DESIGN OF STIFFENED SLABS-ON- GRADE ON SHRINK-SWELL
DESIGN OF STIFFENED SLABS-ONGRADE ON SHRINK-SWELL SOILSJean-Louis BriaudPresident of ISSMGE, Professor Texas A&M University, USARemon AbdelmalakGeo-Engineer, Dar Al-Handasah Group, Cairo, EgyptXiong ZhangAssistant Professor, University of Alaska, USAJ.L. Briaud –Texas A&M University.
Threshold of Optimum SimplicityJ.L. Briaud –Texas A&M University.
SOME FUNDAMENTAL REMARKSTHE PROBLEMTHE SOLUTIONS (FOUNDATIONS, DESIGNS)DEVELOPMENT OF THE DESIGN METHOD–––––EQUATION FOR SHAPE OF SOIL SURFACE (FLEX COVER)MAXIMUM WATER TENSION RELATED TO WEATHERMAX MOMENT AND DEFLECTION WHEN SLAB ON SOILPARAMETRIC STUDYDESIGN CHART DEVELOPMENT CASE HISTORYJ.L. Briaud –Texas A&M University.
THE THREE ZONESSoil esGWLSaturatedJ.L. Briaud –Texas A&M University.
WATER NORMAL STRESSTENSIONCOMPRESSION0uw (kPa)(SUCTION)(pF )(PORE PRESSURE)J.L. Briaud –Texas A&M University.
Water Tension200kPaWater Tension100,000kPaSmectiteWaterAl erJ.L. Briaud –Texas A&M University.
GARNER’S STUDY (2002)3 samples at 3 water contents sent to 8 laboratories.WATER CONTENT, %Sample 1Sample 2Sample 3051015202530 %WATER TENSIONlog (uw in kPa)Sample 1Sample 2Sample 3012345 log kPaWATER TENSION, kPaSample 1Sample 2Sample 3015000300004500060000 kPaJ.L. Briaud –Texas A&M University.
Saturated Soils 1 stresscontrols the behavior, theeffective stress, σ - uwUnsaturated Soils 2stress state variablesneeded, σ - ua and uw - uaJ.L. Briaud –Texas A&M University.
For Unsaturated SoilsThe effective stress isσ’ σ – α uw – (1- α) uaσ’ σ – α uwThe effective stress controls thebehavior of the soil skeleton forsaturated soils and forunsaturated soils (in most cases)J.L. Briaud –Texas A&M University.
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wwSWgw/gdShrink-SwellIndex1wSH0DV/VJ.L. Briaud –Texas A&M University.
CLASSIFICATION OF SHRINK-SWELL POTENTIALACCORDING TO SHRINK-SWELL INDEXPotentialIssVery High 60%High40 – 60Moderate20 – 40Low 20%J.L. Briaud –Texas A&M University.
TYPICAL DAMAGE CAUSEDBY SHRINK-SWELL SOILSWINTERSUMMERNo ChangeShrinkSwellSwellShrinkNo change13J.L. Briaud –Texas A&M University.
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FOUNDATION SOLUTIONS Stiffened Slab on Grade Stiffened Slab on Gradeand on Piers Elevated Structural Slab on Piersairgap Thin Post Tensioned Slab18
SOME DESIGN METHODS FORSLAB-ON-GROUND ONSHRINK-SWELL SOILS BRAB (1968) Lytton (1970, 1972, 1973) Walsh (1974, 1978) Swinburne (1980) PTI (1980, 1996, 2004) AS 2870 (1980, 1996) WRI (1981, 1996)J.L. Briaud –Texas A&M University.
Leqv.0 . 0. 00 . 0 . . .LeqvTributaryLoadArea20J.L. Briaud –Texas A&M University.
Q (kN/m)EIMmaxLeqvΔ f ( Q, EI, L)Tolerable DistortionΔ / L 1/480 Edge dropΔ / L 1/960 Edge liftACI 30221J.L. Briaud –Texas A&M University.
WeatherModelSoil- StructureInteraction ModelSoil Volumechange ModelMoistureDiffusionModel
DEVELOPMENT OF THE METHOD1. Develop a realistic shape of the soil mound partiallycovered by a flexible cover, function of ΔlogUff2. Simulate the effect of the weather for 6 cities over a20 year period to get ΔlogUff.3. Place the foundation on top of that mound, andobtain Mmax and Δmax4. Perform an extensive parametric study to find themost important parameters5. Develop simple design charts based on the results oftasks 1 through 4 to obtain the beam depth and thebeam spacing without having to use a computerJ.L. Briaud –Texas A&M University.
VARARIATION OF WATER TENSIONWITH DEPTHAfter Mitchell (1979)0DU0UeDU0Tension, UDepth, zU(z,t) U U 2 t zU log10 uw2zmaxDU(zmax) 0.1 2DU0
2 H 2 Hn 1 2 n 12 1 exp 2 2 2 fieldfield x f g h H DU edge H 22n 1 2 n 12 2 field x cosh n 1 n 12 H 1 1L n 2 cosh n 12 2H Whereρ(x) vertical movementx horizontal distancef the ratio between vertical movement andvolume changeγh slope of the suction vs. volume change curveH the depth of the active zoneΔUedge amplitude of water tension variation at the edge ofthe flexible cover (U log(u))L length of the flexible cover (slab)ω 2 π/T where T is the weather return periodαfield field diffusivity of soil.25J.L. Briaud –Texas A&M University.
Developed a procedure to include the influence of the cracksin the field on the value of alpha in the lab.β ratio of crack depth over depth of active zone (Hact)FCrkDif ratio of field diffusivity over lab diffusivity (αlab)To weather return periodCracked Soil Diffusion FactorBeta 0.666760Beta 0.8050F CrkDifInfluence ofcracks isminimumwhendiffusivityis very largeor very small70Beta 0.54030201001.00E-041.00E-031.00E-021.00E-011.00E 00 lab T0 / Hact226J.L. Briaud –Texas A&M University.
Ran 18 simulations of weatherfor 6 cities andfor 20Edgeyearseach to getDrop Moundthe change in water tension Δuff and Δuedgeymat the ground surfaceusing the FAO-56methodologyFoundation slabΔuedge40 Columns of equalwidth elements0.5LΔuff1.5 LCenter Line ( Line of symmetry)x25 Columns of elements withbias 1.1y20 Columns of elements withbias 1.1L27J.L. Briaud –Texas A&M University.
Osborne (1999)28J.L. Briaud –Texas A&M University.
EVAPOTRANSPIRATION METHODSCurrent available methods Temperature (Thornthwaite, MBC) temp only Radiation (MMBC, Harg, Turc) temp radiation Combination ( FAO 56 PM, ASCE2000 PM) many factorsFAO 56 Penman-Monteith method International standard, globally valid Can use daily or hourly weather data29
FAO 56 PENMAN-MONTIETH METHODMass Transfer ProcessEnergy BalanceAtmosphereF Penman-Montieth MethodET0 900u2 es ea T 273D g 1 0.34u2 0.408D Rn G gRaReflection fromcloudsabsorptionRsWind RsRnlRl, downRnsRn Rns-RnlEarth ET ( es- ed) f (u)G 0 ET (Rn-G)Rl, up30J.L. Briaud –Texas A&M University.
DIFFERENT BOUNDARY CONDITIONSNet water loss, source termBare soil: uw w g zkbare soil surfaceNWL (m / s )78.64 10Grass root zone: S grass VNWL / Vs NWL / 8.64 107 H grass ( s 1 )Tree root zone: Stree VNWL (tree)/ Vs NWL / 8.64 107 H tree ( s 1 )NWL ETC P (bare soils and grass root zone)NWL ETC(tree root zone)31
4032J.L. Briaud –Texas A&M 1Daily Acumulative Rainfallof Arlington, Texas02/01/01812/01/0010010/01/001008/01/00Daily Mean Wind Speedof Arlington, Texas06/01/00006/01/00004/01/00Daily MeanTemperatureof Arlington, 01/0002/01/0012/01/9910/01/9908/01/99(m/s)Input Weather Data (FAO 56)Daily Mean Relative Humidityof Arlington, Texas40
.7881.283H (m)3.32.41.8ISS tion AntonioAustinDallas Houston .687J.L. Briaud –Texas A&M University.
CALIBRATIONS OF MODEL AGAINST LARGE SCALE LAB EXPERIMENTJ.L. Briaud –Texas A&M University.
CALIBRATIONS OF MODEL AGAINST LARGE SCALE LAB EXPERIMENTMeasured and Predicted Average Movements at soil surface44 rows of elements &60 columns of elementseach element is 10 X 10 mmzrTank bottom baseMovements (mm)Free surfaceTank perimeterwallAxis of symmetryFoundation cover, R 0.4 m(phase II only)76543210-1 0-2PredictedMeasured306090120150Time (day)180210240270J.L. Briaud –Texas A&M University.
140 Abaqus simulations covering manyweather, soil, and structure parametersEdge Lift CaseEdge Lift MoundymFoundation slaby40 Columns of equalwidth elements0.5L1.5 LCenter Line ( Line of symmetry)25 Columns of elements withbias 1.1x20 Columns of elements withbias 1.1LJ.L. Briaud –Texas A&M University.
140 Abaqus simulations covering manyweather, soil, and structure parametersEdge Drop CaseEdge Drop MoundymFoundation slaby40 Columns of equalwidth elements0.5L1.5 LCenter Line ( Line of symmetry)25 Columns of elements withbias 1.1x20 Columns of elements withbias 1.1LJ.L. Briaud –Texas A&M University.
Edge Drop CaseSoil mound and foundation elevations0.090.08y- coordinate (m)0.070.06Initial Mound Elev.Final Mound Elev.0.050.04Final Found Elev0.030.020.010.00-0.01 012345678x- coordinate (m)J.L. Briaud –Texas A&M University.
Edge Drop CaseBending moments and shearing forces140V (kN) or M (kN.m)120100Shearing Force, VBending Moment, M806040200-20 012345678-40-60x- coordinate (m)J.L. Briaud –Texas A&M University.
0.090.08y- coordinate (m)0.070.06Initial Mound Elev.Final Mound Elev.0.050.04Final Found Elev0.030.020.010.00-0.01 012345678x- coordinate (m)Bending moments and shearing forces140V (kN) or M (kN.m)120100Shearing Force, VBending Moment, M806040200-20 012345678-40-60x- coordinate (m)J.L. Briaud –Texas A&M University.
Weightless PerfectlyFlexible CoveremymInitial SoilMoundDeflectedFoundation SlabLgapDmaxDEFINITIONSFinal Soil DiagramLeqv2M max w41J.L. Briaud –Texas A&M University.
IS-WCommentIss (%)H (m)DU0 (pF)DlogUD (m)L (m)wimposed (kPa)02.04753.4125No moundreferenceIss- Very 2.73Iss- High603.51.30.9163.51.3650.6825Iss- ModerateIss- .53.53.2175H- Very High2.6325H- High1.4625H- Moderate0.8775H- LowDU-Very 52.0475 wimposed-Very Highwimposed -High2.04752.0475 wimposed-Moderate2.04756.60.225wimposed-LowAll maximumsAll minimumsffJ.L. Briaud –Texas A&M University.
Influence of soil surface suction change on LeqvInfluence of soil shrink-swell potential on LeqvLeqv1.210.8Edge drop case0.6Edge lift case0.40.2000.511.52Normalized Iss ( Iss / Iss (reference case) )as a f()of1.2Normalized Leqv(Leqv / Leqv (reference case) )Normalized Leqv(Leqv / Leqv (reference case) )1.410.80.60.2000.8Edge drop caseΔlogUffEdge lift case0.40.202Influence of slab length on LeqvNormalized Leqv(Leqv / Leqv (reference case) )1.210.8Edge drop caseEdge lift case0.40.2HDLwNormalized Leqv(Leqv/ Leqv (reference case) )10.60.40.60.811.2Normalized DU0 ( DU0 / DU0 (reference case))1.41.61.41.210.8Edge drop case0.6Edge lift case0.40.2000.511.5Normalized D ( D / D (reference case) )2Influence of slab imposed loads on Leqv1.2Normalized Leqv(Leqv/ Leqv (reference case) )Normalized Leqv(Leqv / Leqv (reference case) )Iss1.20.511.5Normalized H ( H / H (reference case) )0.2Influence of slab beam depth on Leqv1.40Edge lift case0.4Influence of depth of active moisture zone on Leqv0.6Edge drop case10.80.6Edge drop case0.4Edge lift case0.2000123Normalized L ( L / 2H (reference case))400.51Normalized wimposed ( wimposed / wimposed (reference case) )1.5J.L. Briaud –Texas A&M University.
SOIL WEATHER INDEX IswIsw Iss H ΔlogUedgeΔlogUedge 0.5 ΔlogUffIss shrink-swell index wsw – wsh (e.g. 0.2)H depth of shrink-swell movement (e.g. 3m)ΔlogUff change in water tension in the free field due toweather (e.g. 1.4)ΔlogUedge change in water tension at the edge of thefoundation and at the soil surface (e.g. 0.7)Isw 0.2 x 3 x 0.7 0.42J.L. Briaud –Texas A&M University.
Equivalent xvs 53aIS WLeqv L0 1 bIS W2R2 0.94441001234567Iss HΔlogUDU0 (m)Isw Iss Hff (m)J.L. Briaud –Texas A&M University.
Water Tension based design charts (Edge drop)Leqv design chart (Edge drop)7.00M max 6.00qL2eqv2Leqv (m)5.004.00deq 0.63 mdeq 0.51 mdeq 0.38 mdeq 0.25 mdeq 0.13 m3.002.001.000.0000.20.40.6Iss HIss.ΔlogUH. DUedge(m)edge(m)0.811.246J.L. Briaud –Texas A&M University.
Water Tension based design charts (Edge drop)Lgap (m)Lgap design chart (Edge drop)deq 0.63 mdeq 0.51 m5.004.504.003.503.002.502.001.501.000.500.00deq 0.38 mdeq 0.25 mdeq 0.13 m00.20.40.6IssIss.H H.ΔlogU(m)DUedge(m)edge0.811.247J.L. Briaud –Texas A&M University.
Water Tension based design charts (Edge drop)FDmax design chart (Edge drop)4.504.00deq 0.63 m3.50deq 0.51 mdeq 0.38 mFDmax3.00deq 0.25 m2.50deq 0.13 mD max 2.001.50qL 4eqvF D max EI1.000.500.0000.20.40.6Iss.DUedgeIss HH.ΔlogUedge (m)0.811.248J.L. Briaud –Texas A&M University.
Water Tension based design charts (Edge drop)FV design chart (Edge drop)0.900.800.70FV0.600.50deq 0.63 m0.40deq 0.51 m0.30deq 0.38 mdeq 0.25 mVmax Fv qLeqv0.20deq 0.13 m0.100.0000.20.40.6. H.DUedgeIIssssHΔlogU(m)edge(m)0.811.249J.L. Briaud –Texas A&M University.
Water Tension based design charts (Edge lift)Leqv design chart (Edge lift)8.007.00M max Leqv (m)6.00qL2eqv25.00deq 0.63 m4.00deq 0.51 m3.00deq 0.38 m2.00deq 0.25 mdeq 0.13 m1.000.0000.20.40.6Iss HIssΔlogU. H. DUedge(m)edge(m)0.811.250J.L. Briaud –Texas A&M University.
Water Tension based design charts (Edge lift)FDmaxFDmax design chart (Edge lift)4.50deq 0.63 m4.00deq 0.51 m3.50deq 0.38 m3.00deq 0.25 mdeq 0.13 mD max 2.502.00qL 4eqvF D max EI1.501.000.500.0000.20.40.6H. DUedge (m)IssIss.H ΔlogU0.811.251J.L. Briaud –Texas A&M University.
Water Tension based design charts (Edge lift)FV design chart (Edge lift)1.201.000.80FVdeq 0.63 mdeq 0.51 m0.60deq 0.38 mVmax Fv qLeqv0.40deq 0.25 mdeq 0.13 m0.200.0000.20.40.6H. DUedgeIssIss.H ΔlogU(m)edge (m)0.811.252J.L. Briaud –Texas A&M University.
Developed a simple correlation between theSlope of the SWCC Cw and the shrink-swell index Iss.4525CW 0.51 ISS2040R 0.8893515ISS (%)Cw (%)ISS 0.734 PI2102R 0.4965302552001515202530Iss (%)35404520253035PI (%)404550ThereforeΔwedge Cw ΔlogUedge 0.5 Iss ΔlogUedgeThenISW (for water tension) ISS H ΔlogUedge 2 H ΔwedgeISW (for water content) H ΔwedgeISW (for water tension) 2 ISW (for water content)J.L. Briaud –Texas A&M University.
Water content based design charts (Edge drop)Leqv design chart (Edge drop)7.006.00M max 2eqvqL2Leqv (m)5.004.00deq 0.63 m3.00deq 0.51 m2.00deq 0.38 mdeq 0.25 mdeq 0.13 m1.000.0000.10.20.3H. Dwedge (m)0.40.50.654J.L. Briaud –Texas A&M University.
Water content based design charts (Edge drop)Lgap design chart (Edge drop)5.00deq 0.63 m4.50deq 0.51 mdeq 0.38 m4.00Lgap (m)3.50deq 0.25 mdeq 0.13 m3.002.502.001.501.000.500.0000.10.20.3H. Dwedge (m)0.40.50.655J.L. Briaud –Texas A&M University.
Water content based design charts (Edge drop)FDmax design chart (Edge drop)4.50deq 0.63 m4.00deq 0.51 m3.50deq 0.38 m3.00deq 0.25 mFDmaxdeq 0.13 m2.502.00D max 1.50qL 4eqvF D max EI1.000.500.0000.10.20.3H. Dwedge (m)0.40.50.656J.L. Briaud –Texas A&M University.
Water content based design charts (Edge drop)FV design chart (Edge drop)0.900.800.70FV0.600.50deq 0.63 m0.40deq 0.51 mdeq 0.38 mVmax Fv qLeqv0.30deq 0.25 m0.20deq 0.13 m0.100.0000.10.20.3H. Dwedge (m)0.40.50.657J.L. Briaud –Texas A&M University.
Water content based design charts (Edge lift)Leqv design chart (Edge lift)8.007.00M max Leqv (m)6.00qL2eqv5.002deq 0.63 m4.00deq 0.51 m3.00deq 0.38 m2.00deq 0.25 mdeq 0.13 m1.000.0000.10.20.3H. Dwedge (m)0.40.50.658J.L. Briaud –Texas A&M University.
Water content based design charts (Edge lift)FDmax design chart (Edge lift)4.50deq 0.63 mdeq 0.51 m4.00FDmax3.50deq 0.38 m3.00deq 0.25 m2.50deq 0.13 mD max qL 4eqvF D max EI2.001.501.000.500.0000.10.20.3H. Dwedge (m)0.40.50.659J.L. Briaud –Texas A&M University.
Water content based design charts (Edge lift)FV design chart (Edge lift)1.201.000.80FVdeq 0.63 mdeq 0.51 m0.60Vmax Fv qLeqv0.400.20deq 0.38 mdeq 0.25 mdeq 0.13 m0.0000.10.20.3H. Dwedge (m)0.40.50.660J.L. Briaud –Texas A&M University.
PROPOSEDDESIGN PROCEDURE1.Water content version: one version ofthe method uses the water content of thesoil.2.Water tension version: one version ofthe method uses the water tension in thesoil.61J.L. Briaud –Texas A&M University.
PROPOSEDDESIGN PROCEDURE1.Gather site specific information onactive depth and amplitude of watercontent or water tension variation at thefoundation level.2.Use 3 charts to obtain maximumbending moment, maximum shear force,and maximum deflection (distortion)62J.L. Briaud –Texas A&M University.
Design exampleSoil and weather data:Depth of movement zone, H 3.0 mSoil surface water content change Δwff 20%Slab data:Slab dimensions 20 X 20 mBeam spacing, s 3.0 m (for both directions)Beam depth, h 1.2 mBeam width, b 0.3 mSlab load, w 10 kPaJ.L. Briaud –Texas A&M University.
Soil-Weather Index Is-wΔwedge 0.5 Δwff 0.5 x 0.2 0.1 or 10%Is-w Δwedge x H 0.1 x 3 0.3 mSlab bending stiffnessEI E bh3/12 2 x 107 x 0.3 x 1.23 / 12 8.64 x 105 kN.m2Equivalent slab thicknessb h3/12 s deq3/12deq h (b/s)1/3 1.2 (0.3/3)1/3 0.56 mValues from chartsLeq 5.3 m for maximum momentLgap 3.6 m for informationFΔmax 2.9 for maximum deflectionFv 0.8 for maximum shearJ.L. Briaud –Texas A&M University.
Maximum bending momentq 10 x 3 30 kN/m line load on elementMmax 0.5 q Leq2 0.5 x 30 x 5.32 421.3 kN.mMaximum deflectionΔmax q Leq4 / f Δmax EI 30 x 5.34 / 2.9 x 8.64 x 105Δmax 9.5 x 10-3 mMaximum shearVmax Fv q Leq 0.8 x 30 x 5.3 127.2 kNDistortionL / Δmax 10 / 9.5 x 10-3 1050Leq / Δmax 5.3 / 9.5 x 10-3 558J.L. Briaud –Texas A&M University.
ELLISON BUILDING CASESTUDY66J.L. Briaud –Texas A&M University.
PLAN VIEWCROSS SECTION67J.L. Briaud –Texas A&M University.
Boring68J.L. Briaud –Texas A&M University.
CASE HISTORY DATASoil properties-Soil type: CHPL 30%,LL 80%,PI 50%Percent clay 60%Allowable bearing pres. 75 kPaDepth to constant suction 2.1 mModulus of Elasticity 7000 kPaTotal unit weight 20 kN/m3Loads- No interior load- Perimeter loading 32 kN/m- Live load 2 kPaLocationCollege Station, TX, USAConcrete Slab properties-Compressive Strength 20 MPaCreep Modulus 10000 MPAUnit Weight 23 kN/m3Beam width 0.3 mSlab thickness 100 mmAllowable distortion Δ/L 1/50069J.L. Briaud –Texas A&M University.
#4@16" OCEW0.1 m3-#6#3 TIES @ 24" C-C1.05 m2-#56 MIL POLY3-#60.3 m70J.L. Briaud –Texas A&M University.
Site Preparation - 11 June 2004J.L. Briaud –Texas A&M University.
Fill and Compaction - 14 July 2004J.L. Briaud –Texas A&M University.
Excavation and steel - 16 July 200473J.L. Briaud –Texas A&M University.
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Installing Tell Tales – 13 Aug 200480J.L. Briaud –Texas A&M University.
d3.0mV.EHalf inchrodLubricantHalf inchrodSandCROSS SECTIONPVCSleeve5.0mV.E81J.L. Briaud –Texas A&M University.
Installing Benchmark - 13Aug 200482J.L. Briaud –Texas A&M University.
Installing Slab Bolts – 13 Aug 200483J.L. Briaud –Texas A&M University.
Steel Framing - 13-25 Aug 200484J.L. Briaud –Texas A&M University.
Wall Construction - Sept 200485J.L. Briaud –Texas A&M University.
Completed BuildingJ.L. Briaud –Texas A&M University.
INITIALELEVATIONS - 1 Sept 2004Elevation is referenced to the lowest point on Sept 1, 20040.0250.02Elevation (m)0.0150.010.0050Length (m)0.04.48.913.317.722.226.63
behavior of the soil skeleton for saturated soils and for unsaturated soils (in most cases) . Mass Transfer Process Energy Balance Atmosphere OET ( e s - e d) f (u) R l, down R l, up 2 0 2 900 0.408 273 1 0.34 R
in stringer-stiffened shells because the postbuckling zone slope becomes less. As a result more instability is observed(see Figs. 6 and 7). Fig. 4. Buckling loads of the ring- stiffened and stringer-stiffened cylindrical shells with different width Fig. 5. Buckling and postbuckling of the ring- stiffened cylindrical shells with different width
tion of these slabs. Topping slabs have many of the same issues that slabs-on-ground and structural concrete slabs have. Concrete practices related to crack control, shrinkage and temperature control, concrete jointing, concrete mixture design, and concrete curing for elevated slabs and slabs-on-grou
usually one and two-way spanning slabs Punching shear –e.g. flat slabs and pad foundations Shear There are three approaches to designing for shear: When shear reinforcement is notrequired e.g. usually slabs When shear reinforcement isrequired e.g. Beams, se
chapter 2 structural behavior of two-way slabs 17 2.1 types of two way slabs 19 2.2 behavior of two-way slabs 22 2.3 analysis methods for two way slabs 25 2.4 review of elastic plate bending theory 32 2.3 finite element analysis for two-way slabs 38 chapter 3 theoretical analysis of two-
soil properties, and the beam depth, to calculate the distortion of the slab under load. If the distortion is too large for the type of structure considered, the beam depth is increased until the acceptable value is reached. Introduction Stiffened slabs-on-grade (Fig.1) are one of the most efficient and inexpensive
This dissertation presents an in-depth computational study on the buckling, postbuckling and strength of stiffened composite panels. It follows up the finished COCOMAT project, supported by the European Commission, with the aim of exploiting large strength reserves in stiffened carbon fiber reinforced polymer (CFRP) fuselage structures.
Rectangular duct, stiffened with transverse corrugations to reduce the risk of noise generation. Larger di-mensions have stiffened with rods or profiles. Duct standard lengths are 1250 mm and 2000 mm, when a or b 1200, standard length L 1250. Can be supplied in other lengths. Stiffening 1. Duct is stiffened with rods and corner bits (standard):
FACTORS AFFECTING THE DESIGN TIDCKNESS OF BRIDGE SLABS: DESIGN AND PRELIMINARY VERIFICATION OF TEST SETlTP by J. H. Whitt,J. Kim, N. H. Burns, andR. E. Klingner Research Report Number1305·1 Research Project 0-1305 Factors Affecting Design Thickness ofBridge Slabs conducted for the TEXAS DEPARTMENT OF TRANSPORTATION in cooperation with the
