7)    Amount of bonded non-prestressed reinforcing.
            影响无粘结的梁的极限弯矩能力，但不影响或者根本不影响相同方式下的有粘结的梁的变量包括如下：
1)    钢筋束中的有效应力大小；
2)    跨高比；
3)    材料特性；
4)    加荷方式（弯矩图的形状）；
5)    施加预应力的钢筋束的断面；
6)    在施加预应力的钢筋和导管之间的摩擦系数；
7)    有粘结的非预应力钢筋的数量。
           A method of computing the ultimate strength of prestressed members (with unbonded tendons) that takes into account（考虑）the variables listed above has been proposed by Pannell. This method is based upon experimental data and is considered slightly conservative.
            Pannell已经建议用以计算考虑上述列出变量的（具有无粘结的钢筋束的）预应力构件极限强度的方法。该法是基于试验数据，并且考虑时稍有保守。
             It should be recognized that the ultimate moment capacity of a member stressed with unbonded tendons, unlike members with bonded tendons, may be adversely（反过来）affected by unintentional（不经意的）variations in the effective prestress. Hence, it is considered prudent（谨慎的）to exert（给予）more care in estimating the losses of prestress and in supervising（监控）the stressing（加压）of unbonded members than would be considered necessary for bonded members, in order to assure the desired results are obtained.
            应该承认，不象具有有粘结的钢筋束的构件，受到无粘结的钢筋束施加应力的构件的极限弯矩能力，可能会反过来受到有效应力不经意的变化的影响。因此，为了确保获得期望的结果，比起需谨慎考虑有粘结的构件而言，在估计预应力损失和监控无粘结的构件加压时更加予以小心谨慎，这被认为是谨慎的（做法）。

Unit 10 第十单元
Structure Steel
结构钢
Advantages of Steel as a Structural Material
钢材作为结构材料的优点
           A person traveling in the United States might quite understandably decide（清楚地断定）that steel was the perfect structural material. He or she would see an endless number of（无穷无尽的）steel bridges, buildings, towers, and other structures comprising, in fact, a list too lengthy to enumerate（列举）. After seeing these numerous steel structures this traveler might be quite surprised to learn（了解）that steel was not economically made in the United States until late in the nineteenth century and the first wide-flange beams were not rolled（轧制）until 1908.
一位在美国旅行的人可能会很清楚地断定钢材是理想的结构材料。他或她将看到无穷无尽的钢桥、钢的建筑物、钢塔以及其它的钢结构，实际上包含的名单太长了以至于无法列举。在观看了这些数量众多的钢结构后，这位旅行者可能会非常惊讶地了解到在美国直到19世纪后期钢材才被经济地制造，并且直到1908年才轧制出第一根宽翼缘的梁。
           The assumption of the perfection（完美）of this metal, perhaps the most versatile（通用的）of structural materials, would appear to be even more reasonable（合理的）when its great strength, light weight, ease of fabrication（制作）, and many other desirable（理想的） properties are considered（考虑）. These and other advantages of structural steel are discussed in detail（详细地）in the following paragraphs.

当考虑这种金属具有高强、轻质、易制作以及很多其它理想的性能时，认为其完美的假定甚至显得更合理，或许它是最通用的建筑材料。这些和其它的结构钢的优势将在下面的段落中详细地讨论。
    High Strength　　The high strength of steel per unit of weight means that structure weights will be small. This fact is of great importance for long-span bridges, tall buildings, and structures having poor foundation conditions（薄弱地基条件）.

    高强度　　钢材每单位重量的高强度意味着结构的重量将是小的。这个事实对大跨的桥梁、高层建筑以及有着薄弱地基条件的结构具有重要意义。
    Uniformity　　The properties of steel do not change appreciably（明显地）with time, as do those of reinforced-concrete structure.

    一致性　　钢材的性能随时间的变化不明显，正如钢筋混凝土结构的性能也随时间变化不明显。
    Elasticity　　Steel behaves closer to（更接近于）design assumptions than most materials because it follows（遵循）Hooke’s law up to fairly high stresses. The moments of inertia（惯性矩）of a steel structure can be definitely（确切地） calculated, while the value obtained for a reinforced-concrete structure are rather indefinite（不确切）.

    弹性　　比起大多数材料，钢材的运行更接近于设计的假定，因为它直到相当高的应力仍然遵循虎克定理。一个钢结构的惯性矩可以确切地被计算，而钢筋混凝土结构得到的该值是非常得不确切。