Reflecting the changing currents in engineering design and material availability, the American Concrete Institute has updated its 318 standard at ACI 318-25, with a new updated sustainability and information guide on deep foundations for seismic design, shear friction and performance-based wind design.
The ACI structural concrete standard 318 for non-construction buildings and structures-which serves as a guide for casting concrete systems on the site, prefabricated, shotcrete, plain, pretended, not borrowed and compounds-is the first major updating of the rule from ACI 318-19 in 2019.
ACI published the printed edition of ACI 318-25 on July 9 and is also available as an updated digital version continuously known as ACI 318-25 Plus.
New in the guide is a supplementary guide for sustainability, which, instead of the use of sustainable materials and practices, offers frames and templates to meet the requirements applied locally, explains Greg Ziesler, a senior engineer and secretary of the ACI 318 Committee. “A code usually puts a limit on everything you do: you have a lot of steel and this is the space,” he says. “This is more than local jurisdiction says you need [meet] this gwp [Global Warming Potential]So how do you find it with that? We now have a framework to meet these requirements. “”
The Sustainability Section offers guidelines for fulfilling carbon neutrality and low carbon objectives in design and selection of materials. It also includes resilience against various natural disasters such as tornadoes and tsunamis, which the CORE ACI standard does not call directly, but offers guidelines on the types of structures that would face these challenges. The appendix offers recommendations on how to achieve the resilience goals they work from what is already covered in the existing code. “These are different types of loads, not the body of the code. So now if anyone says you have to do this, you have a knowledge to do it,” says Ziesler.
And the carbon low concrete is covered according to its own standard, says Mike Tholen, CEO of ACI Technical Operations. But the 318-25 appendix offers a new way to meet sustainability requirements without establishing a new standard. “We still support local jurisdictions to define the limits, but there are some default options, depending on the size of the project and what types of goals you need to meet for GWP,” he says. “One of the reasons that has a separate level is that it is not the law of the land until the local jurisdiction adopts it.”
Clarifications and updates required
As in many standard updates, ACI 318-25 includes multiple reviews to clarify information in the previous ACI 318-19 edition. “In particular, changes in seismic design are based on a new information provided with 318-19,” says Ziesler. “Very soon in the cycle, we received a lot of questions from California, Washington and Oregon, areas very affected by seismic design conditions.” Changes in the 318-25 seismic design include a large amount of detailed clarifications on what was 318-19. ) [A lot of what] We have changed on 318-25, it will help seismic engineers in these high seismic regions to obtain some more efficient designs, “says Ziesler.
Other clarifications include an enlarged section on deep foundations, which Zielser says is based on the work begun on 318-19, which was the first review to include deep foundations. While in 318-19 the first attempt was seen to bring the deep foundations of the international building code to the ACI standard, review 318-25 has consolidated all the information of the IBC Deep Foundation in one place.
An update more than 318-19 can be found in the section on the shear friction, particularly in certain types of basements and withholding walls. A government agency said that the provisions of 318-19 were causing some problems for its existing designs and Ziesler says that the Committee requested 318-25 to clarify the rule so that some calculations were not too wide. “He simply created some emotion … Sometimes when you go from one part of industry to another, different people have done more evidence in performance certification and could show that it works with a different equation than on 318-19.” The updated version of 318-25 aims to address some of these discrepancies, but Ziesler says that more clarifications may occur in the next update.
Wind design based on performance
Another great additional addition to the ACI 318-25 is the inclusion of the design of the wind-based wind. As with the Sustainability Section, this is not part of the basic code standard, but a guide to properly deploy PBWD when a client or local jurisdiction asks for it.
“Wind design based on performance, that this [inclusion] It is a response to the Committee’s member industry. We have many members of the Committee who make high and supertall buildings, “says Ziesler. While the American Society of Civil Engineers already published a PBWD’s Postandard in 2019, ACI offers only one consulting section on the method of modeling loads.” It is not an appendix to the code; Is not found in the main body of code; It only applies when you do it, “says Ziesler.
Use PBWD, either through modeling in a real wind tunnel or with advanced computer simulations, has an additional cost and ACI does not require it for any particular structure. Rather, “the moment you take a design on a wind tunnel to better nail the design, with a high or supertall structure of a city, you probably have to talk about making a wind -based wind design,” he says.
The key to offering an optional standard for PBWD was to reach the point where all involved feel that they have reached a good final design, says Ziesler. )[The committee] I spent a great effort on this … There are many detailed requirements that will not affect many structures and [those designers] You will not think about doing it, but when you reach the height of a city or a supertall, you will think about doing it, and this defines a standard for it. “
ACI 318-25 is available for the purchase of ACI, both in printed and digital formats.
