【正文】 (5) Moral and psychological views. The definition of all these parameters, for a given safety factor, allows construction at the optimum cost. However, the difficulty of carrying out a plete probabilistic analysis has to be taken into account. For such an analysis the laws of the distribution of the live load and its induced stresses, of the scatter of mechanical properties of materials, and of the geometry of the crosssections and the structure have to be known. Furthermore, it is difficult to interpret the interaction between the law of distribution of strength and that of stresses because both depend upon the nature of the material, on the crosssections and upon the load acting on the structure. These practical difficulties can be overe in two ways. The first is to apply different safety factors to the material and to the loads, without necessarily adopting the probabilistic criterion. The second is an approximate probabilistic method which introduces some simplifying assumptions ( semiprobabilistic methods ) . 。 (3) Cost of physical and material damage due to the failure of the construction。 (4) Predicted life of the structure. All these factors are related to economic and social considerations such as： (1) Initial cost of the construction。 (2)Number of human lives which can be threatened by this failure。 (3) Uncertainty of the predicted live loads and dead loads acting on the structure。 and corrosion. Computational methods used to verify structures with respect to the different safety 11 conditions can be separated into: (1)Deterministic methods, in which the main parameters are considered as nonrandom parameters. (2)Probabilistic methods, in which the main parameters are considered as random parameters. Alternatively, with respect to the different use of factors of safety, putational methods can be separated into: (1)Allowable stress method, in which the stresses puted under maximum loads are pared with the strength of the material reduced by given safety factors. (2)Limit states method, in which the structure may be proportioned on the basis of its maximum strength. This strength, as determined by rational analysis, shall not be less than that required to support a factored load equal to the sum of the factored live load and dead load ( ultimate state ). The stresses corresponding to working ( service ) conditions with unfactored live and dead loads are pared with prescribed values ( service limit state ) . From the four possible binations of the first two and second two methods, we can obtain some useful putational methods. Generally, two binations prevail: (1)deterministic methods, which make use of allowable stresses. (2)Probabilistic methods, which make use of limit states. The main advantage of probabilistic approaches is that, at least in theory, it is possible to scientifically take into account all random factors of safety, which are then bined to define the safety factor. probabilistic approaches depend upon : (1) Random distribution of strength of materials with respect to the conditions of fabrication and erection ( scatter of the values of mechanical properties through out the structure )。 early or excessive cracks。 elastic or plastic deformation or creep that cause a substantial change of the geometry of the structure。 failure of some sections and subsequent transformation of the structure into a mechanism。 and the articulated type of about m 179。, and the largest standard types are of about m 179。 struck capacity ( 25 m 179。many makers build scrapers 10 of 8 cubic meters struck capacity, which carry 10 m 179。 7 2 外文翻譯 Reinforced Concrete Plain concrete is formed from a hardened mixture of cement ,water ,fine ag