Reinforced Concrete Design

Check if SRB or DRB by

As_max VS As_act

Beta1 [0.65, 0.85]

0.85-(0.05/7)(fc_prime-28)

c_max

3d/7

a_max

beta1*c_max

C (force)

0.85fc_prime*a*b

T (force)

As*fs

fs

600((d-c)/c)

Relationship of a, beta1 & c

a=beta1*c

As_max

0.85fc_prime*a_max*b=As_max*fy

As_act <As_max

SRB

As_act>=As_max

DRB

Check Steel

rho_act VS rho_bal

rho_act

As_act/bd

rho_bal

0.85fc_prime*beta1(600/(600+fy))

rho_act>rho_bal

fs=600((d-c)/c) —— steel doesn’t yield

rho_act<=rho_bal

fs=fy ———- steel yields

Mn=?? ; T(force)

As*fs(d-a/2)

Mn=?? ; C (force)

0.85fc_prime*ab(d-a/2)

phi [0.65, 0.90]

0.65+0.25((fs-fy)/(1000-fy))

Mu

phi*Mn

C=T (DRB)

Cc+Cs=Ts

Cc+Cs

0.85fc_prime*b+As_prime*fs

fs_prime

600((c-d_prime)/c)

rho_max

0.85fc_prime*beta1(3/7)/fy

rho_min ; IF fc_prime<31.36MPa

1.4/fy

rho_min ; IF fc_prime>31.36MPa

SQRT(fc_prime)/4fy

1st Step of Analysis RB

Check if SRB or DRB

1st Step of SRB Analysis

Check Steel

2nd Step of SRB Analysis

C=T ; find a & c

3rd Step of SRB Analysis

solve Mn

4th Step of SRB Analysis

solve phi

5th Step of SRB Analysis

solve Mu

1st Step of DRB Analysis

Find a & c ; Cc+Cs=Ts w/ fs &fs_prime = fy

2nd of DRB Analysis

fs & fs_prime VS fy

3nd of DRB Analysis (correct assumption)

solve phi [0.65, 0.90]

Mn (DRB)

Cc(d-a/2)+Cs(d-d_prime)

3nd of DRB Analysis (wrong assumption)

Redo step 1-2 w/ fs=fy, fs_prime=600((c-d_prime)/c)