Need a book? Engineering books recommendations...
RE: Banging Bolts?[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: RE: Banging Bolts?
- From: "Casey K. Hemmatyar" <khemmatyar(--nospam--at)gmail.com>
- Date: Tue, 3 Jul 2007 10:37:37 -0700
Here's the information I had from Charles Carter of AISC and am forwarding it to you about "banging bolts" :
Periodically, I've answered a call where an engineer architect, building owner, or some other related entity has a client or some tenants that reported hearing sharp sounds like rifle shots coming from "the building". Some heard one. Some have heard them a handful of times over a number of years.
What they are all describing is something called "banging bolts". Bolt-banging results when bolted connections slip into bearing under load. In the majority of buildings, bolted connections settle in during construction and the occupants never hear a thing. In other cases, the slip into bearing occurs after occupancy. It's an instantaneous occurrence that makes a loud sound...just like a rifle shot. Fortunately, there is no structural significance to this as the connections can carry the load in bearing by design. That is, there's no threat to life safety here. It just scares the heck out of everyone who hears it from the president of the company down to the summer intern.
To minimize the occurrence (I don't think you could hope to eliminate it entirely), I suggest that engineers specify their bolted connections as snug-tight bearing connections whenever possible. This minimizes the potential for the intentional or incidental slip resistance that eventually might lead to a connection that doesn't slip into bearing until after occupancy.
Also, I suggest that erectors tell their crews not to tighten any bolts until after the drift pins have been removed from the connections. Leaving the drift pin in as bolts are installed and tightened tends to center the holes in the connected plies and increase the potential for slip in the connection.
Actually, the latter recommendation (about drift pin usage) is probably more important than the first. Unfortunately, some decision makers take more extreme measures, like unilaterally requiring field-welded connections, which may do nothing more than eliminate steel as an option.
Casey (Khashayar) Hemmatyar
A friend of mine works in a new building where there have been strange sounds which have been difficult to identify. The e-mail message below is what he received from management to explain the problem:
It has been over two weeks since we have had a report of the loud noises that were occurring in the building. We believe we have identified the source and would like to share the following information with you.
The project design and construction team conducted a thorough inspection of the building, including the plumbing, mechanical and structural systems. A couple of independent consultants also assisted in this effort. All of the systems at Carson One were found to be safe and sound.
The suspected cause of the noise is a phenomena known as "banging bolts". The team is confirming this information and will issue a report for the record. The cause of the noise is the high strength bolts at the structural steel connections making final adjustments as the building is loaded; it is a natural occurrence and does not reflect on the building's structural integrity. Most of these adjustments occur during construction, some occur early in occupancy (as many of you have heard) and eventually they stop completely. These adjustments have been reported as long as two years after construction of a building.
We will update you as new information is received and appreciate your patience as we deal with these issues.
Does this sound reasonable? I've never heard of "banging bolts", but I don't do a lot of steel work, so maybe it is common.
T. William (Bill) Allen, S.E.Consulting Structural Engineers
V (949) 248-858
- Re: Banging Bolts?
- From: Sean Martin
- Re: Banging Bolts?
- Prev by Subject: Banging Bolts?
- Next by Subject: Re: Banging Bolts?
- Previous by thread: Re: Banging Bolts?
- Next by thread: Re: Banging Bolts?