design of girde bl

8/2/2019 Design of Girde BL

1/8


2/8

C/C distance B/w angles

Horizontally = 958.8 mm

Vertical = 758.8 mm

Permissible stresses in bolts of property class 5.6 as per table 3 IS 802 (part1)-1977

shear stress = 310 MpaBearing Stress = 436 Mpa

Capacity of bolt

In single shear = 4194 Kg

In bearing = 3467 Kg

Allowable shear on each Bolt = 3467 Kg

Case1 withot deviation

Normal Short circuit

Vertical BM = 2887.39 Kgm 2887.39 KgmHorizontal BM = 9139.09 Kgm 12320.91 Kgm

Maximum compressive Force = 9532 Kg 12850 Kg

Maximum Tensile Force = 9532 Kg 12850 Kg

FOS against Comp = 1.93 1.43


3/8

MAIN LEG MEMBER (middle)

Member designation 90 X 90 X 6

Cg XX = 24.2 mm

Cg YY = 24.2 mm

Yield strength of steel = 250 Mpa

Effective length of buckling in XX dir = 2000 mm

Effective length of buckling in vv dir = 1000 mmRadus of gyration, rxx = 27.7 mm

Radus of gyration, rvv = 17.5 mm

Outer to outer diatance B/n angles Hz = 1000 mm

Outer to outer diatance B/n angles Ver = 800 mm

KL/rxx = 72.20

KL/rvv = 57.14

Design value of KL/r = 72.20

b = X 75 mm

t = 6 mm

b/t = 12.5

ebsilan e Sqrt(250/Fy) = 1

(b/t)lim = 13.28

IS 802 part1 sec2: 1992 cl. 5.2.2.1

> b/t henceOk

Maximum allowable slenderness Ce = 125.6637

IS 802 part1 sec2: 1992 cl. 5.2.2

Allowable stress, Fa = 209 Mpa

IS 802 part1 sec2: 1992 cl. 5.2.2

No of bolts along the width = 1

Assumed Dia of Bolt = 13 mm

Assumed Dia of hole = 14 mm

C/S area = 1044 mm2

Area of connecting leg A1 = 438 mm2Area of outstanding leg A2 = 522 mm2

Net cross/s area in tension (A1+A2) = 960 mm2

K = (3A1/(3A1+A2) = 0.716

Effective cross/s area in tension (A1+A2K) = 812 mm2

IS 802 part1 sec2: 1992 cl. 9.1

Permissible compression = 22237 Kg

Permissible Tension = 20704 Kg


4/8



Vertical = 751.6 mm



Dia of bolt = 16 mm

Capacity of bolt











5/8

MAIN LEG MEMBER (middle)

Member designation 45 X 45 X 5

Cg XX = 12.9 mm

Cg YY = 12.9 mm

Yield strength of steel = 250 Mpa

Effective length of buckling in XX dir = 1255 mm

Effective length of buckling in vv dir = 1255 mmRadus of gyration, rxx = 13.6 mm

Radus of gyration, rvv = 8.7 mm

Outer to outer diatance B/n angles Hz = 1000 mm

Outer to outer diatance B/n angles Ver = 800 mm

KL/rxx = 92.28

KL/rvv = 144.25

Design value of KL/r = 144.25

b = 34.5 mm

t = 5 mm

b/t = 6.9

ebsilan e Sqrt(250/Fy) = 1

(b/t)lim = 13.28

IS 802 part1 sec2: 1992 cl. 5.2.2.1

> b/t henceOk

Maximum allowable slenderness Ce = 125.6637

IS 802 part1 sec2: 1992 cl. 5.2.2

Allowable stress, Fa = 95 Mpa

IS 802 part1 sec2: 1992 cl. 5.2.2

No of bolts along the width = 1

Assumed Dia of Bolt = 13 mm

Assumed Dia of hole = 14 mm

C/S area = 425 mm2

Area of connecting leg A1 = 142.5 mm2Area of outstanding leg A2 = 212.5 mm2

Net cross/s area in tension (A1+A2) = 355 mm2

K = (3A1/(3A1+A2) = 0.668

Effective cross/s area in tension (A1+A2K) = 284 mm2

IS 802 part1 sec2: 1992 cl. 9.1

Permissible compression = 4114 Kg

Permissible Tension = 7256 Kg


6/8



Vertical = 774.2 mm



Dia of bolt = 16 mm

Capacity of bolt











7/8

Reliability level(EHV transmission lines up to 400KV class) 1

Terrain category 2

As per specification;Design wind pressurePd 960 N/m2

Wind load on Tower or Girder Fwt=PdXCdtXAeXGT

a) Pd=Design wind pressure in N/m2b)Cdt=Drag co-efficient for pannel under 2.58

consideration(From table 5) for solidity ratio 0.286

c)Ae=total net surface area

d)GT= Gust response factor(Height above ground 8.9m) 1.92

Total area of Girder by considering boundery 9.71 m2

Exposed area for wind 2.777 m2

Solidity ratio 0.286

Wind Pressure on tower (in kg) 485 KG/m2

Wind Pressure on tower (in kn) 4.76 KN/m2

(for total load this is to be multipli


8/8

ed by solidity ratio)

design of girde bl

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