Structural behaviour of GFRP modular composite wall system under monotonic loading

Structural behaviour of GFRP modular composite wall system under monotonic loading

The implementation of modular construction is growing rapidly due to its high quality, quick construction, and low environmental impact. Fibre reinforced polymer (FRP) composites are becoming an effective alternative to conventional building materials because of their high strength-to-weight ratio, durability, and speed of construction. However, there is still limited understanding of the structural performance of FRP composites for the modular wall systems, especially with reference to their behaviour under different monotonic loading actions. In particular, the effects of design parameters, such as wall width, connection details, and wall openings, on the behaviour of a composite wall system have not been determined yet. This research systematically evaluated the behaviour of modular walls made from the assembly of glass FRP (GFRP) composites under axial compression, flexural load, and in-plane shear.

The first study investigated the behaviour of GFRP wall systems under axial compression to simulate the effect of service live and gravitational loads in a building. The mechanical properties and failure behaviour of the constituent materials were evaluated. Compression tests using full-scale wall panels were then implemented to evaluate the effect of sheathing type and thickness, types of connections between the sheathing and the frame, and panel width. The results showed that the behaviour of full-scale GFRP wall panels is governed by the behaviour of their constituent material. Adhesively bonded panels provided a continuous connection between sheathing and frames and performed better than the riveted panels. Moreover, a significant increase in panel stiffness and strength was achieved by extending the wall studs. The finite element (FE) analysis validates through experimental results and predicts the failure behaviour, capacity, and stiffness of a full-scale extended stud panel configuration.

Moreover, the flexural behaviour under the effect of wind loading acting perpendicularly to the surface of the modular wall system was evaluated as part of the second study. The moment capacity of the full-scale panel under a uniformly distributed load (UDL) was comparable to that of four-point (4P) load. The results showed that the loading configuration had no effect on the flexural stiffness of the wall panel, but the UDL exhibited significantly higher bending strength than the 4P load, as it eliminated the local interlaminar delamination of wall studs under the loading point. Moreover, the adhesive – rather than the riveted – connection provided higher composite action, resulting in higher flexural capacity and stiffness, whereas an inter-panel bolted connection yielded higher flexural capacity and showed more progressive failure behaviour compared to bonded wall panels. The loading direction had a significant effect on the flexural capacity and stiffness, with the panels in a ii longitudinal direction exhibiting better performance than those in a transverse direction. In conclusion, the simplified equation developed, which considers the ratio of initiation of sheet buckling load and ultimate sheet delamination load, reliably predicts the flexural strength and stiffness of the composite wall panels.

The third and last study investigated the performance of composite wall panels under an in-plane shear load to simulate wind loading acting parallel to the surface of the modular wall system. For this, 6 full-scale composite wall panels with different sheathing heights, wall openings, types of angle brackets, and numbers of wall panels were tested. The wall panel with a 10 mm offset from the bottom of the sheathing performed significantly better than the wall with a full sheathing height, as it minimised the compression stress in the sheathing and avoided premature delamination failure at the bottom plate. The presence of a wall opening reduced the shear stiffness of the wall panel, with the percentage reduction directly correlating to the ratio of the wall opening area to the total wall area. The two customised angle brackets attached at the diagonal corners made the wall panel stiffer and stronger. However, it must be noted that providing brackets in all corners will not further increase the loading capacity and stiffness of the wall. The normalised loading capacity per unit width in single- and double-frame wall panels is almost similar; however, the stiffness of the single wall panel is significantly lower than that of the double wall panel.

This systematic research provides an extensive understanding of how critical parameters and different monotonic loading conditions affect the overall performance of GFRP composite wall system. Moreover, the experimental results offer useful knowledge on its capacity, stiffness, and failure behaviour that is validated and predicted by an FE analysis. Additionally, the analytical results offer simplified design equations for future researchers, designers, and engineers to effectively design and develop a load-bearing modular composite wall system to uplift the confidence of engineers in this new construction method and to adopt this innovative concept for real-world applications.

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