CIVIL ENGINEERING FORMULAS

CONCRETE FORMULAS 117

TENSILE STRENGTH OF CONCRETE

The tensile strength of concrete is used in combined-stress design. In normal-
weight, normal-density concrete the tensile strength can be found from

(5.5)

REINFORCING STEEL

American Society for Testing and Materials(ASTM) specifications cover ren-
forcing steel. The most important properties of reinforcing steel are

1.Modulus of elasticity Es, lb/in^2 (MPa)

2.Tensile strength, lb/in^2 (MPa)

3.Yield point stress fy, lb/in^2 (MPa)

4.Steel grade designation (yield strength)

5.Size or diameter of the bar or wire

CONTINUOUS BEAMS AND ONE-WAY SLABS

The ACI Codegives approximate formulas for finding shear and bending
moments in continuous beams and one-way slabs. A summary list of these for-
mulas follows. They are equally applicable to USCS and SI units. Refer to the
ACICodefor specific applications of these formulas.

For Positive Moment

End spans

If discontinuous end is unrestrained

If discontinuous end is integral with the support

Interior spans

For Negative Moment

Negative moment at exterior face of first interior

support

Two spans

More than two spans

Negative moment at other faces of interior supports wl^2 n 11

wln^2  10

wln^2  9

wln^2  16

wln^2  14

wln^2  11

fr0.7 2 fc MPa in SI units

fr7.5 2 fc lb/in^2 in USCS units