Pavement Design Seminar PDF

DESIGN STANDARDS  STANDARDS HAVE BEEN DEVELOPED AS GUIDE IN THE DESIGN OF HIGHWAYS AND TO ENSURE THAT MOTORIST’S CONVENIENCE, ENVIRONMENTAL SAFETY AND AESTHETIC CONSIDERATIONS ARE IMPLEMENTED IN THE MOST ECONOMICAL MANNER CONSISTENT WITH HIGHWAY SERVICE CO...

DESIGN STANDARDS  STANDARDS HAVE BEEN DEVELOPED AS GUIDE IN THE DESIGN OF HIGHWAYS AND TO ENSURE THAT MOTORIST’S CONVENIENCE, ENVIRONMENTAL SAFETY AND AESTHETIC CONSIDERATIONS ARE IMPLEMENTED IN THE MOST ECONOMICAL MANNER CONSISTENT WITH HIGHWAY SERVICE CONDITIONS. DESIGN POLICIES AND STANDARDS GENERALLY REPRESENT MINIMUM VALUES. EFFECTS OF POOR HIGHWAY DESIGN Introduction to Pavement Design TWO MAIN TYPES OF PAVEMENT Comparison of the characteristics of ACP and PCCP Asphalt Pavement Concrete Pavement Loads are distributed in small areas whose Loads influence large areas whose structural structural capacity is sum of multi-layers capacity is supplied mainly from the slab itself Easy and rapid construction Need curing time Layered construction is possible Long life Quiet and comfort to ride Durable to heavy truck RIGID PAVEMENT DESIGN PORTLAND CEMENT CONCRETE PAVEMENT RIGID PAVEMENT  Generally Consist of a roadbed underlying a layer of pavement slab.  Used for its durability and its ability to hold shape. Types of Rigid Pavement Jointed Plain Concrete Pavement(JPCP Jointed Reinforced Concrete Pavement (JRCP) Continuously Reinforced Concrete Pavement (CRCP) Jointed Plain Concrete Pavement  Uses contraction joints that are spaced at equal distance to avoid transverse cracking in between said joints due to temperature and moisture stresses.  Does not use any reinforcing steel bars along the slab.  The use of load transfer devices such as dowel bars are typically used at transverse joints.  Tie bars are used in longitudinal joints. L Typical Roadway Cross- Section of Rigid Pavement Design Controls Design Life Width of Pavement Soil Properties(CBR) Material Properties (Concrete and Steel) Loadings (Traffic) Design of Rigid Pavement Joint Load Slab Length Slab Thickness Transfer Design Length of Dowels Depth of Joint Spacing Keys PCCP Aggregate Interlocks Slab Length  AASHTO Pavement Design Guide, page II-49  Joint spacing (Transverse and longitudinal) depends on local conditions of materials and environment.  Expansion Joints and Construction Joints depends on layout and construction Capabilities Slab Length  AASHTO Pavement Design Guide, page II-49  Contraction Joint spacing depends on:  Thermal Coefficient  Temperature change  Subbase Frictional Resistance  Concrete Tensile Strength 𝐶𝐿 (∝𝑐 × 𝐷𝑇𝐷 +𝑧) ∆𝐿 = × 100 𝑆 Slab Length 𝐶𝐿 (∝𝑐 × 𝐷𝑇𝐷 +𝑧) ∆𝐿 = × 100 𝑆  Where:  ∆𝐿 = Joint opening caused by temperature changes  C = Adjustment Factor due to subbase – slab friction 0.65 for stabilized subbase, 0.80 for granular base  S = Allowable strain of joint sealant, usually 25% -35%  ∝𝑐 = Thermal Coefficient  𝐷𝑇𝐷 = Temperature range in ℉  L = Joint Spacing  Z = Drying Shrinkage Coefficient Slab Length  As a rough guide, joint spacing (in feet) should not greatly exceed twice the slab thickness (in inches)  L = 2D (Empirical relationship)  Where:  D = Thickness of Slab in inches (in)  L = Length of Slab in feet (ft)  Example:  For 8 in thick PCCP  L = 2 (8)  L = 16 ft ≈ 4.80 m Slab Length  As per DPWH Standards L = 4.50 m Joint Designs LOAD TRANSFER DEVICES FOR DISCONTINUITIES ON SLAB  L Contraction/ Construction Aggregate Joint Interlock w/ Dowel Bars Longitudinal Joint (Keyed Joint w/ Tie bars) DOWEL BARS  Usually applied on Contraction Joint and Transverse Construction Joints.  Diameter of dowel (As per AASHTO)  ∅ = Thickness/8 spaced at 300 mm on center  Diameter of dowel may vary based on available material on the area, however, corresponding change to the spacing should be applied to achieve equivalent steel area.  As per AASHTO length is usually 18 in (450 mm)  AS per DPWH Standards length 600 mm Butt Joint with Dowel Bars Usually installed on transverse construction Joints. Dowel Bars with Steel Baskets Usually installed for PCCP designed with dowels on contraction joints as load transfer device. Keyed Joint with Tie Bars  Usually Installed on Longitudinal Joint and Construction Joints within the middle third of the slab.  Spacing of Tie Bars 𝐴𝑠 𝑌= × 100 𝑃𝑡 𝐷 𝐿𝐹 𝑃𝑡 = 2 𝐹𝑠  Where:  L = Slab length  𝐹𝑠 = Steel Working Stress  F = Friction Factor  𝑃𝑡 = Percent of Steel Reinforcement  𝐴𝑠 = Area of single steel reinforcement  D = Thickness of Concrete  Y = Tie bar Spacing Keyed Joint with Tie Bars Usually installed at: Transverse construction joint located at the middle third of the slab longitudinal joints having one lane paving at a time Key serves as the load transfer device Tie bars prevents the joint from opening. Aggregate Interlocks Mechanism that transfers load across a crack in concrete by means of interlocking between irregular aggregate and cement paste surfaces on each side. Aggregate Interlock, cracks on weakened plane joints. Aggregate Interlock with Tie bars Usually seen on longitudinal joints with two lane paving. Rigid Pavement SLAB THICKNESS PORTLAND CEMENT CONCRETE PAVEMENT  Plot the values derived on Figure 3.7 of the AASHTO guide or use the following equation to determine the design slab thickness (D): ∆𝑃𝑆𝐼 log 4.5;1.5 log 𝑊18 = 𝑍𝑅 𝑆0 + 7.35 log(𝐷 + 1) − 0.06 + 1.624𝑥107 + 1+ 𝐷:1 8.46  𝑆 ′ 𝑐 ×𝐶𝐷 (𝐷0.75 −1.132) (4.22 − 0.32𝑃𝑡 ) × log 18.42 215.63×𝐽(𝐷0.75 − 𝐸𝑐 0.25 𝑘 Thickness Design Parameters for PCCP  Roadbed Soil  Resilient Modulus of Subgrade, MR  Composite Modulus of Subgrade Reaction, k∞  Corrected Modulus of Subgrade Reaction, k  Design traffic load, W18  Reliability = 85%  Overall Standard Deviation, S0 = 0.35  Design Serviceability loss, ΔPSI = PI – PT = 4.5 – 2.5 = 2.0  Drainage Coefficient, CD = 1.00  Load Transfer Coefficient, J = 3.8 for undoweled and 3.2 for doweled  Concrete Modulus of Rupture, S’c = 635.55 psi  Concrete Modulus Of Elasticity, Ec = 3.37E6 psi Reliability (R)and Standard Deviation (𝑆0 )  Accounts for both chance variation in traffic prediction and the normal variation in pavement performance prediction for a given traffic loading.  As per DPWH standards:  R = 85 % with 𝑍𝑟 = -1.037 (based on table)  𝑆0 = 0.35 (range from 0.3 to 0.4) Recommended Level of Reliability, R Functional Classification Urban Rural Freeways 85 – 99.9 80 – 99.9 Principal Arterials 80 - 99 75 - 95 Collectors 80 - 95 80 - 99 Local 50 - 80 50 - 80 Reliability and Standard Normal Deviate Standard Standard Reliability Normal Deviate Reliability Normal Deviate R% ZR R% ZR 50 0.000 93 -1.476 60 -0.253 94 -1.555 70 -0.524 95 -1.645 75 -0.674 96 -1.751 80 -0.841 97 -1.881 85 -1.037 98 -2.045 90 -1.282 99 -2.327 91 -1.340 99.9 -3.090 92 -1.405 99.99 -3.750 Serviceability  Is expressed in terms of Present Serviceability Index (PSI) based on the comfort and convenience of traveling public (User)  The PSI is obtained from measurements of roughness or distress at a particular time during the service life of the pavement.  As per DPWH Standards for Rigid Pavement  PI = 4.5 for rigid pavement  PT = 2.5 for major highways and 2.0 for lesser traffic volume Drainage Coefficient  Can be derived based on the quality of drainage and percent of time that the pavement structure is exposed to moisture levels approaching saturation.  Quality of Drainage Quality of Drainage Water Removed Within Excellent 2 hours Good 1 day Fair 1 week Poor 1 month Very Poor (water will not drain) Drainage Coefficient Joint and Load Transfer Coefficient  A factor to account for the ability of a concrete pavement to transfer or distribute load across discontinuities such as joints or cracks. Condition J Factor Undoweled PCC on crushed aggregate 3.8 surfacing Doweled PCC on crushed aggregate 3.2 surfacing Doweled PCC on HMA (without widened 2.7 outside lane) and tied PCC shoulders CRCP with HMA shoulders 2.9 – 3.2 CRCP with tied PCC shoulders 2.3 – 2.9 PCC Modulus of Rupture (psi), S’c  The flexural strength at 28 days determined using third point loading.  As per DPWH Specification S’c = 550 psi for 14 days  As per AASHTO specification, if construction specification will be used as data, necessary adjustments should follow.  𝑆 ′ 𝑐 𝑚𝑒𝑎𝑛 = 𝑆𝑐 + 𝑧 𝑆𝐷𝑠  Where:  S’c = Estimated Mean Value for PCC Modulus of rupture  Sc = Construction Specification on PCC Modulus of Rupture  SDs = Standard Deviation of Concrete Modulus of Rupture (PSI)  Z= Standard Normal Deviate PCC Modulus of Rupture (psi), S’c Standard Normal Percent of Strength Deviate (z) Distribution (PS) 0.841 20 % 1.037 15 % 1.282 10 % 1.645 5% 2.327 1% PCC Modulus of Rupture (psi), S’c  𝑆 ′ 𝑐 𝑚𝑒𝑎𝑛 = 𝑆𝑐 + 𝑧 𝑆𝐷𝑠  Sc = 550 psi for 14 days  SDs = PS(Sc) =0.15 x 550  Z= 1.037  𝑆 ′ 𝑐 𝑚𝑒𝑎𝑛 = 550 + 1.037 (0.15 𝑥 550)  𝑆 ′ 𝑐 𝑚𝑒𝑎𝑛 = 635.55 psi Design S’c should be verified for 28 days. Elastic Modulus (psi) 𝐸𝑐  The materials stress-strain behavior under normal pavement loading condition.  Can be obtained using the formula: 𝐸𝑐 = 57,000(𝑓′𝑐 )0.5 where: 𝐸𝑐 = Elastic Modulus of Concrete(psi) 𝑓′𝑐 = PCC compressive strength(psi), 3500 psi 𝐸𝑐 = 57,000(3500)0.5 𝐸𝑐 = 3.37 x 106 psi Design CBR  Design CBR shall be obtained from no. of samples garnering 90% probability that the difference between the true mean and the sample mean is not greater than 20%.  Using Standard Deviation: (𝑋𝑖 −𝑋)2 S= , Design CBR = X – (2 3)S 𝑛−1  Where:  S = Standard Deviation  X = Mean CBR  𝑋𝑖 = Individual CBR  n = number of samples Design CBR  To obtain 90% probability for 20% difference between the true mean and sample mean, the conditions set in this table should be met.  Solve for S/X  Check if min. CBR samples were met. If not, provide additional sample and recompute. Resilient Modulus of Subgrade, MR  Obtained based on recoverable strain under repeated load.  Can be estimated by correlating with the design CBR  MR= 1500(𝐶𝐵𝑅) , for CBR not greater than 10% Composite Modulus of Subgrade Reaction (k∞)  The level of slab support that can be provided based on the subbase characteristics and seasonal variation of roadbed soil resilient modulus.  Can be determined from figure 3.3 of the AASHTO pavement design guidelines 1993  Example:  Dsb = 6 inches  Esb = 20 000 psi  𝑀𝑅 = 7 000 psi Loss of Support Computing for k corrected Design Traffic Load  𝑊18 = cumulative 18-kip Estimated Single Axial Load (ESAL )  The procedure is to convert a mixed traffic stream of different axle loads and axle configuration into a designed traffic number and convert each expected axle load into an equivalent number of 18-kip single axle loads and to sum this over the design period.  Computation is based on D.O. 22 series of 2011. Design Traffic Load  Determine the Design traffic for each vehicle type: (1+𝑖)𝑛 −1  Design Traffic= 𝑃𝑖 365 𝑖  Where:  𝑃𝑖 = Annual Average Daily Traffic  i = Traffic growth rate, usually assumed as 4%  n = design life period Design Traffic Load  Determine the Traffic Equivalence Factor  Converting all single axle load of the truck to equivalent 8.2 tons single axle load 𝑎𝑥𝑙𝑒𝑙𝑜𝑎𝑑(𝑡𝑜𝑛𝑠) 4  EF = 8.2 Traffic Equivalence factor  Example  In a 2-axle truck with GVW=16,880 kg: 3.38 4 13.5 4  𝐸𝐹 = + = 7.38 8.2 8.2 Design Traffic Load  Determine the directional and lane distribution factor:  𝐷𝐷 = Directional distribution factor (100% for 1 way, 50% for 2 way)  𝐷𝐿 = Lane Distribution factor Number of lanes in each Percentage of 18 kips ESAL Direction in Design Lane 1 100 2 80 – 100 3 60 – 80 4 50 - 75 Design Traffic Load  Compute the Cumulative Single Axle Load (CESAL)  CESAL = 𝐷𝑒𝑠𝑖𝑔𝑛 𝑇𝑟𝑎𝑓𝑓𝑖𝑐 × 𝐸𝐹 × 𝐷𝐷 × 𝐷𝐿 Flexible Pavement Design ASPHALT CONCRETE PAVEMENT Flexible Pavement  Generally consists of a prepared roadbed underlying layers of subbase, base and bituminous surface course.  Loads are distributed in a small area whose structural capacity is sum of multi-layers. Typical Roadway Cross- Section of Flexible Pavement Flexible Pavement Design  Two formulas  1) log 𝑊18 = ∆𝑃𝑆𝐼 log 4.2;1.5 𝑍𝑅 × 𝑆0 + 9.36 × log(𝑆𝑁 + 1) − 0.20 + 1094 + 2.32 × 0.40+ 5.19 𝑆𝑁:1 log(𝑀𝑅 ) − 8.07  2) 𝑆𝑁 = 𝑎1 𝐷1 + 𝑎2 𝐷2 𝑚2 + 𝑎3 𝐷3 𝑚3 Structural Number, SN  An abstract number representing structural strength required for a given combination of soil support, design traffic, serviceability index and environment. Thickness Design Parameters for ACP  For formula 1, Solve for Structural Number (SN):  Resilient Modulus of Subgrade, 𝑀𝑅  Design traffic load, 𝑊18  Standard Normal Deviate, 𝑍𝑅 = -1.037, based on 85% reliability  Design Serviceability loss, ΔPSI = PI – PT = 4.2 – 2.5 = 1.7  PI=4.2 for flexible pavement  Overall Standard Deviation, 𝑆0 = 0.45  𝑆0 range from 0.4-0.5 for flexible pavement Thickness Design Parameters for ACP  For formula 2, Solve for thickness of layers (𝐷𝑖 ):  Layer Coefficient, 𝑎𝑖  Drainage Coefficient, 𝑚𝑖  1.00 for both subbase and base layer Structural Layer Coefficient, 𝑎𝑖  A measure of relative thickness of a given material to function as a structural component of a flexible pavement. Structural Layer Coefficient, 𝑎𝑖  Basic layers of flexible pavement:  Asphaltic concrete surface course, 𝑎1 = 0.44  Crushed stone base course, 𝑎2 = 0.14  Sandy gravel subbase, 𝑎3 = 0.11 Structural Layer Coefficient (ai ) Pavement Component Layer Coefficient Asphalt Concrete, good condition 0.38* Asphalt Concrete, fair condition 0.20 – 0.30 Asphalt Concrete, bad condition 0.15 Bituminous Surface Treatment 0.20 Bituminous Macadam 0.20 Cement Concrete, good condition 0.44** Cement Concrete, fair condition 0.35** Cement Concrete, bad condition 0.20** Cement Concrete, very bad 0.15** condition 0.23 0.20 0.17*** Crushed Gravel Base 0.15*** Broken Stone Macadam Base 0.14 Granular Sub-Base (passing specs.) 0.11 Sub-Base(poorly graded or 0.07 containing Value clay) material can also be determined from Figures 2.5, of (ai ) of different 2.6, 2.7, 2.8 and 2.9 Drainage Coefficient, 𝑚𝑖 Flexible Pavement Design  Solve for Structural number:  log 𝑊18 = ∆𝑃𝑆𝐼 log 4.2;1.5 𝑍𝑅 × 𝑆0 + 9.36 × log(𝑆𝑁 + 1) − 0.20 + 1094 + 2.32 × 0.40+ 5.19 𝑆𝑁:1 log(𝑀𝑅 ) − 8.07  Assign thickness for base, subbase and AC that will satisfy the following equation.  𝑆𝑁 = 𝑎1 𝐷1 + 𝑎2 𝐷2 𝑚2 + 𝑎3 𝐷3 𝑚3 END THANK YOU   PUP Civil Engineering Department #WeLearnAsOne The construction of a new railway line is a capital-intensive project and each kilometer of a new railway line costs depending upon the topography of the area, the standard of construction, and such other features. It is, therefore, natural that a lot of thought be given when making a final decision as to whether a new railway line is at all necessary or not. ▪ Strategic Reasons ▪ Political Reason ▪ Development of Backward areas ▪ To connect new Trade Center ▪ To Shorten the existing rail Tack Preliminary Investigations for a New Railway Line The railway administration determines how the proposed line will fit in with the general scheme of future railway development. The preliminary investigations are normally based on a careful study of the following: Existing topo sheets and other maps of the area Published figures of trade and population of the area to be served Statistical data of existing railway lines in similar terrain in other areas Module 3 | Pavement Learning Objectives Upon successful completion of this course, the student should be able to: Understand the two major types of pavement present in the Philippines; Understand the different concrete and asphalt pavement activities; Learn basic understanding of the required design data, design criteria and standards, and design procedures of Portland Cement Concrete Pavement (PCCP), Asphalt Concrete Pavement (ACP), and AC overlay over PCCP. Course Material 4. PAVEMENT 4.1. Types of Pavement - Road pavement is of two major types - rigid pavement (PCCP) and flexible pavement (ACP). Load Distribution for Rigid and Flexible Pavement 46  PUP Civil Engineering Department #WeLearnAsOne 4.1.2. Rigid Pavement - A rigid pavement generally consists of three layers: the concrete slab, subbase and subgrade as described below: Slab - The slab is made of reinforced or plain concrete which also includes load transfer devices and joint sealing materials. The concrete slab acts like a bridge girder over the subgrade. Subbase - The slab is made of reinforced or plain concrete which also includes load transfer devices and joint sealing materials. The concrete slab acts like a bridge girder over the subgrade. Subgrade - It is the bottom portion of the pavement structure which consists of suitable embankment materials or existing road bed. 4.1.3. Flexible Pavement - A flexible pavement generally consists of four layers: surface course, base course, subbase and subgrade (which is the prepared roadbed) as described below: Surface Course - It consists of a mixture of mineral aggregates and bituminous materials constructed on a prepared base course. Base Course - It is the portion of a pavement structure immediately beneath the surface course. It consists of aggregates such as crushed stone, crushed slug, crushed or uncrushed gravel and sand or a combination of these materials placed and compacted on a prepared subbase. Subbase It is the portion of the pavement structure between the subgrade and the base course. It consists of a compacted layer of granular materials placed on a prepared subgrade. Subgrade - It is the bottom portion of the pavement structure which consists of suitable embankment materials or existing road bed. 4.2. Quality Control for PCCP - The Contractor shall perform all sampling, testing and inspection necessary to assure quality control of the component materials of the concrete. The Contractor shall be responsible for determining the gradation of fine and coarse aggregates and for testing the concrete mixture for slump, air content and temperature. He shall conduct his operations so as to produce a mix conforming to the approved mix design. 4.3. Design Mix and Trial Paving - The Contractor is obliged to formulate the design mix, conduct trial mix and trial paving for approval of the Project Engineer before commencement of pavement construction as illustrated in figure below. Flow Chart of Preparatory Work for Conceptual Paving 4.4. Admixtures or Additives - Admixture/additive shall be added only to the concrete mix to produce some desired modifications to the properties of concrete whenever necessary, but not as partial replacement of cement. The admixtures shall conform to the requirements as tabulated below: 47  PUP Civil Engineering Department #WeLearnAsOne Requirements for Admixtures 4.5. Concrete Paving for Activities - The following photos show concrete pouring activities: 4.6. Types of Form Works - There are two types of formworks for concrete paving - fixed-form and slip form. The use of slipform paver is required in DPWH road projects as per D.O. 219 Series of 2000. 4.7. Weakened Plane Joint All joints shall be protected from the intrusion of injurious foreign material until sealed. All joints shall be cut within 4 to 24 hours after pouring and thereafter sealed with asphalt sealant. The depth of the weakened plane joint shall not be less than 50 mm while the width not more than 6 mm. Only concrete saw is permitted in the cutting of weakened plane joints. According to international practice, dowel bars are required in all contraction joints (at 4.5m) as load transfer 48  PUP Civil Engineering Department #WeLearnAsOne device for PCCP with thickness of more than 200 mm. The PCCP slabs without dowel bars at weakened joint will cause various defects in the medium to long term, especially for the road route on which heavy trucks are dominant. The types and functions of PCCP joints are summarized below: 4.8. Rigid Pavement (PCCP) Rigid Pavements generally consists of prepared roadbed underlying a layer of subbase and pavement slab. AASHTO formula used in the analysis of Rigid Pavement: 𝑙𝑜𝑔 [ ∆𝑃𝑆𝐼 ] 10 4.5 − 1.5 𝑙𝑜𝑔 𝑊 = 𝑍 × 𝑆 + 7.35 × 𝑙𝑜𝑔 (𝐷 + 1) − 0.06 + 10 18 𝑅 𝑂 10 1.624 × 107 1+ (𝐷 + 1)8.46 ‫ﻟ‬ 1 I I 𝑆′ × 𝐶 [𝐷0.75 − 1.132] + (4.22 − 0.32𝑝 ) × 𝑙𝑜𝑔 𝑐 𝑑 (𝑒𝑞𝑢𝑎𝑡𝑖𝑜𝑛 1 − 1) 𝑡 10 ❪ 18.42 ❵ 215.63 × 𝐽 [𝐷0.75 − ] I 𝐸𝐶 0.25 I 𝗅 (𝑘) 𝖩 Where: 𝑊18 = predicted number of 18-kips equivalent single axle load (ESAL) application 𝑍𝑅 = Standard normal deviate 𝑆𝑂 = Combined standard error of the traffic prediction and performance prediction 𝐷 = Thickness (inches) of pavement slab ∆𝑃𝑆𝐼 = Difference between the initial serviceability index (Po) and the design terminal service ability (Pt) 49  PUP Civil Engineering Department #WeLearnAsOne 𝑆𝑐′ = Modulus of rupture (psi) for Portland Cement Concrete Sc + Z(Sds) 𝐽 = Load transfer coefficient used to adjust for load transfer characteristics of a specific design 𝐶𝑑 = Drainage coefficient 𝐸𝐶 = Elastic Modulus of PCC 𝑘 = Composite Modulus of subgrade reaction Step 1: Cumulative Equivalent Single Axle load (CESAL), W18 (refer to DO 22 series of 2011) Design Traffic Design Traffic for each vehicle type can be solved using the formula below: (1 + 𝑔)𝑛 − 1 𝐷𝑒𝑠𝑖𝑔𝑛 𝑇𝑟𝑎𝑓𝑓𝑖𝑐𝑖 = 𝑃𝑖 [ ] × 365 𝑔 Where:𝑃𝑖=Annual Average Daily Traffic 𝑔= Traffic Growth Rate 𝑛= Design Perio Equivalence Factor, EF Equivalence Factor (EF) for each vehicle type can be solved using the formula below: 𝑎𝑥𝑙𝑒 𝑙𝑜𝑎𝑑 (𝑡𝑜𝑛𝑠) 4 𝐸𝐹𝑖 = ∑ [ ] 8.2 Distribution Factors a. Directional distribution Factor – Generally 50% for two (2) way roads b. Lane distribution Factor – Please Refer to Table 1 for the range of value based on the number of lanes per direction. Compute the Cumulative Equivalent Single Axle Load (CESAL) for each vehicle type. 𝐶𝐸𝑆𝐴𝐿𝑖 = 𝐷𝑒𝑠𝑖𝑔𝑛 𝑇𝑟𝑎𝑓𝑓𝑖𝑐𝑖 × 𝐸𝐹𝑖 Add the CESAL for all vehicle types multiplied by the distribution factors. 𝐶𝐸𝑆𝐴𝐿 = ∑ 𝐶𝐸𝑆𝐴𝐿𝑖 × 𝐷𝐷 × 𝐷𝐿 Step 2: Level of Reliability, R Standard Normal Deviate (ZR) A variable in the AASHTO Formula that is dependent on the Reliability Factor (R). The normally used reliability factor for national roads in the Philippines is 85%. Suggested Levels of Reliability for Various Function Classification Functional Classification Recommended Level of Reliability Urban Rural Interstate & other freeway 85-99.9 80-99.9 Principal Arterial 80-99 75-95 Collectors 80-95 75-95 50  PUP Civil Engineering Department #WeLearnAsOne Based on Reliability Reliability R Standard Normal Deviate ZR 50 0 60 -0.253 70 -0.524 75 -0.674 80 -0.841 85 -1.037 90 -1.282 91 -1.340 92 -1.405 93 -1.476 94 -1.555 95 -1.645 96 -1.751 97 -1.881 98 -2.054 99 -2.327 99.9 -3.090 99.9 -3.750 Step 3: Combined Standard Error of the Traffic Prediction and Performance Prediction (So) The Overall Standard Deviation (SO) is one of the criteria required for the consideration of reliability. Although it is possible to estimate this parameter through analysis of variance of all design factors, an approximate value must be considered. Values of between 0.30 - 0.40 have been used for SO for rigid and values of between 0.40 - 0.50 for flexible pavement as mentioned in the AASHTO Guide.. Step 4: Design Serviceability Loss, ∆𝑷𝑺𝑰 Initial Serviceability Index, Pi Pi is equal 4.5 for Rigid Pavement Terminal Serviceability Index, Pt Pt is equal to 2.5 or higher for major highways and 2.0 for lesser traffic volumes Use the equation below to solve for Design Serviceability Loss, ∆𝑷𝑺𝑰 ∆ 𝑃𝑆𝐼 = 𝑃1 − 𝑃2 Where: P1 : PSI immediately after overlay P2 : PSI at time of next rehabilitation Step 5: Modulus of Rupture (S’c) As per DPWH specification S’c= 550 psi for 14 days. As per AASHTO 1993, if construction specification will be used, then necessary adjustments should follow using the formula below: 𝑆′(𝑚𝑒𝑎𝑛) = 𝑆 + 𝑧(𝑆𝐷 ) 𝑐 𝑐 𝑠 51  PUP Civil Engineering Department #WeLearnAsOne Where: 𝑆𝑐′ = estimated mean value for PCC modulus of rupture 𝑆𝑐 = construction specification on concrete modulus of rupture (psi) 𝑆𝐷𝑠 = estimated standard deviation of concrete modulus of rupture (psi) 𝑆𝐷𝑠 = 𝑃𝑆(𝑆𝑐), PS value refer to Table 5 𝑧 = standard normal deviate Usual value used for design: 𝑆𝑐 = 550 psi for 14 days 𝑆𝐷𝑠 = 𝑃𝑆(𝑆𝑐) = 0.15 × 550 𝑧 = 1.037 𝑆𝑐(𝑚𝑒𝑎𝑛) = 550 + 1.037(0.15 × 550) ′ 𝑆𝑐′(𝑚𝑒𝑎𝑛) = 635.55 𝑝𝑠𝑖 Step 6: Load Transfer Coefficient, J Measure joint load transfer in the outer wheel path at a representative transverse joints. Do not measure load transfer when the ambient temperature is greater than 80°F. Place the load plate on one side of the joint with the edge of the plate touching the joint. Measure the deflection at the center of the load plate and at 12 inches from the center. Compute the deflection load transfer from the following equation. Load Transfer Co-efficient Percent Load Transfer “J” >70 Load 3.2 50- 70 Transfer 3.5