This work presents the numerical analysis of the RG8 test performed by the French research program Concrack2 in 2011. It consisted in a large RC beam specimen loaded in bending after restrained shrinkage. The specimen is composed of a central thinner part and two massive heads linked by two cylindrical struts that restrained strains due to thermal effects and autogenous shrinkage occurring in the concrete central part. After 8 weeks, the beam was loaded near to its ultimate capacity. The numerical model is based on the 3D fibre beam approach, capable of reproducing the response since early ages. The cross-section is discretized into fibres to take into account the different maturity levels within the crosssection. The analysis is divided into three phases: i) the thermal analysis determines the development of temperatures due to cement hydration and heat transfer, solar radiation and night cooling effects, ii) nonlinear mechanical analysis for early ages including creep, autogenous shrinkage and ageing and iii) nonlinear mechanical analysis for loading phase includes the interaction of normal and shear forces. Performance is compared against experimentation and the development of early age stresses discussed.