CRSI |
ENGINEERING
DATA REPORT NUMBER 28 |
REINFORCED CONCRETE DESIGN
Includes Approval of Details |
 A
SERVICE OF THE CONCRETE REINFORCING STEEL INSTITUTE
933 N. Plum Grove Rd., Schaumburg, Illinois 60173-4758 |
INTRODUCTION
Many perhaps most, failures of reinforced concrete structures
involve faulty details, most often at connections of main structural elements. After such
an event all parties concerned usually disclaim all responsibility for the defective
details. Yet details are an integral part of the design procedure that are shown
schematically on design drawings.
Traditionally the master architect, and more recently the structural
engineer, performs the complete structural analysis and indicates the necessary
reinforcement on the structural drawings as required by the building code in effect. Some
minor dimensions are not shown or repeated in each element since many commonly used
details prescribed by the code are standard, such as minimum embedment of bottom bars (6
in.). The reinforcing steel supplier employs detailers who interpret contract drawings and
specifications in preparing placing drawings. The standard reference is ACI 315-80
(Revised 1986)1 and the ACI Detailing Manual.2
The detail drawings ideally are submitted in advance of construction to
the structural engineer for approval. After any corrections required by the structural
engineer are performed, the detail drawings are used by the reinforcing steel supplier to
fabricate the material. Ideally a competent inspector examines the steel in its final
location as prescribed by the design drawings and the placing drawings.
COMMON
PROBLEMS IN PRESENT PRACTICE
The traditional procedures have been influenced by increasing costs of
liability insurance and litigation. The structural engineer's time is more costly in part
because of liability insurance costs, which may result in less complete structural
drawings. All parties involved receive legal advice to limit their exposure to liability
The structural drawings show fewer details and a proliferation of notes to the detailer
to"... follow the ACI Code,3 Uniform Building Code,4 local building codes, and/ or the ACI Detailing Manual."
Some code requirements have always been ambiguous, even to structural
engineers, and newer code requirements are not yet shown in the detailing manual. The
increasing use of computers in design has also caused the structural engineer to lose some
familiarity with important details that should be reviewed. Many structural engineers use
the ACI Building Code frequently but are not as familiar with and may seldom refer to the
ACI Detailing Manual.
The problem is further complicated in that some frequently used
connection details, tested over the last 10 years, have been found to be deficient,
providing as little as 20 percent of the strength required for the design. Preferred
details, testing 90 to 120 percent efficient, are shown in the latest ACI 315-80 (Revised
1986) Standard, but are not proper for inclusion in the ACI Building Code. Many structural
engineers may not be familiar with this research.5
© Copyright 1988 by the Concrete Reinforcing Steel Institute
