This paper describes the preliminary engineering and design, by EBA Engineering Consultants Ltd. (EBA), of a National Cooperative Highway Program (NCHRP) 350: Test Level 4 (TL-4) high-tension (pre-stretched post-tensioned) cable barrier installed in May 2007 in the depressed median of an 11 km stretch of the Deerfoot Trail in Alberta, Canada. The paper reports the results of the research regarding the available TL-4 cable barriers approved by the US Federal Highway Administration (FHWA). The paper discusses important design considerations, such as the post spacing and allowable maximum deflection of the cable barrier, and the recent revisions to the AASHTO Roadside Design Guide. For the Deerfoot Trail project, a design deflection of 2.4 m (8 ft) and a maximum post spacing of 6.1 m (20.0 ft) was specified. The median cable barrier was placed 4.0 m from the edge of the travel lane (the painted shoulder line). This minimized the interaction with existing barrier systems, and allowed for emergency vehicles to park or pass on the inside shoulder. The authors believe that the research and design of the high tension cable barrier described in this paper should be of interest to future similar projects in Canada. For the covering abstract of this conference see ITRD number E216511.
Samenvatting