Vehicle barrier load
Vehicle barrier load
(OP)
Section 1607.7.3 of the 2003 IBC requires a 6000# horizontal load (due to vehicle impact) applied on a 1.0 square foot area. I have a parking garage situation with CMU infill wall along part of the edge, which must be designed for this load. My question is, how wide of a "design strip" would seem appropriate for analyzing as a vertical "beam" - obviously 1 foot is way too conservative considering the effect of the horizontal bars, but going much past 3 feet sounds uncomfortable...and even a 3-ft width seems to require solid grout for shear and a whole lot of rebar...
Any advice?
Any advice?






RE: Vehicle barrier load
In a similar situation (not my design, but a project I was involved in) the engineer of record specified a steel guarding rail with the horizontal at ~600 (2ft), and argued that with it in place, the code clause requiring the horizontal thrusting load for the wall no longer applied (the cars would, at least in theory, never impact the wall).
Hope that helps at least a little. Tough situation... Good luck, and let us know how it all turns out!
B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...
RE: Vehicle barrier load
But more importantly, who do I send my resume to in order to get a structural engineering job in New Zealand?
RE: Vehicle barrier load
a. bar spacing
b. 6x wall thickness
c. 72"
I would also think that you would want to solid grout the wall no matter how the numbers calc out. A car hitting the hollow part of a partially grouted wall could send a lot of small missiles flying.
RE: Vehicle barrier load
ACI 2.3.3.3 is the "Effective compressive width per bar". I don't think it applies here, as that would mean that the design strip width would increase with wider bar spacings.
WAstruc10-
AASHTO (17th Ed.) Article 2.7.1.3.6 calls for a 10 kip transverse force on concrete barrier walls to be spread over a longitudinal length of 5 feet.
RE: Vehicle barrier load
A concentrated force on the wall will produce high localized stresses near the point of application. These stresses will diminish with distance. But to simplify the problem and produce a workable solution, you can assume uniform stresses over an effective width. Whether the concentrated load is an internal force due to the reinforcement tension or an externally-applied point load, the concept is the same. For a typical 8" thick wall, you could use 6x the thickness and come reasonably close to the 5 foot width you cited.
RE: Vehicle barrier load
The 5’ distribution width from AASHTO that jmiec cited is standard in the design of highway bridges. I have used this extensively in the design of bridge railings and decks for vehicle impact loads.
You could also assume a 1:1 distribution from the application of the point load to the base of wall/barrier where your design moment occurs, if this gives a more conservative distribution width. This is a common engineering assumption for distributing concentrated loads in this type of situation.
RE: Vehicle barrier load
I did a barrier wall design for a parking garage in Florida. Basically the barrier wall is cantilevered off the spandrel beam or slab. In my case, I did not have spandrel beams so the moment from the cantilever barrier wall has to be carried by the edge slab. It was a post-tensioned slab and did not have the capacity to do so even at 9" thick. I ended up pouring a concrete beam between supporting columns to take the vehicular impact load. I found the 8" cmu wall reinforced with #7 @ center of cell @ every cell was not sufficient to take the load even distributing over 3 cells. 12" block will work but the placement of reinforcement is toward the edge and hard to enforced during construction. Be certain the supporting structure of the barrier of wall is suffieient to carry the induced moment from the impact.