## 2 Methodology
### Methods  
The test was set up based on actual position of cross-arm in latticed transmission tower. The creep test was performed on the specialised cantilever beam creep test rig used for cross-arm testing. To evaluate the strain measurement, ten dial gauges were positioned 0.61 m in between five points under two main members. Figure 1 illustrates the positions and the length of between the dial gauges under the wooden cross-arm. The load was implemented at the bottom side of the joining parts of all members.  
Detail drawing with dimensions of cantilever beam creep test rig with wooden cross-arm is displayed in Figure 2. The test rig was manufactured from mild steel square hollow section with dimension of 100 mm \(\times\) 100 mm and 1.9 mm thickness. The rigidity and specifications of the test rig can be found in Table 1[19]. The wooden cross-arm was installed on the test rig using forklift and it is manually fixed on the test rig's fastener brackets. A dead load was assembled at free end of the cross-arm to mimic the actual cross-arm conditions in the transmission tower as shown in Figure 3. In general practice, the wooden cross-arm is installed in suspension latticed transmission tower to carry the electric cables and insulators [32]. To be specific, the cross-arm was mounted on the test rig at height of 2100 mm from ground to hang the dead load for the creep test.  
Figure 1: Positions of dial gauges under the cross-arm to measure creep strain pattern, in meter.  
Figure 2: Schematic diagram of wooden cross-arm used in creep test rig.  
The geometry and dimensions of latticed transmission tower is shown in Figure 3[33]. The steel tower and wooden cross-arm was connected using specialised fittings. The assemblymen of wooden cross-arm to steel tower is manually fixed by bolt and nut. Based on Figure 4, the cross-arm was attached to the steel tower by sandwiching two steel plate fittings with end cross-arm member and they are manually connected by using bolt and nut.  
As shown in Figure 5, the bracing members were connected with cross-arm's members via custom-made fastener brackets as aforementioned. The custom-made steel fastener bracket was designed and manufactured specifically to fit the shape of cross-arm. For the assembly process, the brackets were manually installed by using bolt and nut after the cross-arm was completely placed and fixed at the test rig. Figure 6 displays schematic diagram of two set configurations of cross-arm structure, which are current design (without braced arms) and braced design (with braced arms) configuration.  
\begin{table}
\begin{tabular}{c c} \hline
**Properties** & **Specification** \\ \hline Material & Mild steel \\ Tensile strength, MPa & 766 \\ Yield strength, MPa & 572 \\ Pipe shape & Square hollow section \\ Pipe size (width/height/thickness), mm & 100/100/1.9 \\ Total size (width/length/height), mm & 1525/430/4100 \\ \hline \end{tabular}
\end{table}
Table 1: Specification of material of creep test rig [19].  
Figure 3: Dimension of latticed transmission tower. Adapted with permission from IEEE, 2021 [33].  
In term of dead load, a hanging load was weighed based on actual working load of cross-arm (6.347 kN) before the experiment started. The test fulfilled the requirement time as in ASTM D2990, which evaluated the creep test at 1000 h of operation. Specifically, readings were taken at several specific time periods (0.1, 0.2, 0.5, 1, 2, 5, 20, 50, 100, 200, 500, 700 and 1000 h) to observe creep deformation. The condition of the experiment was set at open area that constantly exposed to actual tropical weather. At the end of experiment, the comparison of current (without bracing members) and braced (with bracing members) cross-arm designs was carried out in terms of long-term creep properties.  
Figure 4: Connection of cross-arm to steel tower using steel plate fittings.  
Figure 5: Mild steel fastener bracket joins the braced arms with tie members.  
Figure 6: Cross-arm configurations: (**a**) current design configuration; and (**b**) braced design configuration.