CONCRETE DESIGN METHOD (AMERICAN CONCRETE INSTITUTE 318)

In design of reinforced concrete structures, members shall be designed in accordance with a load factor method (or limit strength method) in ACI 318-89.

1.1          Minimum Rebar Diameter,  minimum diameter as follow :

-              For flexural reinforcement :  Deform bar 13 (D-130)

-              For shear reinforcement : Plain bar  10 ( Ø-10)

1.2          Classification of concrete grade

1.3          Minimum and Maximum Flexural Reinforcement

where: 

r =	ratio of non -pre stressed tension reinforcement area (As) and concrete effective compression area ( b * d )
rb =	reinforcement ratio producing balance strain condition
=	(0.7225 fc’/fy) (87000/(87000+fy))	f ’c =	275 kg/cm²   (3912 psi)	(structural concrete)
		=	125 kg/cm2   (1778 psi)	(plain concrete)
		fy  = =	60,000 psi 40,000 psi	(deformed bar) (plain bar)
b =	width of concrete compression face
d =	distance from the extreme compression fiber to the center of tension reinforcement

1.4          Minimum Shear Reinforcement

For all items stated in paragraph 7.2 when minimum shear reinforcement is required, the minimum shear reinforcement area should be calculated as follows:

                      Av min =  50 . bw . S / fy

where: 

bw          =  web width

S             =  spacing of shear or torsion reinforcement in direction parallel to longitudinal

In case where minimum shear reinforcement is not required, stirrups or ties shall be provided with a pitch of 200 mm. For structural frame proportioned to resist force induced by earthquake motion, the confinement requirement must be considered.

1.5          Spacing Limit for Rebar

Bar spacing (clearance) shall be at least 2 times bar diameter and at least 4/3 times the maximum aggregate size and at least 2 inch spacing whichever is greater.

1.6          Maximum Coarse Aggregate Size

1.7          Minimum Concrete Cover

The following minimum concrete cover shall be provided for reinforcement: