RE: stainless steel cable[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: stainless steel cable
- From: "Yi Yang" <YI(--nospam--at)summit-sr.com>
- Date: Tue, 24 May 2005 10:38:39 -0700
We just did a project, included a exact same scenario as you described. It was a pedestrian wood bridge on a private property, with 4x4 IPE post. The cables were spaced at 3" apart, so to satisfy the requirement, the max deflection for the cable needs to be 1" or less with 50lbs point load at mid span.
I calculated the tension on the cable to be about 350 lbs for it have a 1" or less deflection when a 50lbs force is at the mid span (ignore the cable weight). When the cable was installed, the post had a little splitting problem, so they put the steel plate on the back side. The contractor put a bucket of sand, 50lbs, at the middle, and tighten the cable, while measuring it with a level and tape, until the deflection is about 1". The cable supplier had a spring loaded gage to measure the tension, and it came out to be about 360 lbs. The county building inspector was happy with that.
Y i Y a n g, S. E.
SUMMIT ENGINEERING INC.
Santa Rosa, California
From: S. Gordin [mailto:mailbox(--nospam--at)sgeconsulting.com]
Sent: Monday, May 23, 2005 9:36 PM
Subject: Re: stainless steel cable
Thank you, Harold.
It is a guard rail for a pedestrian bridge. The manufacturer sang me a good old "We've done it for many years, worked just fine."
To make a long story short, after I posted my question, I searched online, and found the spec for such railing at Johnson Architectural Site. That spec generally conformed what I found earlier analytically - the maximum spacing of the posts and cables, and pretension required not to allow a 4" sphere to pass through. The "good old" solution came out to be not that adequate.
But seriously, who would want to actually pull those cables apart and stick his head in? Can happen though...
V. Steve Gordin, PhD
Registered Structural Engineer
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