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Mechanics. Loadings. 3 Basic Types of Loadings Static Dynamic Environmental. Constant. Applied Stress. t. Static Loadings. Slowly applied Sustained for period of time Slowly removed Classifications Dead Loads Live Loads. Periodic. Applied Stress. Amplitude. t. Applied

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loadings
Loadings

3 Basic Types of Loadings

  • Static
  • Dynamic
  • Environmental

CE 336

static loadings

Constant

Applied

Stress

t

Static Loadings
  • Slowly applied
  • Sustained for period of time
  • Slowly removed

Classifications

    • Dead Loads
    • Live Loads

CE 336

dynamic loadings

Periodic

Applied

Stress

Amplitude

t

Applied

Stress

t

to

Transient

Applied

Stress

t

Dynamic Loadings
  • Impulse or Shock
  • Vibration
    • Random
    • Transient
    • Periodic

CE 336

environmental loadings
Environmental Loadings
  • Physical
  • Chemical

Many Classifications

    • Thermal, Moisture…
    • Abrasion, Hydraulic…
    • Oxidation, Acid, Base…

CE 336

static forces and stresses
Static Forces and Stresses
  • Flexure Stress,  = Mc/I
  • Bending Shear  = VQ/It
  • Direct Compression Stress,  = -P/A
  • Direct Tension Stress,  = P/A
  • Torsional Shear  = Tr/Ip

CE 336

review of mechanics
Review of Mechanics
  • Equilibrium (internal vs. external)
    • Combined Stresses
  • Yield, (0.2% offset)
    • Elastic Limit,
    • Proportional Limit,
  • Limitations of elastic theory

CE 336

stress vs strain
Stress vs. Strain

Linear

Non-Linear

ult

y

ult

y

0.002

CE 336

overview of mechanics
Overview of Mechanics
  • Modulus of Elasticity
    • tangent
    • secant
    • chord
  • Shear Modulus

CE 336

overview of mechanics10
Overview of Mechanics
  • Elastic
  • Plastic
  • Ductility
  • Toughness
  • Resilience
  • Hardening

CE 336

elasticity
Elasticity
  • Ability to store energy and recover strain when unloaded

Perfectly elastic materials return to their original geometry when fully unloaded.

CE 336

plasticity
Plasticity
  • Ability to absorb energy upon loading

Perfectly plastic materials maintain the deflected shape after loading is removed.

CE 336

ductility
Ductility
  • The ability to sustain plastic deformation without fracture

 = ult/y

CE 336

toughness
Toughness
  • Toughness: Mechanical measure of total absorbed and stored energy at fracture

CE 336

resilience
Resilience
  • Resilience: Mechanical measure of storing energy at yield

CE 336

review of mechanics16
Review of Mechanics
  • Deformations and Strains, = E
    • Flexural, Mx/EI = 
      • (plane sections remain plane)
    • Compression and Tensile, /L = 
    • Shear deformations G(distortions)
    • Poisson Strains l = x

CE 336

review of mechanics17
Review of Mechanics
  • Poisson ratio

concrete = 0.15

steel = 0.25

  • Dilatation (cubical dilation)

e = (V’-V)/V

e = ex(1-2)

CE 336

elastic vs plastic behavior

y

y

Elastic vs. Plastic Behavior

Linear

Non-Linear

CE 336

environmental mechanical strain
Environmental/Mechanical Strain
  • Coefficient of Thermal Expansion
  • Creep,
  • Shrinkage,
  • Relaxation
  • Chemical Resistance

CE 336

review of mechanics21
Review of Mechanics
  • Stiffness: Load necessary to cause a unit deformation
    • Modulus
    • Shape, I, J, L, e.g. EI/L or AG
    • Restrain Conditions
  • Distribution of Forces according to Stiffness

CE 336

review of mechanics22
Review of Mechanics
  • Material Compatibility in composite
  • Material Compatibility in environments

CE 336

ductility and fracture characteristics
Ductility and Fracture Characteristics
  • Ductile Behavior

Advantages and Disadvantages

  • Brittle Behavior

Advantages and Disadvantages

CE 336