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