An investigation of hooped concrete columns . ix held at the proper pitchby means of two spacing bars. In the five and ten-ft. columns,this spiral was in one piece but in the 20-ft. ones it was. madeof two 10-ft, sections having the ends anchored at the centercf the length cf the column by bending the end of the spiraltoward the center of the column. The spacing bars in all ofthese extended the full length of the column. The spacing tarswere made of 3/l6-in. x. 1 l/2-in. flats having slots cut at theproper distances apart to receive the spiral. The wires were heldby bending down the tongues le
An investigation of hooped concrete columns . ix held at the proper pitchby means of two spacing bars. In the five and ten-ft. columns,this spiral was in one piece but in the 20-ft. ones it was. madeof two 10-ft, sections having the ends anchored at the centercf the length cf the column by bending the end of the spiraltoward the center of the column. The spacing bars in all ofthese extended the full length of the column. The spacing tarswere made of 3/l6-in. x. 1 l/2-in. flats having slots cut at theproper distances apart to receive the spiral. The wires were heldby bending down the tongues left in cutting the elots. It was desired to use the same pitch of spiral of1-in. in all the columns, but it was found that the manufacturerswere unable to make a spiral having a pitch of 1-in. with thesize of wire necessary to give four to five per cent of spiral,so for the largest per cent of spiral a pitch of 1 l/2-in. wasused. From previous tests it was thought that the variationsin pitch within these small limits would have practically no. 10 effect upon the strength or behavior of the columns. In shipment, the long spirals were bent double in plac-ing in the car (the two spacing bars permitting this) and alsosome of the shorter lengths had bad kinks in them when they werereceived. When the spirals were straightened out in the labora-tory, it was found that in places the spirals had become loosein the spacing bars and had untwisted, thus making variationsin the diameter of the column. This untwisting had also causedthe spacing bars to assume a curved shape, as shown in the pho-tograph page 211. These difficulties made it almost impossibleto make straight columns of uniform diameter. This trouble couldhave been obviated by using three spacing bars, as is, oftendone. Auxiliary Three 6-in. cubes and onecylinder 8-in. x 16-in. were made from each batch of concretein order to determine the strength and modulus of elasticityof the concrete used. The auxiliary specimens
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttheses, bookyear1914
