Strengthening of axially compressed bars in lattice towers under load – experimental investigations

This paper presents the results of experimental research, in which hot‐rolled single steel angle members L65×65×7 were strengthened under axial compression. Strengthening was carried out by attaching an additional angle (L65×65×7 or L50×50×5) by a clamp system. The reinforced angle, the reinforcing element and the clamps were hot‐dip galvanized. The paper compares the difference between buckling behaviour and the ultimate load capacity elements strengthened under no load with the elements having the same geometry, in which the strengthening was carried out under the load. The level of force transmission from the reinforced to the reinforcing member is also recognized. The results show the influence of the size of the reinforcement element, the slenderness of the reinforced member, and the spacing of the clamps on the effectiveness of reinforcement. The effect of preload on the ultimate load capacity of the axially loaded element was found to be insignificant in the study conducted (no more than ±4.2%).