ACI 421.2R-10 Guide to Seismic Design of Punching Shear Reinforcement in Flat Plates Copyright American Concrete Institute Provided by IHS under license with ACI Not for Resale No reproduction or networking permitted without license from IHS.
Figures 3.1 and 3.3 show that the curves representing experiments of flat plate-column connections with shear reinforcement fall well above the horizontal lines. Curves 2 and 3 of Fig. 3.1 are not perfect his because of the scatter of experimental data. The uncertainty of the curves, however, does not change the conclusion that no limit on (V11IV.) is needed for slabs with shear reinforcement exceeding the minimum amount given in Chapter 4 to sustain the 0.025 design story drift ratio required by IBC 2006. Figure 3.1 also shows that the drift capacity for slabs with SSR is higher than slabs with stirrups.
3.4—Design recommendations for flat plates with and without shear reinforcement
As discussed in Section 3.l, the lateral-force-resisting structural system should have sufficient stiffness to control the story drift. Slab shear reinforcement is required when the maximum shear stress at d12 from the column face exceeds 4w, where v. is the value given by Eq. (3-I) to (3-3) divided by b1,d. In addition, flat plate-column connections should have shear reinforcement equal to or exceeding the minimum amount given in Chapter 4, except when the value of V is less than 0.2O4V, and = 0.75 (AC! 318, Section This requirement ensures that the connections can sustain the design story drift ratio DR = 0.025. If it can be shown by analysis that when the maximum story drift ratio DR, including the inelastic deformations, is between 0.015 and 0.025, shear reinforcement is required when V exceeds 4lVc(0.70 20DR). This is the same as required by AC! 31 8, Section 21.13.6(b), that shear reinforcement be provided when DR, exceeds [0.035 — 0.05 VI(QV)J.
Curve I in Fig. 3.1 shows that for slabs without shear reinfonenient. DI?, can reach 00l5 only when V  04OtV. The same curve also shows conservatively that 1)I?, can reach 0.025 without shear reinforcement when V  0.20’. The same two conclusions can be reached ii’ Curve I is replaced by the bilinear graph of Iluese and Wight (1999), plotted in the same figure. The bilinear graph represents an approximation of the same test data used in Fig. 3.1 for slabs without shear reinforcement combined with data from seven more references.ACI 421.2R pdf download.