scope:

ACI CODE-440.11 format and scope

Relative to the type of FRP reinforcement, ACI CODE-440.11-22 limits the scope of the code to solid, round glass fiber-reinforced polymer (GFRP) reinforcing bars constructed using vinyl ester resins and that conform to ASTM D7957/7957M-22. Although there are other shapes of FRP reinforcing bars (square and rectangular cross sections and hollow bars or tube sections), other resin types that may be used (vinyl esters, polyesters, epoxies, and other polymers have all been used to produce FRP bars), and other types of fiber comprising the FRP material (basalt and carbon fiber being the most notable), the scope of ACI CODE-440.11 is limited to solid, round, GFRP bars made with vinyl ester polymers. This scope limitation is based on the preponderance of research data and field experience using this type of FRP reinforcement as well as the acceptance and availability of the ASTM D7957/7957M material standard for this type of reinforcement. As of the publication of this manual, there is now an ASTM standard that includes basalt fiber-reinforced polymer bars (BFRP): ASTM D8505/D8505M. This may allow for inclusion of BFRP bars in future editions of ACI CODE-440.11; however, the current code limits the use to bars conforming to ASTM D7957/7957M. (Indications are that future editions of the code will include reference to both material standards to allow bars conformance to either standard. Additional discussion of these standards is in Chapter 4 of this manual.) The ACI PRC-440.1 design guide also serves as a resource for using FRP reinforcing bars of many various types.

ACI CODE-440.11-22 follows the same structure and format as ACI CODE-318-19(22), "Building Code Requirements for Structural Concrete-Code and Commentary." The intent of ACI CODE-440.11 is to maintain all the requirements of ACI CODE-318 and only replace requirements that would change when using GFRP reinforcement instead of steel reinforcement. Some chapters of ACI CODE-318 are omitted in ACI CODE-440.11 where there is not sufficient research into the use of GFRP reinforcement (such as Chapter 12 on Diaphragms); these chapters are marked "Not Addressed". Other chapters where GFRP reinforcement would not be used (such as Chapter 14 on Plain Concrete) are marked "Not Applicable". However, most topics pertaining to regularly reinforced concrete structures are covered in ACI CODE-440.11. Table 1.1 provides a comparison of the chapters that ACI CODE-440.11 covers versus the chapters that ACI CODE-318-19(22) covers.

In addition to the chapters indicated in Table 1.1 that ACI CODE-440.11 excludes, there are other topics that the code does not cover. These include provisions for the use of lightweight concrete, the use of shotcrete, and the design of deep beams. Additionally, the code does not cover prestressed concrete; however, FRP prestressing systems (using prestressed FRP bars or tendons) do exist and there is a guideline available from ACI on this topic: ACI PRC 440.4-04(11), "Prestressing Concrete Structures with FRP Tendons." Neither ACI CODE-318 or ACI CODE-440.11 cover topics such as slabs-on-ground, residential construction, or environmental structures. FRP bars are, however, common in many of these applications. ACI PRC-440.1-15 and the ACI Recommended Practice Guidelines for FRP Bars in Pre-Engineered Projects (MNL-6) provide recommendations on slabs-on-ground, and MNL-6 provides recommendations on residential foundation walls.

All the chapter and section numbers in ACI CODE-440.11 mirror the chapter and section numbers in ACI CODE-318-19(22). This has been done to allow the user familiar with ACI CODE-318 to easily navigate the requirements in ACI CODE- 440.11 and to allow for direct comparisons between the requirements of each code. Code provisions in ACI CODE 440.11 that are direct copies of code provisions in ACI CODE-318 are marked with a superscript equal sign (=) before the provision to further assist the user in comparing requirements in the two codes (refer to Fig. 1.1 for an example). Some provisions of ACI CODE-440.11 are marked "Not Applicable" where the corresponding code requirement in ACI CODE-318 would not apply to GFRP reinforcement (such as provisions for plain concrete or epoxy-coated steel reinforcement). Other provisions of ACI CODE-440.11 are marked "Out of Scope" where there is not sufficient data, research, or experience to include provisions for the corresponding requirement in ACI CODE-318 (such as flexural reinforcement in prestressed slabs). Provisions marked "Out of Scope" generally are provisions that could apply to GFRP-reinforced concrete and may become part of future editions to the code, but are currently beyond the state of current knowledge and research.

There are two other important topics that are specifically limited in terms of the scope of ACI CODE-440.11 and where GFRP reinforcement is allowed for use. Those are fire resistance and seismic resistance. The code limits the use of GFRP reinforcement to structures that do not require a fire rating due to the lack of detailed fire testing of these elements. However, the code does allow for building officials and designers to implement rational fire methods for achieving fire ratings when necessary, and there is commentary language to support this type of approach.

Further information on fire resistance is provided in Chapter 12 of this manual and Section 4.11 of the code (and Commentary Section R4.11).

Similarly, the code limits the use of GFRP reinforcement to buildings depending on their assigned Seismic Design Category (SDC) due to the lack of knowledge on the seismic performance of FRP-reinforced concrete structures. The code allows GFRP reinforcement to be used in all structural elements of buildings assigned to SDC A; GFRP reinforcement can only be used in elements that are not part of the seismic-force-resisting system in SDC B and C (that is, they can only be used in gravity-load-resisting structural members); and they are not permitted to be used in any structural element in buildings assigned to SDC D, E, or F. Additional information is provided in Chapter 4 of this manual and in Section 4.4.6 of the code (and Commentary Section R4.4.6).