The Shaft transverse reinforcement within the noncontact lap splice zone shall not be less than #6 @ 6” pitch.
The requirements of the AASHTO Guide Specifications for LRFD Seismic Bridge Design Article 8.8.12 on
The development length of column longitudinal reinforcement in drilled shafts shall be per BDM Article 7.4.4 per TRAC Report WA-RD 417.1 titled "Noncontact Lap Splices In Bridge Column-Shaft Connections". The requirements of the AASHTO Guide Specifications for LRFD Seismic Bridge Design Article 8.8.10 for development length of column bars extended into oversized pile shafts for SDC C and D may not be used.
The requirements of the AASHTO Guide Specifications for LRFD Seismic Bridge Design Article 8.8.13 shall be used for Lateral Confinement for Non-Oversized Strengthened Shafts for SDC C and D.
The requirement for noncontact lap splice of the TRAC Report titled "Noncontact Lap Splices in Bridge Column-Shaft Connections" is based on the assumption that all column longitudinal bars are in direct tension. This may not be true for column to shaft connection at plastic hinging state that only portion of column bars within the tensile region of the neutral axis are in tension. This ratio is within 40% to 60% and could be safely approximated to 50%. It should be mentioned that the strength contribution of steel casing is completely ignored per WSDOT practice.
cc: Mohammad Sheikhizadeh, Bridge Construction - 47354