ACI 549.1R-18 Design Guide for Ferrocement.
L3efore considering the efficiency ratios of various systems. it is instructive to compare the performance of various reinforcing systems in terms of the relationship between actual ultimate flexural strength measured by test and the eflc(j ’e area of reinforcement in the longitudinal direction. A comparison was made with the various reinforcements in their nonnal orientations (as previously delined for expanded metal, square mesh, and hexagonal mesh) at two levels of reinforcement strength (Fig. 3.3.3a). The distribution of the reinforcing layers was assumed unilbnn throughout the depth of cross section. and skeletal reinforcing bars were not considered. The comparison showed that expanded metal and square welded mesh perform significantly better than woven meshes or conventional bars with end anchorage. Conventional bar reinforcement was included for comparative purposes only and would not be permitted by the ACI 318 because it would not meet cover requirements. Also, woven mesh, conventional bars, and hexagonal mesh perform similarly. Clearly. based on effective longitudinal area of reinforcement, expanded metal and square welded mesh in their normal orientations are more effective in flexure than are other types of reinforcement. despite differences in test specimen size, mortar cover, and the specifIc surface and spacing of the reinforcing layers. The use of the efliciency ratio gives a truer indication of the effectiveness of the various reinforcements. Despite minor differences in the methods of applying ultimate strength analysis to the computation of ultimate moment, the general consensus i that efficiency ratios for expanded metal and welded mesh in their normal orientations are higher than those of woven meshes and are in the range 1.05 to 1.20 (Logan and Shah 1973; Johnston and Mowat 1974: Naaman and McCarthy
1985; Rao and Gowdar 1971). Similar elliciency ratios have also been obtained for both simple uniaxial (Pama et al. 1974; Austnaco et al. 1975) and biaxial (Greenius 1975a) loading (circular slabs with a central load) using hexagonal mesh laid in alternate layers with skeletal bars between them. The performance of these reinforcing systems meets and slightly exceeds expectations based on strength analysis. Some additional strength is apparently imparted by the two-way nature of the reinforcements, as already noted for tensile strength,ACI 549.1R pdf download.