Experimental investigation of prestressing in double-layer grids

Practical designs of double-layer grids often fail to achieve full utilization of the structural efficiency inherent in this spatial framework. This inefficiency is due partly to the tendency to use a small number of different cross-sections, and partly to the sensitivity of compression members with `brittle type' buckling characteristics to imperfections. Prestressing can enhance structural efficiency through recruitment of unutilized member capacity. The procedure also enables improvement of ductility through some controlled strength trade-off. Results of the experimental work presented in this paper indicated increased strength of 40% compared with the non-prestressed configuration as well as enhanced ductility in the peak load region. Larger enhancements are feasible in large grids.