PCI Big Beam Contest

PCI Big Beam ContestTeam 1 (XDF)

Junfeng QianShiyu WangQi Wang

OutlineIntroduction BackgroundProblem StatementDesign GoalsJob DescriptionField TripConcrete MixBeam DesignDesign Matrix Final DesignFabrication

Analysis & PredictionBeam TestTest ResultsTimelineConclusionLessons LearnedRecommendations for PCI Big Beam ContestAcknowledge Reference

Introduction PCI Big Beam Contest for 2012-2013 academic yearSponsored by Tpac CompanyA challenge project

BackgroundPre-stressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose those found when in use.

Compressive stresses are induced in prestressed concrete either by pretensioning or post-tensioning the steel reinforcement. (In pretensioning, the steel is stretched before the concrete is placed)The principle behind prestressed concrete is that compressive stresses induced by high-strength steel tendons in a concrete member before loads are applied will balance the tensile stresses imposed in the member during service.

4Problem StatementPrestressed Concrete Beam20 ft. long and tested as a 18 ft. spanBeam shall carry a total live load between 32 kips-39kipsBeam shall not crack under a total applied load of 20 kips

Design GoalsDesign accuracy

Low cost

Low weight

Largest measured deflection at maximum total applied load

Meet the requirement of ACI-318-08 and PCI Design Handbook, 7th Edition

Job DescriptionQi Wang Project Manager

Shiyu Wang Coordinator

Junfeng Qian Project Engineer

Field Trip

Concrete MixSelf-Consolidating ConcreteLightweight ConcreteProsEasy to achieve high strength transfer and ultimate.Low Water Cement ratio assists with permeability.Easy to place concrete with maximum consolidation.Proven Performance.High shear values at transfer and 28 days.Low unit weightGood to above average 28 day compression strength for lightweight.Low Water Cement ratio assists with permeability.Easy to place concrete with maximum consolidation.High fire rating.ConsHigh unit weight.No air entrainment for severe weather conditions.Low fire rating.Low shear values at transfer and 28 days.Specific gravity of lightweight material is unstable.Low transfer strengths if proper curing procedures are not used.Beam DesignCross-SectionI beam, T beam, Box beam

Microsoft Excel software8 design optionsAdjustments for qualified design options based on weight and cost

Beam Design Cont.

Design Matrix Cost (35%), Max Deflection (30%), Weight (35%)

Beam 1Beam 2Beam 3TypePercentileMeasured ValueGradeMeasured ValueGradeMeasured ValueGradeCost ($)351251013191437EI (kip-in2)30617664499654422298683353287Weight (lb.)351909.59101900.06101990.316Total (10)1009.49.356.65Final DesignCross-Section DetailsMaterial cost

MaterialsAmountUnit CostCostNormal Weight Concrete0.47 cu yd.$ 100/cu yd.$ 47Prestressing Strand3*20 ft.$ 0.30/ft.$ 18A615 #5 Rebar5*20 ft.$ 0.45/lb.$ 47Welded Mesh25.8 lb.$ 0.50/lb.$ 13A615 #4 Rebar4*0.7 ft.$ 0.45/lb.$1.5Total Cost$ 126.5Fabrication

Analysis & Prediction

Prediction: Cracking load, Maximum Deflection, Ultimate LoadCracking Load & Ultimate Load: Excel SpreadsheetDeflection: Response 2000 Computer Software & Excel

Deflection PredictionBeam TestVisual Indication of DeflectionString PotentiometerVideo

Test ResultsThe point of load cracking is close to the predictionThe maximum point load and deflection at ultimate capacity have a difference to the prediction

Data DescriptionPredictedActualPercent ErrorPoint Load Cracking (kips)23.823.22.52%Ultimate capacity(kips)36.3541.5414.3%Deflection at Midspan (in)1.7037.42335.7%Timeline

Conclusion Pros:Successful DesignGood CooperationGain KnowledgeFamiliar with Research ProcessCons:Inaccurate PredictionExceed allowable ultimate load

Lessons LearnedEnrich the knowledge about concrete design and improve abilitiesGets the experience on how to work in a group to study the knowledge of prestressed concrete, computer design, and conduct the beam testLearn how to operate a concrete beam test from this projectIf the team has another opportunity to participate the team will be carefully notice the operation of Response 2000 program and ultimate load prediction.

Recommendations for PCI Big Beam ContestA discussion of future use of the beam should be required in the contest rulesPeople who have different academic background could participate in this contestThe contest committee should assign a technical faculty to each team

ReferenceTechnical Advisor: Dr. TuchschererProject Manager: David L. ChapinSponsor: Tpac CompanyAcknowledge ACI Code 318-08The 7th Edition of the PCI Design Handbook

Questions

Thank you!

Release StressLive Load Equiv

Cross Sectionf'c (ksi)f'ci (ksi)# of strandstop (ksi) bot (ksi)P crack (kip)PU (kip)EI (kip-in2)

8.54.530.365-2.19823.833.661766449

8.54.540.517-3.03734.436.865442229

8.54.540.356-2.15729.840.7868335328

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