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PCI 6 th Edition

PCI 6 th Edition. Preliminary Component Selection. Presentation Outline. Building optimization Preliminary sizing Load tables Additional gravity loading considerations Fire Resistance considerations Vibration considerations Thermal considerations. Building Optimization.

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PCI 6 th Edition

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  1. PCI 6th Edition Preliminary Component Selection

  2. Presentation Outline • Building optimization • Preliminary sizing • Load tables • Additional gravity loading considerations • Fire Resistance considerations • Vibration considerations • Thermal considerations

  3. Building Optimization • Maximize repetitive and modular dimensions • Use simple spans • Standardize openings • Use local component sizes • Minimize component types and sizes

  4. Building Optimization • Consider tolerances in connection design • Avoid over specifying design requirements • Allowable stresses • Allowable cambers • Allowable Deflections • Coatings on reinforcing steel • Embedded hardware • Loose Connection hardware

  5. Building Optimization • Use of exterior wall panels as load bearing components and structural walls • Maximize form use and minimize form differences / variation • Contact a local producer as early as possible during the design development stages of a project for assistance and answering questions

  6. Why estimate component size? • To verify the product fits the application • Establish floor to floor height • Establish floor area • To estimate project cost

  7. Preliminary Analysis Should Include: • Framing dimensions • Span-to-depth ratios • Connection concepts • Gravity and lateral load resisting system • Mechanisms for the control of volume changes

  8. Preliminary Span to Depth Ratios • Hollow-core • Floor slabs 30 to 40 • Roof slabs 40 to 50 • Stemmed Components and Solid Slabs • Floor 25 to 35 • Roof 35 to 40 • Beams 10 to 20

  9. Load Table Assumptions • Flexural strength • Shear strength • Release stresses • Stress limits under service loads

  10. Flexural Strength Control • Equivalent uniform load • Evaluated at critical moment sections • Load factors: 1.2D + 1.6L • Strength reduction factor: f = 0.9

  11. Release Stress Limits • Compression limit: • Tension limit:

  12. Service Loading Stress Limits • Extreme fiber in compression • Prestress plus sustained loads: 0.45f’c • Prestress plus total load: 0.6f’c • Extreme fiber in tension • Double tees and beams: • Flat Deck Members:

  13. Shear Strength Control • Load Factor: 1.2D + 1.6L • Strength Reduction Factor: f = 0.75

  14. Beam Load Tables • Loading is uniform • Strength design - same as double tees • Stress limits - same as double tees

  15. Load Table In-depth PCI Design Handbook, 6th Edition Page 2-16

  16. Load Table In-depth • Section dimensions • Section properties • Material properties • Strand geometry • Depression points

  17. Load Table • Section dimensions • Section properties • Material properties • Strand geometry • Depression points

  18. Load Table • Section dimensions • Section properties • Material properties • Strand geometry • Depression points

  19. Load Table • Section dimensions • Section properties • Material properties • Strand geometry • Depression points

  20. Load Table • Section dimensions • Section properties • Material properties • Strand geometry • Depression points

  21. Load Table Example Given: Section geometry and material properties • 10DT24 roof tee • Lightweight concrete • f’c = 5000 psi • f’cimin = 3500 psi • Design length = 58’-6”

  22. Load Table Example Given: Design Loads • Superimposed Dead Load = 10 psf (roofing) • Superimposed Live Load = 30 psf (snow) Total Service Load = 40 psf (for design tables) Problem: • Determine a suitable strand pattern from load tables

  23. Load Table Example PCI Design Handbook, 6th Edition Page 2-16

  24. Resulting Strand Pattern • (8) ½” f 270ksi strands • Straight strand pattern • 2.6” Camber at erection • 2.2” Camber long term • Assumptions • Initial pull = 0.75fpu • Initial losses = 10% • Total losses = 20% • Always develop a final design based on specific conditions

  25. Load Tables • Limitations • Special materials • Concrete • Strand • Unique geometry • Pie shaped pieces • Blockouts • Special or unique loading conditions • Fire truck loading

  26. Additional Loading Considerations • Snow • Drifting loads

  27. Additional Loading Considerations • Snow • Drifting loads • Corridor loads • Walkways

  28. Additional Loading Considerations • Snow • Drifting loads • Corridor loads • Walkways • Impact • Combination of load

  29. Additional Loading Considerations • Snow • Drifting loads • Corridor loads • Impact • Combination of load • Beware of piling snow • Add Snow gate/chute

  30. Fire Resistance Considerations • Time Ratings • Based on • Square footage • Building type • Cover Requirements

  31. Fire Resistance Considerations • Three Methods to Determine Fire Resistance Rating • Testing (§703) – ASTM E 119 • Prescriptive (§720) • Calculated (§721)

  32. Office Building Example Given: • Exterior bearing wall system • Floor system Assumptions • Unlimited area potential • Using prescriptive methods Problem: • Determine required wall and floor resistance requirements and reinforcing cover

  33. Solution Steps Step 1 - Determine group classification Step 2 - Determine construction type based on building area and available footprint Step 3 - Determine component resistance requirements Step 4 - Determine reinforcing cover requirements

  34. Section 303 IBC 2003 Group Classification Group A – Assembly Group B – Business Group E – Educational Group F – Factory Group H – High Hazard Group I – Institutional Group M – Mercantile Group R – Residential Group S – Storage Group S-2 – Parking Garage Group U – Other / Utility Step 1 – Group Occupancy Classification

  35. Step 2 – Determine Construction Type • Table 503 IBC 2003 • Allowable Height and Building Areas • Based on • Building Group • Building Size • Group – B • Unlimited Footprint • Construction Type Type I - B

  36. Step 3 – Wall Resistance Requirements • Table 602 • IBC 2003 • Function of Building Element and Construction Type • Example – • Exterior Bearing Wall • Type I B 2 hour

  37. Step 3 – Wall Resistance Requirements • Table 602 • IBC 2003 • Function of Building Element and Construction Type • Example – • Floor Construction • Type I B 2 hour 2 hour

  38. Step 4 – Thickness of Insulating Material - Wall • Table 720.1 • IBC 2003

  39. Step 4 – Thickness of Insulating Material - Floor • Table 720.1 • IBC 2003

  40. Example Conclusion • Office • Unlimited Area • Maximum 11 Stories / 160 ft • Type IB Construction • Exterior Bearing Wall • 2 hours • 1 ½” Cover • Floor System • 2 hours • 2 ½” Cover

  41. Code Endurance Table Example Given: The following Double Tee (page 9-49) Assumptions • Strands are ½” diameter • Siliceous aggregate • Normal weight concrete • Topped System • Restrained Problem: For a 2 hr rating determine • The strand cover required • Floor Thickness required

  42. Solution Steps Step 1 – Determine effective cross sectional area and associated cover requirements Step 2 – Compare to cover provided Step 3 – Determine heat transfer requirements and compare to provided conditions

  43. Step 1 – Effective Area and Required Cover • Table 9.3.7.1(5) (Page 49) • Average Stem Width (3.75 + 5.75)/2 = 4.75 in • Effective Flange width = 3 x Avg Stem 3(4.75) = 14.25 in. • Aeff = 22(4.75)+14.25(5)=175.75 in2

  44. Step 2 – Supplied Cover • Side cover provided [3.75 + (3.5/22)(5.75–3.75) – 0.5]/2 = 1.78 in • Bottom cover provided 2 – 0.5/2 = 1.75 in • Both exceed 1 ½ in OK

  45. Step 3 – Heat Transfer • Per Figure 9.3.6.1 5 in Minimum • Provided 2 in tee flange and 3 in topping = 5 in total

  46. Vibration Considerations • Causes • Machinery • Exercise • Cars • Walking • Impact

  47. Minimize Vibration or Affects The goal Decrease the amplitude of the vibration OR Decrease the Systems Natural Frequency • Decrease Span • Increase Mass

  48. Vibration Solution • Based on minimum natural frequencies • Calculations are approximate as estimation of damping and human response is varied

  49. Types of Analysis Methods • Based on excitation • Walking • Rhythmic Activities • Mechanical Equipment

  50. Natural Frequency • Vibration limits are a function of Natural Frequency, fn Where g – Acceleration due to gravity D – Displacement of system

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