Value Engineering, Advanced Design Practices, and Alternate Means and Methods Applications that Lead to Significant Cost Savings for the Seismic Design of Deep Foundations-PPT Presentation

PPT Presentation

Pdf Summary

Timothy W. Mays’s presentation examined how prescriptive and performance-based approaches affect deep-foundation design. Prescriptive codes provide established rules but can create liability and limit the benefits of advanced methods. Performance-based design instead emphasizes intended outcomes and information sharing, though it requires careful coordination and clear assumptions.<br /><br />The presentation reviewed seismic code requirements for several pile types and highlighted that deep-foundation elements do not necessarily share the same performance objectives. It covered updated axial-load limits and detailing requirements for prestressed concrete piles, as well as example detailing for prestressed and auger-cast piles. Mays cautioned that extensive research can create difficulties when research findings are translated into prescriptive code provisions.<br /><br />Value engineering was described as more than substituting one foundation type for another: it may involve changing pile type, size, or quantity while maintaining a similar foundation layout. Advanced design and analysis go beyond conventional delegated pile design, which typically checks pile-head forces without considering the response of the supported structure. Broader approaches can include redesigning piles and pile caps, replacing deep foundations with shallow foundations on rigid inclusions, performance-based design, or applying ASCE 7 Chapter 19. Alternate means and methods may be needed for approaches or materials not addressed by code; independent evaluation can be useful when these are used regularly.<br /><br />Ryan Keiper’s geotechnical discussion emphasized design intent, performance, and collaboration. Seismic design may use multiple analysis methods, with site-specific ground-motion procedures required in certain conditions. Liquefaction assessment involves substantial uncertainty, including differences in methods and assumptions about geology, soil properties, aging, and pile buckling. Ground improvement and intermediate foundations can improve soil performance or share loads, but require geotechnical-structural coordination, defined performance criteria, and attention to code limitations.

Keywords

deep-foundation design

performance-based design

prescriptive codes

seismic code requirements

prestressed concrete piles

auger-cast piles

value engineering

liquefaction assessment

ground improvement

geotechnical-structural coordination