What was Revo Group contracted to do?
Ausgrid contacted the team at Revo Group to assist in updating and improving the foundation design for power poles on their network. The existing calculator was not giving results that were reasonable based on the historical performance experienced by Ausgrid. Ausgrid required a better design method, whilst still being compliant with AS/NZS 7000 and good engineering practice.
Ausgrid is the largest electricity distributor (by customers) on the east coast of Australia servicing over 4 million people each day. With safety, the environment and ongoing cost-effectiveness of key concern, it is important to Ausgrid to be implementing the best possible practices.
Why did Ausgrid reach out to Revo Group?
Ausgrid reached out to us due to the problems with the previous software. The old software was based on the Brinch Hansen method from the AS/NZS 7000 overhead line design standards. This method is simple, but outdated and designed for more rigid foundations than is required (or desired) for utility poles. It is one of many design theories that have been deployed for piles and poles over the last 70 years or more.
Traditionally, Ausgrid had been installing their power line poles at 10% + 0.6m or 1m (depending on location and time period). This was done irrespective of the tip load capacity of the pole or the conditions of the ground for installation.
The Brinch Hansen method required Ausgrid to create deeper pole foundations than historically required and use lots of concrete where not used previously. This led to the designers and site crews losing faith in the software.
We were Ausgrid’s first contact as they knew our interest and expertise in this field. Over the course of a year, scoping discussions were had regarding the best approach, the desired outcomes, and implementation within Ausgrid. After providing Ausgrid with regular communication, they decided to contract Revo Group to start work on researching the most appropriate pole foundation design method and to create software based on the findings of the research.
What was achieved?
The research we conducted concluded that the Brinch Hansen method from AS/NZS 7000 did require more concrete and deeper foundations than necessary when compared to other more commonly used methods like Broms and the P-Y method.
After conducting extensive research, we chose the P-Y method as the most appropriate. The P-Y method is widely used for laterally loaded piles, well tested over time, and is as close as you can get to the actual force distribution below ground in simple and complex soils without going to a finite element model. Given the use of ground line rotation as a common limit in international standards for foundation performance of poles, the P-Y method also has the advantage of determining the groundline rotation and horizontal displacements as outputs that could be set as criteria by Ausgrid for different load combinations. The bending moment and shear distributions below ground are also calculated as an output, which allows a true maximum bending/sheer determination. Finally, the soil properties used were relatable to common geotechnical data, unlike other software that has been developed for the US market.
Working alongside Ausgrid, we were able to create the new software, based on the research conducted, as a checking tool in Microsoft Excel. The excel tool iterates through different pole sizes from the Ausgrid catalogue if longer poles are required to maintain the clearances. The user can choose between steel, concrete, wood and fibreglass pole catalogues, and has control over the backfill type and soil information.
Ausgrid then programmed the tool into a web version, which was checked by Revo Group before technical documentation was drafted. The trick was to build the new software into a format that was easy for a range of people to use, while also linking the soil classification from Ausgrid’s soil database system, and to allow changes based on information relayed from site. This new software is used by Ausgrid and ASP3 designers on their network.
Benefits of the new WebPEC foundation design sofware?
This software has increased the confidence from designers and field crews when determining the correct depth of pole foundations for the network. The alignment between soil found on site and the depth required is excellent, and the speed at which the designs can be modified if different soil properties are found is excellent.
As a result of the new foundation requirements, minimal concrete backfill is required, and the embedment depths are generally very close to the 10% + 600mm, unless the loads and the soils suggest otherwise, but even then, increased embedment depth requirements are minimised – leading to better inspections and durability outcomes particularly for timber poles. The field crews now have a report in their hand that is a valuable tool on the job site, and there is a lot more confidence from the Ausgrid team when the figures are available to them.
According to one Ausgrid employee: “It has been really helpful in the planning of designs, or for quick ad-hoc use on an emergency basis.”
In the first year since implementation, the software has paid for itself twofold.
“More recently with the use of the WebPEC program, the relationship between the field staff and the designers, there’s a lot more confidence when we’ve got the figures there, rather than coming up with a number or an old school method.”
Revo Group now have available an open version of the software for use on non-Ausgrid installations/networks.
In the past, Revo Group has provided foundation design, overhead line design, pole inspection field mobility software, pole tests, foundation tests and non-destructive testing solutions to Ausgrid and many other clients, and we can do the same for you.