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Civil & Environmental Engineering Design

Civil & Environmental Engineering Design. Prof. Michael Chajes, Chair Depart. of Civil & Env. Engineering. Photo by Doug Baker. Webster’s Definition of Design. “to create, fashion, execute, or construct according to plan,” and “to devise for a specific function or end.”.

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Civil & Environmental Engineering Design

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  1. Civil & Environmental Engineering Design Prof. Michael Chajes, Chair Depart. of Civil & Env. Engineering Photo by Doug Baker

  2. Webster’s Definition of Design “to create, fashion, execute, or construct according to plan,” and “to devise for a specific function or end.”

  3. Webster’s Definition of Design “to create, fashion, execute, or construct according to plan,” and “to devise for a specific function or end.”

  4. Design Constraints Safe PE code of ethics states: “Engineers, in the fulfillment of their professional duties, shall hold paramount the safety, health, and welfare of the public.” Functional Economic Aesthetically pleasing No one solution!

  5. Design Example Design a shelf for you dorm room Wood 1” x 8” x 6’ Wall

  6. Design Example Tension Strut Design a shelf for you dorm room

  7. Design Example Design a shelf for you dorm room Compression Strut

  8. LOADS W books = 50 lbs/ft W total = 6 x 50 = 300 lbs Each strut (2 total) = 150 lbs Factor of safety = 2 W books/strut = 300 lbs F=ma, a=0, SF=0 Vertical direction 0 = - 300 lbs + (3/5) F strut F strut = (300) x (5/3) F strut = 500 lbs Design Tension StrutMode of Failure: Fracture 10” 6” 8” F strut Free Body Diagram F shelf W books/strut

  9. Design Tension StrutMode of Failure: Fracture STRUT SIZE Stress = Force/Area Use steel rods Stress Ultimate = 36,000 lb/in Area = Force/Stress = 300/36,000 Area required = 0.008 in 10” 6” 2 8” 2 2 2 A = p r = p d / 4 0.008 = p d / 4 d = 0.10 in. 1/8 = 0.125 in. 2 1/8” diameter rod

  10. LOADS W books = 50 lbs/ft W total = 6 x 50 = 300 lbs Each strut (2 total) = 150 lbs Factor of safety = 2 W books/strut = 300 lbs F=ma, a=0, SF=0 Vertical direction 0 = - 300 lbs + (3/5) F strut F strut = (300) x (5/3) F strut = 500 lbs Design Compression StrutMode of Failure: Fracture 8” 6” 10” Free Body Diagram F shelf F strut W books/strut

  11. Design Compression StrutMode of Failure: Fracture STRUT SIZE Stress = Force/Area Use metal rods Stress Ultimate = 36,000 lb/in Area = Force/Stress = 300/36,000 Area required = 0.008 in 2 8” 6” 2 10” 2 2 A = p r = p d / 4 0.008 = p d / 4 d = 0.10 in. 1/8 = 0.125 in. 2 1/8” diameter rod

  12. P Design Compression StrutAnother Mode of Failure: ? 8” 6” 10” steel rod P

  13. Pcr Euler Buckling Formula Pcr = p EI / L Pcr = Buckling load E = Material stiffness I = Moment of inertia L = Length Pcr = 500 lbs E = 29,000,000 lb/in I rod = pr / 4 L = 10 in. Design Compression StrutMode of Failure: Buckling 2 2 8” 6” 10” 2 4 Pcr

  14. Pcr Design Compression StrutMode of Failure: Buckling Strut Size Pcr = p EI / L 500=(p )(29,000,000)(pr / 4)/(10 ) r = 0.12, d = 0.24, 1/4 = 0.25 in. 8” 2 2 6” 2 2 4 10” 1/4” diameter rod Pcr

  15. 10” 1/8” diameter rod Strength * Strut Design Summary 6” 8” 6” 1/8” diameter rod Strength 10” 1/4” diameter rod Stability * What did we not consider (failure modes, design criteria)?

  16. Bridge Design Bridge Location http://travel.yahoo.com/p-travelguide-577578-map_of_delaware-i Case Study: The New Indian River Inlet Bridge

  17. ExistingIndian River Inlet Bridge

  18. Reason for Replacement: Scour Scour holes greater than 30 m deep

  19. Specificationsfor the New Bridge • Because the piers of the existing Indian River Inlet bridge are in the tidal inlet, scour has become a serious problem • A new bridge will be built by 2010 to replace the existing bridge • The bridge span will be over 900 ft. in order to span the inlet http://www.deldot.gov/static/projects/indian_river_bridge/replacement.shtml

  20. Preliminary Design Courtesy of FIGG Engineering Group

  21. Preliminary Design Courtesy of FIGG Engineering Group

  22. Preliminary Design Courtesy of FIGG Engineering Group

  23. Design Constraints/Decisions How many can you list?

  24. How will it be constructed • How will it be inspected • How will it be maintained • How will it be financed Design Constraints/Decisions Location of bridge Span of bridge Number of lanes Alignment of roadway Type of bridge Bridge aesthetics Type of foundation Scour protection Environmental impact Materials to be used Loadings to consider Size of members

  25. West Point Bridge Design Program http://bridgecontest.usma.edu

  26. Designing a Breakwater

  27. Protecting a Bridge with a Breakwater Plan View Elevation View Bridge Roadway Sandbar Water Surface Bridge Roadway Pier 4.5 in. Sandbar 26 in. 12 in. Breakwater 1 30 Brick Waves 2.25 in. 8 in. 3.5 in.

  28. Questions

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