Con-Tech Systems: Hollow Reinforcing Bar in CSL Testing Crosshole Sonic Logging (CSL) of drilled shafts requires 1.1/2" (38 mm) or 2.0" (51 mm) I.D. sonic access tubes to be installed inside the steel reinforcement cage. The sonic access tubes, made from PVC or smooth steel pipes, do not contribute to the structural capacity of the drilled shaft. The use of Ischebeck TITAN T73/56 CSL/hollow threaded rebar for CSL access tubes combined with patented longitudinal concrete reinforcing in drilled shafts is an alternative method of constructing drilled shafts and CSL probe access. The T73/56 hollow threaded rebar/sonic access tube performs as a high-strength rebar while at the same time creates a 2.2" (56 mm) I.D. sonic access tube. The deformed high-strength hollow bar provides better bond to the concrete, thus reducing the problem of debonding associated with smooth PVC and steel pipe. A cost comparison has shown an advantage over conventional rebar with added sonic access tubes. The use of T73/56 CSL/hollow threaded rebar can reduce both material and labor costs for drilled Legal Advice in 2016 Brian Wood, attorney of counsel with Smith, Currie and Hancock in Washington, D.C., is writing a f e a tur e column in De e p Foundations beginning in 2016 to address legal issues for the deep foundations industry. Prior to his current position, Wood served as general counsel of Keller Foundations and its U.S. and Canadian subsidiaries. Wood holds a B.S. in civil engineering from Florida State University and a J.D. in law from University of Maryland. Prior to becoming an attorney, Wood worked as an intern, project engineer, construction manager, scheduling consultant and resident engineer on projects ranging from heavy highway (road and bridges) and rail (light and heavy commuter rail) to flood control (dams and levees) and vertical/building construction. Wood’s column will address discrete legal issues related to deep foundation engineering, design and construction including differing site conditions, implied warranties of designs and specifications, performance and verification testing, and design-build liabilities, among other topics. It will also cover developments in the law related to government contracting at the city, state and federal level. In this series, Wood plans to capture the perspectives and address the concerns of contractors, design and consulting engineers, equipment and tooling suppliers and other deep foundations industry professionals. To this end, we extend an open invitation for suggestions and requests for topics for future editions. Please send your requests to [email protected] 122 • DEEP FOUNDATIONS • NOV/DEC 2015 Hollow reinforcing bar cross-sections shaft construction and can provide an advantage where longitudinal reinforcing bars plus smooth tubes create congestion. During a recent drilled shaft test program where Con-Tech Systems hollow rebar was installed, not only as a high strength rebar but also as access tubes for CSL, results showed better readout data compared to the smooth pipe. One pile out of four was equipped with the TITAN T73/56 CSL hollow rebar for this test. Following is a summary of the advantages of using hollow bars for CSL access shafts: • Potential for savings in material consumption and labor assembly. • Hollow bars are used for both reinforcing and sonic testing. • Provides opportunity for value engineering of conventional drilled shaft construction and design methods. • Permits larger windows in reinforcing for concrete to pass through. • Debonding of sonic tubes is eliminated as hollow bars perform as rigid reinforcing with deformations. • Permits larger encompassed area to be tested. • The nominal 3” O.D. (73 mm) hollow threaded rebar is much stiffer than normal rebar thereby facilitating rebar cage handling. • Steel mandrels, used to align PVC tubes during cage handling, are eliminated. Independent third-party testing has confirmed that TITAN T73/56 CSL hollow threaded rebar conforms to the physical and chemical requirements of ASTM A615 and A706.
