of the flange, with
a impact load applied at the tip of the taper.

It is often necessary to reinforce the bottom flanges at the joints but even
if this is possible, I dont think that it will overcome the other problems.
The other option would be to make the crawl continuous and providing
longitudinal sliding connections in the top flange support connections.
However these sliding connection would have to be very free moving even
under load. I don't feel comfortable doing this.

I would  appreciate any responses.

-----Original Message-----
From: Blomberg, Paul <Paul.Blomberg(--nospam--at)>
To: seaint(--nospam--at) <seaint(--nospam--at)>
Date: 04 February 1999 10:58
Subject: RE: Runway beam

>I normally provide the expansion joint in between beams and allow the crane
>rail to span over the expansion joint.  Then, within a few feet of the
>structural steel expansion joint, I cut a 60 degree angle on the rail to
>allow the expansion there.  The angle cut allows the expansion but
>positive bearing between the crane wheel and crane rail.
>It's an old detail.  There may be better approaches.
>Paul F. Blomberg
>Jacobs Engineering Group
>Phoenix, AZ
> ----------
>From: Stan Mulder
>To: seaint(--nospam--at)
>Subject: Runway beam
>Date: Thursday, February 04, 1999 12:15PM
>What details are suitable for overhead crawl beam expansion joints. Usually
>gaps at joints should be kept as small as possible (2 mm or say 1/8 ins) to
>enable the trolley wheel to pass smoothly over the joint. Sometimes it is
>necessary to use a long crawl and introduce expansion joints. Possible
>cutting the bottom flange at 45 degrees and reinforcing the bottom flange.
>How big can this gap be (3/8 ins) ? Is there some way of making the gap as
>large as 1 ins ?