CIVIL ENGINEERING FORMULAS

100 CHAPTER THREE

whereebis the eccentricity, in (mm), of the axial load with respect to the plastic

centroid and is the distance, in (mm), from plastic centroid to centroid of ten-

sion reinforcement.

WhenPuis less than Pbor the eccentricity, e, is greater than eb, tension gov-

erns. In that case, for unequal tension and compression reinforcement, the ulti-

mate strength is

(3.38)

where

Special Cases of Reinforcement

For symmetrical reinforcement in two faces, the preceding Puequation becomes

(3.39)

Column Strength When Compression Governs

For no compression reinforcement, the Puequation becomes

 (3.40)

B

1 

e

d

2

 (^2) 
em

d 

Pu0.85fcbd



m 1 

e

d



B

1 

e

d

2

 2  m 1 

d

d



e

d^

Pu0.85fcbd

 1 

e

d

As/bd

As/bd

mm 1

mfy /0.85fc



B

1 

e

d

2

 (^2) (mm)
e
d
m  1 
d
d^
Pu0.85fcbd mm 1 
e
d
d