Project Summary
This section of the project report presents the outcomes of the experimental bending testing phase, which focused on validating the flexural behaviour, load capacity, and constructability performance of the proposed CLT–LGS–CLT sandwich floor system for modular construction applications. The tests were essential to provide empirical evidence supporting the theoretical design models developed in the concept phase.
DBI Partner
A total of six full-scale floor specimens, each measuring 6.0 m in span and 1.2 m in width, were fabricated using a composite arrangement of Cross-Laminated Timber (CLT) panels and Light Gauge Steel (LGS) beams. The floor prototypes were constructed with bolt-connected cleated joints and screw-fastened timber skins, simulating factory-controlled modular assembly processes.
The experimental program was centred on four-point bending tests performed under displacement-controlled loading. Testing objectives included assessing the initial bending stiffness, verifying compliance with serviceability deflection limits, identifying failure mechanisms, and observing the behaviour of modular connection details under increasing flexural demands. The specimens were instrumented with LVDTs, strain gauges, and digital data acquisition systems to capture precise deflection profiles and strain distribution throughout loading. Key findings from the tests indicated that:
- The system exhibited stiffness improvements of 10–18% over analytical predictions in the elastic range.
- All specimens satisfied AS 1170.1 deflection limits (L/300) under service loads, with capacity extending well beyond these thresholds before yielding.
- The ultimate load capacity of the specimens was measured at 2.1 to 2.3 times the code-prescribed design load, demonstrating a robust safety margin suitable for practical construction use.
- Failure modes were ductile, primarily featuring local yielding of steel flanges and minor screw withdrawal or splitting in CLT panels near mid-span, as illustrated in Figure 1.
- No sudden or brittle failures occurred, and the system-maintained load-carrying capacity beyond peak deformation points, supporting its resilience in real-world applications.
In addition to strength testing, the program provided important insights into the constructability aspects of the modular floor system. The bolt-based cleated joints and mechanical screw connections demonstrated excellent performance, with assembly tolerances maintained within ±5 mm and no loosening or connection failure under maximum loading conditions. The consistency of results across six specimens confirmed the reliability of the modular assembly approach and its suitability for off-site prefabrication and rapid on-site installation.
In conclusion, the experimental bending tests confirmed the viability, safety, and structural efficiency of the CLT–LGS–CLT sandwich floor system. The outcomes provide a solid foundation for numerical modelling calibration, cross-section optimisation, and industry translation of the design. These results demonstrate a strong alignment with DBI’s goals for high-performance, sustainable modular construction systems.
