ACI PRC-377-2021 Integrity and Collapse Resistance of Structural Concrete Floor Systems— Report

ACI PRC-377-2021 Integrity and Collapse Resistance of Structural Concrete Floor Systems— Report. 3.3.2.3 The New York City Building Code (2014) Section 1916.2.1 requires all foor slabs to have a continuous mat of bottom reinforcement in two directions with steel rein- forcement not less than the amount required for tempera- ture and shrinkage reinforcement. Section 1916.2.3 requires tension ties composed of the slab bottom reinforcement be provided at each level that develops a tension force equal to the maximum of (a) or (b): (a) Three times the unfactored dead load (considering self- weight of structure only) (b) One and a half times the factored load using the load combinations of (1.2DL + 1.6LL) or 1.4DL For transfer elements only, in place of (a) and (b), the slab tension tie reinforcement should be anchored at all supports. This beam or slab bottom reinforcement should be distrib- uted around the column perimeter and should be extended on all sides of the column into the adjacent slab for at least one-third of the span length. Where reinforcing bars cannot be extended beyond the column (for example, at slab edges and openings), they should be hooked or otherwise devel- oped within the column. Figure 3.3.2.3a shows the struc- tural integrity reinforcement. For more information, refer to Gilsanz et al. (2016). Figure 3.3.2.3b shows the bottom integrity reinforcement requirement based on the New York City Building Code (2014). 4.2.2.3 Catenary action/tensile membrane action— Under larger deformations (approximately more than the element depth), catenary action in beams (Sasani and Kropelnicki 2008; Yi et al. 2008; Su et al. 2009) and tensile membrane action in slabs (Guice and Rhomberg 1988) can be devel- oped, which may provide greater load resistance than beam and compressive membrane actions. Note that following the development of the compressive beam and membrane action, which usually is completed at a defection around the element depth, the catenary or tensile membrane action can start to develop. Catenary action, such as that used in long-span bridges, resists load by mobilizing axial tension throughout the beam. Orton et al. (2009) found that the catenary efect does not occur until the defection is approxi- mately equal to beam depth. A line of tension force is required to develop catenary action (Orton et al. 2009). The line of tension can be provided by continuous reinforcement. However, Stinger and Orton (2013) indicated that ACI 318 provisions for continuous bottom reinforcement...