that provided sufficient anchorage length is available for the bars, failure originating from flexural bond stress does not occur. Flexural bond considerations require the anchorage length to be checked in regions of members where the bending moment is zero (at simple supports and at points of contraflexure). In such regions the area of tension steel may be small and the shear force large, resulting in high flexural bond stresses. 这个方程表明，当外部弯矩的变化率较大时，弯曲粘结应力也会具有高强度。然而，式3只是大体上简化了这种状况，它甚至没有近似预测实际弯曲应力的重要性。这是因为沿构件在混凝土内部的离散裂缝的存在，导致附加的弯曲应力，这要归因于在混凝土裂缝之间产生的拉应力。即便剪力为零（弯矩为常量的区域）弯曲应力也会成长。通过研究发现，即使为钢筋提供了足够的锚固长度，由弯曲粘结应力产生的原产失败也不会出现。弯曲粘结因素需要检查构件中弯矩为零的区域的锚固长度（在简支点和反弯点处）。在这样的区域内拉结钢筋的范围可能比较小，可是剪力会比较大，导致较大的弯曲粘结应力。 第七单元 The structural design of a building is the process by which adequate strength, rigidity, and toughness are obtained. In this case \implies that the structure throughout its usable life will provide satisfactory service to its owners and occupants when natural or man-made loads or combination of loads produce on the structure are, determined by structural load analysis. These load effects are then compared to the capability of the structure so that the adequacy of the
structure, or its components can be assessed.
建筑结构的设计是一个获得足够的强度刚度韧性的过程。这里的“足够”是指当自然或人为荷载或动荷载施加在结构上时，在其使用年限内可以向业主提供满意的服务。为了做到这种设计，通过结构荷载分析来确定不同。荷载和荷载组合对结构产生的效应然后这些荷载效应和结构的承载能力做比较，以便结构或其部分构件得到充分利用。 The initial part of structural design is a collaborative effort with the other members of the design team (architect planner ,and the mechanical ,electrical ,and acoustical engineers) to develop the optimum form of the structural system. Due consideration to these other requirements is essential to the structural performance of the building. 结构设计最初的部分是和设计团队的其他成员（建筑师，平面设计师，机械师，电器师，声学工程师）共同努力来确定结构系统的最优形式。考虑到这些方面，对建筑结构性能的其他方面要求是必要的。 The structural design engineer determines the level of approximation (i.e., the appropriate structural \to be used in the load analysis and also in the member strength analysis. This level varies depending on the particular structure being designed. Frequently, the crudest approximations are all that are needed with little, if any, effect on the overall cost of the project. As the building increases in size and importance, or if members are repetitive. It becomes appropriate to analyze both loads and strength in more detail. Thus while most structural
analysis textbooks emphasize the complex and detailed analytical procedures, it is just as important to understand the methods and limitations of approximations. The determination of the precision required is frequently the most important decision the designer will be required to make.
结构设计师决定荷载分析和强度分析所使用的近似水平（也就是正确的结构模型）这种近似水平的变化取决于设计的某一种特定的结构。通常最原始的近视是那些如果对设计全部费用有影响的话，这种影响也很小的近似，这种近似是必要的，随着建筑尺寸和重要性的增加，或者它的构成是重复的，那么对荷载和强度更详细的分析是正确的。因此，虽然大多数结构分析书上重点强调复杂的和详细的分析步骤。这恰恰和理解近似的极限设计同样重要，需要的精确度的确定通常是需要设计者做的最重要的决定
第八单元 The basic aim of structural design is to ensure that a structure should fulfill its intended function throughout its lifetime without excessive deflection ,cracking or collapse ,and this aim must of course be met with due regard to economy .The designer is assisted in his task by the availability of a code of practice which is based on accumulated experience and research .Up
to the present time ,such codes have sought to ensure the safety and serviceability of masonry structures by specifying permissible stresses for various types and combinations of materials .Thus codes generally give
basic compressive stresses for various types and a range of brick-mortar combinations ,the basic stress in a particular case has then to be adjusted for the slenderness ratio of the element and the eccentricity of the loading. The basic stresses are derived 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.结构设计的基本目标是要保证结构在它整个使用寿命内能够完成它的预期功能而不产生过大的挠度，开裂或破坏。并且这个目标必须考虑经济要求。设计者在完成任务的过程中得到了现行规范的协助。而现行规范则是根据积累的经验和科学研究编制的。到目前为止，规范已经通过为不同类型的各种材料组合的结构确定相应的容许能力来保证砌体结构的安全和使用功能。因此规范为各种砖和砂浆的结合物规定了基本的抗压能力，这个基本的应力在特定的情形下还要根据构件的长细比和偏心荷载予以调解。基本应力来自墙或墙垛，最终应力已经在充分考虑避免工作荷载下产生裂缝的任意安全因素下得以折减。因此，在这种程度上，砌体结构设计已经充分考虑了最大强度和可靠的极限状态。
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 . 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 regulations . The factor γf is a function of several partial coefficients .
γf1 which takes account of the possibility of unfavorable deviation of the loads from the characteristic external loads , thus allowing for abnormal or unforeseen actions
γf2which takes accounts of the reduced probability that various loads acting together will all be simultaneously at their characteristic values .
γf 3 which is intended to allow for possible modification of the loading effects due to
incorrect design assumptions (for example , introduction of simplified support
conditions ,inges ,neglect of thermal and other effects which are difficult to assess)
and constructional discrepancies such as dimensions of cross-section , deviation of
columns from the vertical and accidental eccentricities . Similarly , design strengths of materials , R* are defined by Rk R*= (3)
γm
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