Lateral bracing forces in compressed two-span columns with initial curvature

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Virginia Tech


The main purpose of this study is to find critical loads and full bracing conditions for perfect two-span columns, and to find the reaction forces at the lateral bracing supports and maximum deflections for two-span columns with initial curvature. In each case, the column under consideration may have different bending stiffnesses in each span, and the column is subjected to an axial compressive load. The braces are not assumed to be equally spaced, and may have different spring stiffnesses.

For the perfect columns, it is found that if the internal lateral support is located in the middle of the column , the column can resist a higher applied load than for any other support location. The load resisting capacity of the column depends on the lateral spring stiffness. It is also found that an ideal spring stiffness, corresponding to full bracing, only exists under special conditions.

For the imperfect columns, the initial shape is assumed to be the same as the buckling mode of the perfect column, and its size is specified. It is found that there are no reaction forces when there is full bracing. The reaction forces and maximum deflections are proportional to the size of the initial deflection, so their values for initial deflections of the same shape but different size can be determined directly from the results presented here.