The thickness of the floor of a nuclear power plant is 500mm ~ 800mm. Cracks were found in the floor after the formwork was removed during the construction.By means of ultrasonic testing, water storage test and crack width detection, the fracture distribution, depth and width characteristics are determined. On this basis, by using the input conditions which are basically consistent with the design concrete parameters and the actual temperature conditions, curing conditions, constraint conditions and load conditions, the numerical simulation analysis of hydration heat in the maintenance process is carried out to simulate the possible crack generation and distribution of the floor slab in the maintenance process. The simulation results show that the cracks under the combined action of temperature and shrinkage are consistent with the cracking characteristics of floor slab. Then, by changing the maintenance and insulation conditions and pouring sequence, the paper compares the changes of floor cracking under different conditions, analyzes the influence of pouring and maintenance factors on floor cracking, and puts forward optimization suggestions for block pouring and maintenance in thick slab construction process, so as to guide the construction process of similar workshops in the follow-up.According to the actual crack distribution, combined with the stress characteristics of the floor, through the numerical simulation of the cracked floor and intact floor, the change of the out of plane bearing capacity (bending and shear) of the cracked floor is compared and analyzed. In the model, considering the reduction of the bearing capacity at the crack section and the change of load transfer effect at the crack interface, the concrete model is disconnected according to the known opening situation, and the contact relationship is set on the crack interface to simulate the crack. The contact model has two-stage behavior: when the crack is closed and self-healing forms a certain strength, the concrete on both sides of the interface is in glue bonding state; when the tangential shear stress and normal tensile normal stress of the closed interface reach a certain strength, the crack interface is separated; when the crack is not closed or the interface is separated or staggered, the concrete on both sides of the interface is in hard contact relationship, which can be supported under pressure and friction, but not tension. Through comparative analysis, the mechanical properties of the cracked floor are evaluated, and the refined numerical simulation method of the working components with cracks is proposed.

Cause Analysis and Influence Evaluation of Cracks in Thick Slab Construction

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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