Engineering and Contracting . he diurnal changes in temperatureon the position of the bridge. Measurement of Steel and Concrete Defor-mations.—Tensile deformations of the steelwere measured at the mid-points of the gir-ders and at points about 5 ft. each side of the [anuary 21, 1014. Engineering and Contracting 109 middle, and at two points noar the center ofthe bridge floor. The measurements at thecenter of the girders were taken on the threebars of the bottom layer, and the other girdermeasurements on the middle bar only. Thedeformations of the floor steel were measuredon two %-in. bars abou
Engineering and Contracting . he diurnal changes in temperatureon the position of the bridge. Measurement of Steel and Concrete Defor-mations.—Tensile deformations of the steelwere measured at the mid-points of the gir-ders and at points about 5 ft. each side of the [anuary 21, 1014. Engineering and Contracting 109 middle, and at two points noar the center ofthe bridge floor. The measurements at thecenter of the girders were taken on the threebars of the bottom layer, and the other girdermeasurements on the middle bar only. Thedeformations of the floor steel were measuredon two %-in. bars about 12 ins. apart, near themiddle of the span. Deformations were also greater influence of the temperature changeat the top of the girder is readily found inthe fact that the concrete at this point isheated to a higher degree than elsewhere andthe longitudinal of the concrete dueto this cause has the effect of lengthening thetop chord of the girder, and, since the lowerportion is not thus elongated, the girder must. Ql ae 03 04 OS Ob 07 Center Deflecrion - Inches aa 03 Fig. 4. Load-Deflection Curves for Girders. measured at points near the mid<llc of two%-in. vertical stirrups, about 6 ft. from thenorth end of the west girder. Concrete de-formations were measured at tw-o points atthe middle of the top of each of the .girdersand at single points about 5 ft. each side ofthe middle. .\11 deformation measurementswere made by means of a modified form ofthe Berry strain gage. RESULTS OF TEST. Effect of Temfcralure on the Deflection njthe Girders.— Fig. 3, the relation of tem-perature to the position of the bridge is shownfor the four days preceding the commence-ment of loading. The atmospheric tempera-ture ranged from 67° to 83° F. The thei;-momcter C on top of the west girder indi-cated the effect of heating the concrete. ThisefTcct is most noticeable during the afternoonsafter the girders have been exposed to jhc sunfor a few hours. It is noteworthy that thewest g
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