History
As a vehicle travels on jointed concrete roads the weight of the vehicle passes from one concrete panel to the next. As the vehicle traverses the joints its weight is placed on the edge of the panel, where the panel is least able to withstand the deflection force. This can cause cracks as pavement shears off the edge of the panel. On older highways dowel bars (steel rods) were placed across the joints to help transfer the load from one panel to the next. This was discontinued because the dowel bars tended to corrode and require replacement. Instead, the cohesion between the panels and the strength of the roadbed was relied upon to transfer the load. Over time the joint and roadbed tends to break down, resulting in cracks and displacement of the panels.
In modern highways, dowel bars are once again placed across joints and at intervals along the pavement. Modern dowel bars are coated with epoxy to prevent corrosion.
Read more about this topic: Dowel Bar Retrofit
Famous quotes containing the word history:
“One classic American landscape haunts all of American literature. It is a picture of Eden, perceived at the instant of history when corruption has just begun to set in. The serpent has shown his scaly head in the undergrowth. The apple gleams on the tree. The old drama of the Fall is ready to start all over again.”
—Jonathan Raban (b. 1942)
“History is more or less bunk. It’s tradition. We don’t want tradition. We want to live in the present and the only history that is worth a tinker’s damn is the history we make today.”
—Henry Ford (1863–1947)
“Every member of the family of the future will be a producer of some kind and in some degree. The only one who will have the right of exemption will be the mother ...”
—Ruth C. D. Havens, U.S. suffragist. As quoted in History of Woman Suffrage, vol. 4, ch. 13, by Susan B. Anthony and Ida Husted Harper (1902)