4144.01 DESCRIPTION.
Structural plates for pipe, pipe arches, and arches shall meet the requirements of AASHTO M 167/M 167M for steel or AASHTO M 219/M 219M for aluminum, except as modified in this section.

4144.02 DESCRIPTION OF PLATE.
Plates shall consist of structural units of corrugated metal of the specified thickness.

Plates at longitudinal and circumferential seams shall be connected by bolts. Joints shall be staggered so that not more than three plates come together at any one point. Each plate shall be curved to one or more circular arcs.

4144.03 FORMING AND PUNCHING PLATES.
Each plate shall be curved to the proper radius so the cross-sectional dimensions of the finished structure will be as indicated in the contract documents.

The diameter of the bolt holes in longitudinal seams, except those at plate corners, shall not exceed the diameter of the bolt by more than 1/8 inch (2 mm). If elongated structural plate pipe is specified or called for in the contract documents, the plates shall be formed so the finished pipe is elliptical in shape with the vertical diameter approximately 5% greater than the nominal diameter of the pipe.

4144.04 ASSEMBLY PARTS.
Bolts shall meet requirements of ASTM A 449 or ASTM A 325 or shall be an approved equal. All bolts and nuts shall be galvanized.