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Section 2: Overview of Policy

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2.1 Summary

The following table summarizes the pavement design and construction policies required by the department.

Anchor: #i1014191Table 1-1: Summary of Pavement Design and Construction Policies

Section

Policy

Additional References

Chapter 2

Pavement Design Process

Section 2

Pavement Design Standard Operating Procedure (SOP)

District SOP: The district pavement engineer (DPE) will review and update the District Pavement Standard Operating Procedures (SOP) on an annual basis. This SOP shall be reviewed and updated by September 1st annually with a copy emailed to CST-M&P. If no changes are made from the previous year, send an e-mail to CST-M&P confirming that no changes were made.

 

Pavement Design Communication: The district engineer (DE) is responsible for documenting communication channels for designing, constructing, and maintaining quality pavements.

 

Pavement Design Approval: Authority for pavement design approval may not be delegated below the DE, except for metropolitan districts. In metropolitan districts, pavement design approval authority may be delegated to the deputy district engineer, district director of construction, operations, or transportation, planning and development for projects with estimated construction costs of less than $20 million.

 

Section 3

District Pavement Engineer’s Role

DPE: The DPE is a licensed professional engineer who serves as the district point of contact for the evaluation, preservation, and structural design of pavements.

Section 3 lists general responsibilities for DPE.

Training: The DPE is required to receive approved training in the use of MODULUS, FPS, AASHTO 1993 CPCD procedure, and TxCRCP ME design software.

Other recommended courses for pavement materials and pavement management are included in this section.

Section 5

Pavement Type Selection

Pavement Type Selection: The decision factors considered for pavement design type shall be included in the pavement design report.

Section 5 includes some discussion on decision factors and recommends using the FHWA software RealCost to perform a life cycle cost analysis if warranted.

Section 6

Approved Pavement Design Methods

Pavement Design Methods: Use one of the following analytical methods for designing pavements:

  • FPS 21 for flexible pavements.
  • Modified Texas Triaxial Design Method for flexible pavements.
  • TxCRCP-ME for continuously reinforced rigid pavements.
  • AASHTO design procedure (1993) for CPCD and rigid pavement overlays.

Refer to Chapter 5 for flexible pavement design specifics and Chapter 8 for rigid pavement design specifics.

Section 8

Information Needed for Pavement Design

Evaluate Existing Pavement Condition: The district will take adequate measures to properly characterize the existing functional and structural condition of pavements scheduled for rehabilitation.

Section 8 contains a brief discussion of destructive and nondestructive testing. More information is contained in Chapter 4.

Moisture Damage Mitigation: Department policy on mitigating moisture damage in pavements is evident in many ways, such as establishing a non-erosive base beneath rigid pavements, and establishing HMA QC/QA density requirements and stripping evaluation.

Guidelines are provided for cases where retro-fitting edge drains may be beneficial.

Information about internal (positive) drainage measures is provided in Section 8.

Ground Water: Another major source of free moisture into the pavement structure is ground water.The department’s policy is to intercept ground water outside of the pavement structure to eliminate its impact.

 

Section 9

Pavement Design Reports

Projects Requiring Pavement Design and Pavement Design Reports: A pavement design and a pavement design report are required for the following projects that are over 500 ft. long:

  • new location projects (flexible and rigid),
  • reconstruction projects (flexible and rigid),
  • Rehabilitation (3R) projects (flexible and rigid), or
  • unbonded concrete overlays of existing rigid pavements.

The following list provides examples of special cases that do not require a full design report but do require documentation of the criteria and rationale for the strategy selected for projects greater than 500 ft. long:

  • approaches on a bridge replacement,
  • detours,
  • pavement widening including shoulders,
  • HMA overlays of rigid pavements,
  • bonded concrete overlays on rigid pavements, or
  • thin whitetopping of flexible pavements.

 

Completing Pavement Design Report: Follow procedures outlined in Table 2-5.

Form 2088: Required to include form 2088, Surface Aggregate Selection Form, as part of the flexible pavement design only. Information from this form will determine the appropriate Surface Aggregate Classification (SAC) of the aggregate used for the final hot-mix asphalt (HMA) riding surface.

 

Chapter 5

Flexible Pavement Design

Section 3

FPS 21 Design Parameters

FPS 21 Design Parameters: The required analytical method of flexible pavement design is FPS 21. Input the Design Parameters for flexible pavement as detailed in this section.

Chapter 2, Section 6, and Table 5-1.

Post Design Check: Check the design derived by FPS 21 for full-depth shear strength adequacy using the Modified Texas Triaxial Class (TTC) design method contained in the FPS 21 software.

Tables 5-4 and 5-5.

Traffic Input: Traffic loading must be entered as the 20-yr. cumulative ESALs. A 30-yr. analysis period or longer is allowable, but the designer must still input the projected 20-yr. cumulative ESALs.

 

Section 4

FPS 21 Modulus Inputs and Backcalculation

Modulus Inputs: Determine design modulus values as detailed in this section.

Table 5-6 shows a range of typical design values for various new or reclaimed pavement layer materials.

Use an input value that is indicative of the material likely to be used. For materials to remain in place, use backcalculated moduli, with adjustments as warranted.

Backcalculation: Use the backcalculation procedure to determine modulus input values for in situ pavement materials when these materials are used as-is (unmodified) in FPS design.

See list of considerations enumerated in Section 4.

Section 5

Pavement Detours and Pavement Widening

Structural Design of Detours: The falling weight deflectometer (FWD) shall be used to evaluate the adequacy of any existing structure (e.g., shoulders or bypass routes) to carry detour traffic. Design detours using of the following strategies:

  • FPS 21 and the Modified Texas Triaxial Class (TTC) design procedure (as a standalone design option),
  • the alternate version of the modified TTC check, or
  • districts may employ proven design strategies for detours and can develop catalog designs based on traffic levels and subgrade support.

 

Pavement Widening: Maintain the original cross-section for the widened portion. When the shoulder is to form part of a new lane, perform non-destructive surveys using the falling weight deflectometer (FWD).

Additional detail is given in this section regarding design and location of widening joints for bound, unbound, and dissimilar cross-section widening.

Section 6

Perpetual Pavement Design

Perpetual Pavements:

  • Use perpetual pavements for traffic levels exceeding 30 million ESALs.
  • Design perpetual pavements using FPS 21. Conduct a design check of the limiting strain criteria by activating the FPS 21 mechanistic check.

Use limiting strain criteria given. Follow Table 5-6 details for each step.

Chapter 8

Rigid Pavement Design

Section 1

Overview

Selection of Rigid Pavement Type: The department policy is to utilize Continuously Reinforced Concrete Pavement (CRCP) for new or reconstructed rigid pavements in Texas. The criteria in Chapter 8, Section 1, list the applications where Concrete Pavement Contraction Design (CPCD) can be used instead of CRCP, at the discretion of the district engineer.

 

Performance Period: For rigid pavements, the initial pavement structure shall be designed and analyzed for a performance period of 30 yr.

 

Tied Portland cement concrete (PCC) shoulders: Use tied PCC shoulders. If it is not feasible to provide full-width tied PCC shoulders, use a minimum 2-ft. widened outside lane.

The PCC shoulders must have the same thickness and the same base layers as the main lane pavement.

 

Concrete Pavement Standards:

For CRCP, the steel reinforcement, joints, and other design details are governed by the CRCP standards.

For CPCD, the dowel bars, tie bars, joints, and other design details are governed by the CPCD standard.

Link for CRCP and CPCD standards:

http://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/rdwylse.htm.

Section 2

Approved Design Method

Approved Design Methods:

TxCRCP-ME Design program is the approved design method for CRCP.

The 1993 AASHTO Guide for Design of Pavement Structures is the only approved design method for CPCD projects.

Chapter 8, Section 3, Rigid Pavement Design Process for CRCP.

Chapter 8, Section 4, Rigid Pavement Design Process for CPCD.

Section 3

Rigid Pavement Design Process for CRCP

Design Parameters: Input the Design Parameters for CRCP as detailed in this section.

 

Section 4

Rigid Pavement Design Process for CPCD

Design Parameters: Input the Design Parameters for CPCD as detailed in this section.

 

Section 3 & 4

Pavement Design Processes for CRCP and CPCD

Base Layer Requirements: The department requires one of the following base layer combinations for concrete slab support:

  • 4 in. of hot-mix asphalt (HMA) or asphalt treated base (ATB), or
  • a minimum 1 in. hot-mix asphalt bond breaker over 6 in. of a cement treated base (CTB). Use item 276, Class L.

Width requirement of subgrade/base: The subgrade/base must be designed 2 ft. wider than the concrete slab on each side to accommodate slipform pavement equipment.

 

Section 5

Determining Concrete Pavement Thickness

Determining Concrete Pavement Thickness:

For CRCP designs, the input thickness should be in 1/2 in. increments. The minimum thickness for CRCP is 7 in., and the maximum thickness is 13 in.

For CPCD design, the computed concrete slab thickness should be rounded to the nearest full or half inch. The minimum slab thickness for CPCD is 6 in., and the maximum thickness is 12 in.

 

Section 6

Terminal Anchor Joint Selection for Concrete Pavement

Terminal Anchor Joint Selection for Concrete Pavement: Use the transverse expansion joint details at bridge approaches shown in the concrete pavement standards. Districts may develop a Special Specification to use wide-flange systems. The use of anchor lug systems is no longer allowed.

 

Chapter 9

Rigid Pavement Construction

Section 1-7

Rigid Pavement Construction: Construct the rigid pavement in accordance with the department’s Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges.

Items 360, 421, and 440.

Link for CRCP and CPCD standards:

http://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/rdwylse.htm

Chapter 10

Rigid Pavement Rehabilitation

Section 1-11

Rigid Pavement Rehabilitation: Repair the rigid pavement in accordance with the department’s Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges and the relevant Special Specification of the rehabilitation.

Items 361 and 720.

Link for Repair of Concrete Pavement Standards:

http://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/rdwylse.htm

Chapter 11

Ride Quality

Section 1

Overview

Ride Quality: Measure ride quality in accordance with the department’s Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges.

Items 247, 340, 341, 342, 344, 346, 347, 348, 360, and 585.

Table 11-2 can be used to select the appropriate pay adjustment schedule.

Chapter 13

Load Zoning and Super Heavy Load Analysis

Section 1

Overview for Load Zoning

Executive Order: The department’s executive director sets load limits for individual roadway segments by issuing an Executive Order.

CST-M&P prepares and submits proposed Executive Orders to the executive director.

Texas Transportation Code, §621.102.

Section 2

Changing Load Zones on Roads

Changing Load Zones: Follow the procedures in this section for changing load zones.

See Table 13-1.

Section 3

Emergency Load Zones on Roads

Emergency Load Zones: The district shall notify CST-M&P by telephone or e-mail that an emergency load restriction is required.

See Table 13-2.

Section 4

Changing Load Zones on County Roads and Bridges

County Roads and Bridges: Counties must obtain department concurrence from the district engineer for proposed changes to county road and bridge load limits.

Texas Transportation Code, §621.301.

See Tables 13-3 and 13-4.

Section 6

Super Heavy Load Evaluation Process

Super Heavy Load Analysis: All super heavy loads must be permitted through the Motor Carrier Division (MCD) of the Texas Department of Motor Vehicles (TxDMV). Refer to this section for the required evaluation process.

Texas Transportation Code, §623.071 and §623.142.

See Figure 13-3.

See section 5 for analysis background information.

Section 8

Damage Claim Procedure

Damage Claim Procedure: Refer to this section for the required procedure.

Financial Management Policy Manual, Chapter 4, Section 10, “Claims by TxDOT Concerning Damage to Highway Property.”




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