- Total change in length is zero because the ends are fixed which will not allow the sections to expand or shrink.
- Load or stress is produced by expansion or shrinkage of the section is taken by the ends. Therefore ends carry some load or stress.
- Using principle of superposition the reactions at the end of each section is found from free body diagram. Equate the direction of force in free body diagram to force applied for each section,
- The equation shows that the section AB and BC is under tension and CD under compression. The direction of load in each section can be chosen as we desire, but if the final result is negative then the direction chosen is incorrect but the answer is correct. So in other words tensile force is actually a compressive force vice versa.
- Sum of change in length of each section due to expansion is equal to sum of change in length of each section due to compression. The load P, length L, Area A, and Young‟s modulus E parameters may vary from section to section