4. Structural Mechanics Flashcards
What are types of gravity loads?
Dead Load (D), Live Load (L), Roof Live Load (Lr), Fluid Load (F), Snow (S), Rain Load (R), and Flood (Load).
What are types of Lateral Loads?
Wind (W), Earthquake (E), Lateral Soil and Water Pressure (H), and Thermal Loads (T).
Where do Earthquake and Wind loads act?
Earthquake: forces applied to roof and floor
Wind: forces applied to walls and roof
Both are applied in both direction.
What are the two types of design methods of structural members?
Allowable Stress Design (ASD) and Strength Design or Load and Resistance Factor Design (LRFD).
What are common types of External Instability that can be verified by inspecting the reaction forces?
(1) improper supports (parallel or concurrent reaction forces (2) inadequate supports (n < 0).
What are common types of Internal Instability that be verified by inspection of the structure?
- Three hinges in a row in a beam or frame without any support between them
- Parallel or concurrent forces in a cut in a determinant truss
- In general, if inspection shows that under ANY arbitrary force, equilibrium equations are not satisfied.
What are the three possible states of determinacy of a structure?
(1) n > 0, indeterminate
(2) n = 0, determinate
(3) n < 0, unstable
How do you identify zero-force members in a truss?
(1) If only two members are connected to a joint without any external force or support at that joint, both members carry zero force
(2) If three members are connected to a joint without external force or support at that joint AND two of the members are collinear, the force in the non-collinear member is zero.
(3) If four member are connected to a joint without any external force or support at that joint, AND members are collinear in pairs, the force in collinear members are equal.
What assumption can be made for building frames (with non-rigid connections) used with bracing and resisting lateral forces like a truss?
Braces are assumed to only resist tension, therefore you can eliminate member that would experience compression.
For analysis of shallow footing what assumption can be made on the bearing stress distribution under axial and bending moment from the column to the footing?
The bearing stress is assumed to be linear.
For Retaining Wall Checks what is the factor of safety with regards to Overturning?
FS = 2.0 (cohesive backfill) and FS = 1.5 (granular backfill)
For Retaining Wall Checks what is the factor of safety with regards to Sliding?
FS = 2.0 when passive pressure is included in the calculations. If passive pressure ignored than FS = 1.2
What may be used if FS for sliding is not adequate?
A shear key.
