Presentation on theme: "Introduction to Structural Engineering"— Presentation transcript:
1 Introduction to Structural Engineering Tony Freidman
2 Background Graduate of University of Missouri – Rolla B.S. in Civil EngineeringB.S. in Architectural EngineeringResearch in Architectural specialtiesResearch on V-T-M diagram development for reinforced concrete column designCurrently enrolled as a Ph.D. student at Washington University – St. LouisResearch on MR Damper performanceResearch on Structural Health Monitoring
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. “- 1st 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? Mathematics of designArchitect/ArtistVisionAesthetics of designMediatorLiason between parties on a projectSalesmanMust 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 Inspector Demolitions Take a design, and fit a structural system to thatExpert witnesses in lawsuitsInspectorFieldwork, Job site inspectionsOversee the materials (concrete, steel, etc.)Inspect the building – pre- and post-constructionDemolitionsBuilding deconstructionStructural 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 energyBuilding StructuresHousesSkyscrapersAnything designed for continuous human occupationNon-building StructuresBridgesTunnelsDams
12 ForcesInfluence on an object that causes a change in a physical quantityConsidered “vectors” – magnitude and directionStatic ForceUnchanging with timeWallsFloorsDynamic ForceChanging with timePeopleFurniture
13 Forces Axial Forces Momential (Bending) Force Acting along one axis, directly on a point or surfaceMomential (Bending) ForceActing along an axis, at a certain distance from a point, causes a folding motionM = F*dF
14 Forces Tensile Force Compressive Force Pulling on an object – stretching itSteel shows “necking” when too much tensile force is appliedCompressive ForcePushing on an object – collapsing itConcrete crushes when too much compressive force is applied
15 Forces Strain Stress Compare using stress-strain graph Tensile-related propertyDeformation / LengthStressCompression-related propertyForce / AreaCompare using stress-strain graph
16 What constitutes loading? Loading is a force being enacted on the structureMany sources of loadGravity/WeightWindSnowEarthquakeMan-madeTwo Types of Structural LoadingDead 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 MaterialsTimberMasonryConcreteSteelComposites
18 How do we judge the materials? Common Material PropertiesStrength – Tensile/CompressiveDensityHardnessDuctility / BrittlenessElasticityToughness
19 Strength Ability of a material to withstand loading Tensile strength – ability of a material to withstand a pulling forceSteel is good at this, but concrete performs very poorly.Compressive strength – ability of a material to withstand a pushing forceWood, concrete, steel, and masonry perform well
20 Density Mass per unit volume of a material Units – mass/vol - kg/m3 or lb-m/ft3Typically, 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 $$$$$
21 HardnessAbility of a material to resist permanent deformation under a sharp loadRelates to the elasticity of a materialDiamond is a very hard substance. If we built a wall out of diamond, we could be sure that very few things would scratch it.However, Diamond is incredibly expensive and not as tough as other engineering metals. It wouldn’t stand up as well in impact loading versus other materials.
22 Ductility / Brittleness Ability of a material to deform without fractureWe want materials with high ductility, because they will indicate structural failure without a sudden collapse.– “Brittle failure”
23 ElasticityAbility of a material to deform and return to it’s original shape.Important quantityYoung’s ModulusRatio of stress to strainStress = Force / Area (lbs./in2 or N/m2)Strain = Deformation / Length (unitless)Generates a stress-strain graphRelated to the ductility of a material
24 ToughnessAbility of a material to resist fracture when stressed (amount of energy absorbed per unit volume)Units – J/m3 or Lb-f/ft3Area under the stress-strain curve, evaluated from 0 to the desired strain.
25 So, we know what properties are important in structural materials So, we know what properties are important in structural materials. How do the common materials stack up against each other?
26 Timber Advantages Disadvantages Cheap, renewable resource Good in Tension – ~40 MPaDisadvantagesSusceptible to fire, natureNot very hardNot very strongLimits on shape, size
27 Masonry Concrete blocks, clay bricks Advantages Disadvantages Large compressive strengthCheapGood thermal properties – holds heat wellDisadvantagesNot a cohesive material. The strength could depend on the mortar, other factorsPoor tensile strength, unless reinforcedHeavy material, requires skilled laborers to use $$$$$Height restrictionSusceptible to the weather
28 ConcreteCombination of water, cement, small aggregate, and large aggregate.AdvantagesVery versatile – can be modified with admixtures for different effectsHigh compressive strength (4~7 ksi)Fire resistantMany diverse sizes and shapes - formwork
29 Concrete Disadvantages Long curing time Low tension strength (~0.4 ksi)Fails in shear, unless reinforcedFairly heavy material to work with
30 SteelAdvantagesHigh tensile and compressive strength (A36 Steel ~ 60 ksi)Many varieties, depending on your needCarbon steelStainless steelGalvanized steelElastic materialDuctile materialMany shapes, sizes
32 Put them together and… Reinforced Concrete Concrete with steel reinforcementConcrete handles compressionSteel takes the tensionCan handle nearly 4 times the loading that concrete alone can handleMore expensive material
33 CompositesEngineered compounds that have different physical or chemical propertiesFRP – Fiber reinforced polymersCFRP – Carbon-fiber reinforced polymersPlasticsCategories of GlassCategories of Wood
34 So, now we know what material will best suit our needs So, now we know what material will best suit our needs.. What should we build with it?
35 Structural Shapes Rectangle / Square Triangle Truss Geodesic Dome Interested in stabilityTrussGeodesic Dome
36 Shape Stability Exercise Split into teams of 5Build a triangle and squareSee which shape is the most stableCan the unstable shapes be made stable?How?
37 Rectangle Advantages Disadvantages Proficient in resisting vertical load.DisadvantagesNo lateral support
38 Triangle Advantages Disadvantage Able to withstand lateral & vertical loadingMany triangular shapes availableDisadvantageWide base = $$$$
39 Rectangle Advantages Disadvantages Proficient in resisting vertical load.DisadvantagesNo lateral (horizontal) load supportNeed another bar for lateral support!--BRACING--
49 Foundations Support the building Types Typically attached to columns ShallowSpread footing – concrete strip/pad below the frost lineSlab-on-grade – concrete pad on the surfaceDeepDrilled ShaftsPiles