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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 3 Basic Types of Loadings • Static • Dynamic • Environmental CE 336
Constant Applied Stress t Static Loadings • Slowly applied • Sustained for period of time • Slowly removed Classifications • Dead Loads • Live Loads CE 336
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 • Physical • Chemical Many Classifications • Thermal, Moisture… • Abrasion, Hydraulic… • Oxidation, Acid, Base… 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/Ip CE 336
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 Linear Non-Linear ult y ult y 0.002 CE 336
Overview of Mechanics • Modulus of Elasticity • tangent • secant • chord • Shear Modulus CE 336
Overview of Mechanics • Elastic • Plastic • Ductility • Toughness • Resilience • Hardening CE 336
Elasticity • Ability to store energy and recover strain when unloaded Perfectly elastic materials return to their original geometry when fully unloaded. CE 336
Plasticity • Ability to absorb energy upon loading Perfectly plastic materials maintain the deflected shape after loading is removed. CE 336
Ductility • The ability to sustain plastic deformation without fracture = ult/y CE 336
Toughness • Toughness: Mechanical measure of total absorbed and stored energy at fracture CE 336
Resilience • Resilience: Mechanical measure of storing energy at yield 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 CE 336
Review of Mechanics • Poisson ratio concrete = 0.15 steel = 0.25 • Dilatation (cubical dilation) e = (V’-V)/V e = ex(1-2) CE 336
Generalized Hooke’s Law CE 336
y y Elastic vs. Plastic Behavior Linear Non-Linear CE 336
Environmental/Mechanical Strain • Coefficient of Thermal Expansion • Creep, • Shrinkage, • Relaxation • Chemical Resistance 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 CE 336
Review of Mechanics • Material Compatibility in composite • Material Compatibility in environments CE 336
Ductility and Fracture Characteristics • Ductile Behavior Advantages and Disadvantages • Brittle Behavior Advantages and Disadvantages CE 336