Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
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| 2.3.4 Cost Effectiveness A cost analysis is recommended when selecting among different types of deep foundations for lateral load resistance, particularly when the performance of alternative foundation types are comparable. A cost analysis should consider all aspects of the potential foundation design. Factors such as constructability, seismic design considerations, structural connections, temporary construction works and requirements, etc, can significantly affect the cost of a particular deep foundation system. Failure to understand and consider these factors may increase final costs or may lead to the selection of a foundation type that is not the most economical. Overly conservative designs and inappropriate construction practices may result insignificantly larger foundation costs as well. A cost analysis should include mobilization, materials, installation, locally available practices, local restrictions such as permit requirements or time-of-year restrictions, potential time delays, cost of load testing programs, total number of piles/shafts required, cost of a pile/shaft cap, and other factors that depend on different types of deep foundations and construction operations required for such foundation systems. Cost-efficiency can be analyzed as total cost fora foundation unit or unit cost per linear foot for walls and slope stabilization (linear foot along the length of wall or slope. In general, individual driven piles are less costly than individual drilled shafts. However, drilled shafts often have higher individual axial and lateral load resistance such that fewer drilled shafts can be used in place of a larger quantity of piles. The relative cost is also affected by the project size. For small, single-span bridges in which some lateral resistance is required, the use driven piles are often more economical than installing drilled shafts. For piers of large bridges, more piles and a larger cap would be needed fora foundation unit compared to a group of drilled shafts. A single large diameter drilled shaft can eliminate the need fora group of piles and a pile cap. Batter piles may have some advantages with regard to cost and lateral load resistance compared to drilled shafts. Although this discussion focuses on considerations for lateral load applications, a cost analysis is abroad topic that should include all aspects of the foundation design, including factors for the axial design, structural design, etc. For example, costs for axial load tests may impact the overall cost and selection of the foundation type. In addition, the duration of foundation construction may impact the overall project schedule, with related impact to construction cost. Download 6.03 Mb. Share with your friends:
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