Q: Which construction details for cast-in-place reinforced concrete need to be specified by the design professional, and which can be left to the discretion of the contractor?

A: The first chapter of the American Concrete Institute's 318 Building Code establishes the requirements for design specifications. In particular, Section 1.2.1 lists ten items the design professional must include on the project drawings or specifications.

These include, for instance, the anchorage length of reinforcement and the location and length of lap splices as well as the type and location of all mechanical and welded splices.

Q: How are questions regarding the interpretation of provisions in the ACI 318 Building Code best handled?

A: While CRSI staff may provide personal opinions regarding the background, intent, or interpretation of specific 318 provisions, these are never to be regarded as official interpretations.

For a formal explanation or interpretation of 318 provisions, the ACI has established a procedure to process requests for official code interpretations.

Q: If stuctural analysis is necessary on old, existing reinforced concrete structure, what minimum yield strength should be used in the structural analysis?

A: In the late 1970s, when staff began experiencing a large number of inquiries regarding old reinforcing bars, CRSI published Engineering Data Report 48, "Evaluation of Reinforcing Bars in Old Reinforced Concrete Structures."

Table 5 in that publication provides minimum yield strengths for all reinforcing steel bars produced since 1911 correlated to ASTM specification grades. For more information, see EDR 48 and CRSI's handbook, "Evaluation of Reinforcing Steel Systems in Old Structures."

Q: What options are available in designing a high-tech research or medical facility housing equipment that cannot tolerate any magnetic material, such as carbon steel?

A: ASTM A955 is the ASTM specification for of stainless steel reinforcing bars. The requirements for tensile properties, bend tests, and deformations in ASTM A955 correspond exactly to those in ASTM A615 for carbon steel reinforcing bars.

ASTM A955 also requires the design professional to specify chemical composition (stainless steel grade), heat treatment conditions, and whether requirements for either corrosion testing or magnetic permeability apply.

	For more information, please see CRSI's Engineering Data Report EDR 44, "Commonly Asked Technical Questions Concerning Cast-in-Place Reinforced Concrete Construction"