Author(s):
H.E. Ross, E.R. Post
Publication Date
1971
Abstract
Some highway drainage structures have a geometrical configuration that can cause an errant automobile to stop abruptly or veer out-of-control. One such structure is the end culvert inlet with or without headwalls. In recent years, highway engineers have used sloping inlet and outlet grates which allow an automobile to traverse the culvert opening rather than come to an abrupt stop. Sloping grates are currently designed on judgement and experience because objective criteria are practically nonexistent. Using a mathematical simulation technique, this study investigated the dynamic behavior of a standard size automobile traversing a median containing a crossover and a sloping culvert inlet grate. Twenty-three computer simulations were made in which the effects of vehicle path, ditch side slope, and grate slope were analyzed. It was determined that an 8:1 ditch side slope in conjunction with a 10:1 culvert grate slope would not produce intolerable automobile accelerations to an unrestrained occupant. Steeper combinations of side and grate slopes were found to produce severe accelerations and/or rollover and should be avoided where possible. For purposes of structural design, it was found that the dynamic load factor per tire on 8:1 and flatter grate slopes was about five. And, for 6:1 and steeper grate slopes, the dynamic load factor reached values of about 10.
Report Number:
140-3
Keywords:
Culverts, Highway safety, Math Model, Medians, Sloping Grates, Vehicle Simulation
Link(s):
Document/Product
http://tti.tamu.edu/documents/140-3.pdf
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