The two primary factors driving instability are the magnitude of the stress and the slenderness of the structural element concerned. Slenderness is a measure of how easily a structural element buckles, and is typically defined by the geometry, e.g. width over thickness, and stress distribution of the element. The way a structural element is supported, and the material properties, as well as imperfections, such as minor defects or deviations from the intended shape, also significantly affect the ability of the structure to resist instability.
To prevent instability in structures, engineers need to consider several aspects during the design and construction phases. Proper design analysis should be performed to ensure that the structure can withstand the anticipated loads and environmental conditions. The choice of material and the sizing and shape of the structural elements need to be optimized to ensure they are able to resist instability, while taking account of their slenderness and other factors that affect their stability. It is also important to consider the support boundary conditions of the structural element and any possible imperfections that can affect its stability. Regular inspections and maintenance are also necessary to detect any signs of instability early on and to take appropriate measures to address them.