Standard Specification for Underground Precast Concrete Utility Structures

This specification covers the recommended design criteria and manufacturing practices for monolithic or sectional precast concrete utility structures. Forms shall be accurately constructed and strong enough to maintain the structure's dimensions within the tolerances. Forms shall be cleaned before each use. The aggregates shall be sized, graded, proportioned, and thoroughly mixed in a batch mixer with proportions of cement and water as will produce a homogeneous concrete having the required specified compressive strength. Concrete shall be deposited as nearly as practicable in its final position. Structures shall be cured by an accepted industry method that will develop the required 28-day compressive strength without affecting the long-term durability of the concrete. The elastic method of structural design or the strength design method of reinforced concrete design, shall be used to design the concrete sections, including the reinforcement required, when the structure is subjected to the specified loading conditions. The structural design shall take into consideration the number, placement, and size of access openings. The minimum floor thickness resulting from slope shall be considered as the nominal floor thickness in the design of the structure. Duct terminators, knockouts, and sumps shall be designed to carry the loads imposed upon them. Compressive-strength of the concrete shall be tested to meet the requirements prescribed. Joints in sectional precast concrete structure shall be designed so as to be self-aligning when assembling sections of the structure. Design of lifting devices shall conform to requirements specified.