An investigation of hooped concrete columns . obable that the material acts somewhatlike a granular mass with a thin steel shell around it. Buteven in this case, the granular material is probably one havingan angle of repose (or coefficient of friction) varying with theamount of load to which it has been subjected. It is also proba-ble that there is considerable and variable cohesion among theparticles, and so it ^ould be almost impossible to derive a ra-tional formula that would take account of all of these variablefactors and still be usable. Of course such a formula might bederived for the
An investigation of hooped concrete columns . obable that the material acts somewhatlike a granular mass with a thin steel shell around it. Buteven in this case, the granular material is probably one havingan angle of repose (or coefficient of friction) varying with theamount of load to which it has been subjected. It is also proba-ble that there is considerable and variable cohesion among theparticles, and so it ^ould be almost impossible to derive a ra-tional formula that would take account of all of these variablefactors and still be usable. Of course such a formula might bederived for the ultimate strength of a concrete column, but evenin this case the cohesion and angle of repose would be a variablefor each different concrete. Poth the results of tests and the results given by the above formula indicate that the stress in the spiral at the of the column yield point^ie very small, being at most a few thousand lbs. persq. in. Beyond this point, as explained above, the propertieschange rapidly and the formula no longer 7 1. Materials and The materials used inmaking the concrete for these tests were the same a3 have beenused for a number of years in making the teBt specimens for theEngineering Experiment Station. Universal Portland cement was used, thetensile strength of which is given in table I. TABLE I Tension Tests, Universal Portland CementSample 1. Sample 2. Initial Set. - 4h. - Set - 8h. - 0 m. 7 day . 28 day. No. Neat:1:3 Neat • • : 1:3: 1 . 575:190 : 730 :335: 2 • 590:185 : 750 :2G5: 3 : 620:165 • 755 :295: 4 : 600:185 : 735 :280: 5 : 635: • • Ave. : 604:186 : 742 : 361: H Initial Set, - lh. Set - 5h. - 25m, » • 7 day . 28 day ! No. • • :Neat:1:3: Neat : 1:3 : 1 • 600:180: 705 :189: 2 : 595:190: 705 1 Cj yj KJ . 3 605:200: 675 :295: 4 • 590:205: 650 :275: 5 • 610: : 710 Ave. 60C:194: 689 :288: The sand was a well graded one from the pitsnear Attica, Indiana, being screened
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttheses, bookyear1914
