Analyzing And Controlling Of The Cracks In Reinforcement Concrete External Wall Of Basement

The underground markets, communications and garages have been everywhere with the fast development of building economics and building technologies. However, the problem of cracks in large concrete components like walls, bottom slabs etc. takes people much attention, especially the wall's cracks during the construction.My research is mainly on the controlling cracks of reinforcement concrete underground external wall during construction period. The purpose is to confirm effective measures for controlling cracks through analyzing and computing the influence which is caused by short-term temperature loads and restraints acting on the structure. This is achieved by finite element analysis software SAP2000.The author introduces present research states at home and abroad and the distribution of wall cracks in dissertation. Besides, he analyzes the reason why the cracks occur from both construction and design aspects. General methods and measures about preventing and curing the cracks are simply stated. The author also represents temperature field and stress's conception and computing methods, illustrates the wall's temperature stress is affected by temperature changes of environment, concrete shrinkage and creep besides cement's hydration heat. Get the project's temperature loads through analyzing and computing kinds of factors above in the example, get age tensile strength and age elastic modulus, then apply temperature loads to wall model, at last compare the age tensile strength with the largest tensile stress which multiplies stress coefficient of relaxation. In addition, the author compares the wall's stress situation in different cases, such as different temperature, different length, different casting pattern and different restraint strength. Finally, reaches a conclusion bellow:1. Temperature load is one of the most important factors affecting the wall's crack. More temperature reduction will make bigger temperature stress, and the wall will be much easier to crack. So it is reasonable to reduce temperature fall by any methods, such like the reduction of temperature in the increasing state and keeping of temperature in dropping state. 2. Restraint is another one of the most important factors. Partial rigid restraint like top slab and column will increase the wall's stress. If the restraint is too strong, the stress will grow suddenly and concentrate nearby, and the wall is easy to split. Entire flexible restraint like horizontal distribution bar will reduce the wall's stress, and the wall is not so easy to split. Therefore, we can control the wall's cracks by controlling the restraint's range, properties and strength. The research results of this article provide a useful reference to prevent concrete underground external wall splitting.