Transcript Slide 1

T8. DESIGN OF REINFORCED CONCRETE COLUMN
(axial compression)
Reinforced concrete framed building
Floor plan
Section
Column: Linear member subjected to axial compression (N0).
Axially compressed if M=0 és V=0 (Eccentrically compressed if M0 és V0)
Example:
-Checking column O1
-Design of column O2
page 1.
T8. Design of reinforced concrete column
I. Checking column O1
I.1. Geometry, model, loads
Cross-sectional data:
concrete cover: cnom 
As 4 
(SR p..9)
d
l =3.00m
Material properties: Concrete
C20/25-32
Renforcing steel
B500
f cd 
f yd 
(SR.p.7.)
(SR.
8.)
floor
Loads: (practical T6): pEd

O2
reaction of column O2 approximately: N Ed

O1
self-weigth of column O1: GEd

I.2. Calculation of internal forces
O2
O1
NEd  p Edfloor  2.4  6.0  NEd
 GEd

page 2.
T8. Design of reinforced concrete column
I.3. Ultimate limit state: strength analysis
 f yd 
400

 sd  min

Normal force equilibrium:
Nu  bhfcd  As sd 
 N Ed 
I.4. Stability analysis:
(SR. p.33)
N Rd  Nu  N Ed
calculation of  :
l0  l 
d



l0

d
= 1 about both (y,z) axes
c3 from table,we considerc3  7.0for safety(supposingweak reinforcement)
N Rd  Nu 
II.
 N Ed

+ constructional rules
Design of column O2
II.1 Geometry, static model, loads
Material properties are the same as in example 1
Consider longitudinal reinforcement:
Link: fw=
T8. Design of reinforced concrete column
page 3.
II.2. Calculation of internal forces
N OEd 2 
II.3. Determination of approximate sizes of cross-section
N Ed  bhfcd  b  h 
N Ed

f cd
II.4. Design
(SR. 33.)
N Rd  Nu  N Ed
calculation of  :
d
l0  l 

l0


d
d

 max 

c3  7.0
N
N u  Ed 

Nu  bhfcd  As f sd  As,req 
Constructional rules:
As,min 

 As,app 
 Amax 
As,app 
(SR. p.53.)
Links (SR.p. 53)
12 min 

sw   h min 
 400mm

page 4.
T8. Design of reinforced concrete column
III: Checking of column O1 by the help of interaction curve
M 0  0 because of axial compression, thus ee  0 however all columns are eccentrically compressed:
construction inaccuracy + second order effect (SR.p.29 and 31)
l0

 ei  400, e2 complicated  table (SR p.32.o)
e  ee  ei  e2 
l0
ei  e2




 ei  e2 
d
d

M Ed  eNEd 
Combination of normal force and moment:
Normal force equilibrium:
N  bxc fcd  As f yd  0
h x 
Moment equilibrium about the center of cross-section: M  As f yd z  f cd bxc   c 
2 2 
Interaction curve (SR. p.21.)
d1

h
M
m  2 Ed 
bh f cd

As f yd

bhfcd
N
n  Ed 
bhfcd
SR. p.22. figures
page 5.
T8. Design of reinforced concrete column
IV: Determination of the approximate sizes, structural plan
Rules of thumb:
beam:
slab:
column:
Structural plan:
content + formal requirements
page 6.
T8. Design of reinforced concrete column