Optimum strengthening of a column-supported oil pipeline by a tubular truss

In the case of a statically indeterminate structure, a systematic optimum design procedure should be performed, since the forces in structural parts depend on their dimensions, and the cost function to be minimized is rather complicated. This is so in the case of a column-supported oil pipeline when it is strengthened by a tubular truss. The internal forces in the tubular truss are derived on the basis of a deflection equation. The strengthening tubular truss is optimized to fulfil the design constraints and minimize the cost. Design constraints relate to the stress in the original pipe and in the truss members, as well as to the strength and geometry of the truss joints. The cost function includes the material cost, as well as the costs of cutting of struts, assembly, welding and painting.