3410 TERMINAL AVE 2018-03-09 - Laserfiche WebLink

, M&N 8415-02 February 18,2015 As-Built Pile Axial Capacity and Soil Stiffness Memorandum not more than 1000er percent, with a maximum of 20 percent."ACI defines et as the net tensile strain in the extreme layer of longitudinal tension steel at nominal strength. For the existing pile caps under positive flexure the value of et is equal to 0.0279 in/in, therefore the maximum redistribution from the positive moment demand is 20 percent. The ACI moment redistribution provisions provide designers with a conservative methodology to convert an elastic moment diagram to a plastic moment diagram and account for inelastic action and redistribution of forces in continuous structures at the ultimate limit state. Utilizing these provisions of ACI 318,the positive flexural demand in the existing caps can be reduced by 13 percent between gridlines C and D and 6 percent between E and F, thus bringing their demand-to- capacity ratios to 1.00. In order for plastic static equilibrium to be satisfied, the amount of positive moment reduced is redistributed to the adjacent support locations in negative flexure. Fortunately, the negative moment adjacent to the high positive moment demands are very low. This indicates that the positive moments can be easily redistributed to the adjacent support locations and be carried in negative flexure. Thus, by using the ACI 318-08 provisions for moment redistribution, the existing pile caps are shown to have adequate capacity to resist the factored design loads. Conclusion Based on the reviewed as-built pile information it was found that all of the piles were driven at least to the design tip elevations,the PDA and CAPWAP analyses indicated pile axial capacities were achieved,and use of moment redistribution indicates that the softer soil axial springs will not reduce the load-carrying capacity or the performance of the upgraded South Terminal Wharf. Sincerely, J. pS,. moi. 22s9,1 ,�; Bruce I. Ostbo, PE,SE 'SzoNAt.0- Stuart J Stringer, PE Vice President Engineer Attachments: Appendix A—Shannon&Wilson Pile Logs and Daily Reports Appendix B—Summary Letter from Shannon&Wilson-Pile Axial Capacities and Axial Stiffness 4