The document discusses key concepts in construction including: 1) The variety of forces (e.g. gravity, wind loads) that buildings must withstand and different types of structural loads. 2) Important structural elements like columns, beams, walls and how they transmit loads. 3) The importance of connections in transferring loads between structural elements and how connections can fail in fires.

1. 2 Concepts of Construction

2. Objectives (1 of 2) Identify the variety of forces that buildings are subjected to Identify the different types of loads and how they are applied to buildings

3. Objectives (2 of 2) Identify and define key different types of structural members such as columns, beams, and walls Identify the variety of different types of structural connections and how they behave in a fire

4. Introduction How will the buildings in your community react to fire? Prefire inspection The laws of physics Knowledge gained from the field

5. Gravity Exerts a continued force on a building The gravity resistance system Unintended loads imposed by fire

6. Definition of Loads Forces or other actions that result from the weight of all building materials, occupants and their possessions, environmental effects, differential movement, and restrained dimensional changes

7. Stress and Strain Stress Measured in pounds per square inch (psi) KIP = 1000 pounds Strain Actual percent of elongation (deformation)

8. Three Types of Forces Compression Tension Torsion

9. Dead Loads The weight of the building itself and any equipment permanently attached Added dead load

10. Live Loads (1 of 2) Any load other than a dead load Assumes even distribution Concentrated load Accounts for large heavy objects in a building Larger than live load requirements

11. Live Loads (2 of 2) Water trapped on a roof Firefighting equipment

12. Impact Loads Loads delivered quickly Lateral impact loads

13. Static and Repeated Loads Static loads Applied slowly and remain constant A heavy safe Repeated loads Applied intermittently A rolling bridge crane

14. Wind Loads (1 of 3) A force applied by the wind Small wood buildings are susceptible Masonry buildings are less susceptible

15. Wind Loads (2 of 3) Diaphragm Floors and Bracing Designed to stiffen the building against wind Diagonal braces K-bracing

16. Wind Loads (3 of 3) Types of Bracing Portal bracing Masonry walls Tube construction Core construction

17. Concentrated Loads Heavy loads located at one point in a building A steel beam resting on a masonry wall Piers Short columns used to level floors Create a gap between the floor and related arch

18. Axial Load A force that passes through the centroid of the section Centroid Eccentric load

19. Fire Loads Represents the potential fuel available to a fire and the total amount of potential energy (heat) in the fuel Heat release rate (HRR) Q Caloric value

20. Suspended Loads Suspended from a ceiling or other structure Tie rod Suspended high-rise buildings use suspended beams

21. Safety Factor Represents the ratio of the strength of the material to the safe working stress Ultimate strength Design load is a fraction of the ultimate strength

22. Composite Materials Steel and concrete combined Can be constructed with bar-joist trusses Brick and block-composite wall

23. Structural Elements Beams, columns, arches, and walls Differ on how they support and transfer weight Structural frames

24. Beams Transmits forces perpendicular to the reaction points Deflection Neutral axis Stiffness

25. Carrying Capacity and Depth of Beams Increases as the square of the depth Increases only in direct proportion to increases in width

26. Types of Beams (1 of 2) Simple Continuous Fixed Overhanging Bracket Joist, steel joist, and bar joist Girder

27. Types of Beams (2 of 2) Built-up girder Spandrel girder Lintel Grillage Cantilever beam Suspended beam Transfer beam

28. Beam Loading Distribution of loads along a beam May be concentrated in one area Create excessive beam loading

29. Reaction and Bending Reaction Result of force exerted by a beam on a support Bending moment Load that will bend or break the beam

30. Columns Transmit a compressive force along a straight path Struts or rakers Bent Bay Pillar

31. Decrease in Load-Carrying Capacity Decrease in load-carrying capacity proportionately 12-foot column vs. 6-foot column

32. Shapes of Columns Most efficient Distributes the material equally around the axis As far as possible from the center of the cylinder Difficult to attach beams to round columns

33. Wooden Columns Smoothed off tree trunks Almost always hollow

34. I-Beams vs. H-Beams Steel beams I-shaped Steel columns H-shaped Box shaped Cylindrical

35. Types of Columns Piers Short, squat columns Fail by crushing Long, slender columns Buckle Intermediate columns Fail in either manner

36. Euler’s Law Columns Very long thin columns Critical load Formula: P c = ( π 2 EI)/L 2

37. Temporary Bracing Used in incomplete structures Also known as guy bracing

38. Walls (1 of 3) Transmit the compressive forces applied along the top or received at any point Main divisions of walls: Load-bearing Non-load-bearing Cross

39. Walls (2 of 3) Veneer Composite Header Stretcher Panel Curtain Party

40. Walls (3 of 3) Fire Partition Demising Rubble masonry Wythe

41. Cantilever Walls Severe winds May topple a free-standing wall Eccentric loading Precast concrete tilt slab walls

42. Wall Bracing Serpentine Buttresses Pilasters Wall columns Cavity or hollow

43. Wall Breaching Homogenous walls Act as one unit Obstructed load Window or door Does not follow a vertical path

44. Roofs Vital to the stability of the structure Roof damage Can cause wall collapse

45. Arches Combine the function of the beam and column Tend to push outward at the base Voussoir

46. Rigid Frames Derived from the arch Steel rigid frames Industrial and commercial buildings Wooden rigid frames Churches

47. Shells and Domes Shell Thin, curved plate Concrete Dome A shell and three dimensional arch Geodesic domes

48. Transmission of Loads Transmission Spread from the point of application to the ground Must be continuous Any failure will lead to collapse Accurate knowledge of the ground

49. Foundations Delivers loads to the ground Foundation materials differ Almost all are concrete

50. Connections (1 of 3) Transfer the load from one structural element to another Only as strong as its weakest link

51. Connections (2 of 3) Pinned Elements are connected by simple connectors such as bolts, rivets, or welded joints Rigid-framed building Connections are strong enough to reroute forces if a member is removed

52. Connections (3 of 3) Monolithic concrete Wet joint Plastic design

53. Failure of Connections (1 of 2) Masonry walls shift outward Temporary field bolting of steel Ledger board Steel connectors rust Concrete disintegrates Sand-lime mortar is water soluble.

54. Failure of Connections (2 of 2) Gravity connections Gusset plates Gang nails

55. Overhanging and Drop-in Beams Economical No support from below

56. Spliced Beams If beam not long enough Spliced with connectors Connectors fail in heat

57. Summary Gravity Gravity resistance system Specific terms Structural elements Composite material Connections