A double angle is used as the top chord of a given truss shown in figure 17.7. It is composed of 2 - angles 225 x 100 x 12 mm. with short legs back to back. Thickness of gusset plate is 9 mm. Bracing is provided in the plane of the top chord every 2.2 m. Total length of the top chord is 8.8 m. but bracing between trusses is such that lateral support occurs only at the ends of the top chord. Neglect the contribution of roofing to lateral support. Use A 36 steel. K = 1.0, E,= 200000 MPa. 0 Compute the reduction factor due to local buckling of compression member. Compute the allowable compressive stress for the top chord. 2 Compute the maximum axial compressive force which the top chord can carry safely. 3 Properties of 2 angles 2225 x 100 x 12 mm with short legs back to back A 36 steel CIVIL A = 8064.5 mm² Tx = 26.67 mm ry = 115.57 mm F₁ = 248 MPa ENGINEERING STEEL DESIGN 8.8 m 2.2 2.2 2.2 2.2
A double angle is used as the top chord of a given truss shown in figure 17.7. It is composed of 2 - angles 225 x 100 x 12 mm. with short legs back to back. Thickness of gusset plate is 9 mm. Bracing is provided in the plane of the top chord every 2.2 m. Total length of the top chord is 8.8 m. but bracing between trusses is such that lateral support occurs only at the ends of the top chord. Neglect the contribution of roofing to lateral support. Use A 36 steel. K = 1.0, E,= 200000 MPa. 0 Compute the reduction factor due to local buckling of compression member. Compute the allowable compressive stress for the top chord. 2 Compute the maximum axial compressive force which the top chord can carry safely. 3 Properties of 2 angles 2225 x 100 x 12 mm with short legs back to back A 36 steel CIVIL A = 8064.5 mm² Tx = 26.67 mm ry = 115.57 mm F₁ = 248 MPa ENGINEERING STEEL DESIGN 8.8 m 2.2 2.2 2.2 2.2
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
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Transcribed Image Text:A double angle is used as the top chord of a given truss shown in figure 17.7. It is
composed of 2 - angles 225 x 100 x 12 mm. with short legs back to back. Thickness
of gusset plate is 9 mm. Bracing is provided in the plane of the top chord every 2.2 m.
Total length of the top chord is 8.8 m. but bracing between trusses is such that lateral
support occurs only at the ends of the top chord. Neglect the contribution of roofing
to lateral support. Use A 36 steel. K=1.0, E, 200000 MPa.
Compute the reduction factor due to local buckling of compression member.
2 Compute the allowable compressive stress for the top chord.
3)
Compute the maximum axial compressive force which the top chord can carry
safely.
Properties of 2 angles 225 x 100 x 12 mm with short legs back to back
A 36 steel
CIVIL
A = 8064.5 mm²
rx = 26.67 mm
ry = 115.57 mm
F₁ 248 MPa
2.2
ENGINEERING STEEL DESIGN
8.8 m
2.2 2.2 2.2.
![Solutions:
Ł
=
225 = 18.75
12
Qa=1.0
Q₁ = 1.34-0.76 [4/4] Fy
E
= 1-34-0.76 (18.75).
Q=0.84 a.]
k²
rx
=
кг
K2 - 1.0x2200
115.57
10x8800 = 329.96
26.67
248
200,00
- Use k2 largest
ř
< 200
= 19.036
Assume K=1.0
8m
X axis
4.71√ √2x105
my
248 x0.84
195.93
2007 145.93
:. Elastic
Fe: 11² x 200 ow
(200)²
2.2
2.2
2.2
✓ 4.71√
2.2
y
Fe=49.35
kindly Recheck
work
thank you
CIVIL ENGINEERING STEE DESIGN
aki
2x105
FyxQs
Per= 0.877 Fe
= 0.877 99.35
6. Pcr= 43.28 mPa
(n = 43.28 x 8044.5
lov
c) → Pn= 349.03 kW
Slender Unstiffened Klements, Q,
The reduction factor Q, for slender unstiffened elements is
defined as follows:
505.7.1
1.
2
For flanges, angles, and plates projecting from rolled
columns or other compression members:
a. When
b.
a
3.
b.
When
L
When 0.56
Q. = 1.415-0.74
≤ 0.56
2. = 1.0
When
b.
0.69E
Fy (2)
For flanges, angles, and plates projecting from built-up
columns or other compression members:
When
≤0.64
When 0.64
where:
ke
Q8==
Q=1.415-0.65
a. When
Q. = 1.0
For single angles
Q;=
¬OF
L.03
When
When
where
b-
Ek
<1.03
Eke
-1.17 ER
0.90Ek
Fy (2²
2x = 1.0
0.45
0.45
Q,= 1.34-0.76
另
≤1.17
Qs=
The
and shall not be taken loss
than 0.35 nor greater than
h/t 0.76 for calculation purposes
34-0.76 (2)
(505.7-4)
> 0.91
(505.7-5)
0.53E
Fy()*
(505.7-6)
(505.7-7)
Eke
7
(505.7-8)
(505.7-9)
91
(505.7-10)
(505.7-11)
(505.7-12)
full width of longest angle leg. mm](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fa492bd26-ee44-4470-930f-28e915fd1410%2F943d09ff-42cb-4615-9851-cd17e0005088%2F2t019v_processed.jpeg&w=3840&q=75)
Transcribed Image Text:Solutions:
Ł
=
225 = 18.75
12
Qa=1.0
Q₁ = 1.34-0.76 [4/4] Fy
E
= 1-34-0.76 (18.75).
Q=0.84 a.]
k²
rx
=
кг
K2 - 1.0x2200
115.57
10x8800 = 329.96
26.67
248
200,00
- Use k2 largest
ř
< 200
= 19.036
Assume K=1.0
8m
X axis
4.71√ √2x105
my
248 x0.84
195.93
2007 145.93
:. Elastic
Fe: 11² x 200 ow
(200)²
2.2
2.2
2.2
✓ 4.71√
2.2
y
Fe=49.35
kindly Recheck
work
thank you
CIVIL ENGINEERING STEE DESIGN
aki
2x105
FyxQs
Per= 0.877 Fe
= 0.877 99.35
6. Pcr= 43.28 mPa
(n = 43.28 x 8044.5
lov
c) → Pn= 349.03 kW
Slender Unstiffened Klements, Q,
The reduction factor Q, for slender unstiffened elements is
defined as follows:
505.7.1
1.
2
For flanges, angles, and plates projecting from rolled
columns or other compression members:
a. When
b.
a
3.
b.
When
L
When 0.56
Q. = 1.415-0.74
≤ 0.56
2. = 1.0
When
b.
0.69E
Fy (2)
For flanges, angles, and plates projecting from built-up
columns or other compression members:
When
≤0.64
When 0.64
where:
ke
Q8==
Q=1.415-0.65
a. When
Q. = 1.0
For single angles
Q;=
¬OF
L.03
When
When
where
b-
Ek
<1.03
Eke
-1.17 ER
0.90Ek
Fy (2²
2x = 1.0
0.45
0.45
Q,= 1.34-0.76
另
≤1.17
Qs=
The
and shall not be taken loss
than 0.35 nor greater than
h/t 0.76 for calculation purposes
34-0.76 (2)
(505.7-4)
> 0.91
(505.7-5)
0.53E
Fy()*
(505.7-6)
(505.7-7)
Eke
7
(505.7-8)
(505.7-9)
91
(505.7-10)
(505.7-11)
(505.7-12)
full width of longest angle leg. mm
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