of California in which two major utilities, SDG&E in Southern California and PG&E in the northern part of the state, have their own separate design standards. Yenumula pointed out the problem is compounded by the fact that one of the most often cited codes, National Electrical Safety Code (NESC), does not address foundations at all. He stated that while another oft referenced standard, Institute of Electrical and Electronic Engineers (IEEE) Standard 691, includes a cross section of varying methods for the design of foun- dations for different loading; it does not offer any specific guidance for the design of foundations. Stuedlein echoed the comments expressed. He noted that while there may not be any direct research implications based on the lack of standards and consistency, he felt that the lack of consistent codes across the country makes the integration and evaluation of system performance particularly difficult. Performance Standards The next topic of discussion focused on foundation performance and limits. Yenumula was the first to respond, stating, “The question here is that, as a foundation rotates, deflects or settles, how is that going to impact the performance of work with, they could maximize the opportunity to select a foundation type that would be acceptable from a performance standpoint and also could be less costly.” Chen noted that different utilities have different voltages in their systems. They have 500 kV down to 115 kV lines. Some lines feed the needs of large cities, others smaller communities. Having the guidance to be able to select the appropriate foun- dation type based on structural needs is critical. “As utility engineers we have to be conservative because we design for a family of structures over many miles and through many environments.” Further, “in that design, engineers typically come in late in the process to provide their input on effective, reliable foundation selection, which is already bound by the utility’s normal practice.” Regarding specific design models, Stuedlein offered, “I think that if we intend to go to a reliability-based design, some kind of quantitative probabilistic approach or a full blown performance-based design, you have to have clear communication of what the service and strength limit states are going to be. It’s going to be very difficult to move forward without a firm set of quan- titative measures that can be realistically integrated across all the various load com- binations that you can try to meet.” The panel (left to right) Chen, Salisbury, Yenumula, Murley and Stuedlein Salisbury offered the contractor’s perspective as a design-build contractor as well as the viewpoint of the ratepayer. “Without a unified code of some kind, the owners of projects generally develop their own set of standards. Those standards are coming from their historical base of construction issues as to durability and reliability. Hence, they do not take advantage of newer, less prescriptive and more cost-effective design specifications and practices.” Salisbury would like to see utility owners engage in an Engineer- Procure-Construct (EPC) project delivery model, especially on high-risk, high- volume projects. He feels that this would result in less prescriptive and more performance-based criteria. Costs would be less to the owner and should be reflected in what users pay for electricity. Future Transmission Lines the transmission structure it supports?” He pointed out that, as a foundation deflects and rotates, the wires supported by the pile will move and some of the clearances from these wires to the ground and to the surrounding objects are reduced.” As was the case when discussing standards earlier, there are no common standards for performance across the country. He pointed out that we need to remember that the utility engineer is responsible for the complete line design and they may not be a civil engineer and, therefore, not conversant in the design and construction of foundations. Salisbury added, “Overly stringent performance limits are going to drive up schedule, meaning the time to construct and, therefore, costs. If a designer had a common set of performance standards to Having focused on the current state of affairs relative to the lack of consistency in standards, specifications, risk, ownership and contracting practices, the panel moved on to what the future holds for foundations in the transmission industry. Kandaris noted that, “Electric infra- structure now extends into remote areas. We no longer have power plants next to where people live. When it comes to renewables, we have the challenge of having remote sites, as with wind and solar power. We need to consider the challenges posed by how power will be delivered in the future.” Salisbury stated, “There’s no question that transmission lines are moving to more remote locations. This is being driven by the emergence of new, renewable energy sources.” An example would be wind power often generated in remote locations DEEP FOUNDATIONS • JULY/AUG 2019 • 85
