Title:
Concrete Q & A: Noncontact Splices for Column Bars; and Minimum Average Compressive Stress for Prestressed Concrete
Author(s):
Publication:
Concrete International
Volume:
26
Issue:
10
Appears on pages(s):
144
Keywords:
DOI:
Date:
10/1/2004
Abstract:
Noncontact Splices for Column Bars: I’m a construction manager on a job where a note on the design drawings states that “All column splices shall be Class B tension lap splices.” Does this mean that the splices must be full contact splices to meet code requirements? The contractor prefabricated the reinforcing bar cages for the columns, and when the cages were set in place, the vertical embedded dowels didn’t match up with the vertical bars in the column cage, but they were within 3 in.
Minimum Average Compressive Stress for Prestressed Concrete: When prestressing steel is used for shrinkage and temperature reinforcement, Section 7.12.3.1 of ACI 318-02, “Building Code Requirements for Structural Concrete,” requires that tendons be proportioned “to provide a minimum average compressive stress of 100 psi.” Section 18.12.4 in the prestressed-concrete chapter of ACI 318-02 says to provide a minimum average prestress of 125 psi for slab systems. Why does Section 18.12.4 require an additional 25 psi? And what is the basis for the two numbers?