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Introduction to Structural Engineering Tony Freidman.

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1 Introduction to Structural Engineering Tony Freidman

2 Background Graduate of University of Missouri – Rolla –B.S. in Civil Engineering –B.S. in Architectural Engineering –Research in Architectural specialties –Research on V-T-M diagram development for reinforced concrete column design Currently enrolled as a Ph.D. student at Washington University – St. Louis –Research on MR Damper performance –Research on Structural Health Monitoring

3 yIluI&feature=relatedhttp://www.youtube.com/watch?v=uKeENd yIluI&feature=related fRNRk&feature=relatedhttp://www.youtube.com/watch?v=AsCBK- fRNRk&feature=related pHpc&feature=related Pages/Group1/sld001.htmhttp://em-ntserver.unl.edu/Mechanics- Pages/Group1/sld001.htm

4 Structural Engineering is used so that the events in the preceding videos never take place. “Engineers shall hold paramount the safety, health and welfare of the public and shall strive to comply with the principles of sustainable development in the performance of their professional duties. “Engineers shall - 1 st Fundamental Engineering Canon

5 Structural Engineering Overview What is a Structural Engineer? What do they do? What do they design?

6 Structural Engineering Overview What is a Structural Engineer? What do they do? What do they design?

7 What is a Structural Engineer? Engineer –Mathematics of design Architect/Artist –Vision –Aesthetics of design Mediator –Liason between parties on a project Salesman –Must sell your idea, yourself

8 Structural Engineering Overview What is a Structural Engineer? What do Structural Engineers do? What do they design?

9 What do SE’s do? Designer –Consultant Take a design, and fit a structural system to that Expert witnesses in lawsuits –Inspector Fieldwork, Job site inspections Oversee the materials (concrete, steel, etc.) Inspect the building – pre- and post-construction –Demolitions Building deconstruction Structural Retro-fits

10 Structural Engineering Overview What is a Structural Engineer? What do Structural Engineers do? What do they design?

11 SE’s design/analyze Structures What is a structure? –A system designed to resist or support loading and dissipate energy Building Structures –Houses –Skyscrapers –Anything designed for continuous human occupation Non-building Structures –Bridges –Tunnels –Dams

12 Forces Influence on an object that causes a change in a physical quantity Considered “vectors” – magnitude and direction Static Force –Unchanging with time Walls Floors Dynamic Force –Changing with time People Furniture

13 Forces Axial Forces –Acting along one axis, directly on a point or surface Momential (Bending) Force –Acting along an axis, at a certain distance from a point, causes a folding motion –M = F*d F

14 Forces Tensile Force –Pulling on an object – stretching it –Steel shows “necking” when too much tensile force is applied Compressive Force –Pushing on an object – collapsing it –Concrete crushes when too much compressive force is applied

15 Forces Strain –Tensile-related property –Deformation / Length Stress –Compression-related property –Force / Area Compare using stress- strain graph

16 What constitutes loading? Loading is a force being enacted on the structure –Many sources of load Gravity/Weight Wind Snow Earthquake Man-made –Two Types of Structural Loading Dead Loads – static, ever-present (i.e. Walls, Floors, etc) Live Loads – dynamic, changing (i.e. People, Desk, etc)

17 What should we build our structures out of?? Common Structural Materials –Timber –Masonry –Concrete –Steel –Composites

18 How do we judge the materials? Common Material Properties –Strength – Tensile/Compressive –Density –Hardness –Ductility / Brittleness –Elasticity –Toughness

19 Strength Ability of a material to withstand loading –Tensile strength – ability of a material to withstand a pulling force Steel is good at this, but concrete performs very poorly. –Compressive strength – ability of a material to withstand a pushing force Wood, concrete, steel, and masonry perform well elatedhttp://www.youtube.com/watch?v=WC6AgX2N1Go&feature=r elated ature=related

20 Density Mass per unit volume of a material –Units – mass/vol - kg/m 3 or lb-m/ft 3 –Typically, materials with a high density are very strong and offer great protection. –However, a high density means that they are heavy and difficult to work with $$$$$

21 Hardness Ability of a material to resist permanent deformation under a sharp load –Relates to the elasticity of a material –Diamond is a very hard substance. If we built a wall out of diamond, we could be sure that very few things would scratch it. –However, Diamond is incredibly expensive and not as tough as other engineering metals. It wouldn’t stand up as well in impact loading versus other materials.

22 Ductility / Brittleness Ability of a material to deform without fracture –We want materials with high ductility, because they will indicate structural failure without a sudden collapse. –http://www.youtube.com/watch?v=BXpqW9B0 eT4&feature=related – “Brittle failure”http://www.youtube.com/watch?v=BXpqW9B0 eT4&feature=related

23 Elasticity Ability of a material to deform and return to it’s original shape. –Important quantity Young’s Modulus Ratio of stress to strain –Stress = Force / Area (lbs./in 2 or N/m 2 ) –Strain = Deformation / Length (unitless) Generates a stress-strain graph Related to the ductility of a material

24 Toughness Ability of a material to resist fracture when stressed (amount of energy absorbed per unit volume) –Units – J/m 3 or Lb-f/ft 3 –Area under the stress-strain curve, evaluated from 0 to the desired strain.

25 So, we know what properties are important in structural materials. How do the common materials stack up against each other?

26 Timber Advantages –Cheap, renewable resource –Good in Tension – ~40 MPa Disadvantages –Susceptible to fire, nature –Not very hard –Not very strong –Limits on shape, size

27 Masonry Concrete blocks, clay bricks –Advantages Large compressive strength Cheap Good thermal properties – holds heat well –Disadvantages Not a cohesive material. The strength could depend on the mortar, other factors Poor tensile strength, unless reinforced Heavy material, requires skilled laborers to use $$$$$ Height restriction Susceptible to the weather

28 Concrete Combination of water, cement, small aggregate, and large aggregate. Advantages –Very versatile – can be modified with admixtures for different effects –High compressive strength (4~7 ksi) –Fire resistant –Many diverse sizes and shapes - formwork

29 Concrete Disadvantages –Long curing time –Low tension strength (~0.4 ksi) –Fails in shear, unless reinforced –Fairly heavy material to work with

30 Steel Advantages –High tensile and compressive strength (A36 Steel ~ 60 ksi) –Many varieties, depending on your need Carbon steel Stainless steel Galvanized steel –Elastic material –Ductile material –Many shapes, sizes

31 Steel Disadvantages –Expensive – limited quantities / competition –Susceptible to fire, rust, impurities

32 Put them together and… Reinforced Concrete –Concrete with steel reinforcement Concrete handles compression Steel takes the tension –Can handle nearly 4 times the loading that concrete alone can handle –More expensive material –http://www.youtube.com/watch?v=dGbrp7Mfp 2whttp://www.youtube.com/watch?v=dGbrp7Mfp 2w

33 Composites Engineered compounds that have different physical or chemical properties –FRP – Fiber reinforced polymers –CFRP – Carbon-fiber reinforced polymers –Plastics –Categories of Glass –Categories of Wood

34 So, now we know what material will best suit our needs.. What should we build with it?

35 Structural Shapes Rectangle / Square Triangle –Interested in stability Truss Geodesic Dome

36 Shape Stability Exercise Split into teams of 5 Build a triangle and square See which shape is the most stable –Can the unstable shapes be made stable? –How?

37 Rectangle Advantages –Proficient in resisting vertical load. Disadvantages –No lateral support

38 Triangle Advantages –Able to withstand lateral & vertical loading –Many triangular shapes available Disadvantage –Wide base = $$$$

39 Rectangle Advantages –Proficient in resisting vertical load. Disadvantages –No lateral (horizontal) load support Need another bar for lateral support! --BRACING--

40 Truss Combination of square and triangle

41 Truss Combination of square and triangle Squares

42 Truss Combination of square and triangle Triangles

43 Truss Combination of square and triangle –Both vertical and lateral support

44 Geodesic Dome

45 Domes

46 Advantages –Very strong shape, gets strong as the dome size increases –Perfect load distribution –No need for structural supports –Great aerodynamic performance

47 Structural Components Beams Girders Columns Floors Foundations ColumnGirder Beam

48 Load Path Floor Beams Girders Columns Foundation Soil/Bedrock

49 Foundations Support the building –Typically attached to columns Types –Shallow Spread footing – concrete strip/pad below the frost line Slab-on-grade – concrete pad on the surface –Deep Drilled Shafts Piles

50

51 Columns Carry the load from floors to the foundation –Never want the columns to fail COLLAPSE –Typically reinforced concrete or steel –Many sizes and shapes

52 Girders Attached column- to-column –Take the load from the beams –Transfer it to the columns –Generally shaped as an I-Beam

53 Beams Attached between the girders –Take load from the flooring system –Transfer it to the girders –Generally solid squares, I-beams

54 Flooring Composed of a subfloor and floor covering –Usually leave space for ductwork, wiring, etc. –Floor covering ranges from application to application

55 Picture Credits Geodesic Dome –http://www.ecophotoexplorers.com/images/antarctica/Dome.jpghttp://www.ecophotoexplorers.com/images/antarctica/Dome.jpg Truss –http://www.classictruss.com/art/wodd_truss_types_examples.gifhttp://www.classictruss.com/art/wodd_truss_types_examples.gif Truss 2 –http://www.wwta.ab.ca/images/pic%201.jpghttp://www.wwta.ab.ca/images/pic%201.jpg Truss 3 –http://www.garrettsbridges.com/images/pratt-truss-bridge.jpghttp://www.garrettsbridges.com/images/pratt-truss-bridge.jpg Stress-Strain –http://www.mittalsteel.com/NR/rdonlyres/8E6DAA96-67F0-4C FB D9/0/InlandAutoApps_MildCS_ssGraph.gifhttp://www.mittalsteel.com/NR/rdonlyres/8E6DAA96-67F0-4C FB D9/0/InlandAutoApps_MildCS_ssGraph.gif Crushing Concrete –http://images.google.com/imgres?imgurl=http://cee.engr.ucdavis.edu/faculty/chai/Research/P lanar%2520Wall%2520Stability/Wallcolumn5.jpg&imgrefurl=http://cee.engr.ucdavis.edu/facul ty/chai/Research/Planar%2520Wall%2520Stability/struct- walls.htm&h=432&w=293&sz=38&hl=en&start=10&sig2=u3TW2TnwJ_IRSpfaQhJuUQ&tbnid =7g- JN0VhU59wxM:&tbnh=126&tbnw=85&ei=qUTYR56oL6jmigGFuaiFAg&prev=/images%3Fq %3Dconcrete%2Bcrushing%2Bcompression%26gbv%3D2%26hl%3Den

56 Pile Machine –http://upload.wikimedia.org/wikipedia/commons/5/54/DFmachine.JPGhttp://upload.wikimedia.org/wikipedia/commons/5/54/DFmachine.JPG Pile Machine 2 –http://upload.wikimedia.org/wikipedia/commons/8/8b/PileDriving.jpg Foundation Type –http://upload.wikimedia.org/wikipedia/en/6/66/Found-House-Apt.pnghttp://upload.wikimedia.org/wikipedia/en/6/66/Found-House-Apt.png Rebar Cage –http://i.pbase.com/u29/camera0bug/upload/ P JPGco pyhttp://i.pbase.com/u29/camera0bug/upload/ P JPGco py Circular Columns –http://web.mit.edu/istgroup/ist/images/research_images/microwave/figur e1.gif

57 Timber –http://www.certified-teak.com/images/timber_india.jpghttp://www.certified-teak.com/images/timber_india.jpg –http://www.timberframeworks.com/images/File0001.jpg Steel –http://www.lakewoodconferences.com/direct/dbimage/ /Stainle ss_Steel_Seamless_Tubes.jpghttp://www.lakewoodconferences.com/direct/dbimage/ /Stainle ss_Steel_Seamless_Tubes.jpg –http://ocw.mit.edu/NR/rdonlyres/Global/6/695E8EC B05-B6F1- 8BE09DC40F68/0/chp_steel_struct.jpg Concrete –http://www.lakewoodconferences.com/direct/dbimage/ /Stainle ss_Steel_Seamless_Tubes.jpghttp://www.lakewoodconferences.com/direct/dbimage/ /Stainle ss_Steel_Seamless_Tubes.jpg –http://www.imagico.de/pov/pict/concrete.jpg Masonry –http://www.gomedia.us/arsenal/images/texturepacks/masonry-prev1.jpghttp://www.gomedia.us/arsenal/images/texturepacks/masonry-prev1.jpg –http://www.cca.org.nz/images/masonry.jpg

58 Structural Engineer –http://vaengineer.com/images/mr__snell_0462.jpghttp://vaengineer.com/images/mr__snell_0462.jpg Building –http://www.brasfieldgorrie.com/_images/portfolio/84/2.jpghttp://www.brasfieldgorrie.com/_images/portfolio/84/2.jpg Girder –http://www.popartuk.com/g/l/lgfp0432+men-on-a-girder-having-lunch- new-york-city-collection-poster.jpghttp://www.popartuk.com/g/l/lgfp0432+men-on-a-girder-having-lunch- new-york-city-collection-poster.jpg –http://oldcooperriverbridge.org/small/oct_31_1927_pearman_resting_gir der.jpg Beam –http://www.cedar-log-homes.com/log-homes-images2/beams-glulam- 6.gif Flooring –http://www.domoteck.org/domoteck_com_images/floor_cross_section.jp g


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