Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
Minimum Amount of Transverse Steel Reinforcement
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| 11.3.6 Minimum Amount of Transverse Steel Reinforcement Transverse reinforcement in concrete foundation elements shall meet all the following (minimum) requirements Shear design requirements are governed by AASHTO (2014) Article Minimum requirements for transverse reinforcement determined in accordance with AASHTO (Article 5.7.4.6. Note that this requirement applies to all Seismic Zones ⢠Minimum confinement requirements for seismic design is determined in accordance with AASHTO (2014) Articles d, e and 5.13.4.6. Note that the transverse reinforcement 150 requirements specified for Seismic Zones 3 and 4 under Sections d and e also apply to Seismic Zone 2, per AASHTO Article 5.10.11.3 (2014). For all seismic zones, from the top of the drilled shaft to a depth of at least 3.0 diameters below the calculated depth of moment fixity, the minimum transverse reinforcement can be determined using Equations 11-8 and 11-9: đđ đ đ ⼠0.45 ďż˝ đ´đ´ đđ đ´đ´ đđ â Equation 11-8) Wheres Ratio of spiral or seismic hoop reinforcement to total volume of concrete core. Ag = Gross area of column section (in. Ac = Area of the concrete core measured to the outside diameter of the spiral (in. fâ c = Specified strength of concrete at 28 days (ksi). f yh = Specified yield strength of spiral or hoop reinforcement (ksi). đđ đ đ ⼠Equation 11-9) Wheres Ratio of spiral or seismic hoop reinforcement to total volume of concrete core. f' c = Specified strength of concrete at 28 days (ksi). f yh = Specified yield strength of spiral or hoop reinforcement (ksi). For Seismic Zones 2, 3 and 4, the maximum pitch of spiral reinforcement or spacing of seismic hoops shall be 4.0 inches down to a depth of at least 3.0 diameters below the depth of moment fixity and 9.0 inches below that depth (AASHTO Article b. For Seismic Zone 1, the maximum pitch of spiral reinforcement or spacing of seismic hoops shall be 6.0 inches down to a depth of at least 3.0 diameters below the depth of moment fixity and 12.0 inches below that depth (AASHTO Article 5.13.4.5.2). In all cases, spirals or seismic hoops shall not be smaller than #3 bars. The clear distance between parallel transverse reinforcing bars should not be less than five times the maximum aggregate size or 5.0 inches, whichever is greater (AASHTO Section 5.13.4.5.2). In seismic zones this can be a challenge because high steel ratios are often dictated by the earthquake force effects. An effort should be made to meet the minimum inch spacing requirement by bundling the longitudinal bars, as necessary. Download 6.03 Mb. Share with your friends:
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