In the commercial building industry, z-shaped girts have been used for centuries to provide lateral support, resist wind loads, and connect the building framing with the cladding. With advancements in technology and design, as well as an increased concern for thermal efficiency, there have been changes to the materials used in z-shaped girts. In addition to traditional steel z-shaped girts, there are now fiber reinforced polymer (FRP) and composite metal hybrid (CMH) z-shaped girts available. These three materials offer differing structural advantages and disadvantages.
Traditional Steel Material
Structural steel design practices are routinely done using well-established uniform codes across the United States and the world. Steel materials are homogeneous and isotropic. This means that the properties are the same independent of the direction considered. Among the advantages of steel structural components are:
- Higher modulus of elasticity compared to FRP
- Easier and faster connection using fasteners with durable, large loads
- Better durability, torque retention and pull-out loads when using screws compared to fastening to FRP
However, steel is not thermally efficient and provides a thermal bridge. Thermal bridging can cause decreased thermal efficiency, energy loss, increased energy costs, and condensation.
Generic FRP Material
Fiber reinforced polymer (FRP) composite design is dependent on manufacturer recommendations. These vary tremendously as different approaches and design methods are adopted by different manufacturers. Such status of FRP design practices is not favorable for advancing the successful use of FRP due to variations in the design practice methods used.
FRP is significantly different from steel as its materials are, in general, orthotropic, meaning that their engineering properties are different in each of the three space directions (x, y, z). The properties depend on the direction considered and primarily on the amount of glass fibers oriented along the direction under consideration, which makes the analysis of FRP more involved.
Adding to the complexity of FRP is the fact that it can be customized using different resins, fibers, fillers, color pigments, and the proportions thereof. Each combination of these constituents will compose a different material with unique properties. Furthermore, making FRP highly customizable with respect to its engineering properties.
Composite Metal Hybrid (CMH) Material
Using a continuous metal insert, located in the FRP flange of the cross-linked thermoset Z profile, the GreenGirt Simple Z leverages a composite metal hybrid (CMH) material selection. This CMH hybrid system maximizes beneficial properties of both steel and composite materials, increasing strength and stiffness by 9.5 times, is 2 times better in fastener pull-out, and has greater durability and torque retention, compared to FRP.
|Lighter weight*||Lower transportation costs and faster installation|
|High strength to weight ratio||Structural capacity|
|Higher modulus of elasticity**||Withstands greater stress|
|Improved fastener retention**||Building life product that lasts without fastener pull-through or torque loss|
|Manufacturing process*||Customizable pultrusion process; does not depend on natural resource availability|
|Eliminates thermal bridging||Increased thermal efficiency and decreased energy costs|
*compared to steel
**compared to FRP