Abstract: According to the principle of composite element method(CEM) and the implicit expression of transient temperature field,the thermal governing equations of CEM for mass concrete containing lift interfaces are deduced. The effect of each lift interface can be well simulated and the difficulty of generating meshes around the lift interface is overcome. This algorithm can be incorporated into the conventional finite element analysis program. The element containing no lift interface will be degenerated to traditional finite element automatically. By using this algorithm,a three-dimensional composite element model of Laos Nam Ngum5 RCC gravity dam is established. The three-dimensional transient temperature field is simulated. The computational results agree with the monitored values very well in terms of variation regularity and quantity. The research results indicate that this algorithm is valid and practical in engineering application.

Key words: composite element method, lift interface, RCC dam, transient temperature field