Design pavement structure

12.3.5  Learning Outcome No 4: Design pavement structure

12.3.5.1           Learning Activities

12.3.5.2           Information Sheet No 12/ Lo 4: Design pavement structure

Introduction to learning outcome

This learning outcome covers preparation of pavement structural drawings, development of material schedules and preparation and presentation of a detailed report and material specifications.

Definition of key terms

Subgrade: The in situ materials or improved ground with imported materials that form the platform for a pavement structure.

Sub-base: In transportation engineering, a subbase is a load-distributing layer immediately below and usually of inferior materials to the road base.

Rigid Pavement: This is a pavement whose main structural layer is a concrete slab. They are termed rigid due to their high flexural strength or high modulus of elasticity.

Content/Procedures/Methods/Illustrations

• Acquire resources in accordance with pavement structure requirements.

The design of pavement structures requires the determination of the thickness of layers and composition of materials. The resources and tools required in pavement design can be found through;

• Online USGS store for topographical maps
• Download Road Design Manuals online from the KeNHA web page.
• Visiting the library for literature on pavement structures
  • Estimate traffic load as per traffic survey information.

Traffic loading in transportation engineering is the cumulative load characterized by traffic volume, magnitudes, wheel repetition, and truck weight data.

The procedure for determining traffic loading is:

• Determining the axle load
• Calculating the Equivalent Factor and the number of single axle loads (SAL)
• Calculating the total SAL as Cumulative standard axle
  • Determine road/pavement type (rigid and flexible pavement) as per client/developer/financier requirements and nature of the ground.

Pavement types are categorized into two major types; rigid and flexible pavements.

The procedure for selection of a pavement structure involves:

• Assessing the initial cost of construction
• Evaluating life cycle costs in the pavement maintenance and subsequent rehabilitations
• Determining the traffic loading
• Identifying the topography and land use
  • Design pavement structures (sub-grade, sub-base, base, surface) based on traffic engineering analysis outputs and material testing results

The typical components of a pavement that functions to support and distribute traffic load are what makes a pavement system. The pavement structures; sub-grade, sub-base, base course, surface course are as illustrated below.

(cite)

• Produce pavement structural drawings as per design outputs

Pavement structural drawings are documents that depict the detailed cross-section of a proposed road.

The process of producing structural drawing should include:

• Drawing of cross-sections after every 100m or in areas of a sudden change in gradient.
• The area of fill and cut to be shown at all times
  • Develop materials schedules according to design results

Materials scheduling is the process of organizing and controlling the sequence of delivery of materials on site. Material scheduling requires considerable knowledge of technical specifications for each component in structural design. The procedure to develop material schedule is:

• Identifying and working out quantities of materials needed from the structural drawing
• Identifying where materials will be procured
• Identifying the unit cost of the materials
• Determining the lead times of the materials
  • Prepare and present a detailed report and specifications as per the contract document.

A detailed project report and specifications are prepared and presented once all detailed studies have been completed.

The preparation of a detailed report will involve;

• Collecting information on the final route location
• Collecting the specification for soils and materials
• Collecting and organizing design details of the pavement

Conclusion

This learning outcome covered preparation of pavement structural drawings, development of material schedules and preparation and presentation of a detailed report and material specifications.

Further Reading:

Road Design Manual Part III -Materials and Pavement Design for New Roads

12.3.5.3           Self-Assessment

(This section must be related with the Performance Criteria, Required Knowledge and Skills and the Range as stated in the Occupational Standards)

Knowledge-Based Evidence

Written Assessment

5 multiple choice questions

Rigid Pavements are analyzed by

1. Infinite layer theory
2. Elastic plate theory
3. Rigid plate theory
4. Interlocking of aggregates

The most superior pavement layer is that which distributes loads as

1. Uniformly varying load
2. Uniformly distributed
3. Point load
4. Triangular load

Which among the following is not a contract document?

1. Bill of Quantities
2. Financial Statements
3. Specifications
4. Construction Scheduling

Load transfer in flexible pavements is by

1. Consolidation of sub-grade
2. Grain to grain contact
3. Bending action of layers
4. Shear deformation

Which of the following is not typical layer of flexible pavements

1. Tack coat
2. Road base
3. Sub-base
4. Sub-grade

4 short answer questions

1. Briefly describe the functions of each layer in flexible pavements.
2. What are the advantages of rigid pavements?
3. Briefly describe how material scheduling is conducted.
4. Briefly describe four factors controlling the design of pavements.

1 Essay questions

Oral Assessment

• Two questions

Case Study Assessment

• One Case

Performance Based Evidence

Oral Assessment

• Two questions

Practical Assessment

• one questions

Project Assessment

• one questions

12.3.5.4           Tools, Equipment, Supplies and Materials

• Computers
• Software
• Cameras
• Construction manuals
• Projectors
• Flip charts
• Calculators
• Rulers, pencils, erasers
• Charts with presentations of data
• Drawing sheets
• Internet
• Relevant videos

12.3.5.5           References

(Provide at least three current references in APA)

Author. (Year). Title. City: Publisher

e.g

AVERC. (2019). Developing of Learning Material. Nairobi: Government Printers.

Chandra, Satish (n.d) Pavement versus Rigid Pavement. Retrieved 23 June 2020, from https://www.nbmcw.com/tech-articles/roads-and-pavements/36977-flexible-pavement-versus-rigid-pavement.html

Mannering, F., & Washburn, S. (2019). Principles of highway engineering and traffic analysis.

Road Design Manual Part III -Materials and Pavement Design for New Roads

[Typical Cross-section of flexible pavement] (n.d). Retrieved 23 June 2020, from https://www.nbmcw.com/tech-articles/roads-and-pavements/36977-flexible-pavement-versus-rigid-pavement.html

12.3.6  Learning Outcome No 5: Design pedestrian and cyclist paths

12.3.6.1           Learning Activities            

12.3.6.2           Information Sheet No 12/ Lo 5: Design pedestrian and cyclist paths

Introduction to learning outcome

This learning outcome covers the determination, designing and locating of pedestrian and cyclist path.

Definition of key terms

Pedestrian crossing: This is a specially designated area on a road where pedestrians have the right way.

Information signs: These are traffic signs that function to guide motorists in navigation and offer information on important facilities along the way.

Warning signs: Traffic signs that caution road users of potential dangers along the road.

Content/Procedures/Methods/Illustrations

• Identify and gather required resources as per design requirements

Resources required in the design of pedestrians and cyclists’ paths are materials that will help in determining the thickness and dimensions of the paths. Resources for design include GIS tools, computer tools, and expertise, maps, and travel surveys.

The procedure of identifying and gathering resources include;

• Identifying information on demographical data, legislations for special needs groups, and land use
• Getting the areas plan and the available road reserve.
• Utilize the information to determine the dimensions of the paths
  • Estimate pedestrian and cyclist traffic in accordance with traffic survey information

Pedestrian and cyclist traffic is the aggregation of road users not using vehicular means of transport. According to Nordback, Sellinger, and Phillips (2017), the procedure to estimate this type of traffic involves;

• Evaluating land use and road network connectivity
• Enhancing models to conduct non-motorized trip generations in a smaller zone
  • Determine the pedestrian and cyclist path location according to road profile

Pedestrian and cyclist paths are routes that provide a safe passage from non-motorized road users.

According to Segadilha and Sanches (2014), selection of the location of a pedestrian and cyclist paths according to the road profile is subject to:

• Visibility
• Gradient and crossfall
  • Design pedestrian and cyclist paths as per design manuals and procedures

Pedestrian and cyclist paths should be designed to ensure minimal conflicts and with special consideration to people with impairments.

The design of these paths demands;

• Providing paths dimensions and geometry that accommodate all users
• Surface materials to be selected on the basis of safety and convenience.
• Providing and designing street furniture’s accordingly
  • Produce drawings according to design output

The design drawings for the pedestrian and cyclist path illustrates the cross-section layout of the paths. Design drawings are produced using software such as AutoCAD which will provide information on:

• Dimensions of the paths, including its thickness.
• Dimensions of the street furniture such as Kerb
  • Prepare and present the report and material specifications according to contract document

Reports according to contract documents give information on, but not limited to the project milestones, stages, labor, and equipment. The procedure to make a report will include;

• Collecting and organizing information on project activities, labor, and materials
• Structure the information into relevant segments
• Present the report with accurate charts and spreadsheets.

Conclusion

This learning outcome covered the determination, designing and locating of pedestrian and cyclist path.

Further Reading

The Design of the Pedestrian Network: https://www.nzta.govt.nz/assets/resources/pedestrian-planning-guide/docs/chapter-14.pdf

12.3.6.3           Self-Assessment

(This section must be related with the Performance Criteria, Required Knowledge and Skills and the Range as stated in the Occupational Standards)

Knowledge Based Evidence

Written Assessment

5 multiple choice questions

1. Which among the following is NOT a zone of a footpath?
2. Through route
3. Frontage zone
4. Carriage way
5. Street furniture zone
6. All the following are traffic signs except
   1. Warning signs
   2. Explanatory signs
   3. Information signs
   4. Regulatory Signs
7. The following are design features of a pedestrian and a cyclist path except?
8. Gradient
9. Visibility
10. Width
11. Length
12. All the following are street furniture except
13. Bollards
14. Traffic signs
15. Culverts
16. Rubbish bins
17. A report provides information on
18. Manpower
19. Materials
20. Project milestone
21. All the above

4 short answer questions

1. What is the difference between a zebra crossing and a pedestrian crossing?
2. Given the information acquired, which measures will be most effective in reducing cyclist-motorist collision?

• Give two instances where it is unsuitable for providing a pedestrian footpath along the way.

1. Highlight three surfacing materials used in pedestrian and cyclist paths.

1 Essay questions

Oral Assessment

• Two questions

Case Study Assessment

• One Case

Performance Based Evidence

Oral Assessment

• Two questions

1. Vehicles parking on pedestrian and cyclist path has been a common practice in the recent past. Which measure should be put in place to prevent cars from closing and obstructing side paths?

Practical Assessment

• one questions

Project Assessment

• one questions
• You are required to conduct a traffic survey for cyclists and pedestrians in your locality. Use the data collected to design a combined pedestrian and cyclist path. Your design output should be structural drawings, from AutoCAD or any other software, illustrating the cross-section, and width of the path. Please note to design for safety and aesthetics.

12.3.6.4           Tools, Equipment, Supplies and Materials

• Computers
• Software
• Cameras
• Construction manuals
• Projectors
• Flip charts
• Calculators
• Rulers, pencils, erasers
• Charts with presentations of data
• Drawing sheets
• Internet
• Relevant videos

12.3.6.5           References

(Provide at least three current references in APA)

Author. (Year). Title. City: Publisher

e.g

AVERC. (2019). Developing of Learning Material. Nairobi: Government Printers.

Nordback, K., Sellinger, M., & Phillips, T. (2017). Estimating walking and cycling distance at the state level. Retrieved 24 June 2020, from https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1129&context=trec_reports

Peers, F. (2012). Appendix-A: Resources for Design of Pedestrian Facilities. Retrieved 24 June 2020, from https://www.ci.emeryville.ca.us/DocumentCenter/View/1827/Appendix-A-Pedestrian-Design-Resources?bidId=

Segadilha, A., & Sanches, S. (2014). Identification of Factors that Influence Cyclistś Route Choice. Procedia – Social And Behavioral Sciences, 160, 372-380. doi: 10.1016/j.sbspro.2014.12.149s