Design Standards and Codes for GFRP Rebar
GFRP rebar is a type of reinforcement used in construction that offers many advantages over traditional steel rebar. To ensure the quality of GFRP rebar and how it is used in a construction project, it is important to understand the engineering codes that govern its use.
In this article, we take a look at what codes are used in New Zealand, Australia, and the USA and some of the differences between steel and GFRP rebar.
Compliance with Engineering Codes and Standards
Compliance with engineering codes and standards is essential for ensuring the quality and safety of GFRP rebar in construction projects. These codes provide guidelines for the design, production, and testing of GFRP rebar. It is important for construction professionals and rebar manufacturers to stay up-to-date with the latest codes and standards to ensure that they are followed in all aspects of their projects.
GFRP rebar has been used in construction for over 40 years but it is only in the last decade that there has been a rapid increase in engineers-specific GFRP rebar instead of steel or stainless steel. The uptake of GFRP rebar use is due to a number of factors.
- Widespread education about GFRP rebar among engineers.
- Availability of codes and design standards.
- The growing number of projects using GFRP rebar.
- Advances in technology have enabled price reduction, making it highly competitive with steel and other rebar materials.
What to consider when using GFRP rebar
When comparing steel and GFRP bar, there are material differences that need to be considered including:
- different mechanical and bond behaviour (xxxxx)
- larger stresses under service loads
- higher transverse coefficient of thermal expansion
- it has a lower elastic modulus but higher tensile strength.
Using GFRP rebars during construction
GFRP rebar is 4x lighter than steel so is considerably easier to carry and place. The same method of tying applies and lap joints are similar to steel rebar.
Bend shapes
GFRP rebar bends are prepared in the factory as bending bars on-site is not practical. This is more efficient but does require pre-planning in your schedule.
Standards for GFRP rebar
New Zealand: ASTM (American Society for Testing and Materials) & ACI (American Concrete Institute) standards are commonly used in New Zealand and countries where there are no local codes.
Australia: An Australian specification is being developed and due for release soon. Generally speaking it will be in-line with ASTM & CSA, with a modulus of 60 GPa.
North America: ASTM D7957 - this is the specification for a 45 GPa modulus rebar. It details the necessary geometric and mechanical properties, the minimum inside bend diameter of bent bars, and the test procedures for certification, quality control, and qualification of GFRP bars.
There is a move towards a new standard, which is basically the same, but with a modulus of 60 GPa – the higher modulus version will allow for xxxxxx. This is currently at the review/vote stage but there is nothing to stop engineers using a modulus of 60 GPa with the ASTM D7957.
Europe and Canadian standards are also available. The Canadian standard (CSA S807) is similar to the ASTM with the notable exception of soft eye work where temporary grades, 40GPa and 60GPa are allowed for.
Design Codes for GFRP rebar
Australia: Australian standards are currently being written and the design code will follow though it will be some time away. Until then, ASTM and ACI continue to be the design guides used by engineers.
New Zealand: xxx
North America: The ACI had a design guide until recently. This is now a code, written in mandatory language called, the ACI CODE-440.11-22: Building Code Requirements for Structural Concrete Reinforced with Glass Fiber-Reinforced Polymer (GFRP) Bars. This is available in imperial only, but the metric version will be available soon.
The ACI code is written in language and structure similar to the ACI 318 code for concrete reinforced with steel, which makes it easy to understand for engineers who are familiar with ACI 318.
Understanding the Different Types of Engineering Codes
There are several types of engineering codes that are relevant to the use of GFRP rebar in construction projects. These include building codes, which provide guidelines for the design and construction of buildings and other structures, as well as codes specific to the use of GFRP rebar. It is important for construction professionals to understand these codes and ensure that they are followed in order to ensure the quality and safety of their projects.
Seek Technical Advice
If it is your first time using GFRP rebar, we highly recommend seeking technical advice and working with your provider to ensure they can support you with the right information for an easy transition.
At Pultron, we can provide technical support for engineers looking to change from steel rebar to Mateenbar™ in their projects. If you would like more information about working with Mateenbar™ get in touch with our team.