Finite Strain Tube-Squash Test of Concrete at High Pressures and Shear Angles up to 70 Degrees

Although the e.risting tria.rial tests and colif/lled ullia.rial-straill compression tests achieve lugh pressures, ther ("IIlll/ot achieve Idrge shear strains or deviatoric normal strains that are observed In some types qf (oUapse r:f structures cauSPii hy missile impact, e.rplosiolls, and earthquakes, or in e.[plos/ve tnjprtion (fane/lOTS. A new ~'1)(' of ,oncrete test, called the tubp-squash test, that a,liieves, withoutfracturing under high pressures, enormous shear, and deviatoric strains, is developed. Tubes 76.2 and 68.5 mm ('J.() and 2.5 in.) ill diameter, with wall thicknesses r:f 11.22 amd 12.7 mm (0.56 and 0.50 in.), made of highly ductile step I alloy, are filled with ("()Ilcrpte. ,111fr mring, ther are squashed in a Illgh-capa,itv compressioll testing maclzine to 1/2 their orz:i!;1nal length, jor(ing the tubes to bulge. Xormal and hlghstrength concretes at hydrostatic pressures r:f appro.rilllateir 125 JIPa (i 5,680 psi) arefound to be remarkahll' dudile, rapable o.fsustainillg shear angles over 70 degrpes without visual/v detectahle cracks or VOIds, though signifi"cant distrihuted medzanlcal damage does take place. Tests r:f cores drilled outf/wn squas/zn/ tubes show that, '!/Ter such enormous df/iJr7nation, the concrPle still retains appronmatelv 25 to 35% (!f its initial unia.rial compressioll strength and initial stiffness, and apprr)J"imate~v 10 to 20% (!f its lIIitial split-nl/nder tensile strength. lVhat makes the tube-squash test nUli/lIngfit! IS the developmfllt ofa relatively simple method (!itest results ana(vsIs that aWlds solving the inverse nonlinear ji'llite strain problem with jirzite elemetzts de.,pite high nonufl(fimnit1' (!I' the stralnji"eld. Appro.rill/ate stress-strain diagrams ofmncrete at sitch large shear angles and stmins are obtained hyfi"nlte strain analysis of the middle cross sed ion utilizing the measured lateral e.[pansioll, anal shortening, and bulge proji"le. Thejznde strain tr/anal plastiC constitutive law ~f the steel allo1' needs to be determinedfi"rst, and a method to do that is alsofiJrmulated. ApproJ"imate stress-strain diagrams and Internalfrieliml angles ({concrete are deduced from the tE'st without making an)' h.>pothpses about its constitutive equation. Tests !if tubes jilled In hardened portland cement paste and cement mortar, as weI/lis tubes 'wlth a snug~y~fitted limestone insert, show similar ductilE' shear strains and residual strengths. A separate paper do,ulllents good agreement (!I' the present simplzji"ed method wlth.Jinite eleml'llt ilnalvsis.