Week 9 Lecture Material_watermark.pdf

DESIGN OF BATTEN
PLATES USING BOLT
CONNECTION

Example: A batten column of 10-m long is carrying a factored
load of 1150 kN. The column is restrained in position but not in
direction at both ends. Design a built up column using channel
sections placed back to back.
Design batten plates using bolt connection.

Let us try two ISMC 350 @ 413 N/m
Relevant properties of ISMC 350 [ Table II SP 6 (1): 1964]
𝐴 = 5366 mm2, 𝑟𝑧𝑧 = 136.6 mm,
𝑟𝑦𝑦 = 28.3 mm 𝑡𝑓 = 13.5 mm
𝐼𝑧𝑧 = 10008 × 104 mm4 𝐼𝑦𝑦 = 430.6 × 104 mm4
𝑐𝑦𝑦 = 24.4 mm 𝑏 = 100 mm
Solution:
Design of column:
𝑃 = 1150 kN = 1150 × 103 N
L = 1.0 × 10 × 103 = 10000 mm
Let design axial compressive stress for the column be 125 MPa
Required area =
1150×103
125
= 9200 mm2

For
𝐾𝐿
𝑟 𝑒
= 80.53, 𝑓𝑦 = 250 MPa and buckling class c, the
design compressive stress from Table 9c of IS 800 :2007
𝑓𝑐𝑑 = 136 −
136−121
10
× 0.53 = 135.2 MPa
Therefore load carrying capacity = 𝐴𝑒𝑓𝑐𝑑
= 10732 × 135.2 × 10−3
= 1451 kN > 1200 kN, OK
Area provided = 2 × 5366 = 10732 mm2
𝐿
𝑟𝑧𝑧
=
10000
136.6
= 73.21
The effective slenderness ratio,
𝐾𝐿
𝑟 𝑒
= 1.1 × 73.21
= 80.53 < 180; ok

Spacing of channels:
2𝐼𝑧𝑧 = 2 𝐼𝑦𝑦 + 𝐴
𝑆
2
+ 𝐶𝑦𝑦
2
or 2 × 10008 × 104 = 2 × 430.6 × 104 + 5366
𝑆
2
+ 24.4
2
⇒ 𝑆 = 218.4 mm
Let us keep the channels at a spacing of 220 mm
Spacing of battens:
As per clause 7.7.3 of IS 800: 2007,
𝐶
𝑟𝑦𝑦
< 0.7𝜆
𝑜𝑟 𝐶 < 0.7 × 𝜆 × 𝑟𝑦𝑦 = 0.7 × 80.53 × 28.3 = 1595.3 mm
Also
𝐶
𝑟𝑦𝑦
< 50 or 𝐶 < 50 × 28.3 = 1415 mm
Hence, provide battens at a spacing of 1400 mm.

Size of end battens (cl. 7.7.2.3 of IS 800 :2007):
Provide 20 mm bolts.
Edge distance = 1.5 × ℎ𝑜𝑙𝑒 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 [Cl. 10.2.4.2 IS 800:2007]
= 1.5 × 20 + 2 = 33 mm
Effective depth = 𝑠 + 𝐶𝑦𝑦
= 220 + 2 × 24.4 = 268.8 mm > 2 × 100 mm
Hence, chosen effective depth is safe.
Overall depth = 268.8 + 2 × 33 = 334.8 mm
Required thickness of batten =
1
50
× 220 + 2 × 50 = 6.4 mm
Length of batten = 220 + 2 × 100 = 420 mm
Provide 420×340×8 mm end batten plates.

Size of intermediate battens (cl. 7.7.2.3 of IS 800 :2007):
Effective depth =
3
4
× (220 + 2 × 𝐶𝑦𝑦)
=
3
4
× (220 + 2 × 24.4) = 201.6 mm
> 2 × 100 = 200 mm
Hence adopt an effective depth of 210 mm
Overall depth = 210 + 2 × 33 = 276 mm
Therefore, provide a 420×300×8 mm batten plates @1400 mm
c/c.

Design forces:
Transverse shear, 𝑉 =
2.5
100
× 𝑃 =
2.5
100
× 1150 × 103
= 28750 N
Longitudinal shear 𝑉𝑙 =
𝑉𝐶
𝑁𝑆
Spacing of battens, C = 1400 mm
N = No of parallel planes of battens = 2
S = minimum transverse distance between the centroid of the
bolt/weld group = 220 + 2 × 50 = 320 mm
∴ 𝑉𝑙 =
28750×1400
2×320
= 62891 N
Moment, 𝑀 =
𝑉𝐶
2𝑁
=
28750×1400
2×2
= 10.06 × 106 N-mm

Check
i) For end battens
Shear stress =
62891
340×8
= 23.12 MPa <
250
3×1.1
= 131.22 MPa
Bending stress =
6𝑀
𝑡𝑑2 =
6×10.06×106
8×3402
= 65.27 MPa <
250
1.1
= 227.27 MPa
Hence safe.
b) For intermediate battens
Shear stress =
62891
300×8
= 26.2 MPa < 131.22 MPa
Bending stress =
6×10.06×106
8×3002 = 83.83 MPa < 227.27 MPa
Hence safe.

Connection:
The connection should be designed to transmit both shear and
bending moment.
Assuming 20 mm diameter bolts.
Strength of bolt in single shear
=
𝐴𝑛𝑏×𝑓𝑢𝑏
3×𝛾𝑚𝑏
=
0.78×
𝜋×202
4
×400
3×1.25
× 10−3= 45.27 kN
Minimum pitch, p = 2.5d=2.5×20=50 mm
Minimum end distance, e = 1.5 d0 =1.5×22=33 mm
Provide p = 60 mm and e = 35 mm
kb is smaller of 35/(3×22), 60/(3×22)-0.25, 400/410, 1
Kb = 0.53

Strength of bolt in bearing = 2.5𝑘𝑏𝑑𝑡𝑓𝑢/𝛾𝑚𝑏
= 2.5 × 0.53 × 20 × 8 ×
410
1.25
× 10−3 = 69.5 kN
Hence, strength of bolt = 45.27 kN
Number of bolts required =
62891
45.27×103 = 1.39
Let us provide four bolts to take account the stresses due to
bending moments as well.
Check for combined action: For end battens
Force in each bolt due to shear =
62891
4
= 15723 N
Pitch provided = (D-2e)/3= (340-2×35)/3 = 90 mm.
𝑟2 = 2[(90/2)2+(90+90/2)2) = 2[452+1352] = 40500 mm2

Force due to moment =
𝑀𝑟
𝑟2 =
10.06×106×135
40500
= 33533 N
Resultant force = 157232 + 335332
= 37036 N = 37 kN < 45.26 kN
Hence safe.
Check for combined action: For intermediate battens
Force in each bolt due to shear =
62891
4
= 15723 N
Pitch provided = (D-2e)/3= (300-2×35)/3 = 77 mm.
𝑟2 = 2[(77/2)2+(77+77/2)2) = 2[38.52+115.52] = 29645 mm2
Force due to moment =
𝑀𝑟
𝑟2 =
10.06×106×115.5
29645
= 39195 N
Resultant force = 157232 + 391952
= 42231N = 42.23 kN < 45.26 kN
Hence safe.

ISMC 350
350 mm
220 mm
220 mm
1400
mm
Intermediate batten
420 mm×300 mm×8 mm
End batten
420 mm×340 mm×8 mm
20 mm bolt
Channels back-to-back connected by bolts:

DESIGN OF BATTEN
PLATES USING WELD
CONNECTION

Example: A batten column of 10-m long is carrying a factored
load of 1150 kN. The column is restrained in position but not in
direction at both ends. Design a built up column using channel
sections placed back to back.
Design batten plates using weld connection.

For
𝐾𝐿
𝑟 𝑒
= 80.53, 𝑓𝑦 = 250 MPa and buckling class c, the
design compressive stress from Table 9c of IS 800 :2007
𝑓𝑐𝑑 = 136 −
136;121
10
× 0.53 = 135.2 MPa
Therefore load carrying capacity = 𝐴𝑒𝑓𝑐𝑑
= 10732 × 135.2 × 10;3
= 1451 kN > 1200 kN, OK
Area provided = 2 × 5366 = 10732 mm2
𝐿
𝑟𝑧𝑧
=
10000
136.6
= 73.21
The effective slenderness ratio,
𝐾𝐿
𝑟 𝑒
= 1.1 × 73.21
= 80.53 < 180; ok

Size of end battens (cl. 7.7.2.3 of IS 800 :2007):
Overall depth of batten = 220 + 2 × 𝐶𝑦𝑦
= 220 + 2 × 24.4 = 268.8 ≈ 270 mm
Required thickness of batten =
1
50
× 220 = 4.4 mm
Adopt battens with the thickness of 6-mm
Let provide a 70 mm overlap of battens on channel flange for
welding.
[Overlap > 4 t = 4 × 6 = 24 mm] OK
Length of batten = 220 + 2 × 70 = 360 mm
Provide 360×270×6 mm end batten plates.

Size of intermediate battens (cl. 7.7.2.3 of IS 800 :2007):
Overall depth =
3
4
× (220 + 2 × 𝐶𝑦𝑦)
=
3
4
× (220 + 2 × 24.4) = 201.6 mm
> 2 × 100 = 200 mm
Hence adopt overall depth of 220 mm
Therefore, provide a 360×220×6 mm batten plates.

Check
i) For end battens.
Shear stress =
62891
270×6
= 38.82 MPa <
250
3×1.1
= 131.22 MPa
Bending stress =
6𝑀
𝑡𝑑2 =
6×10.06×106
6×2702
= 138 MPa <
250
1.1
= 227.27 MPa
Hence safe.
b) For intermediate battens.
Shear stress =
62891
220×6
= 47.64 MPa < 131.22 MPa
Bending stress =
6×10.06×106
6×2202 = 207.85 MPa < 227.27 MPa
Hence safe.

Design of weld:
Welding is done on all the four sides as shown in the figure.
Let 𝑡 = throat thickness of weld.
𝐼𝑧𝑧 = 2 ×
70 × 𝑡3
12
+ 70 × 𝑡 ×
220
2
2
+
2 × 𝑡 × 2203
12
Neglecting the term 2 ×
70×𝑡3
12
being insignificant.
Therefore, 𝐼𝑧𝑧 = 346.87 × 104𝑡 mm4
𝐼𝑦𝑦 = 2 ×
𝑡 × 703
12
+ 2 ×
220 × 𝑡3
12
+ 2 × 220 × 𝑡 ×
70
2
2
Neglecting the term 2 ×
220×𝑡3
12
being insignificant.
Therefore, 𝐼𝑦𝑦 = 59.62 × 104𝑡 mm4

𝐼𝑝 = 𝐼𝑧𝑧 + 𝐼𝑦𝑦 = 346.87 × 104
𝑡 + 59.62 × 104
𝑡
= 406.49 × 104
𝑡 mm4
𝑟 =
220
2
2
+
70
2
2
= 115.43 mm
𝑐𝑜𝑠𝜃 =
35
115.43
= 0.30
Direct shear stress (cl. 10.5.9 of IS 800:2007)
=
62891
2×70:2×220 𝑡
=
108.43
𝑡
N/mm2
Shear stress due to bending moment =
10.06×106×115.43
406.49×104𝑡
=
285.67
𝑡
N/mm2

Combined stress due to shear and bending
=
108.43
𝑡
2
+
285.67
𝑡
2
+ 2 ×
108.43
𝑡
×
285.67
𝑡
× 0.3
=
334.59
𝑡
<
410
3 × 1.25
= 189.4
or 𝑡 = 1.77 mm
Size of weld = 1.77/0.7 = 2.5 mm
The size of weld should not be less than 5 mm for 13.5 mm
flange.
Hence provide a 5 mm weld to make the connection.

ISMC 350
350 mm
220 mm
220 mm
1400
mm
Intermediate batten
360 mm×220 mm×6 mm
End batten
360 mm×270 mm×6 mm
5 mm weld
Channels back-to-back connected by welding:

Splices
• A joint when provided in the length of a member is called
splices.
• If a compression member is loaded concentrically,
theoretically no splice is required.
• However, the load is never truly axial and the real column has
to resist bending due to this eccentrically applied load.
Column sections can be spliced in the following cases:
1. When the length of the column is more than the length of
the column section available.
2. In case of multistorey buildings, the section of the column
required for the various storey may be different, as the
load goes on increasing for columns of the lower storeys.

Specifications for the design of splices
• Where the ends of the compression members are faced
for complete bearing over the whole area, these should be
spliced to hold the connected members accurately in
position, and to resist any tension when bending is
present.
• Where such members are not faced for complete bearing,
splices should be design to transmit all the forces to
which these are subjected.
• Splices are designed as short columns.

Various type of splices used in compression member

Steps for the design of splice
1. For axial compressive load the splice plates are provided
on the flanges of the two column sections to be spliced.
If the column has machined ends, the splice is designed only
to keep the columns in position and to carry tension due to the
bending moment to which it may be subjected. The splice
plate and the connection should be design to carry 50% of the
axial load and tension.
If the ends are not machined, the splice and connections are
design to resist the total axial load and any tension, if present
due to the bending moment.

• The load for the design of splice and connection due to axial
load,
𝑃𝑢1 =
𝑃𝑢
4
(for machined ends)
𝑃𝑢1 =
𝑃𝑢
2
(for non machined ends)
Where, 𝑃𝑢 is the axial factored load.
• The load for the design of splice and connection due
bending moment,
𝑃𝑢2 =
𝑀𝑢
𝑙𝑒𝑣𝑒𝑟 𝑎𝑟𝑚
Where, lever arm is the c/c distance of the two splice plates and
𝑀𝑢 is the factored bending moment.

2. Splice plates are assumed to act as short columns (with zero
slenderness ratio). So these plates will be subjected to yield
stress (𝑓𝑦).
3. The cross-sectional area of the splice plate is calculated by
dividing the appropriate portion of the factored load coming
over the splice by the yield stress.
c/s area required =
𝑃𝑢1+𝑃𝑢2
𝑓𝑦
4. The width of splice plate is usually kept equal to the width of
the column flange.
Width of splice = 𝑏𝑓 (width of flange)
The thickness of the splice plate can be found by dividing the
c/s area of the plates with its width.

5. Nominal diameter of bolts for connection is assumed and the
strength of the bolt is computed.
6. In case of bearing plate is to be designed between two
column sections, the length and width of the plate are kept
equal to the size of lower-storey column and the thickness is
computed by equating the ultimate moment due to the factored
load to the moment of resistance of plate section.

Example: A column ISHB 300 @ 576.8 N/m is to support a
factored axial load of 500 kN, shear force of 120 kN and
bending moment of 40 kNm. Design the splice plate and
connection using 4.6 grade bolts. Use steel of grade Fe 410.
Solution:
For steel of grade Fe 410: 𝑓𝑢 = 410 MPa, 𝑓𝑦 = 250 Mpa
For bolts of grade 4.6: 𝑓𝑢𝑏 = 400 MPa
Partial safety factors for material:(Table 5 IS 800:2007)
𝛾𝑚0 = 1.10 𝛾𝑚𝑏 = 1.25
The relevant properties of ISHB 300 @ 576.8 N/m are (Table I,
SP 6-1)
𝐴 = 7485 mm2 𝑏𝑓 = 250 mm,
𝑡𝑓 = 10.6 mm 𝑡𝑤 = 7.6 mm

Assume the ends of the column sections to be machined for
complete bearing. As the column ends are flush, it is assumed that
50% of the load is transferred directly and 50% is transferred
through the splice and fastenings. Therefore,
The direct load on each splice plate = 50% 𝑜𝑓
500
2
= 125 kN
Load on splice due to moment =
𝑀𝑢
=
40×103
300+6
= 130.72 kN
(Assuming 6 mm thick splice plate, the lever arm = 300 + 6 mm)
Total design load for splice, 𝑃𝑠 = 125 + 130.72 = 255.72 kN
Sectional area of splice plate required =
𝑃𝑠
𝑓𝑦
=
255.72×103
250
= 1022.9 mm2

Width of the splice plate should be kept equal to the width of
the flange.
Here, the width of the splice plate = 250 mm
Hence, thickness of splice plate =
1022.9
250
= 4.09 mm ≮ 6 mm
Provide a 250×6 mm splice plate.
The length of the splice plate depends upon the number of
bolts in vertical row.
Let us provide 20 mm diameter bolts of grade 4.6.
Strength of 20 mm diameter bolt in single shear (cl. 10.3.3, IS
800:2007)
=
𝐴𝑛𝑏
𝑓𝑢𝑏
3
𝛾𝑚𝑏
=
245×
400
3
1.25
× 10−3 = 45.26 kN

Strength of bolt in bearing = 2.5𝑘𝑏𝑑𝑡𝑓𝑢/𝛾𝑚𝑏 (cl. 10.3.4, IS
800:2007)
For 20 mm diameter bolts the minimum edge distance,
𝑒 = 1.5 × 𝑑0 = 1.5 × 20 + 2 = 33 mm
The minimum pitch, p = 2.5 × 20 = 50 mm
Let us provide an edge distance (e) of 35 mm and pitch (p) of
60 mm.
𝑘𝑏 is smaller of
𝑒
3𝑑0
=
35
3×22
= 0.53 ,
𝑝
3𝑑0
− 0.25 =
60
3×22
− 0.25 = 0.66 ,
𝑓𝑢𝑏
𝑓𝑢
=
400
410
= 0.98 and 1.0
Hence 𝑘𝑏 = 0.53

∴ Strength in bearing = 2.5 × 0.53 × 20 × 6 ×
410
1.25
× 10−3
= 52.15 kN
Hence, the strength of bolt (Bv) = 45.26 kN
Number of bolts required, n =
𝑃𝑠
𝐵𝑣
=
255.72
45.26
= 5.65 ≈ 6
Provide 6 bolts for each splice.
Length of the splice plate = 2 × (2 × 60 + 2 × 35) = 380 mm
Provide a splice plate 380×250×6 mm on column flanges as
shown in the figure.

Design of Column
Splices due to Shear

Example: A column ISHB 300 @ 576.8 N/m is to support a
factored axial load of 500 kN, shear force of 120 kN and
bending moment of 40 kNm. Design the splice plate and
connection using 4.6 grade bolts. Use steel of grade Fe 410.

Solution:
For steel of grade Fe 410: 𝑓𝑢 = 410 MPa, 𝑓𝑦 = 250 Mpa
For bolts of grade 4.6: 𝑓𝑢𝑏 = 400MPa
Partial safety factors for material:(Table 5 IS 800:2007)
𝛾𝑚0 = 1.10𝛾𝑚𝑏 = 1.25
The relevant properties of ISHB 300 @ 576.8 N/m are (Table I,
SP 6-1)
𝐴 = 7485 mm2𝑏𝑓 = 250 mm,
𝑡𝑓 = 10.6mm 𝑡𝑤 = 7.6 mm

Assume the ends of the column sections to be machined for
complete bearing. As the column ends are flush, it is assumed that
50% of the load is transferred directly and 50% is transferred
through the splice and fastenings. Therefore,
The direct load on each splice plate = 50% 𝑜𝑓
500
2
= 125 kN
Load on splice due to moment =
𝑀𝑢
=
40×103
300+6
= 130.72 kN
(Assuming 6 mm thick splice plate, the lever arm = 300 + 6 mm)
Total design load for splice, 𝑃𝑠 = 125 + 130.72 = 255.72 kN
Sectional area of splice plate required =
𝑃𝑠
𝑓𝑦
=
255.72×103
250
= 1022.9mm2

Width of the splice plate should be kept equal to the width of
the flange.
Here, the width of the splice plate = 250 mm
Hence, thickness of splice plate =
1022.9
250
= 4.09 mm ≮ 6 mm
Provide a 250×6 mm splice plate.
The length of the splice plate depends upon the number of
bolts in vertical row.
Strength of 20 mm diameter bolt in single shear (cl. 10.3.3, IS
800:2007)
=
𝐴𝑛𝑏
𝑓𝑢𝑏
3
𝛾𝑚𝑏
=
245 ×
400
3
1.25
× 10−3
= 45.26 kN

Strength of bolt in bearing = 2.5𝑘𝑏𝑑𝑡𝑓𝑢/𝛾𝑚𝑏(cl. 10.3.4, IS
800:2007)
For 20 mm diameter bolts the minimum edge distance,
𝑒 = 1.5 × 𝑑0 = 1.5 × 20 + 2 = 33 mm
The minimum pitch, p = 2.5 × 20 = 50 mm
Let us provide an edge distance (e) of 35 mm and pitch (p) of
60 mm.
𝑘𝑏 is smaller of
𝑒
3𝑑0
=
35
3×22
= 0.53 ,
𝑝
3𝑑0
− 0.25 =
60
3×22
− 0.25 = 0.66 ,
𝑓𝑢𝑏
𝑓𝑢
=
400
410
= 0.98 and 1.0
Hence 𝑘𝑏 = 0.53

∴ Strength in bearing = 2.5 × 0.53 × 20 × 6 ×
410
1.25
× 10−3
= 52.15kN
Hence, the strength of bolt (Bv) = 45.26 kN
Number of bolts required, n =
𝑃𝑠
𝐵𝑣
=
255.72
45.26
= 5.65 ≈ 6
Provide 6 bolts for each splice.
Length of the splice plate = 2 × (2 × 60 + 2 × 35) = 380 mm
Provide a splice plate 380×250×6 mm on column flanges as
shown in the figure.

Splice plates for shear:
The splice plate for the shear force is provided on the web. A pair
of splice plate (one on each side of web) are provided.
Strength of bolt in double shear = 45.26 × 2 = 90.52 kN
Strength in bearing = 2.5𝑘𝑏𝑑𝑡𝑓𝑢/𝛾𝑚𝑏
Where, 𝑘𝑏 = 0.53 (taking 𝑒 = 35 mm and p = 60 mm),
𝑡 = 7.6 mm (web thickness)
∴ Strength in bearing = 2.5 × 0.53 × 20 × 7.6 ×
410
1.25
× 10−3 =
66.06 kN
Hence, strength of 20 mm bolt = 66.06kN

Shear force in the web, 𝑉 = 120 kN
Number of bolts required =
120
66.06
= 1.8 ≈ 2
Provide 2, 20 mm diameter bolts on each side of the splice.
Length of the splice plate = 4 × 35 = 140 mm
Width of the splice plate = 60 + 2 × 35 = 130 mm
Design shear strength of splice plate (cl. 8.4, IS 800:2007),
𝑉𝑑 =
𝑓𝑦
3 × 𝛾𝑚0
× ℎ × 𝑡
=
250
3 × 1.1
× 130 × 2𝑡𝑠 × 10−3
= 34.12 𝑡𝑠 kN

Now, 𝑉𝑑 > 𝑉
or 34.12 𝑡𝑠 > 120
Thickness of the splice plate required,
𝑡𝑠 =
120
34.12
= 3.52 mm ≮ 6mm
So provide a pair of 140×130×6 mm shear splice plates on each
side of the web as shown in the figure.

35
35
35
35
60
60
60
60
60
35 35
140
ISHB
300
20 mm
bolts
Front view Side view

INTRODUCTION TO FLEXURAL
MEMBERS: BEAMS

INTRODUCTION
• Flexural members or bending members are commonly called
BEAMS.
• A beam is a structural member subjected to transverse loads
i.e., loads perpendicular to the longitudinal axis.
• The load produce Bending moment & Shear forces.

http://wasatchsteel.blogspot.in/
http://www.steel-bridges.com/

DIFFERENT TYPES OF BEAMS
• JOIST: A closely spaced beams supporting floors or roofs of
building but not supporting the other beams.
• GIRDER: A large beam, used for supporting a number of
joists.
• PURLIN: Purlins are used to carry roof loads in trusses.
• STRINGER: In building, beams supporting stair steps; in
bridges a longitudinal beam supporting deck floor & supported
by floor beam.
• FLOOR BEAM: A major beam supporting other beams in a
building; also the transverse beam in bridge floors.

• SPANDREL BEAM: In a building, a beam on the outside
perimeter of a floor, supporting the exterior walls and outside
edge of the floor
• GIRT: A horizontal beam spanning the wall columns of
industrial buildings used to support wall coverings is called a
GIRT.
• RAFTER: A roof beam usually supported by purlins.
• LINTELS: This type of beams are used to support the loads
from the masonry over the openings .
DIFFERENT TYPES OF BEAMS

NATURE OF FORCES ACTING ON BEAMS
• It is assumed that the beam is subjected to only transverse
loading.
• All the loads and sections lie in the plane of symmetry.
• It follows that such a beam will be primarily subjected to
bending accompanied by shear in the loading plane with no
external torsion and axial force.

• The problem of torsion can not completely be avoided in a
beam even if the beam shape is symmetrical and loads are in
the plane of symmetry.
• The reason is the instability caused by compressive stresses.
Such instability is defined as LATERAL BUCKLING .
When it is involving only local components of a beam it is
called LOCAL BUCKLING.
• Local buckling is a function of width-thickness ratio.
NATURE OF FORCES ACTING ON BEAMS

Primary modes of failure of beams are as follows:
1. Bending failure
2. Shear failure
3. Deflection failure
1. Bending failure: Bending failure generally occurs due to
crushing of compression flange or fracture of tension flange of
the beam.
2. Shear failure: This occurs due to buckling of web of the beam
near location of high shear forces. The beam can fail locally
due to crushing or buckling of the web near the reaction of
concentrated loads.
3. Deflection failure: A beam designed to have adequate strength
may become unsuitable if it is not able to support its load
without excessive deflections.
MODES OF FAILURE

CONSIDERATIONS IN DESIGN OF BEAMS
• Beams should be proportioned for strength in bending
keeping in view of the lateral and local stability of the
compression flange.
• The selected shape should have capacity to withstand
essential strength in shear and local bearing .
• The beam dimension should be suitably proportioned for
stiffness, keeping in mind their deflections and deformations
under service conditions .

LIMITATIONS OF ANGLES , T-SECTIONS AND
CHANNELS
• Angles and T-sections are weak in bending.
• Channels only be used for light loads.
• The rolled steel channels and angle sections are used in those
cases where they can be designed and executed satisfactory.
• This is because the load is not likely to be in the plane, which
removes torsional eccentricities .
• Also, it is complicated to calculate the lateral buckling
characteristics of these sections .

Week 9 Lecture Material_watermark.pdf

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Week 9 Lecture Material_watermark.pdf