Concrete Beam Design Based on ACI 318-99

Design for ACI 318-99 This chapter describes in detail the various aspects of the concrete design procedure that is used by SAP2000 when the user selects the ACI 318-99 Design Code (ACI 1999). Various notations used in this chapter are listed in Table III-1. The design is based on user-specified loading combinations. But the program provides a set of default load combinations that should satisfy requirements for the design of most building type structures. SAP2000 provides options to design or check Ordinary, Intermediate (moderate seismic risk areas), and Special (high seismic risk areas) moment resisting frames as required for seismic design provisions. The details of the design criteria used for the different framing systems are described in the following sections. English as well as SI and MKS metric units can be used for input. But the code is based on Inch-Pound-Second units. For simplicity, all equations and descriptions presented in this chapter correspond to Inch-Pound-Second units unless otherwise noted.

Design Load Combinations The design load combinations are the various combinations of the prescribed load cases for which the structure needs to be checked. For the ACI 318-99 code, if a

Design Load Combinations

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SAP2000 Concrete Design Manual

Acv Ag As As¢ As (required ) Ast Av a ab b bf bw Cm c cb d d¢ ds Ec Es f c¢ fy f ys h Ig I se k L

Area of concrete used to determine shear stress, sq-in Gross area of concrete, sq-in Area of tension reinforcement, sq-in Area of compression reinforcement, sq-in Area of steel required for tension reinforcement, sq-in Total area of column longitudinal reinforcement, sq-in Area of shear reinforcement, sq-in Depth of compression block, in Depth of compression block at balanced condition, in Width of member, in Effective width of flange (T-Beam section), in Width of web (T-Beam section), in Coefficient, dependent upon column curvature, used to calculate moment magnification factor Depth to neutral axis, in Depth to neutral axis at balanced conditions, in Distance from compression face to tension reinforcement, in Concrete cover to center of reinforcing, in Thickness of slab (T-Beam section), in Modulus of elasticity of concrete, psi Modulus of elasticity of reinforcement, assumed as 29,000,000 psi Specified compressive strength of concrete, psi Specified yield strength of flexural reinforcement, psi Specified yield strength of shear reinforcement, psi Dimension of column, in Moment of inertia of gross concrete section about centroidal axis, neglecting reinforcement, in4 Moment of inertia of reinforcement about centroidal axis of member cross section, in4 Effective length factor Clear unsupported length, in Table III-1 List of Symbols Used in the ACI code