【正文】 ge。 Elastic deformation of the change of the structure geometry significantly or plastic deformation or creep。 Structure on the sensitivity of the alternating load, fire and explosion.2. Use limit state, which corresponds to the structure of the use function and durability. Examples include structure instability before too large deformation and displacement。 Too much early cracking or fracture。 The larger vibration and corrosion.Under conditions of different degree of safety, can put the structure checking calculation methods are divided into:(1) deterministic methods, in this method, the main parameters as nonrandom parameters.Probability method, in this method, the main parameters are considered to be random parameters.In addition, according to the different USES of factor of safety, can put the calculation method of the structure can be divided into:1. The allowable stress method, in this method, the structure stress and the maximum load calculation are in accordance with the provisions of safety coefficient after the reduction of strength of materials.2. The limit state method, in this method, the structure of the working condition is measured by its biggest strength as the basis. By theoretical analysis to determine the maximum intensity should not be less than structure calculation under load by calculate the intensity of the (limit). Computational load is equal to the multiplied by the coefficient of load live load and dead load separately. The sum of The corresponding to not multiplied by the coefficient of load live load and dead load working conditions (using) the stress pared with the specified value (using limit state).According to the former two methods and the four possible binations of the two methods, we can get some practical calculation methods. Usually adopt the following two kinds of calculation methods: deterministic method, this method USES the allowable stress. Probability method, this method adopts the limit state. At least in theory, the main advantage of the probability method can be science considers all random safety coefficient, and then these random safety coefficient bination into a certain safety coefficient. Probability method depends on:1. In the process of production and installation of random distribution of the material strength, the mechanical performance of the whole structure of numerical dispersion)。2. The cross section geometry size and structure of uncertainty (caused by structure production and installation error and defect caused by)。 The effect on the structure of live load and dead load forecast uncertainty。 Adopted by the approximate calculation method about the inaccuracy of (the actual stress and calculated stress deviation). In addition, the probability theory means can be based on the following several factors to determine the risk of allowing, for example:1. The importance of building and building damage caused by the dangerous。2. Due to the building destruction threatens the life of the population。3. The possibility of repair of buildings。4. The structure of the life expectancy.All these factors are related to economic and social conditions, such as:1. The structure of the initial construction cost。2. Building use within the period of depreciation。3. Due to destruction of buildings caused by the material and material damages。4. The adverse effects in the society。5. Mental and psychological considerations.