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Masterclass in Structural BehaviourETS3
Structural Scheme Design
Cíaran Malik
Third Year, First Term
2019-2020
Brief: Hooke Park in Bedford SquareSpecialisms
Structure
Environment
MaterialsConstruction
Sustainability
ThermalStructure
Sustainability• Embodied Carbon• Operational
Carbon• Carbon Capture• Ecology• Material Reuse• Circular Economy
Construction
Water
Acoustics
Light
Materials
Cost + Programme
Good Design
References
Schedule
4
Time Activity By
14:00-14:25 2.1 Structural Scheme Design Cíaran
14:30-14:55 2.2 Structural Scheme Design Exercise Cíaran
15:00-15:25 2.3 Long Span Structures Giancarlo
15:45-16:00 2.4 Tutorials 2,7,12,17
16:00-16:15 2.4 Tutorials 3,8,13,18
16:15-16:30 2.4 Tutorials 4,9,14,19
16:30-16:45 2.4 Tutorials 3,10,15,20
16:45-17:00 2.4 Tutorials 1,6,11,16
Key Points
1. Importance of Span and Depth
2. Sizing based on Span and Depth
3. Not included in Span to Depth
4. Design Example
5. Reference
5
h1
Cross sectionDifferent shapes are stronger and deflect less
Strength
Section modulus for rectangle section
Z = bh² / 6
Stiffness
Second moment of area for a rectangle
I = bh³ / 12
b1
b2
h2
100mm = h1
Cross sectionDifferent shapes are stronger and deflect less
Strength
Z 1 = b1h1² / 6
Z 1 = 400 x 100² / 6
Z 1 = 666,000 mm³
Strength
Z 2 = b2h2² / 6
Z 2 = 100 x 400² / 6
Z 2 = 2, 666,000 mm³
Z 2 > Z 1 x 4
400mm = b1
100mm = b2
400mm = h2
Same amount of material
4 times stronger
100mm = h1
Cross sectionDifferent shapes are stronger and deflect less
Stiffness
Z 1 = b1h1³ / 12
Z 1 = 400 x 100³ / 12
Z 1 = 33, 000,000 mm⁴
Stiffness
Z 2 = b2h2³ / 12
Z 2 = 100 x 400³ / 12
Z 2 = 533, 000,000 mm⁴
Z 2 > Z 1 x 16
400mm = b1
100mm = b2
400mm = h2
Same amount of material
16 times stiffer
SpansDifferent arrangements have differentdeflections
Simply supported beam
Deflection
δ = FL³ / 48EI
δ = F(2L)³ / 48EI = 8 FL³ / 48EI
9
Fixed end cantilever
Deflection
δ = FL³ / 3EI
δ = F(2L)³ / 3EI = 8 FL³ / 3EI
FORCE = F FORCE = F
Length = L
Twice the span, 8 times the deflection
Span = L
Beams and CantileversDesign by strength, stiffness, section, span and depth
Simply supported beam
Fixed end cantilever
Bending moment depends on:
• Span
• Support Arrangement
• Load
10
Strength and stiffness depend on
• Depth of section
• Shape of section
Span to Depth DesignSteel Beam
11Structural Engineering for Architects A Handbook (Silver, McLean, Evans) page 78
Building Structures Illustrated (Ching, Onouye, Zuberbuhler) 2nd edition page 119 12
Span to Depth DesignSteel Beam
Span to Depth DepthSteel Beam
Span to depth ratio is 15:1
Span = 15 x Depth
Depth = Span / 15
Depth = 9000mm / 15 = 600mm
Depth = 9m / 15 = 0.6m
13Structural Engineering for Architects A Handbook (Silver, McLean, Evans) page 78
FORCE = w
Span = 9m
Span to Depth DepthSteel Beam
14Structural Engineer's Pocket Book 2nd Edition (Fiona Cobb) page 218
FORCE = w
Span = 9m
Span to depth ratio is 15:1
Span = 15 x Depth
Depth = Span / 15
Depth = 9000mm / 15 = 600mm
Use a 610 x 229 x 101 beam
Span to Depth Design
Span to Depth Design provides an initial design.
It does not mean it is safe15
Structural Engineer's Pocket Book 2nd Edition (Fiona Cobb) page 42 16
Not included in Span to DepthThe weight of finishes
Not included in Span to DepthDifferent Live Loads
Self-weight
(approximately)
Timber floor = 0.5 kN/m²
Steel and concrete=2.5 kN/m²
250mm concrete = 6.0 kN/m²
Permanent
(approximately)
Resi Partitions = 0.5 kN/m²
Office Partitions = 1.0 kN/m²
Ceiling = 0.1 kN/m²
Services = 0.1 kN/m²
Timber Floor =0.2 kN/m²
Insulation = 0.05 kN/m²
17
Variable (approximately)
Maintenance = 0.6 kN/m²
Residential = 1.5 kN/m²
Resi Balcony = 2.5 kN/m²
Office/School = 3.0 kN/m²
Retail = 4.0 kN/m²
Gym/Club = 5.0 kN/m²
Road = 5.0 kN/m²
Workshop = 5.0 kN/m²
Plant Room = 7.5 kN/m²
Not included in Span to DepthTransfer structures
18Building Structures Illustrated (Ching, Onouye, Zuberbuhler) 2nd edition page 157
Not included in Span to DepthFloor to Ceiling Heights
19Building Structures Illustrated (Ching, Onouye, Zuberbuhler) 2nd edition page 325
Not included in Span to DepthDifferent Span Arrangements
20
Simply supported beam
Multi-span beam
Cantilever with backspan
Fixed end beam
Section-Active, Beam Grid, Crown Hall, Ludwig Mies Van Der Rohe 21
Design Example
Design ExampleColumn Design
22
15m
15m
15m
5m
5m
30m
2.5m
Span = L = 30m
5m
15m
15m
15m
5m
6m
Structural Engineer's Pocket Book 2nd Edition (Fiona Cobb) page 82 23
Design ExampleColumn DesignEffective Length
Metric Handbook Planning and Design Data (Littlefield) 3rd edition page 36-38 24
Design ExampleColumn DesignEffective Length
Design ExampleColumn Design
25
Single storey typical height 2-8m
Height / Depth = 20 to 25
Height/20 to Height/25 = Depth
6m/20 to 6m /25 = Depth
0.3mm to 0.24m = Depth
h = 6m
Design ExampleColumn Design
Single storey typical height 2-8m
Height / Depth = 20 to 25
Height/20 to Height/25 = Depth
6m/20 to 6m /25 = Depth
0.3mm to 0.24m = Depth
26
Use Depth = D =0.254m
Design ExamplePrimary Beam Design
27
15m
15m
15m
5m
5m
30m
2.5m
Span = L = 30m
Tributary Area
28
Design ExamplePrimary Beam Design
Span / Depth = 16 to 24
Span/16 to Span/24 = Depth
30m/16 to 30m /24 = Depth
1.875m to 1.25m = Depth
29
Span = L = 30m
Use Depth = h =1.25m
Roof, with low loads (snow, wind) so use smaller end of scale
15m
15m
15m
5m
5m
30m
2.5m
Design ExampleSecondary Beam Design
30
5m
15m
15m
15m
5m
Tributary Area
31
Design ExampleSecondary Beam Design
Span / Depth = 16 to 24
Span/16 to Span/24 = Depth
15m/16 to 15m /24 = Depth
0.94m to 0.63m = Depth
32
Use Depth = h =0.63m
Roof, with low loads (snow, wind) so use smaller end of scale
5m
15m
15m
15m
5m
Design ExampleDecking Design
33
15m
15m
15m
5m
5m
30m
2.5m
34
Design ExampleDecking Design
35
15m
15m
15m
5m
5m
30m
2.5m
Span / Depth = 30 to 50
Span/30 to Span/50 = Depth
2500mm/30 to 2500mm /50 = Depth
84mm to 50mm = Depth
Use h =130mm
Metal deck thinnest is normally 130mm, so you have to think a bit
ReferenceExtract Metric Handbook Planning and Design Data on Website
36
AA TS3 Littlefield, D (2008) Metric Handbook Planning and Design Data
Cobb, F. (2003) Structural Engineer’s Pocket Book
Engal, H. (2009) Tragsysteme/Structure Systems
McLean W., Silver P., Evans P. (2014) Structural Engineering for Architects
Ching F., Onouye B., Zuberbuhler D. (2014) Building Structures Illustrated
Silver P., McLean S., King L. (2013) Introduction to Architectural technology
ReferenceWaffle Slab
37Metric Handbook Planning and Design Data (Littlefield) 3rd edition page 36-28
ReferenceMasonry Arch
38Metric Handbook Planning and Design Data (Littlefield) 3rd edition page 36-14
ReferenceSuspension Roof
39Metric Handbook Planning and Design Data (Littlefield) 3rd edition page 36-40
ReferenceMasonry Retaining Walls
40Metric Handbook Planning and Design Data (Littlefield) 3rd edition page 36-15
ReferenceTension Structure
41Metric Handbook Planning and Design Data (Littlefield) 3rd edition page 36-46
Key Points
1. Importance of Span and Depth
2. Sizing based on Span and Depth
3. Not included in Span to Depth
4. Design Example
5. Reference
42
Masterclass in Structural BehaviourETS3
Structural Scheme Design
Cíaran Malik
Third Year, First Term
2019-2020
Schedule
44
Time Activity By
14:00-14:25 2.1 Structural Scheme Design Cíaran
14:30-14:55 2.2 Structural Scheme Design Exercise Cíaran
15:00-15:25 2.3 Long Span Structures Giancarlo
15:45-16:00 2.4 Tutorials 2,7,12,17
16:00-16:15 2.4 Tutorials 3,8,13,18
16:15-16:30 2.4 Tutorials 4,9,14,19
16:30-16:45 2.4 Tutorials 3,10,15,20
16:45-17:00 2.4 Tutorials 1,6,11,16
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