For most of the composite tilt-up panel market's history, the performance claims of competing systems have been difficult to compare independently. Each manufacturer published their own data. Design guidance was fragmented.Engineers specifying composite systems were largely relying on manufacturer literature.
The TCA Research Program at University of Nebraska Lincoln changed that.
The Tilt-Up Concrete Association commissioned a comprehensive independent testing program to evaluate composite tilt-up connector systems under identical conditions. The program was funded by TCA alongside five industry manufacturers, including Thermomass and Dayton Superior. All five contributed funding. All five had their systems tested.
The researchers: Marc Maguire PhD and Salam Al-Rubaye PhD of the Durham School of Architectural Engineering at University of Nebraska Lincoln, tested full-scale panels on 40-foot spans. The test conditions were identical across all five groups. The instrumentation measured inter-wythe slip, flexural performance,and composite action under load.
Source: TCA Research Report , University of Nebraska Lincoln,acknowledgments and Chapter 2 methodology
This wasn't a manufacturer-commissioned test. It was funded by the industry's own association, with all competing manufacturers at the table.
Group A used a welded steel wire truss , continuous diagonal steel wires running through the EPS core connecting the two concrete wythes. Groups B through E used FRP (fiber reinforced polymer) connector systems in four different configurations. The FRP groups included Thermomass, one of the most widely deployed systems in the global tilt-up market with over 40 years of history,and Dayton Superior, the largest supplier of concrete accessories in NorthAmerica.
The key finding is in the Executive Summary of the report: Group A panels 'performed very close to fully composite making them well predicted by the Slender Wall Method.'
The Slender Wall Design Method is the standard ACI 318-based approach that most tilt-up structural engineers already use for solid concrete wall design. Group A's compatibility with it, without modification , means that engineers familiar with conventional tilt-up already know how to design for the wire truss composite system.
The FRP systems told a different story. All four groups experienced horizontal shear failures in some specimens. The researchers developed two new analytical methods: Shear Flow and Shear Slip , specifically to analyze the FRP groups 'behavior. These methods are not in current standard engineering practice.
Source: TCA Research Report Chapter 6.3 Conclusions, p.239;Executive Summary p.ii
For an EOR specifying a composite panel system today, the practical difference is this: Group A uses the methodology already in your library. The FRP systems require methodology from a research report.
The structural reason for the performance difference is the connector geometry, not just the material.
FRP connectors transfer shear through a polymer element relying primarily on material stiffness. The wire truss creates a true space-frame geometry through the EPS core , diagonal steel wires working in compression and tension. This geometric shear transfer mechanism is more reliable under sustained load than a material-stiffness-based system, which is why Group A showed minimal inter-wythe slip while the FRP systems experienced shear failures in some specimens.
The TCA Design Guide incorporating these research findings is expected to be published. When it arrives, it will become the default specification reference for composite tilt-up systems , a TCA-endorsed document that engineers and GCs can reference in design and procurement decisions.
Engineers who have read the research will be ahead of the conversation when the Guide lands.
RSG3-D uses the wire truss architecture tested as Group A. ICC-ES ESR-2435 is the code compliance documentation, active to April 2027, publicly available at icc-es.org.
