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<br />barrels as long as that distance is less than half the opening length of the <br />adjacent barrels. <br /> <br />3-1.2 Precast Concrete Pipe. <br /> <br />Precast concrete pipe is manufactured in six standard shapes: circular, arch, <br />horizontal elliptical, vertical elliptical, pipe arch, and box section, as <br />shown in exhibit 10. With the exception of box culverts, concrete culvert <br />pipe is manufactured in up to five standard strength classifications. The <br />higher the classification number the higher the strength. Box culverts are <br />designed for various depths of cover and live loads. All of the standard <br />shapes are manufactured in a wide range of sizes. Circular and elliptical <br />pipes are available with standard sizes as large as 144 inches in diameter, <br />with larger sizes available as special designs. Standard box sections are <br />also available with spans as large as 144 inches. Precast concrete arches on <br />cast-in-place footings are available with spans up to 40 feet. A listing of <br />standard sizes is provided in the appendix. <br /> <br />3-1.3 Cast-in-Place Concrete Culverts. <br /> <br />Reinforced culverts that are cast-in-p1ace are typically either rectangular or <br />arch-shaped. The rectangular or box shape is more common and is usually <br />constructed with multiple cells (barrels) to accommodate longer spans. One <br />advantage of cast-in-place construction is that the culvert can be designed to <br />meet the specific requirements of a site. Due to the long construction time <br />of cast-in-place culverts, precast concrete or corrugated metal culverts are <br />often selected. However, in many areas cast-in-place culverts are more <br />practical and represent a significant number of installations. <br /> <br />3-1.4 Corrugated Steel. <br /> <br />Corrugated steel culverts are constructed from factory made corrugated steel <br />pipe or field assembled structural plate products. Structural plate steel <br />products are available as structural plate pipes, box culverts, or long span <br />structures. Standard shapes for corrugated steel culverts are shown in <br />exhibit 11. <br /> <br />a. Corrugated Steel Pipe--Factory made pipe is produced in two basic <br />shapes, round and pipe arch. Both shapes are produced in several wall <br />thicknesses, several corrugation sizes, as shown in exhibit 12, and with <br />annular (circumferential) or helical (spiral) corrugations. Pipes with <br />annular corrugations have riveted, spot welded, or bolted seams. Pipes with <br />helical corrugations have continuously welded seams or lock seams. Corrugated <br />steel pipe and pipe arch are usually zinc coated (galvanized). Other metallic <br />coatings such as aluminum and aluminum zinc alloy coatings have recently been <br />developed. Additional protective coatings are used with the metallic coating <br />when there are potential corrosion or abrasion problems. <br /> <br />18 <br />