# Fire Tests of Load-Bearing, Light-Steel-Framed Wall Systems Insulated with Polyurethane Foam
## 2 Experimental Study  
### Test Specim Components and Construction  
The experimental study was conducted on three load-bearing LSF wall panel specimens consisting of a steel frame, PUR foam as cavity thermal insulation and GFBs as sheathing wallboards. The dimensions of the specimens were 1.5 m wide and 3.0 m high. The members of the steel frame steel (studs, tracks and noggings), consisted of 0.95 mm thick C-sections with dimensions of 89 \(\times\) 42 \(\times\) 10 mm. The C-sections were made of S550 GD steel sheets. A total of four studs (labelled S1, S2, S3 and S4) with a length of 2995 mm, two tracks (labelled T1 and T2), and two noggings (labelled N1 and N2) with a length of 1500 mm were used to construct the steel frame, as shown in Figure 1b.  
The studs were located at 486 mm from the centre axis off-centre, while the noggings were located 984 mm off-centre from the top and bottom tracks. A total of 16 nodes (numbered 1-16 in Figure 1a) were formed. The members of the steel frame were fixed with self-tapping flat-head screws with dimensions 6 \(\times\) 19 mm and a diameter of 3.5 mm. To ensure the physical distance between the inner sheathing wallboards and the steel frame, 6 steel Z shaped spacers (Figure 1b) were placed on both sides of the specimen at certain positions along the length of studs S2 and S3 and noggings N1 and N2. The spacers were made of the same type of steel as all other steel members.  
The steel frame was lined on both sides with two or three layers of GFBs, respectively. Two types of 12.5 mm GFBs were used from the same manufacturer (James Hardie Europe, GmbH, Dusseldorf, Germany), GFB with density 1150 \(\pm\) 50 kg/m\({}^{3}\) and reaction to fire A2, s1-d0 [31], A2 GFB onwards, and GFB with improved fire properties (density 1250 \(\pm\) 50 and reaction to fire A1 [32]), A1 GFB onwards. Two of the specimens (designated as Specim P1 and Specim P2, Figure 2a) were of the same composition, double-lined on both sides with A1 GFB, while one specimen (designated as Specim 3, Figure 2b) was triple-lined with an outer layer of A1 GFB and two inner layers of A2 GFB. A2 GFBs are shown in green, while the A1 GFBs are shown in light orange.  
Three differently cut pieces with approximate dimensions of 500 \(\times\) 1990 mm, 1000 \(\times\) 1990 mm and 1005 \(\times\) 1500 mm were used for each layer of the sheathing, as shown in Figure 3.  
Figure 1: Layout of the LSF wall frame and characteristic connection details: (**a**) steel frame; (**b**) Z-shaped spacers near the node, (**c**) cut-out of the steel frame. Red circles numbered 1–16 indicate the 16 nodes formed in the steel frame.  
Figure 2: Wall configurations used in the fire tests: (**a**) Cross section of the double lined specimens (P1 and P2); (**b**) cross section of triple lined specimen (P3).  
The layout of the ambient side wallboard is a mirror image of the fire-side wallboards. The joints of the base layer boards (GFB2, GFB3 for double-lined specimens and GFB3 and GFB4 for triple-lined specimens) were secured with mesh and paper tape and filled with the fireproof joint filler. In addition, joints, screw holes and the wallboard strips on S1, S4, N1 and N2 were coated with a thin layer of fireproof joint filler. After lining the steel structure, the cavity of the panel was filled with a two-component PUR foam with the following properties: density 45 kg/m\({}^{3}\) with a tolerance of \(\pm\)5%, thermal conductivity in the range of 0.020-0.023 W/ mK and reaction to fire class E according to the manufacturer's specifications. Injection of PUR into the test specimens was performed with a low-pressure injector at a pressure of 5-10 bar and was completed within an hour for each specimen.