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STRUCTURAL ENGINEERING

STRUCTURAL ENGINEERING. What Does a Structural Engineer Do?. What Does a Structural Engineer Do?. Roles of a Structural Engineer. Lead engineer/Project engineer Consultant for an architect Consultant for another engineer, insurance companies, lawyers, etc. As well as: Aerospace design.

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STRUCTURAL ENGINEERING

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  1. STRUCTURAL ENGINEERING

  2. What Does a Structural Engineer Do?

  3. What Does a Structural Engineer Do?

  4. Roles of a Structural Engineer • Lead engineer/Project engineer • Consultant for an architect • Consultant for another engineer, insurance companies, lawyers, etc. • As well as: • Aerospace design. • Product design, etc. for industries. • Facilities engineer.

  5. Lead or Project Engineer • Defines project goals • Costs • Performance requirements • Supervises design based on these requirements. • Outlines tasks • What needs to be done & who will do it • Organizes Project • Calendar • Sequence

  6. Tie Zong ©2006 WashDOT

  7. Palm Valley Interchange

  8. Lower Granite Dam Lock Repair – Jarrod Milligan

  9. Consulting for an Architect or Engineer • The architect works with the client to establish project requirements: • space requirements and relationships • siting • aesthetics • lighting • budget

  10. Consulting for an Architect or Engineer • The engineer’s job is to make the architect look good. • Ensure integrity of structure • Provide economical solutions. • Develop innovative ways to solve new problems and use new materials.

  11. Boise Air Terminal

  12. Mark Hedge, Jess Haldeman, Riley MahaffeyLochsa Engineering

  13. Forensic Engineering • Finding out what went wrong. • Insurance companies • Lawyers

  14. Construction Management • Etc.

  15. Major Graves

  16. Major Graves

  17. Research

  18. Nick McDowell

  19. Design Loads • Design loads include: • Dead loads • Self-weight, • “Permanent” contents. • Live loads • Occupants, • Transient contents • Environmental loads • Wind, snow, earthquake, etc.

  20. Uncertainty • Dead loads can be predicted with some confidence. • Live load and environmental load predictions are much more uncertain. • E.g., it is nearly impossible to say what will be the exact maximum occupancy live load in, say, a classroom. • It is also difficult to say how that load will be distributed in the room.

  21. Uncertainty (cont.) • Structural codes account for this uncertainty two ways: • We chose a conservative estimate (LARGE estimate) for the load: • E.g., a “50-year” snow load, which is a snow load that occurs, on average, only once in 50 years. • We factor that estimate upwards just to be sure.

  22. Load Factors • Newer codes have separate load and resistance factors: • Load factors “overestimate” the load. • Resistance factors “underestimate” the strength of the structure. • Dead load factors range from 1.1 to 1.4 • Smaller uncertainty. • Environmental and live load factors range from 1.7 to 2.0 and higher. • Higher uncertainty

  23. Simplified Wind Loads • Since we can’t predict exactly the maximum load a given structure will experience, the code provides: • Rational procedures for estimating a reasonable maximum value • Procedures for arranging the loads on the structure. • Experience has shown that if the engineer follows these procedures he/she can expect the structure to perform properly (i.e., not collapse, etc.)

  24. Wind Loads • What factors should the wind design loads consider?

  25. Summary • Design loads used by engineers represent rational estimates of loads that we should consider in our design. • Experience has shown if we design for these loads, the building should survive for a reasonable amount of time (50 years or more).

  26. Summary (cont.) • The models try to consider situations that will have a significant effect on the design load. • Max wind speed, building height and shape, etc. • The maximum loads estimated by the design codes are then factored to add a safety margin to our calculations.

  27. Example Building

  28. Design Methods • Method 1 – Simplified Procedure: • Simple diaphragm building, • Low-rise, • Enclosed, • Regular geometry, symmetric, • Not flexible, prone to flutter/vortex shedding, torsion etc. • Method 2 – Analytic Procedure. • Method 3 – Wind Tunnel Procedure.

  29. Wind Loads on Structures

  30. Gust Factor, G • G = 0.85 for rigid, low rise buildings

  31. Wall Pressure Coefficients, Cp

  32. Wind Velocity Pressure

  33. Importance Factor • Agriculture Buildings Category I • “Typical” Buildings Category II • Hazardous Buildings Category III • Essential Facilities Category IV

  34. Wind Load Map: Western US Wind speeds in MPH (kph)

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