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:
“My good friends, this is the second time in our history that there has come back from Germany to Downing Street peace with honour. I believe it is peace for our time. We thank you from the bottom of our hearts. And now I recommend you to go home and sleep quietly in your beds.”
—Neville Chamberlain (1869–1940)
“The history of the world is none other than the progress of the consciousness of freedom.”
—Georg Wilhelm Friedrich Hegel (1770–1831)
“What is most interesting and valuable in it, however, is not the materials for the history of Pontiac, or Braddock, or the Northwest, which it furnishes; not the annals of the country, but the natural facts, or perennials, which are ever without date. When out of history the truth shall be extracted, it will have shed its dates like withered leaves.”
—Henry David Thoreau (1817–1862)