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Once a proper selection has been made of feasible wall types that satisfy the necessary constraints, design consists of determining the earth pressure against the back of the wall and then proportioning the wall so that it will be structurally sufficient to satisfy a number of traditional checks. These checks include stability against sliding and […]

Evaluation factors that can be used on selected conceptual wall designs include the following: • Constructibility • Maintenance • Schedule • Aesthetics (appearance) • Environment • Durability or proven experience • Available standard designs • Cost The sum of all weight factors should be 100 points. To simplify the selection process, minor factor(s) may be […]

A classification system is an essential part of the description and selection of different earth retaining wall types. Figure 8.1 indicates the many types of walls that are possible. Earth pressure walls can be classified logically into three categories according to their basic mechanisms of retention, or into three categories based on their source of […]

A. J. Siccardi, PE. Formerly, Staff Bridge EngineerColorado Department of TransportationDenver, Colorado S. C. (Trever) Wang, Ph. D., P. E. Senior Engineer Colorado Department of TransportationDenver, Colorado Retaining walls are an important element in highway construction. They are most fre­quently constructed in the highway environment to retain a mass of earth. They are also used […]

The following criteria are necessary to ensure satisfactory impact performance of luminaire supports. • Use only designs that have been approved as crashworthy by the FHWA. • The FHWA has established upper limits on the support mass and height of luminaire supports. These limits are applicable even when the breakaway characteristics have proven acceptable by […]

Maintenance activities usually fall into one of two categories: demand or routine. Demand-responsive maintenance is response to random occurrences such as luminaire failures—i. e., lamps, fuses, ignitors, ballasts—or pole knockdowns. Routine mainte­nance is scheduled activities such as group lamp replacement or luminaire cleaning that are intended to produce a certain level of performance of the […]

Maintenance must be considered from the earliest design stages of a lighting project. Top-quality materials should be specified and then arranged or located to protect the components from the potential hazards of the environment, whether these be rain, mois­ture, ultraviolet degradation, or threat of vehicular impact. After a system is installed and tested for operation […]

Before any lighting system is accepted as complete, or preferably before the electricity is turned on, several tests should be conducted to ensure the quality of the components: Insulation tests. The contractor should measure the conductor insulation resistance to ground of each lighting circuit using a 500-V megohm-range type instrument. A record should be made […]

The conventional method of supplying electric energy to the high mast ring, with the luminaires at the top of the pole, uses a normal twist-lock plug and cap set. Some of these have a neoprene cover to provide some degree of waterproofing, but oftentimes this cover is either poorly installed or missing entirely. The result […]

7.28.1 Conduit on Bridges and Median Barriers The current design standards for bridge rail and median barrier rail are very similar. Consequently, the method for installing conduit for one is applicable to the other. In the past, the most common method for installing bridge conduit was to attach it to the underside of the bridge […]