外文翻译--组合作用的基础及抗剪连接(编辑修改稿)

外文翻译--组合作用的基础及抗剪连接(编辑修改稿)内容摘要：

from tests on walls or piers , the ultimate stresses having been divided by an arbitrary factor of safety sufficiently large to avoid cracking at working loads. Thus, to this extent, brickwork design has always been related to ultimate strength and to a serviceability limit state. In recent years a more rational procedure has been evolved for dealing with structural safety and serviceability through consideration of the relevant limit states“ . A structure, or part of a structure, reaches a limit state when it bees incapable of fulfilling its function or when it no longer satisfies the conditions for which it was designed. Two categories of limit state normally have to be considered, namely , ultimate limit states corresponding to failure or collapse and serviceability limit states at which deflections or cracking bee excessive. The general method of applying the limit states approach to the design of structures is outlined in a publication of the International Organization for Standardization in which the criterion for a satisfactory design is expressed in terms of design loading effects (S * )and design strengths (R * )as follows **SR (1) Design loading effects are determined from the characteristic actions from the relationship S * = effects of ( kfQ ） (2) where γf is a multiplier (or partial safety factor) and kQ is a characteristic load which, if defined in statistical terms , is given by ）（ k1mk  where mQ is the value of the most unfavourable load with a 50 per cent probability of its being exceeded once in the expected life of the structure δ is the standard deviation of the distribution of the .maximum loading k is a coefficient depefldin8 on a selected probability of maximum loadings being greater than kQ It is usual to take the characteristic load as that which will have a 5 per cent probability of being exceeded during the lifetime of the structure.④ In many situations, however,statistical data are not available and the characteristic loads have to be based on nominal values given in codes of practice or other factorγf is a function of several partial coefficients. 1f which takes account of the possibility of unfavourable deviation of the loads from the characteristic external loads ,thus allowing for abnormal or unforeseen actions 2f which takes account of the reduced probability that various loads acting together will a11 be simultaneously at their characteristic values. 3f which is intended to allow for possible modification of the load effects due to incorrect design assumptions (for example, introduction of simplified support conditions, hinges, neglect of thermal and other effects which are difficult to assess) and constructional discrepancies such as dimensions of crossse。