1) The document provides the design of a concrete filled tube (CFT) column with given dimensions and loadings. 2) The CFT column is checked for various design limitations and requirements. 3) The available compressive strength and effective flexural rigidity of the CFT column are calculated. 4) Both LRFD and ASD design methods are used to check if the column strength is adequate for the applied loads.

1. Welcome To CE 413
J. M. Raisul Islam Shohag
B.Sc. in Civil Engineering (RUET)
Lecturer
Department of Civil Engineering
Daffodil International University.
Lecture-10

2. Submitted By
Mehedi Hasan
ID-183-47-817
Evening Shift, E1 Section
Department of Civil Engineering
Daffodil International University
Aynul Fahad Peal
ID-183-47-828
Evening Shift, E1 Section
Department of Civil Engineering
Daffodil International University
Emtiaz Ahmmed
ID-183-47-824
Evening Shift, E1 Section
Department of Civil Engineering
Daffodil International University

3. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU
Design of (CFT) Column
Problem-1 :
Figure given below is Concrete Filled Tube Column (CFT).
Given data : Span = 14’
x
y
B=6’’
H=10’’
L=14’
PD = 32.0 kips
PL = 84.0 kips
HSS
HSS=10*6*
3
8

4. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU
Given data :
Normal wt of concrete =145 lb/𝑓𝑡3
Concrete Compressive strength , f’c = 5 ksi
ASTM GA 500 Grade B , Fy = 46 ksi , Fy = 58 ksi
Geometric Properties of HSS 10*6*3/8 are follows
As = 10.4 ⅈ𝑛2 , H = 10 in , B = 6.00 in
l min = 0.349 in ( Design Wall Thickness )
l/t = 25.7 , b/t = 14.2
I sx = 137 ⅈ𝑛4
I sy = 661.8 ⅈ𝑛4
Design of (CFT) Column

5. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU
Solution:
Limitation of AISC specification:
1) Concrete strength: 3 ksi ≤ f’c ≤ 10 ksi
Here , f’c = 5 ksi → ok
2) Specified minimum yield stress of structural steel :
Fy ≤ 75 Ksi
Here, Fy = 46 ksi → ok
3) Cross Sectional area of steel section : As ≥ 0.01 Ag
Here, As = 10.4 ⅈ𝑛2
Design of (CFT) Column

6. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU
Internal Clear distance :
h i = h - 2t =10-2×0.349 = 9.3 in
b i = B - 2t = 6 – 2 × 0.349 = 5.3 in
Area of concrete, Ac = 9.3 ×5.3 = 49.29 ⅈ𝑛2
Ag = Ac + As = 49.29 + 10.4 = 59.69 ⅈ𝑛2
0.01Ag = 0.5969 ⅈ𝑛2 < As ∴ As > 0.01 Ag → ok
Check For local buckling:
𝜆b = 2.26
𝐸
𝐹𝑦
[h = 10 – 3 × 0.349]
Design of (CFT) Column
Solution:

7. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU
= 2.26
29000
46
=56.7
ℎ
𝑡
=
10−3× 0.349
9.349
= 25.7
𝜆 Controlling = Max
ℎ
𝑡
= 25.7
𝑏
𝑡
= 14.2
= 25.7
𝜆 Controlling < 𝜆p → ∴ Section is compact
Available compressive Strength:
Pno = Fy As + C2 f’c ( Ac + Asr
𝐸𝑠
𝐸𝑐
) Here,C2 = 0.85 for rectangular section
Pno = 46 × 10.4 + 0.85 × 5 × (49.29+0) = 687.88 kip ≈ 688 kip
Design of (CFT) Column
Solution:

8. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU
Now, EI eff = Es Isy + Es Isr + C3 Ec Icy
C3 = 0.6 + 2 (
𝐴𝑠
𝐴𝑐+𝐴𝑠
) ≤ 0.9
= 0.6 + 2 ×
10.4
49.29+10.4
= 0.947 ≤ 0.9 = 0.9
Ec = 𝑤𝑐1.5
f’c = (145)1.5
5 = 3900 ksi
Icy =
𝐻−4𝑡 𝑏𝑖3
12
+
𝑡(𝐵−4𝑡)3
6
+
9𝜋2−64 𝑡4
36𝜋
+ π𝑡2(
𝐵−4𝑡
2
+
4𝑡
3𝜋
)2
=
10−4∗0.349 ∗5.33
12
+
0.349∗ (6−4∗0.349)3
6
+
9𝜋2−64 ∗0.3494
36𝜋
+
𝜋 ∗ 0.3492
(
6−4∗0.349
2
+
4∗0.349
3𝜋
)
2
= 116.7𝑖𝑛4
≈ 115𝑖𝑛4
Design of (CFT) Column
Solution:

9. Design of (CFT) Column
Alternative:
Icy = Ig – Isy = 10∗63
12
− 61.8 = 118.2 ⅈ𝑛4
Alternative
Icy =
H−2t ∗(B−2t)3
12
= 115 .5 ⅈ𝑛4
Solution:

10. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU
∴ EI eff = 29000 * 61.8 + 0 + 0.9 * 3900 * 115
= 2195850 ≈ 2200000 kip-𝑖𝑛2
Pe =
𝜋2(EI cft)
(𝐾𝐿)2 =
𝜋2∗2200000
(1∗14∗12)2 = 769 kips
Pn𝑜
Pe
=
688
769
= 0.895 < 2.25
∴ Pn = Pno [ 0.658
Pn𝑜
Pe ] = 688*0.6580.895
= 473 kips
LRFD
Pu = 1.2 PDL + 1.6 PLL
= (1.2*32) + (1.6*84) = 173 kips
Design of (CFT) Column
Solution:

11. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU
∅𝑃 𝑛 = 0.75*473 = 355 kips (∅𝑃𝑛 > 𝑃𝑢)→ 𝐨𝐤
ASD
Pu = P DL + P LL
= 32 + 84
= 116 kips
𝑃𝑛
Ω
=
473
2.00
= 236.5 kips
∴
𝑃𝑛
Ω
> Pu → ok
Design of (CFT) Column
Solution:

12. J. M. Raisul Islam Shohag, Lecturer, Civil Engineering Department, DIU