structural analysis

1. CEE-311
Structural Analysis-I
(3.0 credit)
Lecture:3
Bijit Kumar Banik
Assistant Professor, CEE, SUST
Room No.: 115 (“C” building)
bijit_sustbd@yahoo.com
Department of Civil and Environmental Engineering

2. Trusses
Types:
i) Planar
ii) Space
Two broad categories:
i) Roof truss
ii) Bridge truss
First truss structure was made about 2500 BC ;
and it was made up of timber

3. Trusses
Bridge truss
Through Bridge
Deck Bridge

4. Trusses
Trusses of economic proportion
Depth : Length = 1:5 to 1:8
Diagonals make angles of 45˚ - 60˚ with horizontal
Analysis of truss
a) Geometric or graphical method
b) Algebraic method
i) Method of joints
ii) Method of sections

5. Trusses
6@ 8 ft
12 ft
L0
L1 L2 L3 L4 L5
L6
U1
U2
U3
U4
U5
3.2 k3.2 k
3.2 k 3.2 k
3.2 k
Prob.-1: Find forces on the marked members (S & V. P-168)
Solution: R1 = R2 = (5*3.2)/2 = 8 k
R1=8 k R2=8 k
1
1
2
1

6. Trusses
Section 1-1
1
2 L0L1
L0U1
√5
8k
∑Fy =0
L0U1*(1/√5) + 8 = 0
L0U1 = - 8* √5 = 17.89 k (C)
∑Fx =0
L0L1= L0U1*(2/ √5) = 16 k (T)

7. Trusses
6@ 8 ft
12 ft
L0 L1 L2 L3 L4 L5
L6
U1
U2
U3
U4
U5
3.2 k3.2 k
3.2 k 3.2 k
3.2 k
R1=8 k R2=8 k
2
1
2
2
Section 2-2
U1U2
L0U1 = 17.89 k
3.2 k
L1U1
L0U1 = U1U2 = 17.89 k (C)
∑Fy =0
L1U1 = 3.2 k (C)

8. Trusses
6@ 8 ft
12 ft
L0 L1 L2 L3 L4 L5
L6
U1
U2
U3
U4
U5
3.2 k3.2 k
3.2 k 3.2 k
3.2 k
R1=8 k R2=8 k
2
1
3 3
Section 3-3
∑Fy =0
L1U2*(1/√2) – 3.2 = 0
1
1
L1U2
L1U1
L1L2L0L1
1
1
L1U2 = 4.53 k (T)

9. Trusses
6@ 8 ft
12 ft
L0 L1 L2 L3 L4 L5
L6
U1
U2
U3
U4
U5
3.2 k3.2 k
3.2 k 3.2 k
3.2 k
R1=8 k R2=8 k
2
1
Section 4-4
L2L3*12 +3.2*8 +3.2*16 – 8*24 = 0
1
1
L2L3 = 9.6 k (T)
4
4
∑Mu3 = 0 +ve
∑ML2 = 0 +ve
U2U3* (2/√5)*8 +8*16 -3.2*8 = 0
U2U3 = 14.31 k (C)
L0 L1 L2 L3
U1
U2
U3
2
1
4 ft
4 ft
4 ft
8 ft 8 ft 8 ft
3.2 k
3.2 k