Truss Beam with Tendon Diagonals: Mechanics and Designs

Abstract

A straightforward means to reduce the mass of some truss beams is to replace rigid diagonals with prestressed tendons. Pretension, however, aggravates the deployment challenge, loads the remaining struts, as well as affects the design in more subtle ways. The present paper helps navigating this trade-off by reviewing the mechanics of and some design considerations for a regular triangular truss beam with three lacing options: one redundant and two statically determinate combinations of tendon diagonals with diagonal pretensioning. Considered are member vibration, the interaction of mission loads with parasitic forces (redundant design), truss face accuracy and longeron compression eccentricity effects (determinate designs), as well as stiffness issues. A scrutiny of shear effects reveals that some shear compliance formulas regularly used for truss beam Timoshenko continuum modeling are incorrect.