Advantages and Disadvantages of Statically Indeterminate Structures Lesson 2 Advantages and Disadvantages of Statically Indeterminate Structures
Advantages/Disadvantages
Geometric changes cause indirect stresses
Geometric changes cause indirect stresses Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Fabrication Error If this is accidentally Fabricated too long… Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Fabrication Error If this is accidentally Fabricated too long… All joints just move to New positions Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Fabrication Error If this is accidentally Fabricated too long… Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Fabrication Error If this is accidentally Fabricated too long… Then it must be Compressed into place Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Fabrication Error Which puts these in tension If this is accidentally Fabricated too long… Then it must be Compressed into place Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Fabrication Error Which puts forces on all members If this is accidentally Fabricated too long… Then it must be Compressed into place Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Fabrication Error Which puts forces on all members No Stresses. Members go together. Members must be forced to fit. Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 2. Temperature Changes SUN Heated Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 2. Temperature Changes SUN Heated No Stresses. Positions just change Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 2. Temperature Changes Joints restricted by truss-action SUN SUN Heated Heated No Stresses. Positions just change Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 2. Temperature Changes SUN SUN Heated Heated No Stresses. Positions just change Thermal causes stresses Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 2. Temperature Changes SUN SUN If Expansion Joint does not Allow expansion, this duct Is statically indeterminate Heated Heated No Stresses. Positions just change Thermal causes stresses Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 2. Temperature Changes SUN SUN If Expansion Joint does not Allow expansion, this duct Is statically indeterminate Heated Heated No Stresses. Positions just change 800F high-temperature gas causes it to Crumple like a beer can Thermal causes stresses Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses Simple Beam Simple Beam Pier Pier Pier Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 3. Foundation Settlement Simple Beam Simple Beam Pier Pier Pier Any Settlement: Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 3. Foundation Settlement Simple Beam Simple Beam Pier Pier Pier Any Settlement: No Curvature. No moment Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 3. Foundation Settlement Simple Beam Simple Beam Pier Pier Pier Any Settlement: No Curvature. No moment Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 3. Foundation Settlement Simple Beam Simple Beam Continuous Beam Pier Pier Pier Pier Pier Pier Any Settlement: No Curvature. No moment Statically Determinate Statically Indeterminate
Statically Indeterminate Disadvantages Geometric changes cause indirect stresses 3. Foundation Settlement Simple Beam Simple Beam Continuous Beam Pier Pier Pier Pier Pier Pier Any Settlement: No Curvature. No moment Any Settlement: Curvature! Moment! Statically Determinate Statically Indeterminate
Pier Pier Pier Pier Pier Pier Statically Determinate Statically Indeterminate
Statically Indeterminate Advantages Pier Pier Pier Pier Pier Pier M M Statically Determinate Statically Indeterminate
Statically Indeterminate Advantages Pier Pier Pier Pier Pier Pier wL2/8 M M Statically Determinate Statically Indeterminate
Statically Indeterminate Advantages 1. Lower Stresses Pier Pier Pier Pier Pier Pier wL2/8 wL2/21.4 M M M M Statically Determinate Statically Indeterminate
Statically Indeterminate Advantages 2. Greater Stiffness Pier Pier Pier Pier Pier Pier D = Statically Determinate Statically Indeterminate
Statically Indeterminate Advantages 2. Greater Stiffness Pier Pier Pier Pier Pier Pier D = 5wL4/384EI Statically Determinate Statically Indeterminate
Statically Indeterminate Advantages 2. Greater Stiffness Pier Pier Pier Pier Pier Pier D = 5wL4/384EI Statically Determinate Statically Indeterminate
Statically Indeterminate Advantages 2. Greater Stiffness Pier Pier Pier Pier Pier Pier D = 2.1wL4/384EI D = 5wL4/384EI Statically Determinate Statically Indeterminate
Statically Indeterminate Advantages 2. Greater Stiffness Pier Pier Pier Pier Pier Pier Statically Determinate DOIs = ?? Statically Indeterminate
Statically Indeterminate Advantages 2. Greater Stiffness Pier Pier Pier Pier Pier Pier Statically Determinate DOIs = 0 Statically Indeterminate DOIs = 1
Statically Indeterminate Advantages Pier Pier Pier Pier A catastrophic event eliminates the middle pier Statically Determinate DOIs = 0 Statically Indeterminate DOIs = 1
Statically Indeterminate Advantages 3. Greater Robustness – May survive redundant loss of massive overload Pier Pier Pier Pier Will NOT Survive (zero redundancy) MAY Survive (if the beam can take a Substantial increase in moment) A catastrophic event eliminates the middle pier Statically Determinate DOIs = 0 Statically Indeterminate DOIs = 1