（3）由于极限抗弯能力受到混凝土中的应变而不是应力的限制，因此，它是混凝土和钢筋弹性模量的函数。作为一个规律，这类构件极限弯矩的大小也能被预测在结构设计所预期的正常的允许误差范围内。 配筋不足截面的极限弯矩不能以与上面描述的少量配筋的构件相同的精度来预测，因为配筋不足的构件的极限弯矩是钢筋弹性性能和预应力钢筋中的有效应力的函数，而少量配筋构件的极限弯矩能力则不是。
    （4）Failure due to crushing of the concrete        Flexural members that have relatively large amounts of prestressing steel or relatively small compressive flanges are referred to as being overreinforced（超配筋的）. Overreinforced members, when loaded to destruction, do not attain the large deflections associated with underreinforced members – the steel stresses do not exceed the yield point and failure is the result of the concrete being crushed. Computation of the ultimate moments of overreinforced members is done by a trial and error （试算） procedure，involving assumed strain patterns（模式）, as well as by empirical relationships（经验关系式）.
    （4）混凝土压碎引起的失效      有着相对大量预应力筋或相对小的受压翼缘的受弯构件称为是超配筋的。当受荷至破坏的超配筋构件没有达到与配筋不足构件有关联的大挠度-钢筋的应力没有超过屈服点，因而失效是混凝土被压碎的结果。通过试算过程以及经验关系式来计算超配筋构件的极限弯矩，包括假定应变模式。
            It must be emphasized that there is no clear distinction（明显的区别）between the different classifications（类别）of failure listed above. For convenience of design, certain parameters, which are a function of the percentage of steel, are used by different authorities（权威）to distinguish between the different types of failure that would be anticipated（预测）.
            必须强调在上面列出的不同的失效类别之间没有明显的区别。为了便于设计，通过不同的权威采用某些参数（这些参数是钢筋百分率的函数）来区别被预测的不同类型的失效。
            In order to simplify the explanation of the theory related to the computation of the ultimate moments, a rectangular section will be assumed throughout（在整个..的过程中）the derivation, in order to eliminate（消除）the variable（变化因素）of flange width which is frequently encountered with I or T sections. In addition, the following assumptions, some of which differ slightly from those contained in ACI-318, are made:
            为了简化与极限弯矩计算有关的理论的解释，在整个推导的过程中将假定一个矩形截面，以消除翼缘宽度的变化因素，其常常被遇到是I或T形截面。而且，作以下假定，其中一些稍许不同于ACI-318中包括的假定：
1)    Plane sections are assumed to remain plane.
2)    The stress-strain properties（特点）of the steel are smooth curves without a definite（确定的）yield point.
3)    The limiting strain of the concrete is equal to 0.0034, regardless of the strength of the concrete.
4)    The steel and concrete are completely bonded.
5)    假定平截面依然是平面的；
6)    钢筋的应力-应变特点是光滑的曲线，上面没有确定的屈服点；
7)    混凝土的极限应变等于0.0034，不考虑混凝土的强度；
8)    钢筋与混凝土是完全粘结的；
Principles of Ultimate Moment Capacity for Unbonded Members  
无粘结的构件极限弯矩能力的规则
          Because the prestressing tendons can slip (with respect to the concrete) during loading of an unbonded member, the relationships for ultimate moment capacity do not apply to（适用于）unbonded beams. Because the tendons can slip with respect to the concrete, other variables（另外的变量）affect the ultimate moment capacity of unbonded prestressed concrete members.
            由于在对无粘结的构件加荷期间，施加预应力的钢筋束会相对于混凝土滑移，因此极限弯矩能力的关系式不适用于无粘结的梁。由于该钢筋束会相对于混凝土滑移，因此另外的变量影响了无粘结的预应力混凝土构件的极限弯矩能力。
             Variables that affect the ultimate moment capacity of an unbonded beam, but which do not affect bonded beams in the same manner or not at all（一点也不）, include the following:
1)    Magnitude of the effective stress in the tendons.
2)    Span to depth ratio（跨高比）.
3)    Characteristics of the materials.
4)    Form of loading (shape of the bending moment diagram).
5)    Profile（断面）of the prestressing tendon.
6)    Friction coefficient between the prestressing steel and duct（导管）.