Project 2
Questions:
1. Design a Warehouse Building located in Chennai using STAAD Pro Connect Edition. The specification must be as follows:
|
Width |
30m |
|
Length |
50m |
|
Eave Height |
9m |
|
Bay spacing |
6m |
|
Soil type |
Medium |
|
Safe Bearing Capacity |
200 kN/m2 |
|
Roof slope |
1 in 12 |
Assume suitable sections for structural elements. Follow IS800:2007, IS1893 and IS 875
- Prepare a Design Basis Report for the project.
- Create structural model using STAAD Pro Connect Edition.
- Prepare DL, LL, WL and EQL load calculations as per IS 875 standards.
- Design using MS – Excel;
- Steel column.
- Rafter.
- Base plate.
- Pedestal.
- Z- purlin.
- Design Foundations using STAAD Foundation.
- Attach necessary sketches and drawings wherever required.
- All stipulations, assumptions and design parameter must adhere to Indian Standards.
Solution:
1] Roof Slope Calculation:
Roof Slope = 1 in 12
Width, b = 30 m
X / (b/2) = 1/12
X = (30/2) / 12 = 15/12
X = 1.25 m
Total height =9 +1.25 =10.25
2] Modeling in staad pro:
Create structural model using STAAD Pro Connect Edition:
Step 1: Model Creation:
Step 2: Assign Properties:
3D View:
Material : Steel
BETA Angle 90 degree for wind / gable columns
Step 3: Specification:
- Member Tension
- End MY MZ
- Start MY MZ
Step 4: Support:
- Pinned
Step 5: Load Case Definition:
Seismic Definition:
Wind Load Definition:
Step 8:Define parameters:
Step 9:Define commands:
Step 10:Run analysis:
3] Prepare DL, LL, WL and EQL load calculations as per IS 875 standards
Calculation of Design Loads
1)Calculation of Dead load:
UDL on Rafter (Main frame):
Weight of roof sheeting = 5 Kg/m2
Weight of sag rods and braces = 5 Kg/m2
Collateral load = 10 Kg/m2
Total load = 20 Kg/m2 = 0.2 KN/m2
UDL on Rafters:
Bay spacing = 6m
UDL = 0.2 X 6 = 1.2 KN/m
UDL on Rafters from purlin:
Choose suitable purlin section for weight of purlin (IS-811)
Say Z = 270 X 75 X 20 X 2.55 = 8.77 Kg/m
Weight on rafters from purlin = (Number of purlin X Length of purlin)/Length of rafter
= ( 5 X 6 X 8.77)/15
= 17.54 Kg/m = 0.175 KN/m
UDL on main frame = 1.2 + 0.175 = 1.375 KN/m
UDL on gable frame = 1.375/2 = 0.687 KN/m
UDL on Column (Main frame):
Weight of side wall sheeting = 5 Kg/m2
Weight of sag rod and braces = 5 Kg/m2
Load from sag rods & braces = 10 Kg/m2 = 0.1 KN/m2 = 6 X 0.1 = 0.6 KN/m
Weight of grit (270 X 75 X 20 X 2.55) = 8.77 Kg/m
Weight on column = (5 X 6 X 8.77)/6 = 43.85 Kg/m = 0.438 KN/m
Total Load = 0.6 + 0.438 = 1.038 KN/m
UDL on Column (Gable frame):
Total load = 1.038/2 = 0.565 KN/m
Load on wind column:
Load from sheet and sag rods = 0.1 X 6 = 0.6 kN/m
Weight of grits (230 X 75 X 20 X 2) = 6.32 KG/m
Load on wind column = (6X 6.32 X 6)/6 = 37.92 Kg/m = 0.38 KN/m
Total load = 0.6 + 0.38 = 0.98 KN/m
Dead Load on eave strut & Gutter:
Point load:-
Weight of Eave strut = CS 270 X 75 X 20 X 3.15 = 10.7 Kg/m
Weight of eave gutter = 0.25 X 0.25 X 0.001 = [0.25 + 0.25 + 0.25] X 0.001 X 7850
=5.89 Kg/m
Load due to eave strut & gutter = 10.7 + 5.89 = 16.59 Kg/m
Load due to eave strut & gutter (Main frame) = 16.59 X 6 = 99.54 Kg
= 0.995 KN
Load due to eave strut & gutter (Gable frame) =0.497 KN
2) Calculation of Live load:
Live load on roof = 0.75 KN/m2 (IS 875- II)
UDL on Rafter:
Main frame rafter = 0.75 X 6 = 4.5 KN/m
Gable frame rafter = 0.5 X 4.5 = 2.25 KN/m
Eave gutter (250 X 250 X 1mm)
Load due to weight of water in gutter:
Main frame = [0.25 X 0.25 X 9 X 6] = 3.375 KN
Gable frame = [0.5 X 3.375] = 1.687 KN
3) Calculation of wind load:
Basic wind speed = 50 m/s for Chennai.
K1 - 1.00
K2 - 1.0
K3 - 1.00
K4 - 1.15
Kd -0.9
Ka (Rafter) - 0.8 or as per tributary area.
Ka (Column) - 0.8245 or as per tributary area.
Ka (Purlin) - 0.9721 or as per tributary area.
Ka (Side Runner) - 0.978 or as per tributary area
Kc -0.9
Design wind pressure = pd = kd x ka x kc x 0.6 x (Vb x k1 x k2 x k3 x k4)^2= 0.652 kN/m2
But should not be less than 0.7 Pz = 0.7 x 1.006 = 0.704 kN/m2
Cpe - As per table 5 & 6 of IS: 875 (Part 3) – 2015
Cpe On wall:
|
Direction |
A |
B |
C |
D |
|
0 deg. |
0.7 |
-0.25 |
-0.6 |
-0.6 |
|
90 deg. |
-0.5 |
-0.5 |
0.7 |
-0.1 |
Cpe On Roof:
Roof angle = 2.86
|
Direction |
EF |
GH |
EG |
FH |
|
0 deg. |
-0.86 |
-0.4 |
||
|
90 deg. |
-0.8 |
-0.4 |
Cpi = 0.2
Wind Load on Column in (+X)-direction:
Wind Load on Columns = (Cpe – Cpi) x A x Pd
Wind about X Direction + Cpi = (0.7 – 0.2) x 8 x 0.704 = 2.816 kN/m on Wall A
Wind about X Direction + Cpi = (-0.25 – 0.2) x 8 x 0.704 = -2.534 kN/m on Wall B
Wind about X Direction + Cpi = (-0.6 – 0.2) x 6.75 x 0.704 = -3.802 kN/m on Wall C & D
Wind Load on Column in (-X)-direction:
Wind about X Direction - Cpi = (0.7 + 0.2) x 8 x 0.704 = 5.069 kN/m on Wall A
Wind about X Direction - Cpi = (-0.25 + 0.2) x 8 x 0.704 = -0.282 kN/m on Wall B
Wind about X Direction - Cpi = (-0.6 + 0.2) x 6.75 x 0.704 = -1.9 kN/m on Wall C & D
Wind Load on Column in (+Z)-direction:
Wind about Z Direction + Cpi = (-0.5 – 0.2) x 8 x 0.704 = -3.942 kN/m on Wall A
Wind about Z Direction + Cpi = (-0.5 – 0.2) x 8 x 0.704 = -3.942 kN/m on Wall B
Wind about Z Direction + Cpi = (0.7 – 0.2) x 6.75 x 0.704 = 2.376 kN/m on Wall C
Wind about Z Direction + Cpi = (-0.1 – 0.2) x 6.75 x 0.704 = -1.425 kN/m on Wall D
Wind Load on Column in (-Z)-direction:
Wind about Z Direction - Cpi = (-0.5 + 0.2) x 8 x 0.704 = -1.689 kN/m on Wall A
Wind about Z Direction - Cpi = (-0.5 + 0.2) x 8 x 0.704 = -1.689 kN/m on Wall B
Wind about Z Direction - Cpi = (0.7 + 0.2) x 6.75 x 0.704 = 4.276 kN/m on Wall C
Wind about Z Direction - Cpi = (-0.1 + 0.2) x 6.75 x 0.704 = 0.475 kN/m on Wall D
Wind Load on Rafters in (+X)-direction:
Wind Load on Rafters = (Cpe – Cpi) x A x Pd
Wind about X Direction + Cpi = (-0.86 – 0.2) x 8 x 0.704 = -5.970 kN/m on Side A Rafter
Wind about X Direction + Cpi = (-0.4 – 0.2) x 8 x 0.704 = -3.378 kN/m on Side B Rafter
Wind Load on Rafters in (-X)-direction:
Wind about X Direction - Cpi = (-0.86 + 0.2) x 8 x 0.704 = -3.716 kN/m on Side A Rafter
Wind about X Direction - Cpi = (-0.4 + 0.2) x 8 x 0.704 = -1.125 kN/m on Side B Rafter
Wind Load on Rafters in (+Z)-direction:
Wind about Z Direction + Cpi = (-0.8 - 0.2) x 6.75 x 0.704 = -4.752 kN/m Side C Rafter
Wind about Z Direction + Cpi = (-0.4 - 0.2) x 6.75 x 0.704 = -2.851 kN/m Side D Rafter
Wind Load on Rafters in (-Z)-direction:
Wind about Z Direction - Cpi = (-0.8 + 0.2) x 6.75 x 0.704 = - 2.851kN/m Side C Rafter
Wind about Z Direction - Cpi = (-0.4 + 0.2) x 6.75 x 0.704 = -0.950 kN/m Side D Rafter
Wind Load on Canopy:
Cp - As per table 8 of IS: 875 (Part 3) – 2015
Roof Angle 2.86 deg.
Cp -ve = 1.08
Cp +ve = 0.35
Wind Load on Canopy (Upward) = 1.08 x 8 x 0.704 = 6.082 kN/m
Wind Load on Canopy (Downward) = 0.35 x 8 x 0.704 = 1.971 kN/m
4) Seismic Load:
As per IS: 1893 - 2016
Seismic zone - III - Z = 0.16
Rf - 4.0
I - 1.0
SS - 3.0
25% of Live Load on roof considered for calculation of seismic forces.
100% of collateral load on roof considered for calculation of seismic forces.
50% of (Live load + Collateral load) on mezzanine floor considered for calculation of seismic forces.
100% of Dead load considered for calculation of seismic force.
4] Design using MS – Excel
- Steel column
- Rafter
- Base plate
- Pedestal
- Z- purlin
1.DESIGN OF STEEL COLUMN:
Flange thickness = T = 12.7 mm.
Overall height of Column ISMB400 = h = 400 mm.
Clear depth between flanges = d = 400 – (12.7 x 2)
= 374.6 mm.
Thickness of web = t = 10.6mm.
Flange width = 2b = bf = 250 mm.
Hence, half Flange Width = b = 125 mm.
Self –weight = w = 0.822 kN/m.
Area of cross-section = A = 10466 mm2.
Radius of gyration about x = rx = 166.1 mm.
Radius of gyration about y = ry = 51.6 mm.
Type of section:
b/T = 125/12.7= 9.8 < 10.5
d/t =374.6/10.6 =35.3 < 42
(Table 3.1 of IS: 800)
Hence, cross-section can be classified as “COMPACT”.
Effective Sectional Area, Ae = 10,466 mm2
(Since there is no hole, (Clause 7.3.2 of IS: 800)
no reduction has been considered)
Effective Length:
As, both ends are pin-jointed effective length, KLx = KLy = 3m
Slenderness ratios:
KLx/rx = 9000/166.1 =54.1
KLy/ry = 9000/51.6 =174.41
Non-dimensional Effective Slenderness ratio, λ">λ:
λ">λ
= (sqrt2.5X(174)^2)/(pi^2X2X10^5`= 3.83
Value of ϕ">ϕ from equation:
Hence, α">α = 0.34 for buckling class ‘b’ will be considered.
Hence, ϕ">ϕ= 0.5 x [1+0.34 x (0.654-0.2)+0.6542] = 0.791
Calculation of x:
= 0.809
Calculation of fcd from the following equation:
= 0.809 x 250/1.1 = 183.86 N/mm2
Factored axial load in kN.
pd = Ag fcd
= 10466 x 183.86/1000 = 1924.28 kN.
2. DESIGN OF RAFTER:
Span of Rafter = 6 m
Dead load = 18KN/m
Imposed load = 40KN/m
support bearing = 100mm
yield strength = 250N/mm2
Design load calculation:
Factores load 1.5(DL+LL) =87 KN/m
Factores Bending moment = Wl28">Wl28��28= 65.25 KN/m
Section modulus Required:
Z reqd = (65.25 x106106 x1.1) /250 =287100 mm3 = 287.1 cm3
Section classification:
ISMB-200
A = 323.3 mm2
D = 200mm
B = 100mm
t = 5.7 mm
T = 10.8 mm
Ixx = 2235.4 cm4
Iyy = 150 cm4
Zp = 375.35 cm3
Moment of resistence of the cross-section:
Md = βbZpfyγm0��������0
= (1 x 375.35 x 250) / ( 1.1)
Md = 85.306 > 65.25 KN/m
3. DESIGN OF BASE PLATE:
Strength of concrete, Fcu = 40 N/mm2
Yield strength of steel, fy = 250 N/mm2
Material factor, γm">γm= 1.1 KN
Factoresl Load = 1500 KN
Steel column section:
Thickness of flange, T = 12.7 mm
Area required:
Bearing strength of concrete = 0.4fcu = 0.4 x 40 = 16 N/mm2
= (1500x1000) /( 16)
= 93750 mm2
Let size of plate , Bplate = 450 mm
Dplate = 300 mm
Area of plate= 135000 mm2
projection on each side = a=b =25mm
W = (1500x1000) /( 450 x 300)
= 11.11 N/mm2
Therefore, Thickness of Base Plate, clause 7.4.3.1
`t s = √ 2.5 w ( a 2 − 0.3 b 2 ) γ m 0 f y > t f`
ts= 7.3 mm < 12.7 mm
Size of Base plate 450 x 350 x 16 mm
4.DESIGN OF PEDESTAL:
Grade of concrete = 40 N/mm2
Load = 200 KN
Moment = 120 KN
Horizontal shear = 20 KN
Yield strength = 250 N/mm2
Length of base plate = 450 mm
Width of base plate = 350 mm
C/C distance of bolt in group-Z = 300 mm
C/C distance of bolt in group-X = 180 mm
Bearing strength of concrete Fc = 16 N/mm2
Depth of Column = 300 mm
Width of Column = 250 mm
Anchor Bolt Details:
Dia of anchor bolts =24 mm
No:of anchor bolts in each side = 4
Total no. of anchor bolts, n = 8
Gross area of the bolt ;Asb' = 452.16 mm2
Net area of bolt 'Anb' = 352 mm2
Ultimate tensile strength of bolt 'fub' = 400 N/mm2
Fyb (anchor bolts) = 240 N/mm2
Base plate Details:
Ultimate tensile strength of plate 'fu' = 490 N/mm2
Thickness of plate = 16 mm
Yield stress of plate = 330 N/mm2
Anchor bolt design:
Area of the plate = 157500 mm2
Stress,
Stress, Maximum pressure =`F/A +(6XMz)/(BL^2`
= 10.6 N/mm2 < 16 Hence OK
Minimum pressure =`F/A - (6XMz)/(BL^2`
= -9.04 N/mm2 < 16 Hence OK
Centroid = `(LXsigma1)/(sigma1+sigma2)`= 242.89 mm
a =L/2-C/3 = 144.04 mm
e = (L-Ld) / 2 =75 mm
y = (L - C/3-e) = 294.04 mm
Tension in anchor bolt along the length of plate, FT = (Mz - Fa)/Y
= 364.38
Tension per bolt = 91 KN
Shear per bolt = 1.63 KN
Shear Check:
Factored shear force = Vsb = 1.63 KN
Vd,sb = 81290.9 N
= 81 KN
Factored shear force = 65.03 KN
Tensile Check:
Factored tensile force in bolt, Tb = 91.1 KN
Tensile strength of bolt:
Ts,b = Tn,b /`gammamb`= 126 KN
Td,b = 98.65 KN
Combined Unity Check:
Vsb/Vdb = 0.025
Tb/Tdb = 0.92
Unity check = 0.85 < 1, Hence OK
Anchor Bolt Length:
Bond strength in tension, `taubd`= 1.4 N/mm2
Anchor length required = Tb(3.14*`taubd`)
= 863.44 mm
Let Anchor Bolt Length = 900 mm
5.DESIGN OF Z-PURLIN:
Span of the purlin = 6 m
Spacing of purlin = 1.5 m
No. of sag rods = 1
Slope of the roof = 4.76 = 5 degree
Dead load:
Weight of sheeting = 6kg/m2
self weight of purlin = 4.22 kg/m2
Additional load = 10% = 0.42 kg/m2
Total Dead load = 0.106 kg/m2
Live load:
Live load on roof = 75 kg/m2
Wind Load:
Basic wind speed = 50 m/s
Terrain caterogy = 2
Building class = B
K1 = 1
K2 = 1
K3 = 1
Design wind speed, Vz = 57 m/s
Design wind pressure, Pz = 1949.9 m/s = 1.94 KN
Length of building, L = 50 m
Breadth of building, W = 30 m
Height of building, H = 10.25 m
Height of eaves, = 9 m
h/w = 0.34
L/w = 1.667
External Pressure Co-eeficient:
Maximum downward =Cpe = -0.4
Maximum upward =Cpe = -0.7
Internal Pressure Co-eeficient:
Maximum positive =Cpi = 0.5
Maximum negative =Cpi = -0.5
For Maximum upward wind force:
Max upward Cpe = - 0.7
Cpi = - 0.5
Cpe + Cpi = -1.2
Pz = 1.95
Wind Pressure for Purlin Design = - 2.339 KN/m2
For Maximum upward wind force:
Max upward Cpe = - 0.4
Cpi = - 0.5
Cpe+Cpi = -0.1
Pz = 1.95
Wind Pressure for Purlin Design = 0.195 KN/m2
Design Load Calculation:
Spacing of purlin = 1.5 m
Slope of roof = 5 degree
Total dead load = 0.096
DL Normal component = 0.144 KN/m
DL Tangential component = 0.013 KN/m
Total Live load = 0.75
LL Normal component = 1.121 KN/m
LL Tangential component = 0.098 KN/m
Total Wind load = -2.339
WL Normal component = - 3.496 KN/m
WL2 WL load = 0.195 KN/m
WL Normal component = 0.291 KN/m
Maximum Normal component = DL+LL = 1.265 KN/m
Purlin section:
Selected section Z200 x 6 x 2.3
Area = 8.07 cm2
Weight of purlin = 6.335 kg/m.
1] Design Foundations using STAAD Foundation.
Click on Staad foundation:
2. Design a simply supported gantry girder to carry electric overhead travelling crane
Given:
Span of gantry girder = 7 m
Span of crane girder = 9 m
Crane capacity = 250 kN
Self-weight of trolley, hook, electric motor etc. = 40 kN
Self-weight of crane girder excluding trolley = 100 kN
Minimum hook approach = 1.0 m
Distance between wheels = 3 m
Self-weight of rails = 0.2 kN/m.
Solution:
Step:-1
Maximum moment due to vertical load
Weight of trollley + Crane capacity = 40 + 250 = 290 kN
Self-weight of crane girder excluding trolley = 100 kN
For maximum reaction on gantry girder, the moving load should be as close the gantry girder as possible.
Ra=`(290X8)/9+100/2=307.77 KN`
This load is transferred to gantry girder, through two wheels, the wheel base being 3m.
So load on gantry girder from each wheel = 307.77/2 = 158.88 KN
Factored load = 158.88 x 1.5 =230.83 KN
Maximum moments due to moving loads occur under a wheel when the c.g of wheel load.
RD= 230.83 x (3-1.5-0.75) + 230.83 x (3+0.75)/7 = 148.40 KN
Max. moment, Me = 148.40 x 2.25 = 333.90 KNm.
Moment due to impact = 0.25 x 333.90 = 83.47 KNm.
Assume self weight of girder = 2KNm.
Dead load due to self weight + rails = 2+0.2= 2.2 KNm.
Factored Dead Load = 2.2 x 1.5 = 3.3 KNm.
Moment due to Dead Load = `3.3X7^2/8`= 20.21 KNm.
Factored moment due to all vertical loads,
Mz = 333.90 + 83.47 + 20.21 = 437.58 KNm.
Step :- 2
Maximum moment due to Lateral force:
Horizontal force transferred to rails = 10% of weight of trolley plus load lifted = (10/100) x (250+40) = 29 KN
This is distributed over 4 wheels.
So, horizontal force on each wheel = 29/4 = 7.25 KN
Factored horizontal force on each wheel = 1.5 x 7.25 = 10.875 KN
For maximum moment in gantry girder the position of loads is same as earlier except that it is horizontal, hence by proportioning we get.
My = (10.875/230.83) x 333.90 = 15.73 KNm.
Step :- 3
Shear force:
Vertical shear due to wheel loads = 230.83 + (230.83 x 3) / 7 = 329.75 KN
Step :- 4
Priliminary Section:
Minimum economic depth, L/12 = 7000/12 = 583.33 mm
Width of the compression flange may be taken as (1/40) to (1/30) of span;
So, flange width can be taken as, L/40 = 7000/40 = 175 mm to L/30 = 7000/30 = 233.33 mm.
Required, Zp = 1.4 x M/fy = `1.4 X (437.58 X 10^6)/(250)` = 2450 x `10^3`mm3
Let us try a ISMB 600 with ISMC 400 on compression flange.
Step :- 5
| ISMB | 600 @1.22 kN/m. |
| A | 15600 sq.mm. |
| h | 600 mm. |
| b | 210 mm. |
| tf | 20.3 mm. |
| tw | 12 mm. |
| Izz | 91800 X `10^4``mm^4` |
| Iyy | 2650 X `10^4``mm^4` |
| R | 20 mm. |
| ISMC | 400 @0.49 kN/m. |
| A | 6380 sq.mm. |
| h | 400 mm. |
| b | 100 mm. |
| tf | 15.3 mm. |
| tw | 8.8 mm. |
| Izz | 15200 X `10^4``mm^4` |
| Iyy | 508 X `10^4``mm^4` |
| Cyy | 2.42 mm. |
Step :-6
Let the distance of N>A> from the tension range by y:
388.93 mm.
Izz = 1348.13x10^6mm^4
Zez = 3466240mm^3
For compression flange about y-y axis
I = 16766.7x10^4mm^4
Zey = 838333mm^3
Total area of section = 21980mm^2
Let plastic N>A> be at a distance
Yp = 580.88mm
Zpz = 4410317mm^3
For top flange Zpy = 1078488mm^3
Step :- 7
Section classfication:
For ISMB b/t = 4.90
< 9.4
d/t = 43.28
< 84
For ISMC b/t = 5.96
< 9.4
Hence section is plastic
Step :- 8
Check for local moment capacity:
Local moment capacity for bending in vertical plane
Mdz = fyZp/1.1
= 1002.34kNm
Mdz = 1.2Zefy/1.1
= 945.34kNm
For top flange
Mdy = 245.11kNm
Mdy = 228.64kNm
In the above whichever the minimum value is taken
Mdz = 945.34kNm
Mdy = 228.64kNm
Step : 9
Check for combined local capacity :
(812.99/945.34)+(18.35/228.64)<1
0.947<1
Step : 10
Check for buckling resistance :
Md = βbZpfbd
βb = 1
Lt = 7000mm
E = 200000N/mm^2
hf = 597.5mm
Iy = 17850x10^4mm^4
A = 21980mm^2
ry = 90.12mm
fcr,b = 417.43N/mm^2
λ = 0.744
φ = 0.95
= 0.97N/mm^2
fbd = 166.591
Mdz = 734.72kNm
Mdy = 202.84kNm
Hence 1.20>1
Hence section is unsafe against torsional buckling
Step : 11
Check for shear:
Vz = 714.59kN
Shear capacity = Avfyw/(3^0.5x1.1)
= 944755N
= 944.755kN
> 714.59
Now = 566.853kN
Low shear
Step : 12
Check for web buckling:
b = 175mm
n1 = 232.6mm
d = 519.4mm
t = 12mm
= 104.746
Fcd = 128.6N/mm^2
Buckling resistance = 629008kN > 714.59kN
Step : 13
Check for deflection at working load:
Vertical deflection:
Serviceability vertical wheel load = 251kN
Deflection at mid span a = 2000mm
Izz = 1348.13x10^5mm^4
δ = 25.32mm
Horizontal deflection
I = 16766.65x10^4mm^4
δ = 4.88mm
L/750 = 9.33mm
Unsafe in vertical direction but Safe in lateral direction.