NUMERICAL ANALYSIS ON SHRINKAGE CRACKS OF CONCRETE CAST SLAB IN BRICK AND CONCRETE STRUCTURE

A three-dimensional finite element model was established using finite element software ANSYS. The numerical analysis on shrinkage cracks of a multi-span continuous concrete slab was conducted using the finite element model. The cast slab had 8 compartments in the longitudinal direction and 2 depths in the transverse direction. The shrinkage action of the cast slab was simulated by an equivalent temperature difference method. After a numerical calculation, the stress contour plot of the cast slab could be checked in the post-processor. The relation curves between first principle stress and the location of the longitudinal and transverse directions could be gained by the path operation method. The biggest tension stress caused by concrete shrinkage of the cast slab mainly located in the four corners and the boundaries between the wall and the slab, and the tension stress was little in the middle of the slab. Along the longitudinal direction of the slab, the tension stress caused by concrete shrinkage became bigger from an end room to a central room, and the increasing rates were from 5 percent to 7 percent. The difference of the tension stress between the longitudinal and transverse directions of the slab was small. The maximum tension stress appeared at the boundaries between the wall and the cast slab when there was no thread tube in the middle part of the slab. Because there was stress concentration phenomena due to the existence of a thread tube, the shrinkage cracks appeared at places. The shrinkage stress depended on the lateral rigidity of the walls which was direct proportional to the crossing area of the walls. The lateral rigidity of the walls could be reduced with the increasing of space. Therefore, the level of the shrinkage stress could be reduced by increasing cross-wall space.