土木工程毕业设计外文翻译3-建筑结构(编辑修改稿)

土木工程毕业设计外文翻译3-建筑结构(编辑修改稿)内容摘要：

member properties. Two approaches for estimating girder forces due to gravity loading are given here. Girder Forces— Code Remended Values In rigid frames with two or more spans in which the longer of any two adjacent spans does not exceed the shorter by more than 20 %, and where the uniformly distributed design live load does not exceed three times the dead load, the girder moment and shears may be estimated from Table . This summarizes the remendations given in the Uniform Building Code []. In other cases a conventional moment distribution or twocycle moment distribution analysis should be made for a line of girders at a floor level. TwoCycle Moment Distribution []. This is a concise form of moment distribution for estimating girder moments in a continuous multibay span. It is more accurate than the formulas in Table , especially for cases of unequal spans and unequal loading in different spans. The following is assumed for the analysis: 1. A counterclockwise restraining moment on the end of a girder is positive and a clockwise moment is negative. 2. The ends of the columns at the floors above and below the considered girder are fixed. 3. In the absence of known member sizes, distribution factors at each joint are taken equal to 1 /n, where n is the number of members framing into the joint in the plane of the frame. TwoCycle Moment Distribution— Worked Example. The method is demonstrated by a worked example. In Fig, , a fourspan girder AE from a rigidframe bent is shown with its loading. The fixedend moments in each span are calculated for dead loading and total loading using the formulas given in Fig, . The moments are summarized in Table . The purpose of the moment distribution is to estimate for each support the maximum girder moments that can occur as a result of dead loading and pattern live loading. A different load bination must be considered for the maximum moment at each support, and a distribution made for each bination. The five distributions are presented separately in Table , and in a bined form in Table . Distributions a in Table are for the exterior supports A and E. For the maximum hogging moment at A, total loading is applied to span AB with dead loading only on BC. The fixedend moments are written in rows 1 and 2. In this distribution only .the resulting moment at A is of interest. For the first cycle, joint B is balanced with a correcting moment of (867 + 315)/4 = U/4 assigned to MBA where U is the unbalanced moment. This is not recorded, but half of it, ( U/4)/2, is carried over to MAB. This is recorded in row 3 and then added to the fixedend moment and the result recorded in row 4. The second cycle involves the release and balance of joint A. The unbalanced moment of 936 is balanced by adding U/3 = 936/3 = 312 to MBA (row 5), implicitly adding the same moment to the two column ends at A. This pletes the second cycle of the distribution. The resulting maximum moment at A is then given by the addition of rows 4 and 5, 936 312 = 624. The distribution for the maximum moment at E follows a similar procedure. Distribution b in Table is for the maximum moment at B. The most severe loading pattern for this is with total loading on spans AB and。