STUDY ON BEHAVIOUR OF SECONDARY STRESSES IN TRUSSES DUE TO CONNECTION ECCENTRICITIES

Abstract

Secondary stresses occur in steel truss members due to fixity at the nodes, which are considered, pinned in primary analysis. It may also occur in the members due to member imperfections or due to temperature variations. When a truss is fabricated with web members directly welded to chord members, secondary stresses may be induced due to eccentricity of member at the node and weld length imbalance at a joint. If loads are applied over a member, flexural stresses are superimposed over axial stresses, thus the member will be a beam – column. This paper aims at studying the secondary stresses occurring in the following problems, pitched roof truss with directly welded connections with loads at nodes, pitched roof truss with concentric connections (with gusset plates), Parallel chord lattice trusses with directly welded connections with loads at nodes, Parallel chord lattice trusses with directly welded connections with loads on chords. Based on the analysis, Elimination of gusset plates will result a considerable economy in the total cost of the roof truss (i.e)5 to 10% of the cost of truss can be omitted, High secondary stresses exist only in some of the members and then only in the extreme fibers at the ends of the members.