A large experimental and numerical program based on fire tests of timber connections under various mechanical loadings was performed in France since 1999. Numerical models, simulating the thermomechanical behavior of these tested connections were developed and validated on the basis of experimental results. The developed model is sufficiently relevant to realize parametrical studies on timber connections. Then, considering the four main parameters influencing the fire resistance of the connections (type and diameter of fasteners, thickness of timber members and load ratio), the model is used to analyze the combined influence of these factors and to realize a calibration based on the experimental design approach. The commonly used thicknesses of timber elements and diameters of fastener are chosen in the study. The experimental design approach based on numerical results considers the main loading cases in timber connections. It is used to propose a simplified formula to predict the fire resistance of timber connections loaded in tension parallel to grain, perpendicular to grain or bending. The proposed formula is then applied to all the available experimental results to check its accuracy.