Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
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| 5.2.3 Other Team Members Other team members include hydraulic engineers and civil engineers, architects, construction engineers, or other specialty disciplines. Hydraulic engineers will determine loads due to hydraulic forces, such as currents and wave impacts, as well as flood elevations and depths of scour for design. Civil engineers will determine site grading which may impact loading conditions, such as cuts or fill that may result in unbalanced earth pressures (resulting in additional lateral loads, or fill that may result in settlement and downdrag loads. Construction engineers will be the project representative during the actual construction. Construction engineers will be responsible for ensuring that the foundations are installed in accordance with the plans and specifications, performing coordination with the contractor regarding construction operations, and will alert the designer if there is a difference in site conditions or the as-built foundation that potentially impacts the design. Other design considerations that maybe primarily determined by other design professionals, such as architects or other engineering disciplines, may include cost estimating, constructability reviews, determination of noise or vibration thresholds limits, or determination of space restrictions for structure or foundation layout. Other professionals may have the lead responsibility for determining the availability of local contractors or materials (which may impact the selection of type of deep foundations whether there is a preferred method of procurement (design-build vs design-bid-build and whether it may impact the type of foundation used whether the project is an emergency response (which may impact the procurement or the type of deep foundation or other considerations that may impact the design tasks outlined in this chapter. 5.3 NEED FOR COMMUNICATION AND COORDINATION As discussed in Sections 5.3.1, 5.3.2, and 5.3.3, there is a need for communication and coordination between team members for the design of deep foundations. Design requirements, such as tolerable deflections, loading conditions, subsurface conditions, or other inputs, must be determined and communicated between team members to avoid using assumed or overly conservative values or to avoid double application of load and resistance factors. Clear communication should include an indication of whether loads and resistances are factored or unfactored/nominal, as well as what load or resistance factors should be applied in analysis, as well as other factors such as group factors. Individual pile/shaft analyses and group analyses performed by one discipline (geotechnical or structural) should be reviewed by the other to confirm that the design is adequate and that there are not missed opportunities for improvement. Coordination is also needed when developing construction plans, specifications, testing requirements, and performing constructability reviews, especially for more complex projects. It is often the case that there is conservatism included in the design parameters or inputs developed at early or preliminary stages. This could be conservatism in the allowable deflection limit, the geotechnical input parameters, the characterization of subsurface conditions, the size and/or type of foundation selected for design, or the magnitude of the design loads. The intent of such conservatism is often to ensure that additional refinements do not result in increases in the size, depth, or number of foundation elements, and therefore result in increases in the overall project cost i.e., the intent is that as the design is refined, the preliminary design will be verified and the potential to optimize the design and reduce costs may arise. Too often, the respective disciplines do not coordinate, choosing instead to provide criteria or parameters that are conservative but reliable from the standpoint of the individual designer. When the design is complete, the initial criteria are often not reassessed to see if a more efficient and economical design can be realized. 63 Without communication and coordination between the disciplines, in particular the structural and geotechnical disciplines, there maybe lost opportunity to improve the economics of the design. For example, IGM materials maybe characterized conservatively as stiff or dense soils, which maybe acceptable for some foundations but may result in excessive depths for other applications. Without the opportunity to review the analysis results, the geotechnical engineer may not be able to assess how his initial characterization impacted the overall design. Similarly, an initial limiting deflection maybe provided by the structural engineer during analysis, the geotechnical engineer may find that a heavy pile section is needed, although a lighter and more economical section could be used with a slightly greater deflection. The geotechnical engineer should communicate this to the structural engineer to see if the initial deflection criteria can be relaxed to allow the more economical design. Similar communication with other disciplines and stakeholders may help avoid other design issues or produce more economical designs. The use of specialty foundations, such as micropiles, maybe more appropriate or economical in some cases, such as avoiding costs associated with mobilizing and creating access for large cranes for piles driving in sites with limited access. As noted in Section 5.2, geotechnical and structural engineers should coordinate in the development of drawings and specifications, and should be included in the constructability review. A well-coordinated project with clear communication between respective disciplines will ensure that an economical design is developed that meets all performance requirements. |