Load bearing concrete panel construction

A load bearing concrete panel structure used as a decking material in a bridge structure and which is designed to be supported between at least a pair of separated support members, said panel structure being comprised of a concrete structure having a length dimension, a width dimension, and a height dimension, said concrete structure having an upper half having an upper surface which is designed to come into contact with or to be closely adjacent to loads which traverse said panel structure, and a lower half having a lower surface which is spaced from loads which traverse said panel structure, and wherein the improvement comprises:

• said panel structure being produced from a shrinkage and temperature resistant concrete composition and in which said concrete composition is specially formatted to resist or limit temperature and shrinkage volume change, and crack formation therefrom, in at least said upper half of said panel structure, by constructing said panel structure of concrete embodying practices of said panel structure selected from the group consisting of the use of temperature and shrinkage limiting concrete compositions, by concrete placement and curing means, by utilizing concrete compositions which set to form concrete resistant to temperature change and shrinkage strain cracking, by including shrinkage volume change compensating additives in concrete compositions, by employing staged panel placement, by employing structural measures which allow temperature and shrinkage volume change deformations to occur without restraint and whereby said practices selected limit temperature and shrinkage volume changes and resist cracking which may result therefrom,
• and which said upper half of said panel structure consists essentially of plain concrete, said plain concrete being a structural concrete in which said plain concrete carries all the flexural tensile stresses and which said plain concrete is characterized as a structural concrete whose maximum flexural strength is attained at the cracking load thereof, said plain concrete having a tensile strength less than about 750 pounds per square inch,
• and which said upper half, intermediate the two support members, is free of flexural reinforcing means for carrying bending moment tension stresses in said panel structure,
• and wherein said lower half of said panel structure includes flexural reinforcing means for carrying bending moment tension stresses that comprises from about at least 1.0% by volume of said lower half of said panel structure, said flexural reinforcing means being disposed no further from said lower surface than one-third said height of said panel structure,
• and wherein said plain concrete of said upper half includes metal rods for temperature and shrinkage crack control purposes in an amount and distribution sufficient to substantially resist crack formation at said upper surface of said panel structure, said metal rods being comprised of a first plurality of said metal rods disposed in said upper half to form a first upper layer of metal rods having a first orientation which extends substantially in the length dimension of said panel structure and parallel to the support members, and a second plurality of said metal rods disposed in said upper half to form a second lower layer having a second orientation which extends substantially transversely to said first upper layer of metal rods.