structural analysis

1. CEE-311
Structural Analysis-I
(3.0 credit)
Lecture:4
Bijit Kumar Banik
Assistant Professor, CEE, SUST
Room No.: 115 (“C” building)
bijit_sustbd@yahoo.com
Department of Civil and Environmental Engineering

2. Trusses
Prob.-2: Find reactions of the following truss structure
(Exercise-12; S & V. P-52)
6@ 15 ft
25 ft
3
4
5
0.6k/ft
0.5 k/ft
3@15ft
R1
RH2
RV2
R2

3. Trusses
6@ 15 ft
25 ft
3
4
5
9
5
10.3
0.6k/ft
0.5 k/ft
3@15ft
R1
RH2
RV2
R2
51.48 ft
9
5
10.3
25.74 k
12.5 k
22.5 k
7.5 ft
12.5 ft
3
4
5
27 k
22.5 ft

4. Trusses
12.5*(45+12.5) + 22.5*7.5 + 27*22.5 – (4/5)*R1*75 – (3/5)*R1*45 = 0
∑MR2 = 0 +ve
R1 = 17.18 k
∑Fx =0
12.5 + 27 – (3/5)*17.18 + RH2 = 0
RH2 = - 29.19 k ≈ 29.2 k (←)
∑Fy =0
RV2 + (4/5)*17.18 – 22.5 = 0
RV2 = 8.76 k (↑ )

5. Trusses
Prob.-3: Find forces in bars A, B, C & D of the truss structure
(Example-85; S & V. P-177)
72 k 36 k
90 k
180 k 18 k
149.3 k
172 k 6@ 15 ft 20 ft30 ft
4@ 10 ft
15ft15ft20ft30ft
20ft30ft30ft10ft
AB
C
D 1
1

6. Trusses
180 k
18 k
4@ 10 ft
30ft10ft
A
m
5ʹ
15ʹ
2
1√5
3
2
√13
x
y
2
√13
318*30 – (2/√5)*m*20 = 0
∑Mx = 0 +ve
m = 30.19 k (T)
18*20 – 180*10 – (2/√5)*30.19*5 - (1/√5)*30.19*10 +
(2/√13)*A*15 + (3/√13)*A*10 = 0
∑My = 0 +ve
A = 102.8 k (T)
Section 1-1

7. Trusses
72 k 36 k
90 k
180 k 18 k
149.3 k
172 k 6@ 15 ft 20 ft30 ft
4@ 10 ft
15ft15ft20ft30ft
20ft30ft30ft10ft
AB
C
D
2
2

8. Trusses
149.3 k
172 k30 ft20ft30ft
B
M
30ft
1
1
√2
∑MM = 0 +ve
B = 352 k (T)
(1/√2)*B*30 - 149.3*50 = 0
Section 2-2

9. Trusses
72 k 36 k
90 k
180 k 18 k
149.3 k
172 k 6@ 15 ft 20 ft30 ft
4@ 10 ft
15ft15ft20ft30ft
20ft30ft30ft10ft
AB
C
D
3

10. Trusses
CH = DH
At point 3 C
D
1
1
√2
1
1
√2
CV
CH
DV
DH
Again,
CH = CV (1:1)
DH = DV
CV = DV

11. Trusses
72 k 36 k
90 k
180 k 18 k
149.3 k
172 k 6@ 15 ft 20 ft30 ft
4@ 10 ft
15ft15ft20ft30ft
20ft30ft30ft10ft
AB
C
D
4
4

12. Trusses
72 k
149.3 k
172 k
C
D
Left Section of 4-4
∑Fy =0
172 – 72 - CV - DV = 0
C = (√2/1)*50 = 50√2 k (T )
- 2CV = -100
CV = 50
D = 50√2 k (C )

13. Trusses