1. Introduction to Structural Engineering
Tony Freidman

2. Background Graduate of University of Missouri – Rolla
B.S. in Civil Engineering
B.S. in Architectural Engineering
Research in Architectural specialties
Research on V-T-M diagram development for reinforced concrete column design
Currently enrolled as a Ph.D. student at Washington University – St. Louis
Research on MR Damper performance
Research on Structural Health Monitoring

4. Structural Engineering is used so that the events in the preceding videos never take place.
“Engineers shall hold paramount the safety, health and welfare of the public and shall strive to comply with the principles of sustainable development in the performance of their professional duties. “
- 1st Fundamental Engineering Canon

5. Structural Engineering Overview
What is a Structural Engineer?
What do they do?
What do they design?

6. Structural Engineering Overview
What is a Structural Engineer?
What do they do?
What do they design?

7. What is a Structural Engineer?
Mathematics of design
Architect/Artist
Vision
Aesthetics of design
Mediator
Liason between parties on a project
Salesman
Must sell your idea, yourself

8. Structural Engineering Overview
What is a Structural Engineer?
What do Structural Engineers do?
What do they design?

9. What do SE’s do? Designer Consultant Inspector Demolitions
Take a design, and fit a structural system to that
Expert witnesses in lawsuits
Inspector
Fieldwork, Job site inspections
Oversee the materials (concrete, steel, etc.)
Inspect the building – pre- and post-construction
Demolitions
Building deconstruction
Structural Retro-fits

10. Structural Engineering Overview
What is a Structural Engineer?
What do Structural Engineers do?
What do they design?

11. SE’s design/analyze Structures
What is a structure?
A system designed to resist or support loading and dissipate energy
Building Structures
Houses
Skyscrapers
Anything designed for continuous human occupation
Non-building Structures
Bridges
Tunnels
Dams

12. Forces
Influence on an object that causes a change in a physical quantity
Considered “vectors” – magnitude and direction
Static Force
Unchanging with time
Walls
Floors
Dynamic Force
Changing with time
People
Furniture

13. Forces Axial Forces Momential (Bending) Force
Acting along one axis, directly on a point or surface
Momential (Bending) Force
Acting along an axis, at a certain distance from a point, causes a folding motion
M = F*d F

14. Forces Tensile Force Compressive Force
Pulling on an object – stretching it
Steel shows “necking” when too much tensile force is applied
Compressive Force
Pushing on an object – collapsing it
Concrete crushes when too much compressive force is applied

15. Forces Strain Stress Compare using stress-strain graph
Tensile-related property
Deformation / Length
Stress
Compression-related property
Force / Area
Compare using stress-strain graph

16. What constitutes loading?
Loading is a force being enacted on the structure
Many sources of load
Gravity/Weight
Wind
Snow
Earthquake
Man-made
Two Types of Structural Loading
Dead Loads – static, ever-present (i.e. Walls, Floors, etc)
Live Loads – dynamic, changing (i.e. People, Desk, etc)

17. What should we build our structures out of??
Common Structural Materials
Timber
Masonry
Concrete
Steel
Composites

18. How do we judge the materials?
Common Material Properties
Strength – Tensile/Compressive
Density
Hardness
Ductility / Brittleness
Elasticity
Toughness

19. Strength Ability of a material to withstand loading
Tensile strength – ability of a material to withstand a pulling force
Steel is good at this, but concrete performs very poorly.
Compressive strength – ability of a material to withstand a pushing force
Wood, concrete, steel, and masonry perform well

20. Density Mass per unit volume of a material
Units – mass/vol - kg/m3 or lb-m/ft3
Typically, materials with a high density are very strong and offer great protection.
However, a high density means that they are heavy and difficult to work with $$$$$

21. Hardness
Ability of a material to resist permanent deformation under a sharp load
Relates to the elasticity of a material
Diamond is a very hard substance. If we built a wall out of diamond, we could be sure that very few things would scratch it.
However, Diamond is incredibly expensive and not as tough as other engineering metals. It wouldn’t stand up as well in impact loading versus other materials.

22. Ductility / Brittleness
Ability of a material to deform without fracture
We want materials with high ductility, because they will indicate structural failure without a sudden collapse.
– “Brittle failure”

23. Elasticity
Ability of a material to deform and return to it’s original shape.
Important quantity
Young’s Modulus
Ratio of stress to strain
Stress = Force / Area (lbs./in2 or N/m2)
Strain = Deformation / Length (unitless)
Generates a stress-strain graph
Related to the ductility of a material

24. Toughness
Ability of a material to resist fracture when stressed (amount of energy absorbed per unit volume)
Units – J/m3 or Lb-f/ft3
Area under the stress-strain curve, evaluated from 0 to the desired strain.

25. So, we know what properties are important in structural materials
So, we know what properties are important in structural materials. How do the common materials stack up against each other?

26. Timber Advantages Disadvantages Cheap, renewable resource
Good in Tension – ~40 MPa
Disadvantages
Susceptible to fire, nature
Not very hard
Not very strong
Limits on shape, size

27. Masonry Concrete blocks, clay bricks Advantages Disadvantages
Large compressive strength
Cheap
Good thermal properties – holds heat well
Disadvantages
Not a cohesive material. The strength could depend on the mortar, other factors
Poor tensile strength, unless reinforced
Heavy material, requires skilled laborers to use $$$$$
Height restriction
Susceptible to the weather

28. Concrete
Combination of water, cement, small aggregate, and large aggregate.
Advantages
Very versatile – can be modified with admixtures for different effects
High compressive strength (4~7 ksi)
Fire resistant
Many diverse sizes and shapes - formwork

29. Concrete Disadvantages Long curing time
Low tension strength (~0.4 ksi)
Fails in shear, unless reinforced
Fairly heavy material to work with

30. Steel
Advantages
High tensile and compressive strength (A36 Steel ~ 60 ksi)
Many varieties, depending on your need
Carbon steel
Stainless steel
Galvanized steel
Elastic material
Ductile material
Many shapes, sizes

31. Steel Disadvantages Expensive – limited quantities / competition
Susceptible to fire, rust, impurities

32. Put them together and… Reinforced Concrete
Concrete with steel reinforcement
Concrete handles compression
Steel takes the tension
Can handle nearly 4 times the loading that concrete alone can handle
More expensive material

33. Composites
Engineered compounds that have different physical or chemical properties
FRP – Fiber reinforced polymers
CFRP – Carbon-fiber reinforced polymers
Plastics
Categories of Glass
Categories of Wood

34. So, now we know what material will best suit our needs
So, now we know what material will best suit our needs.. What should we build with it?

35. Structural Shapes Rectangle / Square Triangle Truss Geodesic Dome
Interested in stability
Truss
Geodesic Dome

36. Shape Stability Exercise
Split into teams of 5
Build a triangle and square
See which shape is the most stable
Can the unstable shapes be made stable?
How?

37. Rectangle Advantages Disadvantages
Proficient in resisting vertical load.
Disadvantages
No lateral support

38. Triangle Advantages Disadvantage
Able to withstand lateral & vertical loading
Many triangular shapes available
Disadvantage
Wide base = $$$$

39. Rectangle Advantages Disadvantages
Proficient in resisting vertical load.
Disadvantages
No lateral (horizontal) load support
Need another bar for lateral support!
--BRACING--

40. Truss
Combination of square and triangle

41. Truss
Combination of square and triangle
Squares

42. Truss
Combination of square and triangle
Triangles

43. Truss Combination of square and triangle
Both vertical and lateral support

44. Geodesic Dome

45. Domes

46. Domes
Advantages
Very strong shape, gets strong as the dome size increases
Perfect load distribution
No need for structural supports
Great aerodynamic performance

47. Structural Components
Beams
Girders
Columns
Floors
Foundations
Column
Girder
Beam

48. Load Path
Floor
Beams
Girders
Columns
Foundation
Soil/Bedrock

49. Foundations Support the building Types Typically attached to columns
Shallow
Spread footing – concrete strip/pad below the frost line
Slab-on-grade – concrete pad on the surface
Deep
Drilled Shafts
Piles

51. Columns Carry the load from floors to the foundation
Never want the columns to fail COLLAPSE
Typically reinforced concrete or steel
Many sizes and shapes

52. Girders Attached column-to-column Take the load from the beams
Transfer it to the columns
Generally shaped as an I-Beam

53. Beams Attached between the girders Take load from the flooring system
Transfer it to the girders
Generally solid squares, I-beams

54. Flooring Composed of a subfloor and floor covering
Usually leave space for ductwork, wiring, etc.
Floor covering ranges from application to application

55. Picture Credits Geodesic Dome Truss Truss 2 Truss 3 Stress-Strain
Truss
Truss 2
Truss 3
Stress-Strain
Crushing Concrete

56. Pile Machine Pile Machine 2 Foundation Type Rebar Cage
Pile Machine 2
Foundation Type
Rebar Cage
Circular Columns

57. Timber Steel Concrete Masonry
Steel
Concrete
Masonry

58. Structural Engineer Building Girder Beam Flooring
Building
Girder
Beam
Flooring