IntermediateTopic 43 of 112Civil & Structural
Statically determinate structures
Can be solved by equilibrium equations alone.
In depth
Structures where support reactions and internal forces can be found from equilibrium alone (statics). Examples: simply supported beams, cantilevers, three-hinged arches, trusses with m+r=2j. Analysis gives reactions, shear, moment and axial force diagrams without material properties.
Key points
- Check determinacy
- No stresses from settlement
- Basis for more complex analysis
ExampleA simply supported beam with central load has reactions P/2 each.
What is Statically determinate structures?
Can be solved by equilibrium equations alone.
Why is it important to understand statically determinate structures?
Statically determinate structures can be solved with equilibrium alone, so they are the starting point for all structural analysis.
How do I know if a structure is determinate?
Count the unknown reactions and internal forces against the available equilibrium equations. If they match, the structure is determinate.
Why is determinacy useful?
Forces do not depend on member stiffness, so the analysis is simpler and temperature or settlement does not change internal forces.
How is Statically determinate structures used in practice?
Typical applications include finding the reactions of a simply supported beam with a point load, solving the forces in a pin-jointed truss with three supports and checking a cantilever frame for support reactions before detailed design.
What should I learn before Statically determinate structures?
Study "Tunnelling and excavation" first (topic 42 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of Statically determinate structures?
Check determinacy. No stresses from settlement. Basis for more complex analysis.
Can you give an example of Statically determinate structures?
A simply supported beam with central load has reactions P/2 each.
What comes after Statically determinate structures?
The next topic is "Influence lines", which builds directly on this one.
How difficult is Statically determinate structures?
It is classed as Intermediate in Civil & Structural (topic 43 of 112). It is an intermediate topic. Work through the beginner topics in Civil & Structural first.