Here is the word document I complied a summary of what is done, what is to do and any issues to clairify in, aswell as some potential essay ideas. This was useful to help me claer my mind up of what i want to get out of the experiment.
Copy of the document:
Subject | Physics |
Topic | Investigation into lattice girders, how they work and what are their limitations? |
Focus | Taking a warren truss as an example, use a combination of theory, calculation and experimentation to understand how the design features contribute to the strength and efficiency of the truss. |
Title | Efficient load bearing structures |
Research question | How does the configuration of a warren truss determine its ability to bear load? |
Approach | An experimental approach to test the behaviour under loading of three warren truss configurations. Using force analysis calculations and the experimental observations to guide research into relevant failure mechanisms, to explain how the design features contribute to the strength and efficiency of the truss. |
Investigation Plan:
Action | Progress |
Preliminary research | Add book references + content |
Preliminary experiment with single truss | Complete: · realised importance of fixing the truss at each end · need a rig to mount it including a loading mechanism. · Measurement of deflection was problematic |
2nd experiment with three truss arrangements | Complete: · Rig was improvement · Common failure mechanism with all three trusses: buckling of top member in compression. · Need to investigate buckling failure mechanism. · Need more precise measuring equipment · Need to develop testing rig |
Targeted research | · Simple beam theory: bending moments, shear forces, youngs modulus, second moment of inertia, radius of gyration, buckling, effective length of columns · Deflection of trusses: work in progress |
3rd experiment | · Before exams! (mid june) · Repeat loading test on three trusses with nodes on the top chords restrained laterally. · Use a sonar device and logger pro software to measure deflection for greater precision. |
Analyse results and evaluate correlation between theoretical calculated forces and experimental observation | · |
First essay draft | · First two weeks of june (deadline 17th june) |
· |
Questions for Mr. Rawson:
1. Can I use established equations without deriving them if I can reference them?
2. Qualitative and quantative results from experimentation, are both acceptable?
Essay plan:
Introduction:
· Significance: see them all around, used widely, from roofs to bridges
· Invention and history of trusses – very brief
· Context of research question:
· Why it is worth investigating: engineering is about efficient use of materials. Trusses always look lighter weight compared with traditional beams and columns. Understanding how they work and their limitations could be important in a future world as resources become more scarce and engineering challenges become more demanding.
· Scope/focus: using warren truss as an example of a commonly used configuration, simplifying the investigation to three simple versions of a warren truss. Taking a span to depth ratio of 10:1 (reference to be found).
· Relevant physics principles: What is this?? E.g. structural frame analysis, bending moments, axial forces, calculations, principles of stress/strain, tension/compression, simple beam theory
· Research question: see front page
· Concluding statement: later!
Body:
· Background Theory
o Simple beam theory:
§ Loads
§ bending moments
§ Shear forces
§ Tension/compression
o Compression and buckling
§ Effective length of columns
§ Youngs modulus
§ Second moment of inertia
§ Radius of gyration
§ Theoretical buckling load of a member(possibly)
o Theory of trusses
§ Comparaison to simple beam
§ Analysis of axial forces
§ Deflection calculation
· Calculations
o Analysis of forces in the three trusses
o Approximate deflection calculation for 4 section truss
· Experimentation
o Describe experiment (method, rig, material specs...)
o Results
o Analysis of results
o Conclusions
§ Can I explain it
§ Errors
· Conclusion:
o Final argument/idea
o Answer research question
o Unresolved issues
o New questions that have arisen
