Moment and Deflection Coefficients for Two-Way Slabs with Triaxial (0°/60°/120°) Reinforcement Under Different Edge-Continuity Conditions

Two-way slabs are commonly designed with moment-coefficient tables that depend on the aspect ratio and on which edges are continuous. This paper reformulates such coefficients for slabs reinforced with a triaxial 0°/60°/120° bar net for the nine-standard edge-continuity cases from four continuous edges to none. At the ultimate limit state, the normal-moment yield criterion of the net makes the existing coefficients applicable unchanged for normal-moment resistance (twisting-dominated regions require a separate check), and a closed-form rule converts the code steel areas in the two span directions into the areas of the three bar families with the same total steel for any aspect ratio. At the serviceability limit state, the moment and deflection coefficients are recomputed by a finite-difference solution of the especially orthotropic plate for uncracked, cracked orthogonal, and cracked triaxial stiffness states, with the cracked twisting stiffness calibrated against a published torsion-test series. Once cracked, the orthogonal slab loses most of its twisting stiffness and reverts towards the Rankine–Grashof strip moments without the Marcus torsion correction, with positive short-span moments up to about 40% above the plate coefficients; the cracked triaxial slab retains the correction, and its short-span and negative moments stay within about 9% of them (its long-span positive moments are up to about 18% higher). A full design of every edge case under four cracking scenarios shows that a thinner triaxial slab requires two conditions together: cracking under sustained load and discontinuous edges. If the slab remains uncracked, the thickness ratio h_H/h_O is 1.00 in all cases. In the cracked state h_H/h_O is 0.89 for a simply supported square panel (0.93 under partial cracking), 0.94–0.97 for near-square edge panels, 0.96–1.00 for corner panels, and 1.00–1.09 for interior panels and elongated panels with continuous long edges, because clamped edges suppress the twisting that the triaxial net resists and elongated panels bend almost cylindrically. The maximum thickness reduction, about 11% (h_H/h_O = 0.89), is therefore an upper value, relevant to isolated, edge and corner panels that are close to square and cracked in service.