Par. 1. - Definition. - Reinforced concrete shall mean an approved mixture of Portland cement, water and fine and coarse aggregate, reinforced by steel.

Par. 2. - Portland Cement and Aggregate. - The Portland cement and fine and coarse aggregate for reinforced concrete work shall conform to the quality of materials as defined in section fourteen of this act.

Par. 3. - Reinforcements. - Steel for reinforcement shall conform to the Standard Specifications for Steel Reinforcement Bars of the American Society for Testing Materials, as from time to time revised. It shall be free from mill scale and loose rust and shall not be coated in such manner as to weaken the bond.

Par. 4. - Mixing. - The ingredients shall be thoroughly mixed, and the mixing shall continue until the cement is thoroughly distributed and the mass is uniform in color. The consistency shall be such that the concrete will flow freely about and entirely enclose the reinforcement, but shall not be so wet as to cause separation of the ingredients in handling.

Par. 5. - Inspection. - Such portions of section fourteen as apply to inspection shall be taken to apply to this section also.

Par. 6. - Forms. - Forms shall be sufficiently tight to prevent any considerable loss of material in the pouring.

Par. 7. - Placing. - Such portions of section fourteen as apply to the placing of concrete shall be taken to apply to this section also. Concrete shall not be deposited in forms until the reinforcement has been put in place and secured against displacement.

Par. 8. - Columns shall be poured without any interruption to the bottom side of beams or girders which they support, or to the bottom of the flare in flat slab construction. Special care shall be taken in their pouring that no void may result.

Par. 9. - Columns and walls shall be poured not less than three hours in advance of the beams, girders, or slabs, which they support. All columns of the same type in a story shall be of concrete mixed in the same proportions.

Par. 10. - Structural slabs shall be poured the full thickness at the time of pouring floor.

Par. 11, - Stopping Work. - Proper precautions shall be taken in stopping concrete work to stop it at the points of low shear.

Par. 12. - High and Low Temperature. - When fresh concrete is exposed to a hot or dry atmosphere or wind special precautions to prevent premature drying shall be taken.

Par. 13. - Concrete shall not be deposited when the temperature is below thirty-two degrees Fahrenheit, unless adequate precautions are taken to prevent freezing.

Par. 14. - Fire Protection. - Main reinforcement in floor slabs shall be protected by a minimum of three fourths of an inch of concrete; in beams, girders, columns and walls by one and one half inches from the surface of the concrete to the surface of the main reinforcement.

Par. 15. - In columns the outer one and one half inches of concrete shall be regarded as fireproofing which shall be assumed to carry no stress.

Par. 16. - Rust Protection. - In foundations and retaining walls the steel shall be protected and on the side toward the earth or water by a minimum of three inches of concrete.

Par. 17. - Spacing of Reinforcement. - Slab reinforcement bars in tension shall be not farther apart horizontally than two and one half times the total thickness of the slab. In beams and girders the lateral spacing of parallel bars shall be not less than three diameters from centre to centre, and the clear space between two layers of bars shall not be less than one inch.

Par. 18. - Basis for Design. - Calculations shall be made with reference to working stresses and safe loads rather than with reference to ultimate strength and ultimate loads, and shall be based on the following assumptions:

Par. 19. - (a) A plane section before bending remains plane after bending.

Par. 20. - (b) The modulus of elasticity of concrete in compression, within the usual limits of working stresses, is constant. The distribution of compressive stress in beams, therefore, is rectilinear.

Par. 21. - (c) The tensile strength of the concrete in direct resistance to bending is ignored.

Par. 22. - (d) Under compressive stress the two materials are stressed in proportion to their moduli of elasticity.

Par. 23. - (e) Initial stress in the reinforcement due to contraction or expansion in the concrete is neglected.

Par. 24. - Span Length. - The span length for beams and slabs simply supported shall be taken as the distance from centre to centre of supports, but need not be taken to exceed the clear span plus the depth of beam or slab. For continuous or restrained beams or slabs, built monolithi-cally into supports, the span length may be taken as the clear distance between faces of supports. Brackets shall not be considered as reducing the clear span in the sense here intended, except that when brackets which make an angle of forty-five degrees or more with the axis of a restrained beam or the plane of a slab are built monolithi-cally therewith, the span may be measured from the section where the total depth is at least one third more than the depth at the edge of the bracket. Maximum negative moments are to be considered as existing at the end of the span as here defined.

Par. 25. - Bending. - Bending moments for uniformly distributed dead and live loads, in beams and slabs reinforced in one direction only shall be computed upon the following assumptions, where "w" is the total dead and live load per linear foot and "1" is the span length: -

Par. 26. - (a) for a single span freely supported the bending at mid-span is wl2 / 8

Par. 27. - (6) for a single span restrained at the ends, the bending at mid-span is wl2 / 12

Par. 28. - (c) for two equal continuous spans freely supported, the bending at mid-span is wl2 / 10 and at central support it is wl2 / 8

Par . 29. - (d) for two equal continuous spans restrained at supports, the bending at mid-span is wl2 / 12 and at central support it is wl2 / 10