【導讀】將可塑的混凝土拌合物注入到模板內，并將其搗。實，然后進行養(yǎng)護，以加速水泥與水的水化反應，最后獲得硬化的混凝土。制成品具有較高的抗壓強度和較低的抗拉強度。其抗拉強度約為抗壓強度的十分之。因此，截面的受拉區(qū)必須配置抗拉鋼筋和抗剪鋼筋以增加鋼筋混凝土構件中較。由于鋼筋混凝土截面在均質性上與標準的木材或鋼的截面存在著差異，因此，需要對結構設計的基本原理進行修改。將鋼筋混凝土這種非均質截面的兩種組成部。分按一定比例適當布置，可以最好的利用這兩種材料。這一要求是可以達到的。證水泥的水化作用得以進行，必須具備上述條件。這將有損與混凝土的強度，同時也會影響到水泥水化作用的充分進行。的復核與單純的設計分別進行處理。為了降低土方工程費用，填方量應該等于。約為立方米，而最大的標準型翻斗車的容量大約為³。翻斗車車斗向前傾翻而司機坐在后方卸載，因此有。時被稱為后卸卡車。

　　

【正文】 ifferent 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 )。 (2) Uncertainty of the geometry of the crosssection sand of the structure ( faults and imperfections due to fabrication and erection of the structure )。 (3) Uncertainty of the predicted live loads and dead loads acting on the structure。 (4)Uncertainty related to the approximation of the putational method used ( deviation of the actual stresses from puted stresses ). Furthermore, probabilistic theories mean that the allowable risk can be based on several factors, such as : (1) Importance of the construction and gravity of the damage by its failure。 (2)Number of human lives which can be threatened by this failure。 12 (3)Possibility and/or likelihood of repairing the structure。 (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) Amortization funds for the duration of the construction。 (3) Cost of physical and material damage due to the failure of the construction。 (4) Adverse impact on society。 (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 ) .