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Building Optimization Strategies in Component Selection Process

Learn about building optimization techniques, load tables, gravity loading considerations, and fire resistance requirements. Maximize design efficiency with simple spans, standardizing components, and controlling volume changes. Understand thermal, vibration, and connection design considerations for better component selection.

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Building Optimization Strategies in Component Selection Process

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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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