1. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman General Structural Concerns Functionality / Stiffness deformations Stability equilibrium Strength material behaviour 1/28

2. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Stability Loads Supports ●act on structure ●tend to destabilise structure ●must be such as to provide equilibrium ●provide reactions ●also tend to break elements 2/28

3. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Loads Dynamic Static Dead Loads (fixed) Forces due to Settlements, Thermal effects,... Live Loads (movable) Continuous Impact Self-Weight of Structure Fixed Building Elements Earthquakes Wind 3/28 Occupancy Environmental (snow,...)

4. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Loads Two main types l dead loads - self-weight, fixed elements l live loads - occupancy, contents, wind 4/28

5. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Loads (cont.) The building materials impose dead loads (fixed, vertical) Wind and earthquake impose live loads (variable, mostly horizontal) The occupants and contents impose live loads (variable, mostly vertical) 5/28

6. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Dead Loads Permanent weight of structure ●non-moveable partitions ●built-ins, heavy equipment Roof Walls Floors Equipment 6/28 Cowan, Gunaratnam and Wilson (1995). Structural Systems, Department of Architectural and Design Science

7. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Dead Loads (cont.) How much does the stuff weigh? How much of each material is there? Dead loads 7/28

8. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Dead Loads - Typical Values Bulk MaterialWeight/unit volume Concrete, dense Hardwood Steel Brick 23.5 kN/m 3 11.0 kN/m 3 76.9 kN/m 3 19.0 kN/m 3 Sheet MaterialWeight/unit area Gypsum plaster 13mm Fibre cement 6mm 0.22 kN/m 2 0.11 kN/m 2 Appendix A of SA loading code AS1170.1 8/28

9. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Live Loads Furniture, Equipment, People, Snow Moveable Partitions May or may not be acting all the time 9/28 Cowan, Gunaratnam and Wilson (1995). Structural Systems, Department of Architectural and Design Science

10. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Live Loads (cont1.) people move around may get heavy concentrations 10/28

11. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Live Loads (cont2.) Could calculate - but tedious Codes specify loads for various types of occupancies AS 1170.1 specifies minimum floor live loads Concentrated (kN) - e.g. tall bookshelves Uniformly Distributed (kPa) 11/28

12. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Live Loads (cont3.) Building Codes give minimum values Domestic live loads range from 1.5 kPa Corridors and balconies are generally 4kPa, to allow for crowding Most stores and workshops are >= 5 kPa Live loads 12/28

13. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Wind Loads Both Pressure and Suction Always important for tall buildings But also important for low buildings - bracing 13/28

14. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Wind loads on Buildings Pressure on the windward face wind Wind can come from any direction Suction on other faces Suction on lowpitched roofs - < 30 0 Buildings need bracing and tying-down 14/28

15. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Wind Loads on Buildings (cont1.) may need to hold roof down 15/28

16. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Wind Loads on Buildings (cont2.) Wind tends to overturn a tall building Acts as a vertical cantilever Resisting Moment Pressure Suction 16/28 Overturning Moment Reaction

17. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Factors in Wind Speeds General wind speed in the region ●(pressure varies with square of the speed) Local topography affects wind patterns Wind speed increases with altitude Wind speed decreases with terrain roughness Very exposed More sheltered Wind 17/28

18. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Factors in Wind Loads (cont.) Shelter from anything permanent will reduce loads Shape of building affects loads ●Boxy vs streamlined Sheltered by buildings Pinchgut is exposed Curved shapes would need special analysis 18/28

19. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Wind Loads on Elements Timber Framing Code has a procedure for finding maximum wind speeds Timber Framing Code also has simplified rules for bracing single-storey houses In non-cyclone areas, wind loads in the 1kPa range Multiply by the area exposed to wind 19/28

20. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Seismic Loads Earthquakes cause damage by horizontal acceleration - may swing 20/28

21. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Settlement, Temperature Loads Stresses caused by temperature changes Uneven settlement of foundations creates stresses - Gothic Cathedrals 21/28

22. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Loads on Elements So far we have looked at the effect of loads on the building overall Now let’s consider individual elements 22/28

23. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Distributed Loads and Point Loads Floors, walls and roofs are generally distributed loads (kN per m or kPa) Other beams are point loads (kN) Point Loads Distributed Load 23/28 Reactions

24. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Point Load on beam Effect of one Member on Another The forces at the supports are the reactions For equilibrium, the reactions just balance the loads Point Load on column and reaction 24/28 Point Loads from beam to beam Reaction from beam

25. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Types of Reactions Simple Support Beam sitting on supports H simple beam V Rv H Provides vertical support only No horizontal reaction Allows rotation no moment developed V Rv 25/28 Rv

26. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Types of Reactions Roller Support Provides vertical support only a true roller support (only needed on very large structures) deliberately avoids horizontal restraint (allows expansion) 26/28 Rv

27. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Types of Reactions Hinged (pin) Support Provides vertical and horizontal support, Allows rotation - no moment developed a definite ‘hinged’ support (most simple supports just involve a beam sitting on something) RVRV RHRH RVRV RHRH 27/28

28. University of Sydney – DESA 1102 Structures LOADS & SUPPORTS Peter Smith & Mike Rosenman Types of Reactions — Rigid Support Provides V, H, and moment restraint, M Welded steel frame RVRV RHRH M Make sure you can physically achieve it! Cantilever beams or posts, and rigid frames 28/28