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Mechanics. CE 336 Loadings 3 Basic Types of Loadings Static Dynamic Environmental.

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Presentation on theme: "Mechanics. CE 336 Loadings 3 Basic Types of Loadings Static Dynamic Environmental."— Presentation transcript:

1 Mechanics

2 CE 336 Loadings 3 Basic Types of Loadings Static Dynamic Environmental

3 CE 336 Static Loadings 1. Slowly applied 2. Sustained for period of time 3. Slowly removed Classifications Dead Loads Live Loads

4 CE 336 Dynamic Loadings 1. Impulse or Shock 2. Vibration Random Transient Periodic t Applied Stress Amplitude Periodic Applied Stress Transient t toto t Applied Stress

5 CE 336 Environmental Loadings Physical Chemical Many Classifications Thermal, Moisture… Abrasion, Hydraulic… Oxidation, Acid, Base…

6 CE 336 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/I p

7 CE 336 Review of Mechanics Equilibrium (internal vs. external) Combined Stresses Yield, (0.2% offset) Elastic Limit, Proportional Limit, Limitations of elastic theory

8 CE 336 Stress vs. Strain   yy  ult  ult yy Linear Non-Linear

9 CE 336 Overview of Mechanics Modulus of Elasticity tangent secant chord Shear Modulus

10 CE 336 Overview of Mechanics Elastic Plastic Ductility Toughness Resilience Hardening

11 CE 336 Elasticity Ability to store energy and recover strain when unloaded Perfectly elastic materials return to their original geometry when fully unloaded.

12 CE 336 Plasticity Ability to absorb energy upon loading Perfectly plastic materials maintain the deflected shape after loading is removed.

13 CE 336 Ductility The ability to sustain plastic deformation without fracture  =  ult /  y

14 CE 336 Toughness & Resilience Toughness: Mechanical measure of total absorbed and stored energy at fracture Resilience: Mechanical measure of storing energy at yield

15 CE 336 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

16 CE 336 Review of Mechanics Poisson ratio  concrete = 0.15  steel = 0.25 Dilatation (cubical dilation) e = (V’-V)/V e = e x (1-2  )

17 CE 336 Generalized Hooke’s Law

18 CE 336 Elastic vs. Plastic Behavior Linear Non-Linear   yy yy

19 CE 336 Environmental/Mechanical Strain Coefficient of Thermal Expansion Creep, Shrinkage, Relaxation Chemical Resistance

20 CE 336 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

21 CE 336 Review of Mechanics Material Compatibility in composite Material Compatibility in environments

22 CE 336 Ductility and Fracture Characteristics Ductile Behavior Advantages and Disadvantages Brittle Behavior Advantages and Disadvantages


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