Product Technical Guides : US-EN Cast-In Anchor Channel Fastening Technical Guide | Page 196

1. Anchor Channel Systems 2. HAC Portfolio 3. HAC Applications Option (a) of 17.2.3.4.3 Ductility requirement of tension is not available for shear because the cross section of the steel element of the anchor cannot be configured so that steel failure in shear provides any meaningful degree of ductility. ASCE 7-10 chapter 13 Table 13.5.1 Locking t-bolt HBC-N with HAC plain profile Serrated t-bolt HBC-T with HAC-T serrated profile Figure 7.6.4.1: Standard HAC channel with locking t-bolt HBC-C-N. Figure 7.6.4.2 Serrated channel-HAC-T with HBC-T bolts. • Positive connection via mechanical interlock between channel lips and t-bolt head • (4) Notches in channel lip are created by HBC-C-N after installation torque is applied. • The ф value is 0.55 for in which periodical inspection is provided for all t-bolts. • The ф value is 0.65 for in which continuous inspection is provided for M16 and M20 t-bolts. • The steel strength for M12 t-bolts used with continuous inspection an increased value of 2,021lbs should be used with ф value of 0.55. • Positive connection via mechanical interlock between channel lips and t-bolt head. • Channel comes with pre-made serrations. Installation torque is lower than the one required for the notched t-bolt. • The ф value is 0.65 for in which periodical inspection is • provided for M12 to M20 t-bolts. • The ф value is 0.75 for in which continuous inspection is • provided for M12 to M20 t-bolts. • Historically, longitudinal loads in anchor channels have been transferred by means of friction. AC232 requires a positive connection for transferring of the forces. • Traditionally the longitudinal loads are transferred by means of friction • The loads are assumed to be transferred is larger than the frictional resistance caused by tightening the bolts • The bolts are fully pretensioned to cause a clamping force between the connected components, which allows frictional resistance to develop between them • The frictional resistance prevents the connected components from slipping into bearing against the body of the bolt • To ensure successful performance, the faying surfaces require special preparation • The longitudinal load transfer depended on installation and special inspection on site • There were no measures that would include into the design for reduction of capacity In order to validate the global level of safety or conservatism for a product application, AC232 section 1.3.2 states that the load transfer in the longitudinal direction shall not rely on friction. Where compliance is sought for seismic loading or for static shear loading along the longitudinal axis of the anchor channel, the longitudinal loads shall be transferred by a positive load transfer mechanism. The anchor channel must be flush with the substrate surface and installed with specified installation torque to ensure proper interlock between channel lip and t-bolt. AC232 – Page 8 Transfer of shear load in the direction of the longitudinal channel axis from the channel bolt via channel and anchors into the concrete shall use a positive load transfer mechanism that shall be capable to ensure safe and effective behavior under normal and adverse conditions., both during installation and in service. Factors included are installation conditions in concrete and torqueing of the channel bolts. Note: HAC-30 comes with serrated channel lips. HAC-30 matching serrated t-bolts are HBC-B. The transferring of longitudinal forces shall not rely on friction. The cycling nature of seismic loading combined with the long- term relaxation of the nut and the high sensitivity to installation error are some of the major reasons why a positive load transfer mechanism (a connection that does not rely on friction) is required. Ω o Non structural component 14. Design Example Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019 197 Anchor channels provide two options to positively transfer longitudinal forces; using locking channel bolts with smooth channel profiles or serrated channels with serrated bolts. AC232 covers both systems. The load transfer mechanism is mechanical interlock. 196 ASCE 7-10 chapter 12 Table 12.2.1 13. Field Fixes Ω o Structural component 12. Instructions for Use Ω o overstrength factor for architectural component can be obtained from Table 13.5.1 of ASCE 7-10 and for structural components from Table 12.2.1. 11. Best Practices 6. (0.9- 0.2SDS) D + ΩoQE + 1.6H 10. Design Software 5. (1.2+ 0.2SDS) D+ ΩoQE+ L + 0.2S 9. Special Anchor Channel Design • Option c) The anchor or group of anchors shall be designed forthe maximum shear obtained from design load combinations that include E, with E increased by Ω o . This seismic provisions intend to ensure anchors resisting significant seismic forces do not undergo sudden brittle failure. One way to achieve this is to add sufficient extra strength to the anchor by design, so that the failure must occur elsewhere in the system. Increasing the earthquake inertial load with an overstrength factor Ωo has been included in the ACI 318-14 standard as one of four possible options for preventing premature anchor failure. Here ACI refers us back to ASCE 7-10 load combination 5 and 7 of chapter 12. 8. Reinforcing Bar Anchorage • Option b) The anchor or group of anchors shall be designed for the maximum shear that can be transmitted to the anchors by a nonyielding attachment. 7.6.4 TRANSFER OF LONGITUDINAL FORCES 7. Anchor Channel Design Code • Option a) The anchor or group of anchors shall be designed for the maximum shear that can be transmitted to the anchor or group of anchors based on the development of a ductile yield mechanism in the attachment in flexure, shear, or bearing, or a combination of those conditions, and considering both material overstrength and strain hardening effects in the attachment. 6. Loading 17.2.3.5.3 Anchors and their attachments shall be designed using one of options (a) through (c): 5. Base material • Refer to Figure 7.6.3.1 and 7.6.3.2 explaining the requirements in ACI 318-14 Section 17.2.3.5.3 in figure and in a flow chart. 4. Design Introduction