(a) Diaphragms that are cast-in-place slabs
(b) Diaphragms that comprise a cast-in-place topping slab on precast elements
(d) Diaphragms of interconnected precast elements without cast-in-place concrete topping
(a) Diaphragm in-plane forces due to lateral loads acting on the building
(b) Diaphragm transfer forces
(c) Connection forces between the diaphragm and vertical framing or nonstructural elements
(d) Forces resulting from bracing vertical or sloped building elements
(e) Diaphragm out-of-plane forces due to gravity and other loads applied to the diaphragm surface
(a) A rigid diaphragm model if the diaphragm can be idealized as rigid
(b) A flexible diaphragm model if the diaphragm can be idealized as flexible
(c) A bounding analysis in which the design values are the envelope of values obtained by assuming upper bound and lower bound in-plane stiffnesses for the diaphragm in two or more separate analyses
(d) A finite element model considering diaphragm flexibility
(a) For a diaphragm idealized as a beam whose depth is equal to the full diaphragm depth, with moment resisted by boundary reinforcement concentrated at the diaphragm edges, design strengths shall be in accordance with 12.5.2 through 12.5.4.
(c) For a diaphragm idealized with a finite-element model, design strengths shall be in accordance with Chapter 22. Nonuniform shear distributions shall be considered in design for shear. Collectors in such designs shall be provided to transfer diaphragm shears to the vertical elements of the lateral-force-resisting system.
(d) For a diaphragm designed by alternative methods, such methods shall satisfy the requirements of equilibrium and shall provide design strengths at least equal to required strengths for all elements in the load path.
(a) Deformed bars conforming to 20.2.1
(b) Strands or bars conforming to 20.3.1, either prestressed or nonprestressed
(c) Mechanical connectors crossing joints between precast elements
(d) Precompression from prestressed reinforcement
where Acv is the gross area of concrete bounded by diaphragm web thickness and depth, reduced by void areas if present; the value of used to calculate Vn shall not exceed 100 psi; and ρt is distributed reinforcement oriented parallel to the in-plane shear.
where the value of used to calculate Vn shall not exceed 100 psi.
(a) Vn shall be calculated in accordance with Eq. (220.127.116.11), and cross-sectional dimensions shall be selected to satisfy Eq. (18.104.22.168). Acv shall be calculated using the thickness of the topping slab for noncomposite topping slab diaphragms and the combined thickness of cast-in-place and precast elements for composite topping slab diaphragms. For composite topping slab diaphragms, the value of f'c in Eq. (22.214.171.124) and (126.96.36.199) shall not exceed the lesser of f'c for the precast members and f'c for the topping slab.
(b) Vn shall not exceed the value calculated in accordance with the shear-friction provisions of 22.9 considering the thickness of the topping slab above joints between precast elements in noncomposite and composite topping slab diaphragms and the reinforcement crossing the joints between the precast members.
(a) The nominal strength of grouted joints shall not exceed 80 psi. Reinforcement shall be designed to resist shear through shear-friction in accordance with 22.9. Shear-friction reinforcement shall be in addition to reinforcement designed to resist tension due to moment and axial force.
(a) Where shear is transferred through concrete, the shear-friction provisions of 22.9 shall be satisfied.
(b) Where shear is transferred through mechanical connectors or dowels, effects of uplift and rotation of the vertical element of the lateral-force-resisting system shall be considered.
(a) The length required to develop the reinforcement in tension