Behavior of Columns with Pretensioned Stays

The capacity of columns can be increased by using crossarms and pretensioned stays. It is shown that the buckling load of a single crossarm stayed column is a function of the stiffness of the stays, and the ability to achieve that buckling load is a function of the residual tension in the stays at buckling. If the initial pretension is small, then the stays can become slack before the buckling load is reached. If the initial pretension is large, the column will buckle before the stays lose their pretension. It is shown that columns in which stays lose their pretension before buckling occurs have a lower buckling load than columns in which stays do not. It is also demonstrated that initial imperfections reduce the capacity below the buckling load of the perfect column. Loss of pretension for a low initial pretension does not cause failure, but for a high initial pretension precipitates instability. Simple but accurate equations are presented that allow noncomputerized solutions to be generated. The theoretical results are compared with recently published results.