Comparative bridge designs by Clark James Gordon

Author:Clark, James Gordon
Language: eng
Format: epub
Tags: Bridges--Design and construction.
Publisher: Cleveland: James F. Lincoln Arc Welding Foundation
Published: 1954-03-25T05:00:00+00:00

stress to full value.

#3. Pour slab on formwork resting on girder steel. Slab is independent of main structural steel. The slab is poured directly on the top % in. plate with the shear connectors, this plate in turn resting on rollers on the main girder flange.

#4. After setting of slab, connect remainder of main span cables (Y) and prestress against slab. Temporary rollers still in place. If desired the construction may be allowed to stand a short period and readjustment of prestress made to take up shrinkage and plastic flow.

#5. Weld % in. plate to girder flange by continuous side plates shown in the drawings. Henceforth structure acts as a composite under live load. Various live loadings were investigated: #5a. Max. positive moment at center of main span. #5b. Max. negative moment over pier. #5c. Live loads in end spans only.

"The stresses produced by the above loadings, including the various erection stresses, are plotted on Figure 34. . . . It must be noted that the stresses are combined stresses (P/A -|- Mc/I); therefore the conventional plots of maximum moments vs. moment capacity are meaningless for this type of construction, and as a result the stress plot must be employed.

"The initial phase of the erection sequence is predicted upon the construction of the approach spans on falsework bents, the work progressing from the shore to the piers. In this way the box girder section at the piers can be set directly in place by derricks, the sections being allowed to ride the completed portions of the approach span up to the derrick point. Such a sequence was used in the monumental Dusseldorf-Neuss Bridge erection [see K. Schaech-terle and L. Wintergerst, 'Reconstruction of Rhine Bridge at Dusseldorf-Neuss', Bauingenieur, Vol. 27 (1952) No. i, pp. 1-19], and avoids difficulties with field splicing of the deep plate girder sections if attempted from the pier outward; of course, the method is ideally suited to box girder sections, such as is employed in this design at that point.

'The analytical methods of prestressed steel [see Magnel reference], and of prestressed concrete are now so well known that it is not necessary here to elaborate on them. Typical design calculations are appended to this report so as to illustrate the procedures. Suffice it to say that methods similar to those recently expounded

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