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Re: Security Engineering: steel cable security barriers

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For prestressed cable barriers, do you need to give the cable forces required? It would seem the supplier/installer who is designing the anchorages could also quickly come up with the required forces based on your specs.


Will Haynes, P.E.




From: Walter Sawruk <wcsawruk05(--nospam--at)comcast.net>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: Re: Security Engineering:  steel cable security barriers
Date: Sat, 06 Nov 2004 18:22:16 -0500

Maureen,

Yes, such systems have been designed. Here are a couple of reference papers.

1. G. S. Bjorkman and S. P. Harris, "Design Features of a Cable-Bollard Vehicle Barrier System", Nuclear Engineering and Design, 181 (1998) 199-208.

2. H. Presswalla, "Designing Prestressed Barrier Cables", ACI Concrete International, May 1989, pp. 67-73.

I'm assuming you have either determined or were provided with a design basis vehicle (type, weight, size, speed, ... etc.) so now you must come up with a vehicle barrier design to prevent this vehicle from penetrating beyond a certain point.

As far as I know, all of the vehicle barrier designs given in MIL HDBK-1013/14 have been tested by full scale vehicle impacts. If you are looking for 'tested' designs, I don't think you'll find anything of the type you described. I suggest using the two references above as design guides.

Energy absorption capacity is the key concept in the design of such barriers. Cable barriers are usually designed to absorb the full kinetic energy of the vehicle (no credit given to energy dissipated by causing damage to the vehicle). So the design is simply an 'energy balance'. The longer the cable the more (strain) energy it can absorb but the vehicle penetration distance also increases. In some situations, vehicle penetration distance must be limited. Vehicle penetration distances of 10 to 20 ft for a 100 ft span are not uncommon for a high speed vehicle impact. This is the easy part.

One point that I think is sometimes overlooked is the need to design the bollards for a direct impact by the vehicle unless some means of shielding the bollards is provided. If you need to design the bollards for direct vehicle impact, you probably need to do a dynamic analysis in order to account for the inertia of the bollard foundation and soil and the soil resistance. Even if it is a very simplified dynamic analysis, you will find a great reduction in the foundation size needed versus what you would predict by static analysis methods.

Steel pipe bollards can be inserted into permanent sleeves embedded in concrete foundations. These bollards can become heavy as they are usually filled with concrete. Maintenance is an issue - corrosion, debris in holes, ... etc.

Walt Sawruk
--------------------------
Walter Sawruk, P.E.
ABS Consulting
Shillington, PA

At 01:51 PM 06-11-04, you wrote:
Does anyone "design" the post and cable security barriers described in the Army Mil Handbook 1013/14? We are using the post and cable system around the perimeter of the building, but this application is for a large (100 ft) driveway entrance and it needs to be removable. I am wondering if such a system could be designed to be removable, e.g., by use of a turnbuckle below grade, posts in sleeves, etc. Or any other suggestions would be welcome. I need an inexpensive solution for a removable crash rated barrier and all the commercially available options (active or manual bollards) are outside our budget.
Thanks,

Maureen Burke, P.E.
Tullahoma, TN

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