~ # 3. Flowers Beach Power Plant Unit Draft Tube Cracking Impact Studies

The stability of the tail water pile is important to the safety of the whole power station. A crack in the top of the tail water pile is cause by the destroy of some pillars when casting the machine set NO. 3. It's important to analysis the trend of the crack and the alteration of the stress field in the structure. The stress and the stain field of the structure is computed with 3-Dmension nonlinear finite element method. Some conclusions are made by the computation:1. The down displacement will cause pull stress in the steel bar, and this stress will be maximum in case 7. However, the maximum stress is just 79.68MPa, which is much less than allowable stress.2. The down displacement will cause pull stress in the end of the crack, and this stress will be maximum in case 6, which will achieve to 260.7kPa. Prominent stress concentration will happen in the end of the crack.3. Although the down displacement will cause pull stress in the concrete in the end of the crack, the stress is no more than 0.26MPa, which is much less than the allowable stress of the concrete. According to the crack mechanics, the K_I is 0.16 MPa/m^1/2,and is less than the critical crack temper K_IC=0.7 MPa/m^1/2.Consequently, the crack will not go on to exPand, which means serious structure damage will not happen, and this is coincident with the measure in the construction scene.4. The comPare between the case with a crack and the one without the crack indicates that the influence caused by the crack to the characteristic displacement is very little, and the down displacement is almost less than 0.002cm. So, the crack will not cause serious influence to the displacement or the stress.