Designs for Gating Crash Cushions Based on Scrap Tires Embedded in Foamed Concrete

摘要

Scrap tires have frequently been used on automobile racing routes as crash cushions on curves or road dividers. Similarly, foamed concrete has found applications as an impact absorber in front of piers supporting overpasses. Scrap tires have never been generally useful in the latter application because of the problem of fires in tire stacks and the breeding of insects that occurs when water accumulates in tires. Tire stacks also are singularly unattractive and pose serious aesthetic problems. Similarly, foamed concrete has been difficult to use in barrier designs because of the requirement that the concrete be held in place with a conventional concrete base. The best properties of both materials are realized when scrap tires are encased in foamed concrete and become the reinforcement that allows the foamed concrete to be held in position. A new type of gating crash cushion has been developed by modifying scrap tires so that they can be positioned in forms and embedded in a layer of lightweight (40- to 50-pcf density), fiber-reinforced, foamed concrete. The scrap tire is used as a point of attachment so that the composite barrier can be lifted, transported, positioned, and anchored without damaging the concrete. Similarly, the concrete provides a frangible, but tough fireproof cladding that prevents the tires from burning and prevents the tires from becoming an insect breeding ground. The lifting cables threaded through the encapsulated tire stack will allow the unit to fragment and flatten when impacted by a vehicle; but the tires and foamed concrete remain around the vehicle. The end product is an attractive, near-permanent, noncombustible, vandal-resistant element that can be used to absorb the impact of an oncoming vehicle producing fragments that will not intrude into the interior of the vehicle and will not be knocked into nearby traffic lanes. By designing an array of modules that follow the mass distribution used in the rows of sand-filled drums currently used in crash cushions, the identical strategy of transferring the momentum of the vehicle into the barrier elements can be employed. The new crash cushion elements can be fabricated in a variety of sizes, shapes, and colors that can be used as highly visible, permanently colored markers. Barriers can also be pigmented with earth tones to blend into the roadside at rock outcrops or road cuts. They require minimum inspection and are cost-effective. They can be used in places where aesthetic or budgetary considerations will not allow other types of crash cushions to be employed.