A Simplified Design Approach - Simplified Design of Reinforced Concrete Buildings - page 6

￿ Materials: Normal weight concrete › = 4000 psi

Deformed reinforcing bars f y = 60,000 psi

Both material strengths are readily available in the market place and will result in members that are durable* and
perform structurally well. Traditionally cost analyses have shown that for gravity loads, conventionally reinforced
concrete floor systems with › = 4000 psi are more economical than ones with higher concrete strengths. 1.3
One set of material parameters greatly simplifies the presentation of design aids. The 4000/60,000 strength
combination is used in all simplified design expressions and design aids presented in this topic with the following
exceptions: the simplified thickness design for footings and the tables for development lengths consider concrete
compressive strength of › = 3000 psi and › = 4000 psi. The use of › = 4000 psi corresponds to a st an dard β 1 = 0.85.

Further simplification is achieved in the minimum reinforcement equations by excluding the term .

f c ʹ

In most cases, the designer can easily modify the simplified design expressions for other material
strengths. Throughout the topic coefficients, tables, and graphs covering other concrete strengths are given
to help designers expand the scope of the design concept presented in the publication. Also, welded wire
reinforcement and lightweight concrete may be used with the simplified design procedures, with appropriate
modification as required by ACI 318.

￿ Loading: Design dead load, live load, seismic and wind forces are in accordance with American Society of Civil
Engineers Minimum Design Loads for Buildings and Other Structures (ASCE/SEI 7-05) 1.5 , with reductions in
live loads as permitted in ASCE/SEI 7-05. The building code having jurisdiction in the locality of construction
should be consulted for any possible differences in design loads from those given in ASCE/SEI 7-05.

If resistance to earth or liquid pressure, impact effects, or structural effects of differential settlement,
shrinkage, or temperature change need to be included in design, such effects are to be included separately,
in addition to the effects of dead load, live load, and lateral forces (see ACI 9.2). Also, effects of forces
due to snow loads, rain loads (ponding), and fixed service equipment (concentrated loads) are to be
considered separately where applicable (ACI 8.2). Exposed exterior columns or open structures may require
consideration of temperature change effects, which are beyond the scope of this manual. Additionally, the
durability requirements given in ACI Chapter 4 must be considered in all cases (see Section 1.7 of this topic).

￿ Design Method: All simplified design procedures comply with provisions of Building Code Requirements
for Structural Concrete (ACI 318-11), using appropriate load factors and strength reduction factors as
specified in ACI 9.2 and 9.3. References to specific ACI Code provisions are noted (e.g., ACI 9.2 refers to
ACI 318-11, Section 9.2).

* This applies to members which are not exposed to 1) freezing and thawing in a moist condition, 2) deicing chemicals and 3) severe
levels of sulfates (see ACI Chapter 4).