【正文】 (4) Adverse impact on society。 唐 山 學 院 畢 業(yè) 設(shè) 計 11 (3)Possibility and/or likelihood of repairing 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 )。 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。. 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 ”, 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。 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。 F. It is necessary to maintain such a condition in order that the chemical hydration reaction can take place. If drying is too rapid, surface cracking takes place. This would result in reduction of concrete strength due to cracking as well as the failure to attain full chemical hydration. It is clear that a large number of parameters have to be dealt with in proportioning a reinforced concrete element, such as geometrical width, depth, area of reinforcement, steel strain, concrete strain, steel stress, and so on. Consequently, trial and adjustment is necessary in the choice of concrete sections, with assumptions based on conditions at site, availability of the constituent materials, particular demands of the owners, architectural and headroom requirements, the applicable codes, and environmental reinforced concrete is often a siteconstructed posite, in contrast to the standard millfabricated beam and column sections in steel structures. A trial section has to be chosen for each critical location in a structural system. The trial section has to be analyzed to determine if its nominal resisting strength is adequate to carry the applied factored load. Since more than one trial is often necessary to arrive at the required section, the first design input step generates into a series of trialandadjustment analyses. The trialand –adjustment procedures for the choice of a concrete section lead to the convergence of analysis and design. Hence every design is an analysis once a trial section is chosen. The availability of handbooks, charts, and personal puters and programs supports this approach as a more efficient, pact, and speedy instructional method pared with the tr