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Building Design and Construction Handbook - Merritt - Ventech!

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9.43 SPECIAL ANALYSES<br />

CONCRETE CONSTRUCTION 9.45<br />

Space limitations preclude more than a brief listing of some of the special analyses<br />

required for various special types of reinforced concrete construction <strong>and</strong> selected<br />

basic references for detailed information. Further references to applicable research<br />

are available in each of the basic references.<br />

Seismic-loading-resistant ductile frames: ACI 318; ACI Detailing Manual.<br />

High-rise construction, frames, shear walls, frames plus shear walls, <strong>and</strong> tube<br />

concept: ‘‘Planning <strong>and</strong> <strong>Design</strong> of Tall <strong>Building</strong>s,’’ Vols. SC, CL, <strong>and</strong> CB, American<br />

Society of Civil Engineers.<br />

Environmental engineering structures: ‘‘Environmental Engineering Concrete<br />

Structures,’’ ACI 350R.<br />

Bridges: ‘‘Analysis <strong>and</strong> <strong>Design</strong> of Reinforced Concrete Bridge Structures,’’ ACI<br />

343R.<br />

Nuclear structures: ASME-ACI Code for Concrete Reactor Vessels <strong>and</strong> Containments<br />

Structures, ACI 359, also ACI 349 <strong>and</strong> 349R.<br />

It should be noted that the ACI 318 <strong>Building</strong> Code specifically provides for the<br />

acceptance of analyses by computer or model testing to supplement the manual<br />

calculations when required by building officials.<br />

STRUCTURAL DESIGN OF FLEXURAL MEMBERS<br />

9.44 STRENGTH DESIGN WITH FACTORED<br />

LOADS<br />

Safe, economical strength design of reinforced concrete structures requires that their<br />

ultimate-load-carrying capacity be predictable or known. The safe, or service-loadcarrying<br />

capacity can then be determined by dividing the ultimate-load-carrying<br />

capacity by a factor of safety.<br />

The ACI 318 <strong>Building</strong> Code provides for strength design of reinforced concrete<br />

members by use of factored loads (actual <strong>and</strong> specified loads multiplied by load<br />

factors). Factored axial forces, shears, <strong>and</strong> moments in members are determined as<br />

if the structure were elastic. Strength-design theory is then used to design critical<br />

sections for these axial forces, shears, <strong>and</strong> moments.<br />

Strength design of reinforced concrete flexural members (Art. 9.46) may be<br />

based on the following assumptions <strong>and</strong> applicable conditions of equilibrium <strong>and</strong><br />

compatibility of strains:<br />

1. Strains in the reinforcing steel <strong>and</strong> the concrete is directly proportional to the<br />

distance from the neutral axis (Fig. 9.12) except for deep flexural members with a<br />

span-depth ratio less than 1.25 of the clear span for simple spans <strong>and</strong> 2.5 for<br />

continuous spans. See also Art. 9.88.<br />

2. The maximum usable strain at the extreme concrete compression surface<br />

equals 0.003 in/in

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