Normal stress(σ) acts perpendicular to the longitudinal axis of a member.
Shear stress(

State of Stress: a volumetric element of material from the member and is characterized by σx, σy, σz,



Units of stress are Pascals (Pa). 1Pa = N/m^2 , psi, or Kilopound(Kip)
Assumptions for determining the average stress distribution:
- Uniform deformation
- The force applied to the member is along the centroidal axis
- The member remains straight before and after loading
- The member is homogeneous: having the same physical and mechanical properties throughout the volume of the member
- σ is the average normal stress
- P is the internal resultant normal force
- A is the area of the cross section

-
avg is the average shear stress
- V is the internal resultant shear force, determined from equations of equilibrium
- A is the area at that section
Factor of Safety: ensures the safety of members by determining the maximum shear and normal stresses that are safe for a member to hold
F.S. = Ffail / Fallowable
- F.S. is the factor of safety and is always greater than 1 to avoid the member from potential failure
- Ffail can either be σ or
failure
- Fallowable can either be σ or
allowable
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