STRUCTURESAA TS3 GT & AW

Architect or Engineer?

Architect or Engineer?

“An Engineer should design a structure that anarchitect would be ashamed to cover up.”

STRUCTURESAA TS3 GT & AW

Week 1 – Introduction and Axial Forces (Part 1)

Week 2 – Axial Forces (Part 2) & Tutorials

Week 3 – Trusses and Folded Plates & Tutorials

Week 4 – Structural Case study Review & Tutorials

Week 5 - No lecture (AA open week)

Week 6 – Tutorials only (What if questions to be decided)

Week 7 – Lecture (TBC) & Tutorials.

Week 8 – Final Testing event.

Brief 1 - Tower

Evolution of structural systems

Stability elements

SCOUTS TOWER – SINGAPORECentral core transferring the load back to

ground

Brief 2 - Bridge

How long can I span?How long

can I span?How long

can I span?How long

can I span?

UNIVERSITY OF LIMERICK LIVING BRIDGE, IRELAND

ERASMUS BRIDGE Glulam bridge Quebec

kingpost with a burr Arch

Previous Years examples – modelling materials

Previous Years – Model Making.

Think carefully about choice of materials

The right modelling material will yield more meaningful results…

Loading of the model

Use of AA prospectuses is not mandatory…

FOR NEXT WEEK:1 TEAM2 REVIEW BRIEF

3 INDIVIDUAL CASE STUDIES – (showing good architectural

and structural integration)

4 PRELIMINARY DESIGN5 START CONSIDERING THE QUESTIONS BELOW

Our list of questions:1. Structural system and how does it distributes load?2. Size of your structure in reality? (section sizes/ geometry)3. Which loads are acting on the structure4. Support conditions5. Material6. Connection between structural elements.7. Fabrication / construction

CASE STUDY EXAMPLE

Basic Structural Principals

Useful equations.

Master classes in structural behaviour

Stress (σ) = 𝐹𝑜𝑟𝑐𝑒

𝐴𝑟𝑒𝑎unit = N/𝑚𝑚2

Compression Force (Axial)

1 kN = 100Kg1 N = 100g

Failure

Perpendicular Force – Bending stress

The deformed shape causes a bending stress in the beam.

Bending stress ( σ ) = 𝑀𝑦

𝐼

M – Calculated Moment (refer to tables)Y – Vertical distance away from the neutral axisI – Second moment of area for the section

Failure :

Material failure

Excessive deformation.

Bending Moment

Moment = 𝐹𝐿

4(kNm) Moment =

𝑤𝐿2

8(kNm)

Continual curvature due to uniform load

Consider Supports – Fixed Ends

Mid Moment = 𝑤𝐿2

24(kNm)

End Moment = 𝑤𝐿2

24(kNm)

Understanding of ForcesForces flow towards the stiffest elements.

Place material where neededMead Bridge – Price and Myers

Force flow consideration can also impact on a smaller scale

As well as bending strength considerations we also need to look at Stiffness EI

E = young’s modulus

Young's modulus measures the resistance of a material to elastic (recoverable) deformation under load. A stiff material has a high Young's modulus and changes its shape only slightly under elastic. A flexible material has a low Young's modulus and changes its shape considerably.

concrete 15 -35

As well as bending strength considerations we also need to look at Stiffness EI

I = Second moment of Inertia

Area Moment of Inertia" is a property of shape that is used to predict deflection, bending and stress in beams.

Simplified rectangular section:

d

b

I = 𝑏𝑑3

12𝑚𝑚4

Z = Section ModulusThe section modulus of the cross-sectional shape is of significant importance in designing beams. It is a direct measure of the strength of the beam.

Z = 𝑏𝑑2

4𝑚𝑚3

Simply supported example: check moments and deflections

Moment = 𝑤𝐿2

8(kNm)

σ = 𝑀

𝑍or z =

𝑀

σ

σ is the material yield stress.

w

L

Deflection = 5𝑊𝐿4

384 𝐸𝐼(mm)

Z = 𝑏𝑑2

4𝑚𝑚3

Simply supported example: check moments and deflections

What If ?

• The load on the beam is doubled?

• The beam length is doubled?

Simply supported example: check moments and deflections

What If ?

• The load on the beam is doubled?

moment = (2𝑤)𝐿2

8= 𝑤𝐿2

4Deflection =

5 (2𝑤)𝐿4

384𝐸𝐼= 5 𝑤𝐿4

192𝐸𝐼• The beam length is doubled?

Simply supported example: check moments and deflections

What If ?• The load on the beam is doubled?

moment = (2𝑤)𝐿2

8= 𝑤𝐿2

4Deflection =

5 (2𝑤)𝐿4

384𝐸𝐼= 5 𝑤𝐿4

192𝐸𝐼• The beam length is doubled?

moment = 𝑤 (2𝐿)2

8= 𝑤𝐿2

2Deflection =

𝑤(2𝐿)4

384𝐸𝐼

The moment is 4x greater. Deflection is 16x greater

Bending moments versus deflections

Thinking of the deflected shape is helpful as it can help you imagine which parts of the structure is in hogging and which part is sagging.