Composite element algorithm for the thermal analysis of mass concrete: Simulation of lift joint

Based on the principle of composite element method (CEM), the thermal algorithm for the massive concrete containing lift joint is developed, in which the lift joint segments are embedded within the composite elements. The composite element contains sub-elements of arbitrary shape whose temparatures can be interpolated from their corresponding mapped nodal temperatures which, in turn can be solved by a governing equation established on the variational principle similar to that of the finite element method (FEM). If one element contains no lift joints, it will be degenerated to conventional finite element automatically. This particularity enables the composite element program to be incorporated into the finite element program easily. The algorithm allows for simulating the discontinuous characteristics of the temperature across the lift joint by simplified computation mesh. The comparative study between the composite element method and the finite element method is conducted using two numerical examples and one RCC gravity dam project which shows the validity and merits of the composite element algorithm proposed in this paper.