# Thermomechanical Analysis of Steel-to-Timber Connections under Fire and the Material Density Effect
## 3 Results and Discussion
### Temperature, Load-Bearing Capacity, and Stress Level in Connections with Different Wood Densities
According to the work presented by [PERSON] [2], the size of the fasteners considerably affected the fire performance of the connection. At ambient temperature, the big fastener diameter is favorable, but in a fire, it transfers more heat into the inner timber elements, thus charring the timber faster. This result is significant in the case of smaller timber cross-sections. The load-bearing capacity based on the tests had a reduction equal to 57% and 81% at different fire exposure times, with a similar tendency to the observed results in the present work. Figure 20 presents the normal stress for GL30H wood, steel plates, and dowels for the time instant of 300 s. This confirms that the wood around the holes is in tensile when the contacting dowels are in compression. Once the mechanical load is applied to the wood component, with the contact effect of the steel elements, they receive the opposite load behavior. Figure 19: Load-bearing capacity. The combination of tensile and thermal load leads to stress concentration in the holes of the GL32H wood. The normal stress presents a tensile value of 12 MPa in the upper and lower dowels. At the same time, the steel elements have a compressive value of 250 MPa for the same positions. The wood plate is in tensile and the steel elements in compression. The following Figures 21 and 22 represent the values of the stresses observed in the connection with the best performance: the connection with GL32H wood. Figure 21 shows the corresponding temperature and the equivalent von Mises stresses on the steel plates, dowels, and the middle cross-section of the connection for the time 300 s.  
The higher values are observed on the upper and lower dowels with the value of 200 MPa, which corresponds to the value of 22 MPa in the respective holes of the GL32H wood component. As expected, the cross-section exhibits a stress concentration near the dowels. In the middle of the connection, the values of stress are more relieved for both components. The steel plate presents superior to 306 \({}^{\circ}\)C, with the lower temperatures exhibited in the middle section of the dowels. The corresponding equivalent von Mises  
Figure 21: Temperature (**left**) and equivalent stress (von Mises) (**right**) in the steel elements, both with the middle cross-section, at 300 s.  
Figure 20: Normal stress of GL32H wood (**left**), steel plate, and dowels (**right**) at 300 s.  
stress reveals that the maximum value of 280 MPa is also obtained in the middle section of the dowels. Figure 22 represents the temperature and the von Mises stress for the wood element and the middle cross-section of the connection for the time of 300 s.  
In the wood component, the indirect char layer depth is formed in contact with the steel elements, resulting in the loss of strength in this region. In the middle cross-section of the connection, it is observed that the von Mises stresses can reach 22 MPa for the intact regions of the wood component.