专业英语.ppt

Tension members are found in bridge and roof trusses , towers, bracing systems, and in situation where they are used as tie rods(连杆). The selection of a section to be used as a tension member is one of the simplest problems encountered in design. As there is no danger of buckling, the designer needs only pute the factored force(分解力)to be carried by the member and divide that force by a design stress to determine the effective cross-sectional area required
1. Tension Members
. Then it is necessary to select a steel section that provides the required area. Though these introductory calculations for tension members are quite simple, they do serve(完成)the important tasks of getting students started with design ideas and getting their “feet wet” regarding(涉足于) the massive LRFD Manual.
受拉构件在桥梁和屋架、塔、支撑系统以及用作连杆时被见到。用作受拉构件的截面选择是设计中遇到的最简单的问题之一。因为没有屈曲的危险,设计者只需要计算由该构件承受的分解力,并将该力除以设计应力以确定所需的有效横截面面积。然后有必要选择一个钢截面,它提供了需要的面积。尽管这些关于受拉构件的介绍性的计算非常简单,但它们确实完成了这样一个重要的目标,即使学生开始拥有设计的概念,并使他们涉足于大量的LRFD手册。
Load Resistance Factor Design(LRFD)
钢结构设计规范(荷载抗力系数设计)
Allowable Stress Design (ASD)
One of the simplest forms of tension members is the circular rod, but there is some difficulty in connecting it to many structures. The rod has been used frequently in the past, but has only occasional uses today in bracing systems, light trusses, and in timber construction. One important reason rods are not popular with designers is that they have been used improperly so often in the past that they have a bad name; however, if designed and installed correctly, they are satisfactory for many situations.
受拉构件最简单的形式之一是圆钢,但是将其与很多结构连接有一些困难。过去常常采用圆钢,但是如今只偶然用于支撑系统、轻质桁架以及木结构。圆钢不受设计者欢迎的一个重要原因是过去常常被不恰当地使用,以至于落得坏名声;但是如果正确地设计和安装,它们在很多情况下是令人满意的。
The average size rod has very little stiffness and may quite easily sag under its own weight, injuring the appearance of the structure. The threaded rods formerly used in bridges often worked loose and rattled(发出嘎嘎声). Another disadvantage of rods is the difficulty of fabri