Experimental and numerical analyses of rounded dovetail timber connections (RDC) under fire conditions

The use of rounded dovetail connections has gained popularity in timber floor and ceiling structures due to the advance in computerized numeric control machinery. However, European building regulations for fire safety in timber structures from Eurocode 5 standard does not provide a specific method to calculate the fire performance of this kind of connections. In this work, two experimental fire tests were made to evaluate the fire performance and load-bearing capacity of this timber connection. A numerical coupled thermo-mechanical simulation of the tests was developed using the general advanced calculation methods proposed in annex B of Eurocode 5. The experimental tests showed that this connection is not able to accomplish with a R30 fire resistance class, which is the minimum requirement for lightweight timber frame assemblies. A loss of material caused by charring under the tenon of the connection leads to the failure. The general methods proposed in annex B of Eurocode 5 does not take into account the heating inside the connection. However, the simulation results showed an underestimation of the charring rate in the connection. A new simulation considering the thermal flux inside the connection was developed and it shown good agreement with the experimental tests.

Automated summary

The use of rounded dovetail connections in timber structures has become popular, but Eurocode 5 does not provide specific methods for calculating the fire performance of this type of connection. Experimental fire tests revealed that the connection failed to meet the minimum R30 fire resistance and a loss of material due to charring led to failure. The simulation method proposed in annex B of Eurocode 5 underestimated the charring rate, but a new simulation considering thermal flux inside the connection showed good agreement with experimental results.