Structural Detailing of Reinforcement for Economy - Simplified Design of Reinforced Concrete Buildings - page 234

Chapter 8
Structural Detailing of
Reinforcement for Economy

8.1 INTRODUCTION

Structurally sound details and proper bar arrangements are vital to the satisfactory performance of reinforced
concrete structures. The details and bar arrangements should be practical, buildable, and cost-effective.

Ideally, the economics of reinforced concrete should be viewed in the broad perspective, considering all facets
in the execution of a project. While it may be important to strive for savings in materials, many engineers often
tend to focus too much on material savings rather than on designing for construction efficiencies. No doubt,
savings in material quantities should result from a highly refined “custom design” for each structural member
in a building. However, such a savings in materials might be false economy if significantly higher construction
costs are incurred in building the custom-designed members.

Trade-offs should be considered in order to minimize the total cost of construction, including the total in-place
cost of reinforcement. Savings in reinforcement weight can be traded-off for savings in fabrication, placing,
and inspection for overall economy.

8.2 DESIGN CONSIDERATIONS FOR REINFORCEMENT ECONOMY

The following notes on reinforcement selection and placement will usually provide for overall economy and
may minimize costly project delays and job stoppages:

(1) First and foremost, show clear and complete reinforcement details and bar arrangements in the

Contract Documents. This issue is addressed in Section 1.1 of ACI Detailing Manual 8.1 : “…the
responsibility of the Engineer is to furnish a clear statement of design requirements; the responsibility
of the [Reinforcing Steel] Detailer is to carry out these requirements.” ACI 318 further emphasizes that
the designer is responsible for the size and location of all reinforcement and the types, locations, and
lengths of splices of reinforcement (ACI 1.2.1 and 12.14.1).

(2) Use Grade 60 reinforcing bars. Grade 60 bars are the most widely used and are readily available in all

sizes up to and including No.11; No.14 and No.18 bars are not generally inventoried in regular stock.
Also, bar sizes smaller than No.6 generally cost more per pound and require more placing labor per
pound of reinforcement.

(3) Use straight bars only in flexural members. Straight bars are regarded as standard in the industry. Truss

(bent) bars are undesirable from a fabrication and placing standpoint and structurally unsound where
stress reversals occur.