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Design of Rigid PavementsAFANDI BIN SAFIA141506AMIRUL ANWAR BIN MOHD SOLONGA139607MOHD AZMAN BIN SAMERA141428MUHAMMAD TAUFIQ BIN OTHMANA141468

20.1 Materials Used In Rigid Pavements

Portland CementCarefully mix of limestone, marl and clay or shale at high temperature.5 type of Portland cement:type Itype IItype IIItype IVtype V

Coarse aggregate

Fine aggregate

Steel

20.2 Joints In Concrete Pavements

To limit the stress induced by temperature change.To facilitate proper bending of two adjacent section of pavement.4 basic categories of joints

20.3 Types of Rigid Pavement

Three general types:

Jointed Plain Concrete Pavement (JPCP)Has no temperature steel or dowels bars but steel tie often used to provide hinge effect at longitudinal jointOften used at low volume highwaysJointed Reinforced Concrete Pavement (JRCP)Have dowels for transfer of traffic load across jointContinuously Reinforced Concrete Pavement (CRCP)No transverse joint High percentage of steel with minimum at 0.6 percent of cross section of slab

20.4 Pumping of Rigid Pavements

DefinitionDischarge of water and subgrade materials through joints, cracks, and along pavement edges

20.5 Stresses In Rigid Pavement

Three main stress need to be consider in rigid pavement

Stress induced by bendingStress due to traffic wheel loadsStress due to temperature effects

20.6 THICKNESS DESIGN OF RIGID PAVEMENTS

20.6.1 AASHTO Design Method

AASHTO Design ProcedureObjectiveThickness of the concrete pavement

20.6.2 Alternate AASHTO Design MethodThe procedure requires the following inputs:

Estimate ESALsDesign reliability, R%Overall standard deviation, SoDesign serviceability loss, PSI = pi - ptEffective (seasonally adjusted) elastic k value of the subgrade (lb/in.2)Concrete modulus of rupture, Sc (lb/in.2)Concrete elastic modulus, Ec (lb/in.2) Joint spacing, L (in.)

Base modulus, Eb (lb/in.2)Slab/base friction coefficient, Base thickness, Hb (in.)Effective positive temperature differential through concrete slab TD (F)Lane edge support condition:Conventional lane width, 12 ft from free edgeConventional lane of 12 ft width with tied concrete shoulderWide slab; e.g., 14 ft with conventional traffic lane width of 12 ft

Joint Spacing (Refer Table 20.10-20.12)

The suggested hypothetical joint spacing foreach rigid pavement type is given as:Jointed plain concrete pavement (JPCP): Use actual joint spacing (ft). Jointed reinforced concrete pavement (JRCP): Use actual joint spacing when it is less than 30 ft; otherwise, use 30 ft maximum. Continuously reinforced concrete pavement: Use 15 ft.

Base Modulus, Eb and Slab/Base Friction Coefficient, f (Refer Figure 20.16, Table 20.13)

Effective Positive Temperature Differential through Concrete Slab, (F)

whereh = slab thickness (in.)WIND = mean annual wind speed (mi/h)TEMP = mean annual temperature (F)PRECIP = mean annual precipitation (in.)effective positive TD = 0.962 - 52.181/h + 0.341WIND + 0.184TEMP - 0.00836PRECIP

Lane Edge Support Condition, E(Refer Table 20.14)

An adjustment factor is used for each of thelane edge support conditions as given below:E = 1.0 for conventional traffic lane width of 12 ft with free edge = 0.94 for conventional traffic lane width of 12 ft with tied concrete shoulder = 0.92 for wide slab (e.g., 14 ft with conventional traffic lane width of 12 ft)

Design Equations for Rigid Pavement using the Alternate Method (Refer Table 20.16-20.17)

Design Check for Joint Load Position CrackingDetermine the required slab thickness using the midslab load position as the criterion for design.Determine the midslab tensile stress (t) at the bottom of the slab.Estimate a total equivalent negative temperature differential.

Estimate the critical stress at the top of the slab.Compare the tensile stress determined for midslab loading at the bottom of the slab with that obtained at the top of the slab for joint loading.

Design Check for Joint Load Position CrackingJoint Load Transfer

Recommend values:Joint spacing less than 25 ft, critical mean joint faulting = 0.06 in.Joint spacing greater than 25 ft, critical mean joint faulting = 0.13 in.

Procedure for design check:Determine the design thickness of the slab.Use the appropriate model for doweled or undoweled pavement to estimate the expected mean joint faulting.Compare the estimated joint faulting with the recommended mean joint faulting level to prevent significant loss in serviceability.

20.6.3 PCA DESIGN METHODPCA method for concrete pavement design is based on a combination of theoretical studies,results of model and full-scale tests,and experience gained from the performance of concrete pavements.Design Condsiderations: Basic Factors considered in PCA method:1)Flexural strength 2)Subgrade and subbase support3)Traffic load

Flexural Strength of concrete: is given terms of the modulus of rupture*The average 28-day test results is used as input.

Subgrade and subbaseThe Westgaard modulus of subgrade reaction,k is used to define the subgrade and subbase support.

Traffic LoadThe traffic load is computed in terms of the cumulated number of single and tandem axles of different loads.The information required to determine cumulated numbers are the average daily traffic, the average daily truck traffic and axle load distribution.

Design procedure:The procedure is based on a detailed finite-element computer analysis of stresses and deflections of the pavement edges, joints, and corners.The design procedure consists of two parts:Fatigue analysisErosion analysis.

Fatigue analysis:Is to determine the minimum thickness of the concrete required to control fatigue cracking

Erosion analysis:An erosion factor is used instead of the stress factor.

20.6.4 Mechanistic-Empirical Design Guide (MEPDG) MethodFor jointed plain concrete pavement (JPCP).The procedure is similar to that for the flexible pavement.Three Stages:Determination of the input values for trial design analysis of structural capabilityEvaluation of the structural viability

Transverse slab crackingThis may occur either in the bottom-up or top-down modes in a JPCP slab under a typical service conditions.Mean Transverse Joint FaultingDetermined for each month by first computing the incremental faulting during a given month from that of the previous month.

QUESTION?