DESIGN OF ROLLING STOCK MAINTANANCE SHED – ROOF FINAL REVIEW (2)

DESIGN OF ROLLONG STOCK MAINTANANCE SHED ROOF TRUSS

HARSHAVARDHAN.K.P

KRISHNAN.C

UVARAJ.D

TRUSS

In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in forces in the members which are Either tensile or compressive forces. Moments (torques) are explicitly excluded because, and only because, all the joints in a truss are treated as revolutes.

GENERAL

• Roof of rolling stock is proposed with steel trusses covered with metallic sheets.

• There are three types of trusses based on location

ADVANTAGES

• Fully engineered and ease of construction• Reduced site waste, loss and pilferage of materials.• Space saving on site, with no need for timber storage or

carpentry areas.• Material savings: trusses can use up to 40% less timber than a

traditionally built roof.

APPLICATIONS

• Houses and apartments • Warehouses• Sports hall• Hangers• Workshops• Sheds • Factory

• Spacing of truss=8m• Span=8.22+19.78+14.5+25+20+20

Span=107.5m• High and low bays are provided as per architectural drawings

and difference between the high and low bays shall be 2m.• Low bays trusses are proposed with monitors at centre for

ventilation.

• The Rafter and Tie Members have been adequately braced laterally thus preventing out-of-plane buckling.

• The compression member have been designed against buckling in and out of the truss.

• All members of the truss are proposed as Double Angles Back-to-Back.

OBJECTIVE• To design maintenance shed 107.5m X 192m height 20m, roof

slope 1 in 10.

LOCATION • Koyambedu, Chennai

DIMENSIONS• Plan dimensions=107.5 x 192m• Height at centre = 20m• Roof angle = 5º• Slope = 1 in 10• Purlin spacing = 1.325m

LOAD CONSIDERATIONS

Dead Load

Live Load

Wind Load

METHODOLOGY

The structure is designed by Limit State method of Design. IS 800-2007 is followed for limit state method. Structural components to be designed are roof truss, connections and RCC columns to support the truss.

CODE BOOKS

IS 875

IS 800-2007

DESIGN OF ROOF TRUSS

LOAD CALCULATIONS

DATA

• Spacing of truss = 8.00m• Spacing of purlin = 1.325m• Slope of roof = 5˚• Weight of sheeting = 65.00 N/m²• Basic Live Load = 750.00 N/m²

LOADS

• DEAD LOAD:

Span of purlin, l = 8.00m

Weight of Sheeting = 65.00 N/m²

Weight /m = 86.13 N/m

Assume Self Weight of Purlin = 100.00 N/m

Dead Load = 186.13 N/m

• LIVE LOAD:

Design Live Load = 750.00 N/m²

Live Load/m = 993.75 N/m• WIND LOAD:

Basic Wind Speed = 50.00 m/sec

k₁ = 1.10 ( important buildings- projected for 120 years)

k₂ = 0.93 ( category-2 , class-c)

k₃ = 1.00 (surface taken to be plain < 3˚)

vz = 51.15 m/sec

Design Wind pressure = 1569.79

CASE (i) - 0˚ (Perpendicular to ridge)

Windward Direction:

External wind pr co-efficient = (-)0.90 (Ref Table -5 & 16 of IS:875(3) – 1987)

Internal wind pr co-efficient = (+/-)0.50 (Permeability < 5% to 20 %)

Co-eff: Max= -1.40 Min= -0.40

Design wind pr = -2197.71 N/m² (pr. Corresponding to max of two co-eff above)

= -627.92 N/m² ( pr. Corresponding to min of two co-eff above)

WL1W = -2911.77 N/m²

= -831.99 N/m²

Point Load Applied in Model:

Wind Load Fy Fx

Max. Pressure -23.30 kN -23.30 kN -2.03 kN

Min. Pressure -6.66 kN -6.66 kN -0.58 kN

Leeward Direction:

External wind pr co-efficient = (-)0.40 (Ref Table -5 & 16 of IS:875(3) – 1987)

Internal wind pr co-efficient = (+/-)0.50 (Permeability < 5% to 20 %)

Co-eff: Max= -0.90 Min= 0.10

Design wind pr = -1412.81 N/m² (pr. Corresponding to max of two co-eff above)

= -156.98 N/m² ( pr. Corresponding to min of two co-eff above)

WL1L = -1871.98 N/m²

= -208.00 N/m²

Point Load Applied in Model:

Wind Load Fy Fx

Max. Pressure -14.98 kN -14.92 kN -1.30 kN

Min. Pressure 1.66 kN 1.66 kN 0.14 kN

DESIGN

DESIGN FORCES

• MAXIMUM TENSILE FORCE = 1132 kN• MAXIMUM COMPRESSIVE FORCE = 411.68 kN

DESIGN OF WELD

Longer leg of the angle connected to the plate

Strength of weld in shear, fwd = fu/√3 γm1 = 410/√3x1.25= 189.37

Length of the weld required = P/Rw

Where Rw is Weld strength/mm

Size of the weld = 6mm

Rw= 0.7 X size of weld X fwd

= 795.36

Maximum tension on member = 1132 kN

Length of the weld required Lw = 1132X1000/2X795.36 mm

= 711.6 mm

Say = 720.00 mm

Lw-150= l1+l2 = 570.00

Taking moment about l1

P/2 X 35.8 = 150 X 795.36 X 75 + 12 X 795.36 X 150

20261797.6 = 8947774.5+119304 X l2

l1 = 94.8 mm

Say l1 = 100.00 mm

l2 = 470.00 mm

DESIGN OF TENSION MEMBER

Strength governed by block shear

Gusset plate 8 mm is thinner than angle mm therefore block shear is checked for gusset plate Minimum gross area in shear Ag= 8X720 = 5760 mm2 Minimum net area in shear Anet = 8X720 = 5760 mm2

Minimum gross area in tension Atg = 8X150 = 1200 mm2

Minimum net area in Shear Ang = 8X150 =1200 mm2

Tdb1 = 1568 KN

Design tensile strength of the angle = 1568kN

Maximum tension force acting in the member = 1132 kN

Section is O.K.

DESIGN OF COMPRESSION MEMBER

Section classification

For angle section subjected to axial force

ε = (250/fy)1/2

ε = (250/250)1/2

ε =1

b/tf = 150/12 = 12.5 <15.7 ε

d/tf = 150/12 = 12.5 <15.7 ε

(b+d)/tf = (150+150)/12 = 25.0 <25 ε

Section is compact.

Effective length factor K in the plane of gusset = 0.7

ly = √(fy(KL/r)2/ 2E))

= Sqrt(((250X(0.7X1.16X1000/46.l)^2/((pi()^2X200000)))))

= 0.20

f = 0.5(1 +a(l-0.2)+l2)

= 0.5X(1+0.49X(0.20-0.2)+0.20x0.20)

= 0.52

fcd = (fy/gm0)/(f+(f2-l2)0.5)

fcd = (250/1.1)/(0.52+(0.52^2-0.20^2)^0.5)

= 227.48 Mpa

In y direction = fcdy X Ay =227.48 X 6918= 1573697 N = 1573.7 kN

Maximum compressive force acting in the member = 411.688 kN

Section is O.K

COLUMN DESIGN

TYPE I TRUSS

COLUMN C1:

LENGTH:12900.0 mm; CROSS SECTION: 900.0 mm X 600.0 mm; COVER: 40.0 mm

MAIN REINFORCEMENT: Provide 24 - 16 dia. (0.89%, 4825.49 Sq.mm.)

TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 255 mm c/c

Beam AnalysisProperty

DesignProperty

ActualRatio

AllowableRatio

Clause L/C Ax(mm2)

1 ISA75X75X8 ISA30X20X3 0.389 1 Compression 301 282


3 ISA75X75X8 ISA30X20X3 0.972 1 Tension 207 282

4 ISA75X75X8 ISA45X45X6 0.977 1 Tension 307 1.01E 3





9 ISA75X75X8 ISA25X25X5 0.988 1 Tension 207 450


CONCLUSION

Thus we have analyzed and designed the components of a maintenance shed manually and also by using software and the design was done in accordance with the codal provisions as provided in the design of steel structures. The design was done only for one representative of each of the member to be considered overall. The design done will be made use of all the members to be used in the maintenance shed

REFERENCES

Krishna Raju.N, “STRUCTURAL DESIGN AND DRAWING-REINFORCED CONCRETE AND STEEL” University Press, Hyderabad.

Subramanian.N, “DESIGN OF STEEL STRUCTURES”, Oxford University Press, New Delhi.

Satish Kumar.S.R and Santha Kumar.A.R (Indian Institute of Technology Madras) “DESIGN OF STEEL STRUCTURES”

IS 800 Code of Practice for the use of structural steel in general building construction, BIS New Delhi.

IS 875-1987 (parts I-IV), Indian Code of practice for evaluating loads except earthquake loads, BIS New Delhi.

THANK YOU

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DESIGN OF ROLLING STOCK MAINTANANCE SHED – ROOF FINAL REVIEW (2)