Truss design
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Transcript of Truss design
Design of Roof (Pratt) truss
Design Data:-
Plan length of the building l = 10.13mPlan depth of the building w = 5.72mHeight of the building excluding pitched roof h = 3.35mDead weight of AC sheets = 0.13KN/sqmDead weight of purlins,fixtures and false roofing system = 0.45KN/sqmSpan of the truss = 5.49mHeight of the truss = 1.00mSpacing of trusses = 3.30m
0.55KN/sqmDistance between the nodal points(purlin locations) on top rafter = 0.97mWind coefficients:-k1 (risk coefficient assuming 50 years of design life) = 1.00k2 (assuming terrain category 2) = 1.00k3 = 1.0 (topography factor) 1.00
50.00m/sec
0.20Slope of the pitched roof in degrees = 20
Load Calculations:-
Dead Load of roof = 0.58KN/sqm
Dead load/m run on rafter = 1.914KN/m
Live Load = 0.55KN/sqm
Live load/m run on rafter = 1.815KN/m
Calculation of Wind Load:-
Assuming the building is situated in Vijayawada, the basic wind speed is = 50.00m/sec
50.00m/sec
1.50KN/sqm
Wind Load on walls:-
Exposed area of the wall per frame normal to the wind direction, A = 11.06sqm
0.20
Live load on pitched roof (For pitched roof having slope 200 ) =
Basic wind speed Vb =
Internal wind pressure coefficient Cpi (Buildings with low permeability) =
Design wind speed, Vz = k1 k2 k3 Vb =
Design wind pressure, Pd = 0.6*Vz2 =
The wind load, WL acting normal to the individual surfaces is given by
WL = (Cpe – Cpi ) A*Pd
Assuming buildings with low degree of permeability,the internal pressure coefficient Cpi =
For the proposed building, h/w = 0.585664
l/w = 1.770979
From table 4 of IS 875--Part-3:1985,the external wind pressure coefficients are as given below:-
Wind angle Total wind load in KNin degrees Windward Leeward Windward Leeward Windward Leeward
00.7 -0.3 0.20 0.5 -0.5 8.295 -8.2950.7 -0.3 -0.20 0.9 -0.1 14.931 -1.659
90-0.5 -0.5 0.20 -0.7 -0.7 -11.613 -11.613-0.5 -0.5 -0.20 -0.3 -0.3 -4.977 -4.977
Wind Load on Roofs:-
Exposed area of each slope of roof, per frame is 9.64sqm
From table 5 of IS 875--Part-3:1985,the external wind pressure coefficients are as given below:-
Wind angle Total wind load in KNin degrees Windward Leeward Windward Leeward Windward Leeward
0-0.7 -0.5 0.20 -0.9 -0.7 -13.014 -10.122-0.7 -0.5 -0.20 -0.5 -0.3 -7.23 -4.338
90-0.8 -0.6 0.20 -1 -0.8 -14.46 -11.568-0.8 -0.6 -0.20 -0.6 -0.4 -8.676 -5.784
Concentrated loads on nodes :-
Dead load at intermediate node points = 1.75KN(corresponding to purlin locations)
Superimposed load at intermediate node points = 1.66KN(corresponding to purlin locations)
Wind load at intermediate node points on windward side = -2.41KN
Wind load at intermediate node points on leeward side = -1.45KN
Vertical component of wind load on windward side@ = -2.26KNintermediate nodal points
Vertical component of wind load on leeward side@ = -1.36KNintermediate nodal points
Vertical component of wind load @ at ridge = -1.81KN
Horizontal component of wind load on windward side@ = -0.82KNintermediate nodal points
Horizontal component of wind load on leeward side@ = -0.50KNintermediate nodal points
Horizontal component of wind load @ at ridge = -0.66KN
Cpe Cpi (Cpe-Cpi)
Cpe Cpi (Cpe-Cpi)
Load combinations :-
i) 1.5DL + 1.5LL
Vertical load windward = 5.12KN
Vertical load leeward = 5.12KN
Vertical load at ridge = 5.12KN
ii) 1.5DL + 1.5LL+1.05WL
Vertical load windward = 2.74KN
Vertical load leeward = 3.69KN
Vertical load at ridge = 3.22KN
Horizontal load windward = -0.82KN
Horizontal load leeward = -0.50KN
Horizontal load at ridge = -0.16KN (Windward side)
The results of analysis using STADD.Pro.2007 are as given below :-
Design of Roof (Pratt) truss
Design Data:-
Plan length of the building l =Plan depth of the building w =Height of the building excluding pitched roof h =Dead weight of AC sheets =Dead weight of purlins,fixtures and false roofing system =Span of the truss =Height of the truss =Spacing of trusses =
Distance between the nodal points(purlin locations) on top rafter =Wind coefficients:-k1 (risk coefficient assuming 50 years of design life) =k2 (assuming terrain category 2) =k3 = 1.0 (topography factor)
Slope of the pitched roof in degrees =
Load Calculations:-
Dead Load of roof =
Dead load/m run on rafter =
Live Load =
Live load/m run on rafter =
Calculation of Wind Load:-
Assuming the building is situated in Vijayawada, the basic wind speed is =
Wind Load on walls:-
Exposed area of the wall per frame normal to the wind direction, A =
Live load on pitched roof (For pitched roof having slope 200 ) =
Basic wind speed Vb =
Internal wind pressure coefficient Cpi (Buildings with low permeability) =
Design wind speed, Vz = k1 k2 k3 Vb =
Design wind pressure, Pd = 0.6*Vz2 =
The wind load, WL acting normal to the individual surfaces is given by
WL = (Cpe – Cpi ) A*Pd
Assuming buildings with low degree of permeability,the internal pressure coefficient Cpi =
For the proposed building, h/w = 0.5856643356643
l/w = 1.770979020979
From table 4 of IS 875--Part-3:1985,the external wind pressure coefficients are as given below:-
Wind angle Total wind load in KNin degrees Windward Leeward Windward Leeward Windward
00.7 -0.3 0.20 0.5 -0.5 8.2950.7 -0.3 -0.20 0.9 -0.1 14.931
90-0.5 -0.5 0.20 -0.7 -0.7 -11.613-0.5 -0.5 -0.20 -0.3 -0.3 -4.977
Wind Load on Roofs:-
Exposed area of each slope of roof, per frame is
From table 5 of IS 875--Part-3:1985,the external wind pressure coefficients are as given below:-
Wind angle Total wind load in KNin degrees Windward Leeward Windward Leeward Windward
0-0.7 -0.5 0.20 -0.9 -0.7 -13.014-0.7 -0.5 -0.20 -0.5 -0.3 -7.23
90-0.8 -0.6 0.20 -1 -0.8 -14.46-0.8 -0.6 -0.20 -0.6 -0.4 -8.676
Concentrated loads on nodes :-
Dead load at intermediate node points = 2.63KN(corresponding to purlin locations)
Superimposed load at intermediate node points = 2.49KN(corresponding to purlin locations)
Wind load at intermediate node points on windward side = -3.62KN
Wind load at intermediate node points on leeward side = -2.17KN
Vertical component of wind load on windward side@ = -3.40KNintermediate nodal points
Vertical component of wind load on leeward side@ = -2.04KNintermediate nodal points
Vertical component of wind load @ at ridge = -2.72KN
Horizontal component of wind load on windward side@ = -1.24KNintermediate nodal points
Horizontal component of wind load on leeward side@ = -0.74KNintermediate nodal points
Horizontal component of wind load @ at ridge = -0.99KN
Cpe Cpi (Cpe-Cpi)
Cpe Cpi (Cpe-Cpi)
Load combinations :-
i) 1.5DL + 1.5LL
Vertical load windward = 7.68KN
Vertical load leeward = 7.68KN
Vertical load at ridge = 7.68KN
ii) 1.5DL + 1.5LL+1.05WL
Vertical load windward = 4.11KN
Vertical load leeward = 5.54KN
Vertical load at ridge = 4.83KN
Horizontal load windward = -1.24KN
Horizontal load leeward = -0.74KN
Horizontal load at ridge = -0.25KN
The results of analysis using STADD.Pro.2007 are as given below :-
Member Location Nature of force
1--9 Top chord 26.40 Tension9--7 Top chord 18.00 Tension7--10 Top chord 17.70 Tension10--5 Top chord 27.90 Tension1--2 Bottom chord 1.09 Tension2--3 Bottom chord 1.11 Tension3--4 Bottom chord 1.08 Compression
Force(Case-II)in KN
1 2 3 4 5
9
7
10
1.40
[4'-7"]
1.40
[4'-7 1/4"]
1.40
[4'-7"]
1.40
[4'-7"]
1.49
[4'-10 1/2"]
1.49
[4'-10 1/2"]
1.00
[3'-3 1/4"]
SECTION OF THE TRUSS
4--5 Bottom chord 1.12 Compression9--2 Verticals 0.52 Compression7--3 Verticals 6.49 Compression10--4 Verticals 0.50 Compression9--3 Diagonals 7.09 Tension10--3 Diagonals 9.41 Tension
Design of Roof (Pratt) truss
10.13m5.72m3.35m
0.13KN/sqm0.45KN/sqm
5.49m1.00m3.30m
0.55KN/sqm 25.6266 61.91875 1586.7671.46m
1.001.00 212.43061.00
50.00m/sec
0.2020
24.5 58.25 158.56948.75 58.3 56.68056
215.25
0.58KN/sqm33.25 58.25 215.2014
1.914KN/m
0.55KN/sqm1258.63
1.815KN/m 147.222941.868136.7836
50.00m/sec
50.00m/sec
1.50KN/sqm
11.06sqm
0.20
Total wind load in KNLeeward-8.295-1.659
-11.613-4.977
9.64sqm
Total wind load in KNLeeward-10.122-4.338
-11.568-5.784
(Windward side)
1 2 3 4 5
9
7
10
1.40
[4'-7"]
1.40
[4'-7 1/4"]
1.40
[4'-7"]
1.40
[4'-7"]
1.49
[4'-10 1/2"]
1.49
[4'-10 1/2"]
1.00
[3'-3 1/4"]
SECTION OF THE TRUSS
Design of Roof truss
Design Data:-
Plan length of the building l =Plan depth of the building w =Height of the building excluding pitched roof h =Dead weight of AC sheets =Dead weight of purlins,fixtures and false roofing system =Span of the truss =Height of the truss =Spacing of trusses =
Distance between the nodal points(purlin locations) on top rafter =Wind coefficients:-k1 (risk coefficient assuming 50 years of design life) =k2 (assuming terrain category 2) =k3 = 1.0 (topography factor)
Slope of the pitched roof in degrees =
Load Calculations:-
Dead Load of roof =
Dead load/m run on rafter =
Live Load =
Live load/m run on rafter =
Calculation of Wind Load:-
Assuming the building is situated in Vijayawada, the basic wind speed is =
Wind Load on walls:-
Exposed area of the wall per frame normal to the wind direction, A =
Live load on pitched roof (For pitched roof having slope 140 ) =
Basic wind speed Vb =
Internal wind pressure coefficient Cpi (Buildings with low permeability) =
Design wind speed, Vz = k1 k2 k3 Vb =
Design wind pressure, Pd = 0.6*Vz2 =
The wind load, WL acting normal to the individual surfaces is given by
WL = (Cpe – Cpi ) A*Pd
Assuming buildings with low degree of permeability,the internal pressure coefficient Cpi =
For the proposed building, h/w = 0.3065164923572
l/w = 1.8769106999195
From table 4 of IS 875--Part-3:1985,the external wind pressure coefficients are as given below:-
Wind angle Total wind load in KNin degrees Windward Leeward Windward Leeward Windward
00.7 -0.25 0.20 0.5 -0.45 9.0541710.7 -0.25 -0.20 0.9 -0.05 16.29751
90-0.5 -0.5 0.20 -0.7 -0.7 -12.67584-0.5 -0.5 -0.20 -0.3 -0.3 -5.432503
Wind Load on Roofs:-
Exposed area of each slope of roof, per frame is
From table 5 of IS 875--Part-3:1985,the external wind pressure coefficients are as given below:-
Wind angle Total wind load in KNin degrees Windward Leeward Windward Leeward Windward
0-0.88 -0.4 0.20 -1.08 -0.6 -32.28385-0.88 -0.4 -0.20 -0.68 -0.2 -20.32687
90-0.75 -0.6 0.20 -0.95 -0.8 -28.39783-0.75 -0.6 -0.20 -0.55 -0.4 -16.44085
Concentrated loads on nodes :-
Dead load at intermediate node points = 2.34KN(corresponding to purlin locations)
Superimposed load at intermediate node points = 2.70KN(corresponding to purlin locations)
Wind load at intermediate node points on windward side = -6.46KN
Wind load at intermediate node points on leeward side = -4.78KN
Vertical component of wind load on windward side@ = -6.27KNintermediate nodal points
Vertical component of wind load on leeward side@ = -4.64KNintermediate nodal points
Vertical component of wind load @ at ridge = -5.46KN
Horizontal component of wind load on windward side@ = -1.56KNintermediate nodal points
Horizontal component of wind load on leeward side@ = -1.16KNintermediate nodal points
Horizontal component of wind load @ at ridge = -1.36KN
Cpe Cpi (Cpe-Cpi)
Cpe Cpi (Cpe-Cpi)
Load combinations :-
i) 1.5DL + 1.5LL
Vertical load windward = 7.56KN
Vertical load leeward = 7.56KN
Vertical load at ridge = 7.56KN
ii) 1.5DL + 1.5LL+1.05WL
Vertical load windward = 0.98KN
Vertical load leeward = 2.69KN
Vertical load at ridge = 1.84KN
Horizontal load windward = -1.56KN
Horizontal load leeward = -1.16KN
Horizontal load at ridge = -0.20KN
The results of analysis using STADD.Pro.2007 are as given below :-
Member Location Nature of force
1--9 Top chord 26.40 Tension9--7 Top chord 18.00 Tension7--10 Top chord 17.70 Tension10--5 Top chord 27.90 Tension1--2 Bottom chord 1.09 Tension2--3 Bottom chord 1.11 Tension3--4 Bottom chord 1.08 Compression4--5 Bottom chord 1.12 Compression9--2 Verticals 0.52 Compression7--3 Verticals 6.49 Compression10--4 Verticals 0.50 Compression9--3 Diagonals 7.09 Tension10--3 Diagonals 9.41 Tension
Force(Case-II)in KN
Design of Roof truss
23.33m12.43m
3.81m0.13KN/sqm0.45KN/sqm
12.20m1.52m3.30m
0.67KN/sqm 25.6266 61.91875 1586.7671.26m
1.000.98 212.43061.00
50.00m/sec
0.2014
24.5 58.25 158.56948.75 58.3 56.68056
215.25
0.58KN/sqm33.25 58.25 215.2014
1.914KN/m
0.67KN/sqm1258.63
2.211KN/m 147.222941.868136.7836
50.00m/sec
49.00m/sec
1.44KN/sqm
12.57sqm
0.20
Total wind load in KNLeeward
-8.1487539-0.9054171
-12.6758394-5.4325026
20.75sqm
Total wind load in KNLeeward
-17.93547-5.97849
-23.91396-11.95698
3.78
(Windward side)