Название | America's Covered Bridges |
---|---|
Автор произведения | Ronald G. Knapp |
Жанр | Книги о Путешествиях |
Серия | |
Издательство | Книги о Путешествиях |
Год выпуска | 0 |
isbn | 9781462914203 |
Engaging builders for stonework and superstructure
As the nineteenth century progressed, county and local governments gradually assumed greater responsibility for public works and were increasingly able to pay for them using tax dollars. But the formal pattern we know today—calling for sealed bids, selecting the lowest bid (that met specifications), inspecting the project upon completion, and paying in full—only developed towards the end of the Civil War (1860–5). After that, at least in counties where full records were kept, the covered bridge building process becomes better known. In areas where local government was responsible for bridge building, record keeping tended to be unsystematic, and over time many documents disappeared. For example, Pennsylvania’s county records provide limited information to researchers since many counties have “cleaned house” by throwing out what records there were. In the case of Ohio and Indiana, at least, the county commissioners kept moderately detailed records. Nineteenth-century journals were handwritten by a secretary, and depending on that person’s diligence, preserved much or little detail. In counties whose records have been most thoroughly researched, we find the commissioners’ journals listing all the bids for both stonework and superstructure, noting to whom the contract was given, and accounting for all (or most) of the payments. What is missing in most cases are the original bids submitted by builders along with any drawings, plans, or specifications they provided.
During the period from about 1865 to the end of the covered bridge era (1890s for most areas but later for Indiana, the South, and the Far West), officials contracted for two matters, the stonework for the abutments and piers and the wooden superstructure. Stonework was bid by the perch and the wooden superstructure by the lineal foot. One perch of stone was 24.75 cubic feet, equivalent to a unit of blocks, 16.5 feet long, 1.5 feet wide, and 1 foot. Bridge foundations generally used large blocks of cut stone quarried locally, but it was also common in some areas of the country for abutments and piers to be made of flat field stones. Stonework was normally laid up dry, that is, without mortar. These were often built on foundations of wooden piles, though little is known of this aspect (see Chapter 3). In areas where stone was difficult to obtain or too expensive, contractors built the bridges on wooden pilings, often replaced later by metal cylinders filled with cement. This was especially so in areas where creek banks and beds were muddy, thus providing a poor base for stone. Although builders preferred abutments built into the bank on either end, when the creek banks rose only gradually, creating a flood plain, the abutments might be built like piers in the water out from the bank, with open approaches of various lengths and designs. Some bridges, for example many in Georgia, had approaches hundreds of feet long.
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