Prestressed Slender Lattice Frames

Abstract

Previous research on the prestressing of lattice frames dealt with relatively short two‐ and three‐dimensional frames. It was found that prestressing the diagonals in frames with intersecting diagonals did not increase the load‐carrying capacity. Offsetting the diagonals on the crossarm or on the verticals, and prestressing these offset diagonals, increased the load‐carrying capacity. It was felt that in a slender structure the effects of prestressing would be even more pronounced. As a result, it was decided to undertake a study of a slender prestressed lattice frame. The failure mode of this frame, one of Euler‐type buckling, is different from that observed in the short frames, which is essentially one of buckling of the verticals between the panel points. A 23‐story slender lattice frame, prestressed and nonprestressed, with axial load and then with axial and lateral load, was studied experimentally and theoretically. It was found that prestressing the diagonals is beneficial in increasing the load‐carrying capacity and reducing lateral deflection.