维护费用　　大多数钢材在直接暴露于空气和水中时容易锈蚀，因此必须被定时地涂漆。在合适的设计应用中，采用风化的钢材往往能避免该费用。
    Fireproofing Costs　　Although structural members are incombustible（不燃性的）, their strength is tremendously（惊人地）reduced at temperatures commonly（通常）reached in fires when the other materials in a building burn. Many disastrous fires（火灾）have occurred in empty buildings where the only fuel（燃料）for the fires was the buildings themselves. Furthermore, steel is an excellent（极好的）heat conductor（导热体）, nonfireproofed（不耐火）steel members may transmit enough heat from a burning section or compartment（隔间）of a building to ignite（使..燃烧）materials with which they are in contact in adjoining sections of the building. As a result of these facts the steel frame of a building may have to be protected by materials with certain insulating characteristics, or the building may have to include a sprinkler system（自动喷水灭火系统）if it is to meet the building code requirements of the locality in question（正被讨论的地区）.
防火费用　　尽管结构构件具有不燃性，但它们的强度通常在火中达到的温度时会惊人地减少，而建筑中的其它材料则会燃烧。很多火灾发生在空的建筑物中，这里着火的唯一燃料是建筑物自己。而且，钢材是一个极好的导热体，不耐火的钢构件可以将一个房屋燃烧的区域或隔间的足够的热量传送而使邻近建筑区域内与之接触的材料燃烧。根据这些现象，建筑物的钢框架可能不得不采用具有一定绝热性能的材料加以保护，或者该建筑物不得不包含一个自动喷水灭火系统，假如它符合正被讨论地区的建筑规范的要求。
    Susceptibility to Buckling　　The longer and more slender the compression members, the greater the danger of buckling. As previously indicated, steel has a high strength per unit of weight, but when used for steel columns is not very economical sometimes because considerable material has to be used merely to stiffen（加强）the columns against buckling.

    容易屈曲　　受压构件越是长和细的，其屈曲的危险越大。正如前面所显示的，钢材单位重量的强度高，但是用于钢柱时有时并不经济，因为不得不采用相当多的材料仅仅是为了加强柱子以防屈曲。
    Fatigue　　Another undesirable（不受欢迎的）property of steel is that its strength may be reduced if it is subjected to a large number of stress reversals（反向应力）or even to a large number of variations of tensile stress. (We have fatigue problems only when tension is involved.) The present practice（习惯）is to reduce the estimated strengths of such members if it is anticipated（预测）that they will have more than a prescribed（规定的）number of cycles of stress variation.

    疲劳　　钢材另一个不受欢迎的特性是如果它承受大量的反向应力或者甚至承受大量的拉应力的变化，则它的强度可能会降低。（只有包括拉力时我们才有疲劳问题。）目前的习惯是如果预测到会有超过规定数量的应力变化的循环次数，则应降低该构件的估计强度。
    Brittle Fracture　　Under certain conditions steel may lose its ductility, and brittle fracture may occur at places of stress concentration. Fatigue-type（疲劳型）loadings and very low temperatures aggravate（加重）the situation.

    脆性断裂　　某些条件下，钢材可能失去它的延性，并且可能在应力集中处发生脆性断裂。疲劳型荷载和非常低的温度加重了这种情形。
Stress-strain Relationships in Structural Steel
结构钢中的应力-应变关系
In order to understand the behavior of steel structures, it is absolutely essential for the designer to be familiar with the properties of steel. Stress-strain diagrams present valuable（有价值的）information necessary to understand how steel will behave in a given situation. Satisfactory steel design methods cannot be developed（得到）unless complete information is available concerning the stress-strain relationships of the material being used.

为了解钢结构的性能，设计人员绝对有必要熟悉钢材的性能。应力-应变图显示了有价值的信息，它对理解钢材在一个给定的条件下如何运行是必要的。除非获得关于正被使用的材料的应力-应变关系的完整的信息，否则就不能得到满意的钢材设计方法。
If a piece of（一段）ductile structural steel is subjected to a tensile force it will begin to elongate. If the tensile force is increased at a constant（不变的）rate, the amount of elongation will increase constantly（不断地）within certain limits（范围）. In other words, elongation will double when the stress goes（变成）from 6,000 to 12,000 psi (pounds per square inch). When the tensile stress reaches a value roughly（大约）equal to one-half of the ultimate strength of the steel, the elongation will begin to increase at a greater rate without a corresponding increase in the stress.

如果一段延性结构钢承受一个拉力，它便开始伸长。如果该拉力以一个不变的速度增加，则伸长值将在一定的范围内不断地增加。换句话说，当应力从6000磅每平方英寸变成12000磅每平方英寸时，伸长将加倍。当拉应力达到的值约等于钢材极限强度的一半时，伸长开始以一个较大的速度增加，而应力没有相应的增加。