The 9th Street interchange, I 64-2(87)3, was first conceived about 1959. Preliminary design studies began in the early 1960's. Design began about 1964. The idea of heating the ramps was first considered in the early 1960's but was not pursued intently until the final design stage (about 1968). As the design progressed, it became more and more evident that snowing and icing conditions could prevent otherwise normal passage of traffic up and down the ramps. At one point on the structure, a combination of superelevation and grade would produce a 6 1/2 percent slope. The highest ramp or "fly over" would stand about 80 feet in the air and project out over the Ohio River. A single vehicle askew could cause a severe pile-up and back-up of traffic. If cinders and(or) salt could not be brought in, people might abandon their vehicles. A tram system to bring in abrasives and salt was considered as an alternative to an electrical heating system in the deck. Several ideas were explored in an attempt to avoid imbedding wires in the deck slabs. "Heat pipes" were considered; but costs were then very great, and production in sizes and lengths could not be assured. The pro's and con's of imbedding cables in the concrete as compared to imbedding them in a bituminous overlay were weighed; the deciding factors were: (1) the improbability of finding a satisfactory schema for cable replacement in either case, (2) the apparent advantages of providing extra heating capacity together with back-up circuitry. Conduits were rejected because of heat-transfer problems inside the conduit and costs. Of course, the question arose: What will happen to the cables when cracks develop in the concrete? Someone remarked: "There are no cracks on these plans". However, to avoid concentrated deformations and stressing of the cable if cracks occurred, it was decided to lubricate the cable to prevent bonding to the concrete. This would also prevent stress rises due to differential thermal expansion.

Report Date


Report Number

No. 400

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The contents of this report reflect the views of the author who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Bureau of Highways or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.