土木工程建筑外文翻译----钢筋混凝土及土方工程简介-建筑结构(编辑修改稿)

土木工程建筑外文翻译----钢筋混凝土及土方工程简介-建筑结构(编辑修改稿)内容摘要：

to the beginning of the dig to heop to help the nest scraper. Bowl scrapers are often extremely powerful machines。 many makers build scrapers of 8 cubic meters struck capacity, which carry 10 m 179。 heaped. The largest selfpropelled scrapers are of 19 m 179。 struck capacity ( 25 m 179。 heaped )and they are driven by a tractor engine of 430 horsepowers. Dumpers are probably the monest rubbertyred transport since they can also conveniently be used for carrying concrete or other building materials. Dumpers have the earth container over the front axle on large rubbertyred wheels, and the container tips forwards on most types, though in articulated dumpers the direction of tip can be widely varied. The smallest dumpers have a capacity of about m 179。 , and the largest standard types are of about m 179。 . Special types include the selfloading dumper of up to 4 m 179。 and the articulated type of about m 179。 . The distinction between dumpers and dump trucks must be remembered .dumpers tip forwards and the driver sits behind the load. Dump trucks are heavy, strengthened tipping lorries, the driver travels in front lf the load and the load is dumped behind him, so they are sometimes called reardump trucks. Safety of Structures The principal scope of specifications is to provide general principles and putational methods in order to verify safety of structures. The “ safety factor ”, 5 which according to modern trends is independent of the nature and bination of the materials used, can usually be defined as the ratio between the conditions. This ratio is also proportional to the inverse of the probability ( risk ) of failure of the structure. Failure has to be considered not only as overall collapse of the structure but also as unserviceability or, according to a more precise. Common definition. As the reaching of a “ limit state ” which causes the construction not to acplish the task it was designed for. There are two categories of limit state : (1)Ultimate limit sate, which corresponds to the highest value of the loadbearing capacity. Examples include local buckling or global instability of the structure。 failure of some sections and subsequent transformation of the structure into a mechanism。 failure by fatigue。 elastic or plastic deformation or creep that cause a substantial change of the geometry of the structure。 and sensitivity of the structure to alternating loads, to fire and to explosions. (2)Service limit states, which are functions of the use and durability of the structure. Examples include excessive deformations and displacements without instability。 early or excessive cracks。 large vibrations。 and corrosion. Computational methods used to verify structures with respect to the different safety 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 ) . 6 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 appro。