Suggestions for Typical Problems

Abstract

In the process of construction and use of engineering structures, there are often states of metastable equilibrium (state 2) from a state of stable equilibrium to an unstable equilibrium one. As shown in Fig. 6.1, the pile foundation of structure (a) and structure (b) are all in the foundation pit. Structure (a) shows that the crown beam is connected with the column by a hinged connection, and structure (b) shows that the crown beam is connected with the column by compression only without tension support. When there is external force on this kind of structure, structure (a), the ultimate failure will occur only after the external force reaches the ultimate value, and the whole structure will not change in this process, so it belongs to the problem of extreme point instability; on the contrary, when subjected to external force, the columns in structure (b) in the foundation pit have the deformation trend as shown by the arrow, so the deformation often occurs in the whole structure before the structure reaches the ultimate bearing value, This kind of problem belongs to the problem of branch point instability.